mongo data

.idea/goext.iml

@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <module type="WEB_MODULE" version="4">
-  <component name="Go" enabled="true" />
+  <component name="Go" enabled="true">
+    <buildTags>
+      <option name="goVersion" value="1.19" />
+    </buildTags>
+  </component>
   <component name="NewModuleRootManager">
     <content url="file://$MODULE_DIR$" />
     <orderEntry type="inheritedJdk" />

Makefile

@@ -1,9 +1,16 @@
 
+.PHONY: run test version update-mongo
+
 run:
 	echo "This is a library - can't be run" && false
 
 test:
-	go test ./...
+	# go test ./...
+	which gotestsum || go install gotest.tools/gotestsum@latest
+	gotestsum --format "testname" -- -tags="timetzdata sqlite_fts5 sqlite_foreign_keys" "./test"
 
 version:
 	_data/version.sh
+
+update-mongo:
+	_data/update-mongo.sh

README.md

@@ -6,3 +6,36 @@ A collection of general & useful library methods
 This should not have any heavy dependencies (gin, mongo, etc) and add missing basic language features...
 
 Potentially needs `export GOPRIVATE="gogs.mikescher.com"`
+
+
+### Packages:
+
+| Name         | Maintainer | Description                                                                                                   |
+|--------------|------------|---------------------------------------------------------------------------------------------------------------|
+| langext      | Mike       | General uttility/helper functions, (everything thats missing from go standard library)                        |
+| mathext      | Mike       | Utility/Helper functions for math                                                                             |
+| cryptext     | Mike       | Utility/Helper functions for encryption                                                                       |
+| syncext      | Mike       | Utility/Helper funtions for multi-threading / mutex / channels                                                |
+| dataext      | Mike       | Various useful data structures                                                                                |
+| zipext       | Mike       | Utility for zip/gzip/tar etc                                                                                  |
+| reflectext   | Mike       | Utility for golagn reflection                                                                                 |
+|              |            |                                                                                                               |
+| mongoext     | Mike       | Utility/Helper functions for mongodb                                                                          |
+| cursortoken  | Mike       | MongoDB cursortoken implementation                                                                            |
+|              |            |                                                                                                               |
+| totpext      | Mike       | Implementation of TOTP (2-Factor-Auth)                                                                        |
+| termext      | Mike       | Utilities for terminals (mostly color output)                                                                 |
+| confext      | Mike       | Parses environment configuration into structs                                                                 |
+| cmdext       | Mike       | Runner for external commands/processes                                                                        |
+|              |            |                                                                                                               |
+| sq           | Mike       | Utility functions for sql based databases                                                                     |
+| tst          | Mike       | Utility functions for unit tests                                                                              |
+|              |            |                                                                                                               |
+| rfctime      | Mike       | Classes for time seriallization, with different marshallign method for mongo and json                         |
+| gojson       | Mike       | Same interface for marshalling/unmarshalling as go/json, except with proper serialization of null arrays/maps |
+|              |            |                                                                                                               |
+| bfcodegen    | Mike       | Various codegen tools (run via go generate)                                                                   |
+|              |            |                                                                                                               |
+| rext         | Mike       | Regex Wrapper, wraps regexp with a better interface                                                           |
+| wmo          | Mike       | Mongo Wrapper, wraps mongodb with a better interface                                                          |
+|              |            |                                                                                                               |

TODO.md

@@ -0,0 +1,13 @@
+
+
+ - cronext
+
+ - cursortoken
+
+ - typed/geenric mongo wrapper
+
+ - error package
+
+- rfctime.DateOnly
+- rfctime.HMSTimeOnly
+- rfctime.NanoTimeOnly

_data/mongo.patch

@@ -0,0 +1,80 @@
+diff --git a/mongo/bson/bsoncodec/struct_codec.go b/mongo/bson/bsoncodec/struct_codec.go
+--- a/mongo/bson/bsoncodec/struct_codec.go
++++ b/mongo/bson/bsoncodec/struct_codec.go
+@@ -122,6 +122,10 @@ func (sc *StructCodec) EncodeValue(r EncodeContext, vw bsonrw.ValueWriter, val r
+ 	}
+ 	var rv reflect.Value
+ 	for _, desc := range sd.fl {
++		if desc.omitAlways {
++			continue
++		}
++
+ 		if desc.inline == nil {
+ 			rv = val.Field(desc.idx)
+ 		} else {
+@@ -400,15 +404,16 @@ type structDescription struct {
+ }
+ 
+ type fieldDescription struct {
+-	name      string // BSON key name
+-	fieldName string // struct field name
+-	idx       int
+-	omitEmpty bool
+-	minSize   bool
+-	truncate  bool
+-	inline    []int
+-	encoder   ValueEncoder
+-	decoder   ValueDecoder
++	name       string // BSON key name
++	fieldName  string // struct field name
++	idx        int
++	omitEmpty  bool
++	omitAlways bool
++	minSize    bool
++	truncate   bool
++	inline     []int
++	encoder    ValueEncoder
++	decoder    ValueDecoder
+ }
+ 
+ type byIndex []fieldDescription
+@@ -491,6 +496,7 @@ func (sc *StructCodec) describeStruct(r *Registry, t reflect.Type) (*structDescr
+ 		}
+ 		description.name = stags.Name
+ 		description.omitEmpty = stags.OmitEmpty
++		description.omitAlways = stags.OmitAlways
+ 		description.minSize = stags.MinSize
+ 		description.truncate = stags.Truncate
+ 
+diff --git a/mongo/bson/bsoncodec/struct_tag_parser.go b/mongo/bson/bsoncodec/struct_tag_parser.go
+--- a/mongo/bson/bsoncodec/struct_tag_parser.go
++++ b/mongo/bson/bsoncodec/struct_tag_parser.go
+@@ -52,12 +52,13 @@ func (stpf StructTagParserFunc) ParseStructTags(sf reflect.StructField) (StructT
+ //
+ // TODO(skriptble): Add tags for undefined as nil and for null as nil.
+ type StructTags struct {
+-	Name      string
+-	OmitEmpty bool
+-	MinSize   bool
+-	Truncate  bool
+-	Inline    bool
+-	Skip      bool
++	Name       string
++	OmitEmpty  bool
++	OmitAlways bool
++	MinSize    bool
++	Truncate   bool
++	Inline     bool
++	Skip       bool
+ }
+ 
+ // DefaultStructTagParser is the StructTagParser used by the StructCodec by default.
+@@ -108,6 +109,8 @@ func parseTags(key string, tag string) (StructTags, error) {
+ 		switch str {
+ 		case "omitempty":
+ 			st.OmitEmpty = true
++		case "omitalways":
++			st.OmitAlways = true
+ 		case "minsize":
+ 			st.MinSize = true
+ 		case "truncate":

_data/update-mongo.sh

@@ -0,0 +1,95 @@
+#!/bin/bash
+
+
+    set -o nounset   # disallow usage of unset vars  ( set -u )
+    set -o errexit   # Exit immediately if a pipeline returns non-zero.  ( set -e )
+    set -o errtrace  # Allow the above trap be inherited by all functions in the script.  ( set -E )
+    set -o pipefail  # Return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status
+    IFS=$'\n\t'      # Set $IFS to only newline and tab.
+
+
+
+dir="/tmp/mongo_repo_$( uuidgen )"
+
+echo ""
+echo "> Clone https://github.dev/mongodb/mongo-go-driver"
+echo ""
+
+git clone "https://github.com/mongodb/mongo-go-driver" "$dir"
+
+pushd "$dir"
+
+git fetch --tags
+
+latestTag="$( git describe --tags `git rev-list --tags --max-count=1` )"
+
+git -c "advice.detachedHead=false" checkout $latestTag
+
+latestSHA="$( git rev-parse HEAD )"
+
+popd
+
+existingTag=$( cat mongoPatchVersion.go | grep -oP "(?<=const MongoCloneTag = \")([A-Za-z0-9.]+)(?=\")" )
+existingSHA=$( cat mongoPatchVersion.go | grep -oP "(?<=const MongoCloneCommit = \")([A-Za-z0-9.]+)(?=\")" )
+
+echo "===================================="
+echo "ID  (online) $latestSHA"
+echo "ID  (local)  $existingSHA"
+echo "Tag (online) $latestTag"
+echo "Tag (local)  $existingTag"
+echo "===================================="
+
+if [[ "$latestTag" == "$existingTag" ]]; then
+  echo "Nothing to do"
+  rm -rf "$dir"
+  exit 0
+fi
+
+echo ""
+echo "> Copy repository"
+echo ""
+
+rm -rf mongo
+cp -r "$dir" "mongo"
+rm -rf "$dir"
+
+echo ""
+echo "> Clean repository"
+echo ""
+
+rm -rf "mongo/.git"
+rm -rf "mongo/.evergreen"
+rm -rf "mongo/cmd"
+rm -rf "mongo/docs"
+rm -rf "mongo/etc"
+rm -rf "mongo/examples"
+rm -rf "mongo/testdata"
+rm -rf "mongo/benchmark"
+rm -rf "mongo/vendor"
+rm -rf "mongo/internal/test"
+rm -rf "mongo/go.mod"
+rm -rf "mongo/go.sum"
+
+echo ""
+echo "> Update mongoPatchVersion.go"
+echo ""
+
+{
+
+  printf "package goext\n"
+  printf "\n"
+  printf "// %s\n" "$( date +"%Y-%m-%d %H:%M:%S%z" )"
+  printf "\n"
+  printf "const MongoCloneTag = \"%s\"\n" "$latestTag"
+  printf "const MongoCloneCommit = \"%s\"\n" "$latestSHA"
+
+} > mongoPatchVersion.go
+
+echo ""
+echo "> Patch mongo"
+echo ""
+
+git apply -v _data/mongo.patch
+
+echo ""
+echo "Done."

_data/version.sh

@@ -21,6 +21,10 @@ if [ "$( git rev-parse --abbrev-ref HEAD )" != "master" ]; then
   exit 1
 fi
 
+git pull --ff
+
+go get -u ./...
+
 curr_vers=$(git describe --tags --abbrev=0 | sed 's/v//g')
 
 next_ver=$(echo "$curr_vers" | awk -F. -v OFS=. 'NF==1{print ++$NF}; NF>1{if(length($NF+1)>length($NF))$(NF-1)++; $NF=sprintf("%0*d", length($NF), ($NF+1)%(10^length($NF))); print}')
@@ -30,9 +34,17 @@ echo "> Current Version: ${curr_vers}"
 echo "> Next    Version: ${next_ver}"
 echo ""
 
+printf "package goext\n\nconst GoextVersion = \"%s\"\n\nconst GoextVersionTimestamp = \"%s\"\n" "${next_ver}" "$( date +"%Y-%m-%dT%H:%M:%S%z" )" > "goextVersion.go"
+
 git add --verbose .
 
-git commit -a -m "v${next_ver}"
+msg="v${next_ver}"
+
+if [ $# -gt 0 ]; then
+  msg="$1"
+fi
+
+git commit -a -m "${msg}"
 
 git tag "v${next_ver}"
 

bfcodegen/enum-generate.go

@@ -0,0 +1,364 @@
+package bfcodegen
+
+import (
+	"errors"
+	"fmt"
+	"gogs.mikescher.com/BlackForestBytes/goext"
+	"gogs.mikescher.com/BlackForestBytes/goext/cmdext"
+	"gogs.mikescher.com/BlackForestBytes/goext/cryptext"
+	"gogs.mikescher.com/BlackForestBytes/goext/langext"
+	"gogs.mikescher.com/BlackForestBytes/goext/rext"
+	"io"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"time"
+)
+
+type EnumDefVal struct {
+	VarName     string
+	Value       string
+	Description *string
+}
+
+type EnumDef struct {
+	File         string
+	FileRelative string
+	EnumTypeName string
+	Type         string
+	Values       []EnumDefVal
+}
+
+var rexPackage = rext.W(regexp.MustCompile("^package\\s+(?P<name>[A-Za-z0-9_]+)\\s*$"))
+
+var rexEnumDef = rext.W(regexp.MustCompile("^\\s*type\\s+(?P<name>[A-Za-z0-9_]+)\\s+(?P<type>[A-Za-z0-9_]+)\\s*//\\s*(@enum:type).*$"))
+
+var rexValueDef = rext.W(regexp.MustCompile("^\\s*(?P<name>[A-Za-z0-9_]+)\\s+(?P<type>[A-Za-z0-9_]+)\\s*=\\s*(?P<value>(\"[A-Za-z0-9_:]+\"|[0-9]+))\\s*(//(?P<descr>.*))?.*$"))
+
+var rexChecksumConst = rext.W(regexp.MustCompile("const ChecksumGenerator = \"(?P<cs>[A-Za-z0-9_]*)\""))
+
+func GenerateEnumSpecs(sourceDir string, destFile string) error {
+
+	files, err := os.ReadDir(sourceDir)
+	if err != nil {
+		return err
+	}
+
+	oldChecksum := "N/A"
+	if _, err := os.Stat(destFile); !os.IsNotExist(err) {
+		content, err := os.ReadFile(destFile)
+		if err != nil {
+			return err
+		}
+		if m, ok := rexChecksumConst.MatchFirst(string(content)); ok {
+			oldChecksum = m.GroupByName("cs").Value()
+		}
+	}
+
+	files = langext.ArrFilter(files, func(v os.DirEntry) bool { return v.Name() != path.Base(destFile) })
+	files = langext.ArrFilter(files, func(v os.DirEntry) bool { return strings.HasSuffix(v.Name(), ".go") })
+	langext.SortBy(files, func(v os.DirEntry) string { return v.Name() })
+
+	newChecksumStr := goext.GoextVersion
+	for _, f := range files {
+		content, err := os.ReadFile(path.Join(sourceDir, f.Name()))
+		if err != nil {
+			return err
+		}
+		newChecksumStr += "\n" + f.Name() + "\t" + cryptext.BytesSha256(content)
+	}
+
+	newChecksum := cryptext.BytesSha256([]byte(newChecksumStr))
+
+	if newChecksum != oldChecksum {
+		fmt.Printf("[EnumGenerate] Checksum has changed ( %s -> %s ), will generate new file\n\n", oldChecksum, newChecksum)
+	} else {
+		fmt.Printf("[EnumGenerate] Checksum unchanged ( %s ), nothing to do\n", oldChecksum)
+		return nil
+	}
+
+	allEnums := make([]EnumDef, 0)
+
+	pkgname := ""
+
+	for _, f := range files {
+		fmt.Printf("========= %s =========\n\n", f.Name())
+		fileEnums, pn, err := processFile(sourceDir, path.Join(sourceDir, f.Name()))
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("\n")
+
+		allEnums = append(allEnums, fileEnums...)
+
+		if pn != "" {
+			pkgname = pn
+		}
+	}
+
+	if pkgname == "" {
+		return errors.New("no package name found in any file")
+	}
+
+	err = os.WriteFile(destFile, []byte(fmtOutput(newChecksum, allEnums, pkgname)), 0o755)
+	if err != nil {
+		return err
+	}
+
+	res, err := cmdext.RunCommand("go", []string{"fmt", destFile}, langext.Ptr(2*time.Second))
+	if err != nil {
+		return err
+	}
+
+	if res.CommandTimedOut {
+		fmt.Println(res.StdCombined)
+		return errors.New("go fmt timed out")
+	}
+	if res.ExitCode != 0 {
+		fmt.Println(res.StdCombined)
+		return errors.New("go fmt did not succeed")
+	}
+
+	return nil
+}
+
+func processFile(basedir string, fn string) ([]EnumDef, string, error) {
+	file, err := os.Open(fn)
+	if err != nil {
+		return nil, "", err
+	}
+
+	defer func() { _ = file.Close() }()
+
+	bin, err := io.ReadAll(file)
+	if err != nil {
+		return nil, "", err
+	}
+
+	lines := strings.Split(string(bin), "\n")
+
+	enums := make([]EnumDef, 0)
+
+	pkgname := ""
+
+	for i, line := range lines {
+		if i == 0 && strings.HasPrefix(line, "// Code generated by") {
+			break
+		}
+
+		if match, ok := rexPackage.MatchFirst(line); i == 0 && ok {
+			pkgname = match.GroupByName("name").Value()
+			continue
+		}
+
+		if match, ok := rexEnumDef.MatchFirst(line); ok {
+
+			rfp, err := filepath.Rel(basedir, fn)
+			if err != nil {
+				return nil, "", err
+			}
+
+			def := EnumDef{
+				File:         fn,
+				FileRelative: rfp,
+				EnumTypeName: match.GroupByName("name").Value(),
+				Type:         match.GroupByName("type").Value(),
+				Values:       make([]EnumDefVal, 0),
+			}
+			enums = append(enums, def)
+			fmt.Printf("Found enum definition { '%s' -> '%s' }\n", def.EnumTypeName, def.Type)
+		}
+
+		if match, ok := rexValueDef.MatchFirst(line); ok {
+			typename := match.GroupByName("type").Value()
+			def := EnumDefVal{
+				VarName:     match.GroupByName("name").Value(),
+				Value:       match.GroupByName("value").Value(),
+				Description: match.GroupByNameOrEmpty("descr").ValueOrNil(),
+			}
+
+			found := false
+			for i, v := range enums {
+				if v.EnumTypeName == typename {
+					enums[i].Values = append(enums[i].Values, def)
+					found = true
+					if def.Description != nil {
+						fmt.Printf("Found enum value [%s] for '%s'  ('%s')\n", def.Value, def.VarName, *def.Description)
+					} else {
+						fmt.Printf("Found enum value [%s] for '%s'\n", def.Value, def.VarName)
+					}
+					break
+				}
+			}
+			if !found {
+				fmt.Printf("Found non-enum value [%s] for '%s' ( looks like enum value, but no matching @enum:type )\n", def.Value, def.VarName)
+			}
+		}
+	}
+
+	return enums, pkgname, nil
+}
+
+func fmtOutput(cs string, enums []EnumDef, pkgname string) string {
+	str := "// Code generated by enum-generate.go DO NOT EDIT.\n"
+	str += "\n"
+	str += "package " + pkgname + "\n"
+	str += "\n"
+
+	str += "import \"gogs.mikescher.com/BlackForestBytes/goext/langext\"" + "\n"
+	str += "\n"
+
+	str += "const ChecksumGenerator = \"" + cs + "\"" + "\n"
+	str += "\n"
+
+	str += "type Enum interface {" + "\n"
+	str += "    Valid() bool" + "\n"
+	str += "    ValuesAny() []any" + "\n"
+	str += "    ValuesMeta() []EnumMetaValue" + "\n"
+	str += "    VarName() string" + "\n"
+	str += "}" + "\n"
+	str += "" + "\n"
+
+	str += "type StringEnum interface {" + "\n"
+	str += "    Enum" + "\n"
+	str += "    String() string" + "\n"
+	str += "}" + "\n"
+	str += "" + "\n"
+
+	str += "type DescriptionEnum interface {" + "\n"
+	str += "    Enum" + "\n"
+	str += "    Description() string" + "\n"
+	str += "}" + "\n"
+	str += "\n"
+
+	str += "type EnumMetaValue struct {" + "\n"
+	str += "    VarName     string  `json:\"varName\"`" + "\n"
+	str += "    Value       any     `json:\"value\"`" + "\n"
+	str += "    Description *string `json:\"description\"`" + "\n"
+	str += "}" + "\n"
+	str += "\n"
+
+	for _, enumdef := range enums {
+
+		hasDescr := langext.ArrAll(enumdef.Values, func(val EnumDefVal) bool { return val.Description != nil })
+		hasStr := enumdef.Type == "string"
+
+		str += "// ================================ " + enumdef.EnumTypeName + " ================================" + "\n"
+		str += "//" + "\n"
+		str += "// File:       " + enumdef.FileRelative + "\n"
+		str += "// StringEnum: " + langext.Conditional(hasStr, "true", "false") + "\n"
+		str += "// DescrEnum:  " + langext.Conditional(hasDescr, "true", "false") + "\n"
+		str += "//" + "\n"
+		str += "" + "\n"
+
+		str += "var __" + enumdef.EnumTypeName + "Values = []" + enumdef.EnumTypeName + "{" + "\n"
+		for _, v := range enumdef.Values {
+			str += "    " + v.VarName + "," + "\n"
+		}
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		if hasDescr {
+			str += "var __" + enumdef.EnumTypeName + "Descriptions = map[" + enumdef.EnumTypeName + "]string{" + "\n"
+			for _, v := range enumdef.Values {
+				str += "    " + v.VarName + ": \"" + strings.TrimSpace(*v.Description) + "\"," + "\n"
+			}
+			str += "}" + "\n"
+			str += "" + "\n"
+		}
+
+		str += "var __" + enumdef.EnumTypeName + "Varnames = map[" + enumdef.EnumTypeName + "]string{" + "\n"
+		for _, v := range enumdef.Values {
+			str += "    " + v.VarName + ": \"" + v.VarName + "\"," + "\n"
+		}
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func (e " + enumdef.EnumTypeName + ") Valid() bool {" + "\n"
+		str += "    return langext.InArray(e, __" + enumdef.EnumTypeName + "Values)" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func (e " + enumdef.EnumTypeName + ") Values() []" + enumdef.EnumTypeName + " {" + "\n"
+		str += "    return __" + enumdef.EnumTypeName + "Values" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func (e " + enumdef.EnumTypeName + ") ValuesAny() []any {" + "\n"
+		str += "    return langext.ArrCastToAny(__" + enumdef.EnumTypeName + "Values)" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func (e " + enumdef.EnumTypeName + ") ValuesMeta() []EnumMetaValue {" + "\n"
+		str += "    return []EnumMetaValue{" + "\n"
+		for _, v := range enumdef.Values {
+			if hasDescr {
+				str += "        " + fmt.Sprintf("EnumMetaValue{VarName: \"%s\", Value: %s, Description: langext.Ptr(\"%s\")},", v.VarName, v.VarName, strings.TrimSpace(*v.Description)) + "\n"
+			} else {
+				str += "        " + fmt.Sprintf("EnumMetaValue{VarName: \"%s\", Value: %s, Description: nil},", v.VarName, v.VarName) + "\n"
+			}
+		}
+		str += "    }" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		if hasStr {
+			str += "func (e " + enumdef.EnumTypeName + ") String() string {" + "\n"
+			str += "    return string(e)" + "\n"
+			str += "}" + "\n"
+			str += "" + "\n"
+		}
+
+		if hasDescr {
+			str += "func (e " + enumdef.EnumTypeName + ") Description() string {" + "\n"
+			str += "    if d, ok := __" + enumdef.EnumTypeName + "Descriptions[e]; ok {" + "\n"
+			str += "        return d" + "\n"
+			str += "    }" + "\n"
+			str += "    return \"\"" + "\n"
+			str += "}" + "\n"
+			str += "" + "\n"
+		}
+
+		str += "func (e " + enumdef.EnumTypeName + ") VarName() string {" + "\n"
+		str += "    if d, ok := __" + enumdef.EnumTypeName + "Varnames[e]; ok {" + "\n"
+		str += "        return d" + "\n"
+		str += "    }" + "\n"
+		str += "    return \"\"" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func Parse" + enumdef.EnumTypeName + "(vv string) (" + enumdef.EnumTypeName + ", bool) {" + "\n"
+		str += "    for _, ev := range __" + enumdef.EnumTypeName + "Values {" + "\n"
+		str += "        if string(ev) == vv {" + "\n"
+		str += "            return ev, true" + "\n"
+		str += "        }" + "\n"
+		str += "    }" + "\n"
+		str += "    return \"\", false" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func " + enumdef.EnumTypeName + "Values() []" + enumdef.EnumTypeName + " {" + "\n"
+		str += "    return __" + enumdef.EnumTypeName + "Values" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+		str += "func " + enumdef.EnumTypeName + "ValuesMeta() []EnumMetaValue {" + "\n"
+		str += "    return []EnumMetaValue{" + "\n"
+		for _, v := range enumdef.Values {
+			if hasDescr {
+				str += "        " + fmt.Sprintf("EnumMetaValue{VarName: \"%s\", Value: %s, Description: langext.Ptr(\"%s\")},", v.VarName, v.VarName, strings.TrimSpace(*v.Description)) + "\n"
+			} else {
+				str += "        " + fmt.Sprintf("EnumMetaValue{VarName: \"%s\", Value: %s, Description: nil},", v.VarName, v.VarName) + "\n"
+			}
+		}
+		str += "    }" + "\n"
+		str += "}" + "\n"
+		str += "" + "\n"
+
+	}
+
+	return str
+}

bfcodegen/enum-generate_test.go

@@ -0,0 +1,15 @@
+package bfcodegen
+
+import (
+	"testing"
+)
+
+func TestApplyEnvOverridesSimple(t *testing.T) {
+
+	err := GenerateEnumSpecs("/home/mike/Code/reiff/badennet/bnet-backend/models", "/home/mike/Code/reiff/badennet/bnet-backend/models/enums_gen.go")
+	if err != nil {
+		t.Error(err)
+		t.Fail()
+	}
+
+}

confext/confParser.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"reflect"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -22,10 +23,10 @@ import (
 //
 // sub-structs are recursively parsed (if they have an env tag) and the env-variable keys are delimited by the delim parameter
 // sub-structs with `env:""` are also parsed, but the delimited is skipped (they are handled as if they were one level higher)
-func ApplyEnvOverrides[T any](c *T, delim string) error {
+func ApplyEnvOverrides[T any](prefix string, c *T, delim string) error {
 	rval := reflect.ValueOf(c).Elem()
 
-	return processEnvOverrides(rval, delim, "")
+	return processEnvOverrides(rval, delim, prefix)
 }
 
 func processEnvOverrides(rval reflect.Value, delim string, prefix string) error {
@@ -70,103 +71,128 @@ func processEnvOverrides(rval reflect.Value, delim string, prefix string) error
 			continue
 		}
 
-		if rvfield.Type() == reflect.TypeOf("") {
+		if rvfield.Type().Kind() == reflect.Pointer {
 
-			rvfield.Set(reflect.ValueOf(envval))
+			newval, err := parseEnvToValue(envval, fullEnvKey, rvfield.Type().Elem())
+			if err != nil {
+				return err
+			}
+
+			// converts reflect.Value to pointer
+			ptrval := reflect.New(rvfield.Type().Elem())
+			ptrval.Elem().Set(newval)
+
+			rvfield.Set(ptrval)
 
 			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval)
 
-		} else if rvfield.Type() == reflect.TypeOf(int(0)) {
-
-			envint, err := strconv.ParseInt(envval, 10, bits.UintSize)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int (value := '%s')", fullEnvKey, envval))
-			}
-
-			rvfield.Set(reflect.ValueOf(int(envint)))
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval)
-
-		} else if rvfield.Type() == reflect.TypeOf(int64(0)) {
-
-			envint, err := strconv.ParseInt(envval, 10, 64)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int64 (value := '%s')", fullEnvKey, envval))
-			}
-
-			rvfield.Set(reflect.ValueOf(int64(envint)))
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval)
-
-		} else if rvfield.Type() == reflect.TypeOf(int32(0)) {
-
-			envint, err := strconv.ParseInt(envval, 10, 32)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int32 (value := '%s')", fullEnvKey, envval))
-			}
-
-			rvfield.Set(reflect.ValueOf(int32(envint)))
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval)
-
-		} else if rvfield.Type() == reflect.TypeOf(int8(0)) {
-
-			envint, err := strconv.ParseInt(envval, 10, 8)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int32 (value := '%s')", fullEnvKey, envval))
-			}
-
-			rvfield.Set(reflect.ValueOf(int8(envint)))
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval)
-
-		} else if rvfield.Type() == reflect.TypeOf(time.Duration(0)) {
-
-			dur, err := timeext.ParseDurationShortString(envval)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to duration (value := '%s')", fullEnvKey, envval))
-			}
-
-			rvfield.Set(reflect.ValueOf(dur))
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, dur.String())
-
-		} else if rvfield.Type() == reflect.TypeOf(time.UnixMilli(0)) {
-
-			tim, err := time.Parse(time.RFC3339Nano, envval)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to time.time (value := '%s')", fullEnvKey, envval))
-			}
-
-			rvfield.Set(reflect.ValueOf(tim))
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, tim.String())
-
-		} else if rvfield.Type().ConvertibleTo(reflect.TypeOf(int(0))) {
-
-			envint, err := strconv.ParseInt(envval, 10, 8)
-			if err != nil {
-				return errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to <%s, ,int> (value := '%s')", rvfield.Type().Name(), fullEnvKey, envval))
-			}
-
-			envcvl := reflect.ValueOf(envint).Convert(rvfield.Type())
-
-			rvfield.Set(envcvl)
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%v'\n", fullEnvKey, envcvl.Interface())
-
-		} else if rvfield.Type().ConvertibleTo(reflect.TypeOf("")) {
-
-			envcvl := reflect.ValueOf(envval).Convert(rvfield.Type())
-
-			rvfield.Set(envcvl)
-
-			fmt.Printf("[CONF] Overwrite config '%s' with '%v'\n", fullEnvKey, envcvl.Interface())
-
 		} else {
-			return errors.New(fmt.Sprintf("Unknown kind/type in config: [ %s | %s ]", rvfield.Kind().String(), rvfield.Type().String()))
+
+			newval, err := parseEnvToValue(envval, fullEnvKey, rvfield.Type())
+			if err != nil {
+				return err
 			}
+
+			rvfield.Set(newval)
+			fmt.Printf("[CONF] Overwrite config '%s' with '%s'\n", fullEnvKey, envval)
+
+		}
+
 	}
 
 	return nil
 }
+
+func parseEnvToValue(envval string, fullEnvKey string, rvtype reflect.Type) (reflect.Value, error) {
+	if rvtype == reflect.TypeOf("") {
+
+		return reflect.ValueOf(envval), nil
+
+	} else if rvtype == reflect.TypeOf(int(0)) {
+
+		envint, err := strconv.ParseInt(envval, 10, bits.UintSize)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int (value := '%s')", fullEnvKey, envval))
+		}
+
+		return reflect.ValueOf(int(envint)), nil
+
+	} else if rvtype == reflect.TypeOf(int64(0)) {
+
+		envint, err := strconv.ParseInt(envval, 10, 64)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int64 (value := '%s')", fullEnvKey, envval))
+		}
+
+		return reflect.ValueOf(int64(envint)), nil
+
+	} else if rvtype == reflect.TypeOf(int32(0)) {
+
+		envint, err := strconv.ParseInt(envval, 10, 32)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int32 (value := '%s')", fullEnvKey, envval))
+		}
+
+		return reflect.ValueOf(int32(envint)), nil
+
+	} else if rvtype == reflect.TypeOf(int8(0)) {
+
+		envint, err := strconv.ParseInt(envval, 10, 8)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to int32 (value := '%s')", fullEnvKey, envval))
+		}
+
+		return reflect.ValueOf(int8(envint)), nil
+
+	} else if rvtype == reflect.TypeOf(time.Duration(0)) {
+
+		dur, err := timeext.ParseDurationShortString(envval)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to duration (value := '%s')", fullEnvKey, envval))
+		}
+
+		return reflect.ValueOf(dur), nil
+
+	} else if rvtype == reflect.TypeOf(time.UnixMilli(0)) {
+
+		tim, err := time.Parse(time.RFC3339Nano, envval)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to time.time (value := '%s')", fullEnvKey, envval))
+		}
+
+		return reflect.ValueOf(tim), nil
+
+	} else if rvtype.ConvertibleTo(reflect.TypeOf(int(0))) {
+
+		envint, err := strconv.ParseInt(envval, 10, 8)
+		if err != nil {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to <%s, ,int> (value := '%s')", rvtype.Name(), fullEnvKey, envval))
+		}
+
+		envcvl := reflect.ValueOf(envint).Convert(rvtype)
+
+		return envcvl, nil
+
+	} else if rvtype.ConvertibleTo(reflect.TypeOf(false)) {
+
+		if strings.TrimSpace(strings.ToLower(envval)) == "true" {
+			return reflect.ValueOf(true).Convert(rvtype), nil
+		} else if strings.TrimSpace(strings.ToLower(envval)) == "false" {
+			return reflect.ValueOf(false).Convert(rvtype), nil
+		} else if strings.TrimSpace(strings.ToLower(envval)) == "1" {
+			return reflect.ValueOf(true).Convert(rvtype), nil
+		} else if strings.TrimSpace(strings.ToLower(envval)) == "0" {
+			return reflect.ValueOf(false).Convert(rvtype), nil
+		} else {
+			return reflect.Value{}, errors.New(fmt.Sprintf("Failed to parse env-config variable '%s' to <%s, ,bool> (value := '%s')", rvtype.Name(), fullEnvKey, envval))
+		}
+
+	} else if rvtype.ConvertibleTo(reflect.TypeOf("")) {
+
+		envcvl := reflect.ValueOf(envval).Convert(rvtype)
+		return envcvl, nil
+
+	} else {
+		return reflect.Value{}, errors.New(fmt.Sprintf("Unknown kind/type in config: [ %s | %s ]", rvtype.Kind().String(), rvtype.String()))
+	}
+}

confext/confParser_test.go

@@ -2,6 +2,7 @@ package confext
 
 import (
 	"gogs.mikescher.com/BlackForestBytes/goext/timeext"
+	"gogs.mikescher.com/BlackForestBytes/goext/tst"
 	"testing"
 	"time"
 )
@@ -41,13 +42,13 @@ func TestApplyEnvOverridesNoop(t *testing.T) {
 
 	output := input
 
-	err := ApplyEnvOverrides(&output, ".")
+	err := ApplyEnvOverrides("", &output, ".")
 	if err != nil {
 		t.Errorf("%v", err)
 		t.FailNow()
 	}
 
-	assertEqual(t, input, output)
+	tst.AssertEqual(t, input, output)
 }
 
 func TestApplyEnvOverridesSimple(t *testing.T) {
@@ -67,6 +68,7 @@ func TestApplyEnvOverridesSimple(t *testing.T) {
 		V7 aliasstring   `env:"TEST_V7"`
 		V8 time.Duration `env:"TEST_V8"`
 		V9 time.Time     `env:"TEST_V9"`
+		VA bool          `env:"TEST_VA"`
 	}
 
 	data := testdata{
@@ -81,6 +83,7 @@ func TestApplyEnvOverridesSimple(t *testing.T) {
 		V7: "7",
 		V8: 9,
 		V9: time.Unix(1671102873, 0),
+		VA: false,
 	}
 
 	t.Setenv("TEST_V1", "846")
@@ -92,22 +95,24 @@ func TestApplyEnvOverridesSimple(t *testing.T) {
 	t.Setenv("TEST_V7", "AAAAAA")
 	t.Setenv("TEST_V8", "1min4s")
 	t.Setenv("TEST_V9", "2009-11-10T23:00:00Z")
+	t.Setenv("TEST_VA", "true")
 
-	err := ApplyEnvOverrides(&data, ".")
+	err := ApplyEnvOverrides("", &data, ".")
 	if err != nil {
 		t.Errorf("%v", err)
 		t.FailNow()
 	}
 
-	assertEqual(t, data.V1, 846)
-	assertEqual(t, data.V2, "hello_world")
-	assertEqual(t, data.V3, 6)
-	assertEqual(t, data.V4, 333)
-	assertEqual(t, data.V5, -937)
-	assertEqual(t, data.V6, 70)
-	assertEqual(t, data.V7, "AAAAAA")
-	assertEqual(t, data.V8, time.Second*64)
-	assertEqual(t, data.V9, time.Unix(1257894000, 0).UTC())
+	tst.AssertEqual(t, data.V1, 846)
+	tst.AssertEqual(t, data.V2, "hello_world")
+	tst.AssertEqual(t, data.V3, 6)
+	tst.AssertEqual(t, data.V4, 333)
+	tst.AssertEqual(t, data.V5, -937)
+	tst.AssertEqual(t, data.V6, 70)
+	tst.AssertEqual(t, data.V7, "AAAAAA")
+	tst.AssertEqual(t, data.V8, time.Second*64)
+	tst.AssertEqual(t, data.V9, time.Unix(1257894000, 0).UTC())
+	tst.AssertEqual(t, data.VA, true)
 }
 
 func TestApplyEnvOverridesRecursive(t *testing.T) {
@@ -182,35 +187,83 @@ func TestApplyEnvOverridesRecursive(t *testing.T) {
 	t.Setenv("SUB_V3", "33min")
 	t.Setenv("SUB_V4", "2044-01-01T00:00:00Z")
 
-	err := ApplyEnvOverrides(&data, "_")
+	err := ApplyEnvOverrides("", &data, "_")
 	if err != nil {
 		t.Errorf("%v", err)
 		t.FailNow()
 	}
 
-	assertEqual(t, data.V1, 999)
-	assertEqual(t, data.VX, "2")
-	assertEqual(t, data.V5, "no")
-	assertEqual(t, data.Sub1.V1, 3)
-	assertEqual(t, data.Sub1.VX, "4")
-	assertEqual(t, data.Sub1.V2, "5")
-	assertEqual(t, data.Sub1.V8, time.Second*6)
-	assertEqual(t, data.Sub1.V9, time.Unix(947206861, 0).UTC())
-	assertEqual(t, data.Sub2.V1, 846)
-	assertEqual(t, data.Sub2.VX, "9")
-	assertEqual(t, data.Sub2.V2, "222_hello_world")
-	assertEqual(t, data.Sub2.V8, time.Second*64)
-	assertEqual(t, data.Sub2.V9, time.Unix(1257894000, 0).UTC())
-	assertEqual(t, data.Sub3.V1, 33846)
-	assertEqual(t, data.Sub3.VX, "14")
-	assertEqual(t, data.Sub3.V2, "33_hello_world")
-	assertEqual(t, data.Sub3.V8, time.Second*1984)
-	assertEqual(t, data.Sub3.V9, time.Unix(2015276400, 0).UTC())
-	assertEqual(t, data.Sub4.V1, 11)
-	assertEqual(t, data.Sub4.VX, "19")
-	assertEqual(t, data.Sub4.V2, "22")
-	assertEqual(t, data.Sub4.V8, time.Second*1980)
-	assertEqual(t, data.Sub4.V9, time.Unix(2335219200, 0).UTC())
+	tst.AssertEqual(t, data.V1, 999)
+	tst.AssertEqual(t, data.VX, "2")
+	tst.AssertEqual(t, data.V5, "no")
+	tst.AssertEqual(t, data.Sub1.V1, 3)
+	tst.AssertEqual(t, data.Sub1.VX, "4")
+	tst.AssertEqual(t, data.Sub1.V2, "5")
+	tst.AssertEqual(t, data.Sub1.V8, time.Second*6)
+	tst.AssertEqual(t, data.Sub1.V9, time.Unix(947206861, 0).UTC())
+	tst.AssertEqual(t, data.Sub2.V1, 846)
+	tst.AssertEqual(t, data.Sub2.VX, "9")
+	tst.AssertEqual(t, data.Sub2.V2, "222_hello_world")
+	tst.AssertEqual(t, data.Sub2.V8, time.Second*64)
+	tst.AssertEqual(t, data.Sub2.V9, time.Unix(1257894000, 0).UTC())
+	tst.AssertEqual(t, data.Sub3.V1, 33846)
+	tst.AssertEqual(t, data.Sub3.VX, "14")
+	tst.AssertEqual(t, data.Sub3.V2, "33_hello_world")
+	tst.AssertEqual(t, data.Sub3.V8, time.Second*1984)
+	tst.AssertEqual(t, data.Sub3.V9, time.Unix(2015276400, 0).UTC())
+	tst.AssertEqual(t, data.Sub4.V1, 11)
+	tst.AssertEqual(t, data.Sub4.VX, "19")
+	tst.AssertEqual(t, data.Sub4.V2, "22")
+	tst.AssertEqual(t, data.Sub4.V8, time.Second*1980)
+	tst.AssertEqual(t, data.Sub4.V9, time.Unix(2335219200, 0).UTC())
+}
+
+func TestApplyEnvOverridesPointer(t *testing.T) {
+
+	type aliasint int
+	type aliasstring string
+
+	type testdata struct {
+		V1 *int           `env:"TEST_V1"`
+		VX *string        ``
+		V2 *string        `env:"TEST_V2"`
+		V3 *int8          `env:"TEST_V3"`
+		V4 *int32         `env:"TEST_V4"`
+		V5 *int64         `env:"TEST_V5"`
+		V6 *aliasint      `env:"TEST_V6"`
+		VY *aliasint      ``
+		V7 *aliasstring   `env:"TEST_V7"`
+		V8 *time.Duration `env:"TEST_V8"`
+		V9 *time.Time     `env:"TEST_V9"`
+	}
+
+	data := testdata{}
+
+	t.Setenv("TEST_V1", "846")
+	t.Setenv("TEST_V2", "hello_world")
+	t.Setenv("TEST_V3", "6")
+	t.Setenv("TEST_V4", "333")
+	t.Setenv("TEST_V5", "-937")
+	t.Setenv("TEST_V6", "070")
+	t.Setenv("TEST_V7", "AAAAAA")
+	t.Setenv("TEST_V8", "1min4s")
+	t.Setenv("TEST_V9", "2009-11-10T23:00:00Z")
+
+	err := ApplyEnvOverrides("", &data, ".")
+	if err != nil {
+		t.Errorf("%v", err)
+		t.FailNow()
+	}
+
+	tst.AssertDeRefEqual(t, data.V1, 846)
+	tst.AssertDeRefEqual(t, data.V2, "hello_world")
+	tst.AssertDeRefEqual(t, data.V3, 6)
+	tst.AssertDeRefEqual(t, data.V4, 333)
+	tst.AssertDeRefEqual(t, data.V5, -937)
+	tst.AssertDeRefEqual(t, data.V6, 70)
+	tst.AssertDeRefEqual(t, data.V7, "AAAAAA")
+	tst.AssertDeRefEqual(t, data.V8, time.Second*64)
+	tst.AssertDeRefEqual(t, data.V9, time.Unix(1257894000, 0).UTC())
 }
 
 func assertEqual[T comparable](t *testing.T, actual T, expected T) {
@@ -218,3 +271,12 @@ func assertEqual[T comparable](t *testing.T, actual T, expected T) {
 		t.Errorf("values differ: Actual: '%v', Expected: '%v'", actual, expected)
 	}
 }
+
+func assertPtrEqual[T comparable](t *testing.T, actual *T, expected T) {
+	if actual == nil {
+		t.Errorf("values differ: Actual: NIL, Expected: '%v'", expected)
+	}
+	if *actual != expected {
+		t.Errorf("values differ: Actual: '%v', Expected: '%v'", actual, expected)
+	}
+}

cryptext/aes_test.go

@@ -2,6 +2,7 @@ package cryptext
 
 import (
 	"fmt"
+	"gogs.mikescher.com/BlackForestBytes/goext/tst"
 	"testing"
 )
 
@@ -23,13 +24,13 @@ func TestEncryptAESSimple(t *testing.T) {
 		panic(err)
 	}
 
-	assertEqual(t, string(str1), string(str3))
+	tst.AssertEqual(t, string(str1), string(str3))
 
 	str4, err := EncryptAESSimple(pw, str3, 512)
 	if err != nil {
 		panic(err)
 	}
 
-	assertNotEqual(t, string(str2), string(str4))
+	tst.AssertNotEqual(t, string(str2), string(str4))
 
 }

cryptext/hash_test.go

@@ -1,31 +1,20 @@
 package cryptext
 
 import (
+	"gogs.mikescher.com/BlackForestBytes/goext/tst"
 	"testing"
 )
 
 func TestStrSha256(t *testing.T) {
-	assertEqual(t, StrSha256(""), "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")
-	assertEqual(t, StrSha256("0"), "5feceb66ffc86f38d952786c6d696c79c2dbc239dd4e91b46729d73a27fb57e9")
-	assertEqual(t, StrSha256("80085"), "b3786e141d65638ad8a98173e26b5f6a53c927737b23ff31fb1843937250f44b")
-	assertEqual(t, StrSha256("Hello World"), "a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e")
+	tst.AssertEqual(t, StrSha256(""), "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")
+	tst.AssertEqual(t, StrSha256("0"), "5feceb66ffc86f38d952786c6d696c79c2dbc239dd4e91b46729d73a27fb57e9")
+	tst.AssertEqual(t, StrSha256("80085"), "b3786e141d65638ad8a98173e26b5f6a53c927737b23ff31fb1843937250f44b")
+	tst.AssertEqual(t, StrSha256("Hello World"), "a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e")
 }
 
 func TestBytesSha256(t *testing.T) {
-	assertEqual(t, BytesSha256([]byte{}), "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")
-	assertEqual(t, BytesSha256([]byte{0}), "6e340b9cffb37a989ca544e6bb780a2c78901d3fb33738768511a30617afa01d")
-	assertEqual(t, BytesSha256([]byte{128}), "76be8b528d0075f7aae98d6fa57a6d3c83ae480a8469e668d7b0af968995ac71")
-	assertEqual(t, BytesSha256([]byte{0, 1, 2, 4, 8, 16, 32, 64, 128, 255}), "55016a318ba538e00123c736b2a8b6db368d00e7e25727547655b653e5853603")
-}
-
-func assertEqual(t *testing.T, actual string, expected string) {
-	if actual != expected {
-		t.Errorf("values differ: Actual: '%v', Expected: '%v'", actual, expected)
-	}
-}
-
-func assertNotEqual(t *testing.T, actual string, expected string) {
-	if actual == expected {
-		t.Errorf("values do not differ: Actual: '%v', Expected: '%v'", actual, expected)
-	}
+	tst.AssertEqual(t, BytesSha256([]byte{}), "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")
+	tst.AssertEqual(t, BytesSha256([]byte{0}), "6e340b9cffb37a989ca544e6bb780a2c78901d3fb33738768511a30617afa01d")
+	tst.AssertEqual(t, BytesSha256([]byte{128}), "76be8b528d0075f7aae98d6fa57a6d3c83ae480a8469e668d7b0af968995ac71")
+	tst.AssertEqual(t, BytesSha256([]byte{0, 1, 2, 4, 8, 16, 32, 64, 128, 255}), "55016a318ba538e00123c736b2a8b6db368d00e7e25727547655b653e5853603")
 }

cursortoken/direction.go

@@ -0,0 +1,8 @@
+package cursortoken
+
+type SortDirection string //@enum:type
+
+const (
+	SortASC  SortDirection = "ASC"
+	SortDESC SortDirection = "DESC"
+)

cursortoken/filter.go

@@ -0,0 +1,10 @@
+package cursortoken
+
+import (
+	"go.mongodb.org/mongo-driver/mongo"
+)
+
+type Filter interface {
+	FilterQuery() mongo.Pipeline
+	Pagination() (string, SortDirection, string, SortDirection)
+}

cursortoken/token.go

@@ -0,0 +1,184 @@
+package cursortoken
+
+import (
+	"encoding/base32"
+	"encoding/json"
+	"errors"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"strings"
+	"time"
+)
+
+type Mode string
+
+const (
+	CTMStart  Mode = "START"
+	CTMNormal Mode = "NORMAL"
+	CTMEnd    Mode = "END"
+)
+
+type Extra struct {
+	Timestamp *time.Time
+	Id        *string
+	Page      *int
+	PageSize  *int
+}
+
+type CursorToken struct {
+	Mode               Mode
+	ValuePrimary       string
+	ValueSecondary     string
+	Direction          SortDirection
+	DirectionSecondary SortDirection
+	PageSize           int
+	Extra              Extra
+}
+
+type cursorTokenSerialize struct {
+	ValuePrimary       *string        `json:"v1,omitempty"`
+	ValueSecondary     *string        `json:"v2,omitempty"`
+	Direction          *SortDirection `json:"dir,omitempty"`
+	DirectionSecondary *SortDirection `json:"dir2,omitempty"`
+	PageSize           *int           `json:"size,omitempty"`
+
+	ExtraTimestamp *time.Time `json:"ts,omitempty"`
+	ExtraId        *string    `json:"id,omitempty"`
+	ExtraPage      *int       `json:"pg,omitempty"`
+	ExtraPageSize  *int       `json:"sz,omitempty"`
+}
+
+func Start() CursorToken {
+	return CursorToken{
+		Mode:               CTMStart,
+		ValuePrimary:       "",
+		ValueSecondary:     "",
+		Direction:          "",
+		DirectionSecondary: "",
+		PageSize:           0,
+		Extra:              Extra{},
+	}
+}
+
+func End() CursorToken {
+	return CursorToken{
+		Mode:               CTMEnd,
+		ValuePrimary:       "",
+		ValueSecondary:     "",
+		Direction:          "",
+		DirectionSecondary: "",
+		PageSize:           0,
+		Extra:              Extra{},
+	}
+}
+
+func (c *CursorToken) Token() string {
+	if c.Mode == CTMStart {
+		return "@start"
+	}
+	if c.Mode == CTMEnd {
+		return "@end"
+	}
+
+	// We kinda manually implement omitempty for the CursorToken here
+	// because omitempty does not work for time.Time and otherwise we would always
+	// get weird time values when decoding a token that initially didn't have an Timestamp set
+	// For this usecase we treat Unix=0 as an empty timestamp
+
+	sertok := cursorTokenSerialize{}
+
+	if c.ValuePrimary != "" {
+		sertok.ValuePrimary = &c.ValuePrimary
+	}
+	if c.ValueSecondary != "" {
+		sertok.ValueSecondary = &c.ValueSecondary
+	}
+	if c.Direction != "" {
+		sertok.Direction = &c.Direction
+	}
+	if c.DirectionSecondary != "" {
+		sertok.DirectionSecondary = &c.DirectionSecondary
+	}
+	if c.PageSize != 0 {
+		sertok.PageSize = &c.PageSize
+	}
+
+	sertok.ExtraTimestamp = c.Extra.Timestamp
+	sertok.ExtraId = c.Extra.Id
+	sertok.ExtraPage = c.Extra.Page
+	sertok.ExtraPageSize = c.Extra.PageSize
+
+	body, err := json.Marshal(sertok)
+	if err != nil {
+		panic(err)
+	}
+
+	return "tok_" + base32.StdEncoding.EncodeToString(body)
+}
+
+func Decode(tok string) (CursorToken, error) {
+	if tok == "" {
+		return Start(), nil
+	}
+	if strings.ToLower(tok) == "@start" {
+		return Start(), nil
+	}
+	if strings.ToLower(tok) == "@end" {
+		return End(), nil
+	}
+
+	if !strings.HasPrefix(tok, "tok_") {
+		return CursorToken{}, errors.New("could not decode token, missing prefix")
+	}
+
+	body, err := base32.StdEncoding.DecodeString(tok[len("tok_"):])
+	if err != nil {
+		return CursorToken{}, err
+	}
+
+	var tokenDeserialize cursorTokenSerialize
+	err = json.Unmarshal(body, &tokenDeserialize)
+	if err != nil {
+		return CursorToken{}, err
+	}
+
+	token := CursorToken{Mode: CTMNormal}
+
+	if tokenDeserialize.ValuePrimary != nil {
+		token.ValuePrimary = *tokenDeserialize.ValuePrimary
+	}
+	if tokenDeserialize.ValueSecondary != nil {
+		token.ValueSecondary = *tokenDeserialize.ValueSecondary
+	}
+	if tokenDeserialize.Direction != nil {
+		token.Direction = *tokenDeserialize.Direction
+	}
+	if tokenDeserialize.DirectionSecondary != nil {
+		token.DirectionSecondary = *tokenDeserialize.DirectionSecondary
+	}
+	if tokenDeserialize.PageSize != nil {
+		token.PageSize = *tokenDeserialize.PageSize
+	}
+
+	token.Extra.Timestamp = tokenDeserialize.ExtraTimestamp
+	token.Extra.Id = tokenDeserialize.ExtraId
+	token.Extra.Page = tokenDeserialize.ExtraPage
+	token.Extra.PageSize = tokenDeserialize.ExtraPageSize
+
+	return token, nil
+}
+
+func (c *CursorToken) ValuePrimaryObjectId() (primitive.ObjectID, bool) {
+	if oid, err := primitive.ObjectIDFromHex(c.ValuePrimary); err == nil {
+		return oid, true
+	} else {
+		return primitive.ObjectID{}, false
+	}
+}
+
+func (c *CursorToken) ValueSecondaryObjectId() (primitive.ObjectID, bool) {
+	if oid, err := primitive.ObjectIDFromHex(c.ValueSecondary); err == nil {
+		return oid, true
+	} else {
+		return primitive.ObjectID{}, false
+	}
+}

dataext/merge_test.go

@@ -2,6 +2,7 @@ package dataext
 
 import (
 	"gogs.mikescher.com/BlackForestBytes/goext/langext"
+	"gogs.mikescher.com/BlackForestBytes/goext/tst"
 	"testing"
 )
 
@@ -43,10 +44,10 @@ func TestObjectMerge(t *testing.T) {
 
 	valueMerge := ObjectMerge(valueA, valueB)
 
-	assertPtrEqual(t, "Field1", valueMerge.Field1, valueB.Field1)
-	assertPtrEqual(t, "Field2", valueMerge.Field2, valueA.Field2)
-	assertPtrEqual(t, "Field3", valueMerge.Field3, valueB.Field3)
-	assertPtrEqual(t, "Field4", valueMerge.Field4, nil)
+	tst.AssertIdentPtrEqual(t, "Field1", valueMerge.Field1, valueB.Field1)
+	tst.AssertIdentPtrEqual(t, "Field2", valueMerge.Field2, valueA.Field2)
+	tst.AssertIdentPtrEqual(t, "Field3", valueMerge.Field3, valueB.Field3)
+	tst.AssertIdentPtrEqual(t, "Field4", valueMerge.Field4, nil)
 
 }
 

dataext/structHash_test.go

@@ -1,8 +1,8 @@
 package dataext
 
 import (
-	"encoding/hex"
 	"gogs.mikescher.com/BlackForestBytes/goext/langext"
+	"gogs.mikescher.com/BlackForestBytes/goext/tst"
 	"testing"
 )
 
@@ -18,14 +18,14 @@ func noErrStructHash(t *testing.T, dat any, opt ...StructHashOptions) []byte {
 
 func TestStructHashSimple(t *testing.T) {
 
-	assertEqual(t, "209bf774af36cc3a045c152d9f1269ef3684ad819c1359ee73ff0283a308fefa", noErrStructHash(t, "Hello"))
-	assertEqual(t, "c32f3626b981ae2997db656f3acad3f1dc9d30ef6b6d14296c023e391b25f71a", noErrStructHash(t, 0))
-	assertEqual(t, "01b781b03e9586b257d387057dfc70d9f06051e7d3c1e709a57e13cc8daf3e35", noErrStructHash(t, []byte{}))
-	assertEqual(t, "93e1dcd45c732fe0079b0fb3204c7c803f0921835f6bfee2e6ff263e73eed53c", noErrStructHash(t, []int{}))
-	assertEqual(t, "54f637a376aad55b3160d98ebbcae8099b70d91b9400df23fb3709855d59800a", noErrStructHash(t, []int{1, 2, 3}))
-	assertEqual(t, "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", noErrStructHash(t, nil))
-	assertEqual(t, "349a7db91aa78fd30bbaa7c7f9c7bfb2fcfe72869b4861162a96713a852f60d3", noErrStructHash(t, []any{1, "", nil}))
-	assertEqual(t, "ca51aab87808bf0062a4a024de6aac0c2bad54275cc857a4944569f89fd245ad", noErrStructHash(t, struct{}{}))
+	tst.AssertHexEqual(t, "209bf774af36cc3a045c152d9f1269ef3684ad819c1359ee73ff0283a308fefa", noErrStructHash(t, "Hello"))
+	tst.AssertHexEqual(t, "c32f3626b981ae2997db656f3acad3f1dc9d30ef6b6d14296c023e391b25f71a", noErrStructHash(t, 0))
+	tst.AssertHexEqual(t, "01b781b03e9586b257d387057dfc70d9f06051e7d3c1e709a57e13cc8daf3e35", noErrStructHash(t, []byte{}))
+	tst.AssertHexEqual(t, "93e1dcd45c732fe0079b0fb3204c7c803f0921835f6bfee2e6ff263e73eed53c", noErrStructHash(t, []int{}))
+	tst.AssertHexEqual(t, "54f637a376aad55b3160d98ebbcae8099b70d91b9400df23fb3709855d59800a", noErrStructHash(t, []int{1, 2, 3}))
+	tst.AssertHexEqual(t, "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", noErrStructHash(t, nil))
+	tst.AssertHexEqual(t, "349a7db91aa78fd30bbaa7c7f9c7bfb2fcfe72869b4861162a96713a852f60d3", noErrStructHash(t, []any{1, "", nil}))
+	tst.AssertHexEqual(t, "ca51aab87808bf0062a4a024de6aac0c2bad54275cc857a4944569f89fd245ad", noErrStructHash(t, struct{}{}))
 
 }
 
@@ -37,13 +37,13 @@ func TestStructHashSimpleStruct(t *testing.T) {
 		F3 *int
 	}
 
-	assertEqual(t, "a90bff751c70c738bb5cfc9b108e783fa9c19c0bc9273458e0aaee6e74aa1b92", noErrStructHash(t, t0{
+	tst.AssertHexEqual(t, "a90bff751c70c738bb5cfc9b108e783fa9c19c0bc9273458e0aaee6e74aa1b92", noErrStructHash(t, t0{
 		F1: 10,
 		F2: []string{"1", "2", "3"},
 		F3: nil,
 	}))
 
-	assertEqual(t, "5d09090dc34ac59dd645f197a255f653387723de3afa1b614721ea5a081c675f", noErrStructHash(t, t0{
+	tst.AssertHexEqual(t, "5d09090dc34ac59dd645f197a255f653387723de3afa1b614721ea5a081c675f", noErrStructHash(t, t0{
 		F1: 10,
 		F2: []string{"1", "2", "3"},
 		F3: langext.Ptr(99),
@@ -64,7 +64,7 @@ func TestStructHashLayeredStruct(t *testing.T) {
 		SV3 t1_1
 	}
 
-	assertEqual(t, "fd4ca071fb40a288fee4b7a3dfdaab577b30cb8f80f81ec511e7afd72dc3b469", noErrStructHash(t, t1_2{
+	tst.AssertHexEqual(t, "fd4ca071fb40a288fee4b7a3dfdaab577b30cb8f80f81ec511e7afd72dc3b469", noErrStructHash(t, t1_2{
 		SV1: nil,
 		SV2: nil,
 		SV3: t1_1{
@@ -73,7 +73,7 @@ func TestStructHashLayeredStruct(t *testing.T) {
 			F15: false,
 		},
 	}))
-	assertEqual(t, "3fbf7c67d8121deda075cc86319a4e32d71744feb2cebf89b43bc682f072a029", noErrStructHash(t, t1_2{
+	tst.AssertHexEqual(t, "3fbf7c67d8121deda075cc86319a4e32d71744feb2cebf89b43bc682f072a029", noErrStructHash(t, t1_2{
 		SV1: nil,
 		SV2: &t1_1{},
 		SV3: t1_1{
@@ -82,7 +82,7 @@ func TestStructHashLayeredStruct(t *testing.T) {
 			F15: true,
 		},
 	}))
-	assertEqual(t, "b1791ccd1b346c3ede5bbffda85555adcd8216b93ffca23f14fe175ec47c5104", noErrStructHash(t, t1_2{
+	tst.AssertHexEqual(t, "b1791ccd1b346c3ede5bbffda85555adcd8216b93ffca23f14fe175ec47c5104", noErrStructHash(t, t1_2{
 		SV1: &t1_1{},
 		SV2: &t1_1{},
 		SV3: t1_1{
@@ -101,7 +101,7 @@ func TestStructHashMap(t *testing.T) {
 		F2 map[string]int
 	}
 
-	assertEqual(t, "d50c53ad1fafb448c33fddd5aca01a86a2edf669ce2ecab07ba6fe877951d824", noErrStructHash(t, t0{
+	tst.AssertHexEqual(t, "d50c53ad1fafb448c33fddd5aca01a86a2edf669ce2ecab07ba6fe877951d824", noErrStructHash(t, t0{
 		F1: 10,
 		F2: map[string]int{
 			"x": 1,
@@ -110,7 +110,7 @@ func TestStructHashMap(t *testing.T) {
 		},
 	}))
 
-	assertEqual(t, "d50c53ad1fafb448c33fddd5aca01a86a2edf669ce2ecab07ba6fe877951d824", noErrStructHash(t, t0{
+	tst.AssertHexEqual(t, "d50c53ad1fafb448c33fddd5aca01a86a2edf669ce2ecab07ba6fe877951d824", noErrStructHash(t, t0{
 		F1: 10,
 		F2: map[string]int{
 			"a": 99,
@@ -128,16 +128,9 @@ func TestStructHashMap(t *testing.T) {
 	m3["x"] = 1
 	m3["a"] = 2
 
-	assertEqual(t, "d50c53ad1fafb448c33fddd5aca01a86a2edf669ce2ecab07ba6fe877951d824", noErrStructHash(t, t0{
+	tst.AssertHexEqual(t, "d50c53ad1fafb448c33fddd5aca01a86a2edf669ce2ecab07ba6fe877951d824", noErrStructHash(t, t0{
 		F1: 10,
 		F2: m3,
 	}))
 
 }
-
-func assertEqual(t *testing.T, expected string, actual []byte) {
-	actualStr := hex.EncodeToString(actual)
-	if actualStr != expected {
-		t.Errorf("values differ: Actual: '%v', Expected: '%v'", actualStr, expected)
-	}
-}

go.mod

@@ -3,12 +3,30 @@ module gogs.mikescher.com/BlackForestBytes/goext
 go 1.19
 
 require (
-	golang.org/x/sys v0.3.0
-	golang.org/x/term v0.3.0
+	github.com/golang/snappy v0.0.4
+	github.com/google/go-cmp v0.5.9
+	github.com/jmoiron/sqlx v1.3.5
+	github.com/klauspost/compress v1.16.6
+	github.com/kr/pretty v0.1.0
+	github.com/montanaflynn/stats v0.7.1
+	github.com/pkg/errors v0.9.1
+	github.com/stretchr/testify v1.8.4
+	github.com/tidwall/pretty v1.0.0
+	github.com/xdg-go/scram v1.1.2
+	github.com/xdg-go/stringprep v1.0.4
+	github.com/youmark/pkcs8 v0.0.0-20201027041543-1326539a0a0a
+	go.mongodb.org/mongo-driver v1.11.7
+	golang.org/x/crypto v0.10.0
+	golang.org/x/sync v0.3.0
+	golang.org/x/sys v0.9.0
+	golang.org/x/term v0.9.0
 )
 
 require (
-	github.com/jmoiron/sqlx v1.3.5 // indirect
-	go.mongodb.org/mongo-driver v1.11.1 // indirect
-	golang.org/x/crypto v0.4.0 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/kr/text v0.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/xdg-go/pbkdf2 v1.0.0 // indirect
+	golang.org/x/text v0.10.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,50 +1,100 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-sql-driver/mysql v1.6.0 h1:BCTh4TKNUYmOmMUcQ3IipzF5prigylS7XXjEkfCHuOE=
 github.com/go-sql-driver/mysql v1.6.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
 github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/golang/snappy v0.0.4 h1:yAGX7huGHXlcLOEtBnF4w7FQwA26wojNCwOYAEhLjQM=
+github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/jmoiron/sqlx v1.3.5 h1:vFFPA71p1o5gAeqtEAwLU4dnX2napprKtHr7PYIcN3g=
 github.com/jmoiron/sqlx v1.3.5/go.mod h1:nRVWtLre0KfCLJvgxzCsLVMogSvQ1zNJtpYr2Ccp0mQ=
 github.com/klauspost/compress v1.13.6/go.mod h1:/3/Vjq9QcHkK5uEr5lBEmyoZ1iFhe47etQ6QUkpK6sk=
+github.com/klauspost/compress v1.16.6 h1:91SKEy4K37vkp255cJ8QesJhjyRO0hn9i9G0GoUwLsk=
+github.com/klauspost/compress v1.16.6/go.mod h1:ntbaceVETuRiXiv4DpjP66DpAtAGkEQskQzEyD//IeE=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/lib/pq v1.2.0 h1:LXpIM/LZ5xGFhOpXAQUIMM1HdyqzVYM13zNdjCEEcA0=
 github.com/lib/pq v1.2.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
+github.com/mattn/go-sqlite3 v1.14.6 h1:dNPt6NO46WmLVt2DLNpwczCmdV5boIZ6g/tlDrlRUbg=
 github.com/mattn/go-sqlite3 v1.14.6/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A/KQRfk6bU=
 github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe/go.mod h1:wL8QJuTMNUDYhXwkmfOly8iTdp5TEcJFWZD2D7SIkUc=
+github.com/montanaflynn/stats v0.7.1 h1:etflOAAHORrCC44V+aR6Ftzort912ZU+YLiSTuV8eaE=
+github.com/montanaflynn/stats v0.7.1/go.mod h1:etXPPgVO6n31NxCd9KQUMvCM+ve0ruNzt6R8Bnaayow=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
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goextVersion.go

@@ -0,0 +1,5 @@
+package goext
+
+const GoextVersion = "0.0.166"
+
+const GoextVersionTimestamp = "2023-06-19T10:25:41+0200"

gojson/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

gojson/README.md

@@ -0,0 +1,12 @@
+
+
+JSON serializer which serializes nil-Arrays as `[]` and nil-maps als `{}`.
+
+Idea from: https://github.com/homelight/json
+
+Forked from https://github.com/golang/go/tree/547e8e22fe565d65d1fd4d6e71436a5a855447b0/src/encoding/json ( tag go1.20.2 )
+
+Added:
+
+ - `MarshalSafeCollections()` method
+ - `Encoder.nilSafeSlices` and `Encoder.nilSafeMaps` fields

gojson/example_marshaling_test.go

@@ -0,0 +1,73 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json_test
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Animal int
+
+const (
+	Unknown Animal = iota
+	Gopher
+	Zebra
+)
+
+func (a *Animal) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	switch strings.ToLower(s) {
+	default:
+		*a = Unknown
+	case "gopher":
+		*a = Gopher
+	case "zebra":
+		*a = Zebra
+	}
+
+	return nil
+}
+
+func (a Animal) MarshalJSON() ([]byte, error) {
+	var s string
+	switch a {
+	default:
+		s = "unknown"
+	case Gopher:
+		s = "gopher"
+	case Zebra:
+		s = "zebra"
+	}
+
+	return json.Marshal(s)
+}
+
+func Example_customMarshalJSON() {
+	blob := `["gopher","armadillo","zebra","unknown","gopher","bee","gopher","zebra"]`
+	var zoo []Animal
+	if err := json.Unmarshal([]byte(blob), &zoo); err != nil {
+		log.Fatal(err)
+	}
+
+	census := make(map[Animal]int)
+	for _, animal := range zoo {
+		census[animal] += 1
+	}
+
+	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
+		census[Gopher], census[Zebra], census[Unknown])
+
+	// Output:
+	// Zoo Census:
+	// * Gophers: 3
+	// * Zebras:  2
+	// * Unknown: 3
+}

gojson/example_test.go

@@ -0,0 +1,310 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+func ExampleMarshal() {
+	type ColorGroup struct {
+		ID     int
+		Name   string
+		Colors []string
+	}
+	group := ColorGroup{
+		ID:     1,
+		Name:   "Reds",
+		Colors: []string{"Crimson", "Red", "Ruby", "Maroon"},
+	}
+	b, err := json.Marshal(group)
+	if err != nil {
+		fmt.Println("error:", err)
+	}
+	os.Stdout.Write(b)
+	// Output:
+	// {"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}
+}
+
+func ExampleUnmarshal() {
+	var jsonBlob = []byte(`[
+	{"Name": "Platypus", "Order": "Monotremata"},
+	{"Name": "Quoll",    "Order": "Dasyuromorphia"}
+]`)
+	type Animal struct {
+		Name  string
+		Order string
+	}
+	var animals []Animal
+	err := json.Unmarshal(jsonBlob, &animals)
+	if err != nil {
+		fmt.Println("error:", err)
+	}
+	fmt.Printf("%+v", animals)
+	// Output:
+	// [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
+}
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleDecoder() {
+	const jsonStream = `
+	{"Name": "Ed", "Text": "Knock knock."}
+	{"Name": "Sam", "Text": "Who's there?"}
+	{"Name": "Ed", "Text": "Go fmt."}
+	{"Name": "Sam", "Text": "Go fmt who?"}
+	{"Name": "Ed", "Text": "Go fmt yourself!"}
+`
+	type Message struct {
+		Name, Text string
+	}
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+	for {
+		var m Message
+		if err := dec.Decode(&m); err == io.EOF {
+			break
+		} else if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s: %s\n", m.Name, m.Text)
+	}
+	// Output:
+	// Ed: Knock knock.
+	// Sam: Who's there?
+	// Ed: Go fmt.
+	// Sam: Go fmt who?
+	// Ed: Go fmt yourself!
+}
+
+// This example uses a Decoder to decode a stream of distinct JSON values.
+func ExampleDecoder_Token() {
+	const jsonStream = `
+	{"Message": "Hello", "Array": [1, 2, 3], "Null": null, "Number": 1.234}
+`
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+	for {
+		t, err := dec.Token()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%T: %v", t, t)
+		if dec.More() {
+			fmt.Printf(" (more)")
+		}
+		fmt.Printf("\n")
+	}
+	// Output:
+	// json.Delim: { (more)
+	// string: Message (more)
+	// string: Hello (more)
+	// string: Array (more)
+	// json.Delim: [ (more)
+	// float64: 1 (more)
+	// float64: 2 (more)
+	// float64: 3
+	// json.Delim: ] (more)
+	// string: Null (more)
+	// <nil>: <nil> (more)
+	// string: Number (more)
+	// float64: 1.234
+	// json.Delim: }
+}
+
+// This example uses a Decoder to decode a streaming array of JSON objects.
+func ExampleDecoder_Decode_stream() {
+	const jsonStream = `
+	[
+		{"Name": "Ed", "Text": "Knock knock."},
+		{"Name": "Sam", "Text": "Who's there?"},
+		{"Name": "Ed", "Text": "Go fmt."},
+		{"Name": "Sam", "Text": "Go fmt who?"},
+		{"Name": "Ed", "Text": "Go fmt yourself!"}
+	]
+`
+	type Message struct {
+		Name, Text string
+	}
+	dec := json.NewDecoder(strings.NewReader(jsonStream))
+
+	// read open bracket
+	t, err := dec.Token()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%T: %v\n", t, t)
+
+	// while the array contains values
+	for dec.More() {
+		var m Message
+		// decode an array value (Message)
+		err := dec.Decode(&m)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		fmt.Printf("%v: %v\n", m.Name, m.Text)
+	}
+
+	// read closing bracket
+	t, err = dec.Token()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%T: %v\n", t, t)
+
+	// Output:
+	// json.Delim: [
+	// Ed: Knock knock.
+	// Sam: Who's there?
+	// Ed: Go fmt.
+	// Sam: Go fmt who?
+	// Ed: Go fmt yourself!
+	// json.Delim: ]
+}
+
+// This example uses RawMessage to delay parsing part of a JSON message.
+func ExampleRawMessage_unmarshal() {
+	type Color struct {
+		Space string
+		Point json.RawMessage // delay parsing until we know the color space
+	}
+	type RGB struct {
+		R uint8
+		G uint8
+		B uint8
+	}
+	type YCbCr struct {
+		Y  uint8
+		Cb int8
+		Cr int8
+	}
+
+	var j = []byte(`[
+	{"Space": "YCbCr", "Point": {"Y": 255, "Cb": 0, "Cr": -10}},
+	{"Space": "RGB",   "Point": {"R": 98, "G": 218, "B": 255}}
+]`)
+	var colors []Color
+	err := json.Unmarshal(j, &colors)
+	if err != nil {
+		log.Fatalln("error:", err)
+	}
+
+	for _, c := range colors {
+		var dst any
+		switch c.Space {
+		case "RGB":
+			dst = new(RGB)
+		case "YCbCr":
+			dst = new(YCbCr)
+		}
+		err := json.Unmarshal(c.Point, dst)
+		if err != nil {
+			log.Fatalln("error:", err)
+		}
+		fmt.Println(c.Space, dst)
+	}
+	// Output:
+	// YCbCr &{255 0 -10}
+	// RGB &{98 218 255}
+}
+
+// This example uses RawMessage to use a precomputed JSON during marshal.
+func ExampleRawMessage_marshal() {
+	h := json.RawMessage(`{"precomputed": true}`)
+
+	c := struct {
+		Header *json.RawMessage `json:"header"`
+		Body   string           `json:"body"`
+	}{Header: &h, Body: "Hello Gophers!"}
+
+	b, err := json.MarshalIndent(&c, "", "\t")
+	if err != nil {
+		fmt.Println("error:", err)
+	}
+	os.Stdout.Write(b)
+
+	// Output:
+	// {
+	// 	"header": {
+	// 		"precomputed": true
+	// 	},
+	// 	"body": "Hello Gophers!"
+	// }
+}
+
+func ExampleIndent() {
+	type Road struct {
+		Name   string
+		Number int
+	}
+	roads := []Road{
+		{"Diamond Fork", 29},
+		{"Sheep Creek", 51},
+	}
+
+	b, err := json.Marshal(roads)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var out bytes.Buffer
+	json.Indent(&out, b, "=", "\t")
+	out.WriteTo(os.Stdout)
+	// Output:
+	// [
+	// =	{
+	// =		"Name": "Diamond Fork",
+	// =		"Number": 29
+	// =	},
+	// =	{
+	// =		"Name": "Sheep Creek",
+	// =		"Number": 51
+	// =	}
+	// =]
+}
+
+func ExampleMarshalIndent() {
+	data := map[string]int{
+		"a": 1,
+		"b": 2,
+	}
+
+	b, err := json.MarshalIndent(data, "<prefix>", "<indent>")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(string(b))
+	// Output:
+	// {
+	// <prefix><indent>"a": 1,
+	// <prefix><indent>"b": 2
+	// <prefix>}
+}
+
+func ExampleValid() {
+	goodJSON := `{"example": 1}`
+	badJSON := `{"example":2:]}}`
+
+	fmt.Println(json.Valid([]byte(goodJSON)), json.Valid([]byte(badJSON)))
+	// Output:
+	// true false
+}
+
+func ExampleHTMLEscape() {
+	var out bytes.Buffer
+	json.HTMLEscape(&out, []byte(`{"Name":"<b>HTML content</b>"}`))
+	out.WriteTo(os.Stdout)
+	// Output:
+	//{"Name":"\u003cb\u003eHTML content\u003c/b\u003e"}
+}

gojson/example_text_marshaling_test.go

@@ -0,0 +1,67 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json_test
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"strings"
+)
+
+type Size int
+
+const (
+	Unrecognized Size = iota
+	Small
+	Large
+)
+
+func (s *Size) UnmarshalText(text []byte) error {
+	switch strings.ToLower(string(text)) {
+	default:
+		*s = Unrecognized
+	case "small":
+		*s = Small
+	case "large":
+		*s = Large
+	}
+	return nil
+}
+
+func (s Size) MarshalText() ([]byte, error) {
+	var name string
+	switch s {
+	default:
+		name = "unrecognized"
+	case Small:
+		name = "small"
+	case Large:
+		name = "large"
+	}
+	return []byte(name), nil
+}
+
+func Example_textMarshalJSON() {
+	blob := `["small","regular","large","unrecognized","small","normal","small","large"]`
+	var inventory []Size
+	if err := json.Unmarshal([]byte(blob), &inventory); err != nil {
+		log.Fatal(err)
+	}
+
+	counts := make(map[Size]int)
+	for _, size := range inventory {
+		counts[size] += 1
+	}
+
+	fmt.Printf("Inventory Counts:\n* Small:        %d\n* Large:        %d\n* Unrecognized: %d\n",
+		counts[Small], counts[Large], counts[Unrecognized])
+
+	// Output:
+	// Inventory Counts:
+	// * Small:        3
+	// * Large:        2
+	// * Unrecognized: 3
+}

gojson/fold.go

@@ -0,0 +1,141 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+const (
+	caseMask     = ^byte(0x20) // Mask to ignore case in ASCII.
+	kelvin       = '\u212a'
+	smallLongEss = '\u017f'
+)
+
+// foldFunc returns one of four different case folding equivalence
+// functions, from most general (and slow) to fastest:
+//
+// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
+// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
+// 3) asciiEqualFold, no special, but includes non-letters (including _)
+// 4) simpleLetterEqualFold, no specials, no non-letters.
+//
+// The letters S and K are special because they map to 3 runes, not just 2:
+//   - S maps to s and to U+017F 'ſ' Latin small letter long s
+//   - k maps to K and to U+212A 'K' Kelvin sign
+//
+// See https://play.golang.org/p/tTxjOc0OGo
+//
+// The returned function is specialized for matching against s and
+// should only be given s. It's not curried for performance reasons.
+func foldFunc(s []byte) func(s, t []byte) bool {
+	nonLetter := false
+	special := false // special letter
+	for _, b := range s {
+		if b >= utf8.RuneSelf {
+			return bytes.EqualFold
+		}
+		upper := b & caseMask
+		if upper < 'A' || upper > 'Z' {
+			nonLetter = true
+		} else if upper == 'K' || upper == 'S' {
+			// See above for why these letters are special.
+			special = true
+		}
+	}
+	if special {
+		return equalFoldRight
+	}
+	if nonLetter {
+		return asciiEqualFold
+	}
+	return simpleLetterEqualFold
+}
+
+// equalFoldRight is a specialization of bytes.EqualFold when s is
+// known to be all ASCII (including punctuation), but contains an 's',
+// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
+// See comments on foldFunc.
+func equalFoldRight(s, t []byte) bool {
+	for _, sb := range s {
+		if len(t) == 0 {
+			return false
+		}
+		tb := t[0]
+		if tb < utf8.RuneSelf {
+			if sb != tb {
+				sbUpper := sb & caseMask
+				if 'A' <= sbUpper && sbUpper <= 'Z' {
+					if sbUpper != tb&caseMask {
+						return false
+					}
+				} else {
+					return false
+				}
+			}
+			t = t[1:]
+			continue
+		}
+		// sb is ASCII and t is not. t must be either kelvin
+		// sign or long s; sb must be s, S, k, or K.
+		tr, size := utf8.DecodeRune(t)
+		switch sb {
+		case 's', 'S':
+			if tr != smallLongEss {
+				return false
+			}
+		case 'k', 'K':
+			if tr != kelvin {
+				return false
+			}
+		default:
+			return false
+		}
+		t = t[size:]
+
+	}
+	return len(t) == 0
+}
+
+// asciiEqualFold is a specialization of bytes.EqualFold for use when
+// s is all ASCII (but may contain non-letters) and contains no
+// special-folding letters.
+// See comments on foldFunc.
+func asciiEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, sb := range s {
+		tb := t[i]
+		if sb == tb {
+			continue
+		}
+		if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
+			if sb&caseMask != tb&caseMask {
+				return false
+			}
+		} else {
+			return false
+		}
+	}
+	return true
+}
+
+// simpleLetterEqualFold is a specialization of bytes.EqualFold for
+// use when s is all ASCII letters (no underscores, etc) and also
+// doesn't contain 'k', 'K', 's', or 'S'.
+// See comments on foldFunc.
+func simpleLetterEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, b := range s {
+		if b&caseMask != t[i]&caseMask {
+			return false
+		}
+	}
+	return true
+}

gojson/fold_test.go

@@ -0,0 +1,110 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+var foldTests = []struct {
+	fn   func(s, t []byte) bool
+	s, t string
+	want bool
+}{
+	{equalFoldRight, "", "", true},
+	{equalFoldRight, "a", "a", true},
+	{equalFoldRight, "", "a", false},
+	{equalFoldRight, "a", "", false},
+	{equalFoldRight, "a", "A", true},
+	{equalFoldRight, "AB", "ab", true},
+	{equalFoldRight, "AB", "ac", false},
+	{equalFoldRight, "sbkKc", "ſbKKc", true},
+	{equalFoldRight, "SbKkc", "ſbKKc", true},
+	{equalFoldRight, "SbKkc", "ſbKK", false},
+	{equalFoldRight, "e", "é", false},
+	{equalFoldRight, "s", "S", true},
+
+	{simpleLetterEqualFold, "", "", true},
+	{simpleLetterEqualFold, "abc", "abc", true},
+	{simpleLetterEqualFold, "abc", "ABC", true},
+	{simpleLetterEqualFold, "abc", "ABCD", false},
+	{simpleLetterEqualFold, "abc", "xxx", false},
+
+	{asciiEqualFold, "a_B", "A_b", true},
+	{asciiEqualFold, "aa@", "aa`", false}, // verify 0x40 and 0x60 aren't case-equivalent
+}
+
+func TestFold(t *testing.T) {
+	for i, tt := range foldTests {
+		if got := tt.fn([]byte(tt.s), []byte(tt.t)); got != tt.want {
+			t.Errorf("%d. %q, %q = %v; want %v", i, tt.s, tt.t, got, tt.want)
+		}
+		truth := strings.EqualFold(tt.s, tt.t)
+		if truth != tt.want {
+			t.Errorf("strings.EqualFold doesn't agree with case %d", i)
+		}
+	}
+}
+
+func TestFoldAgainstUnicode(t *testing.T) {
+	var buf1, buf2 []byte
+	var runes []rune
+	for i := 0x20; i <= 0x7f; i++ {
+		runes = append(runes, rune(i))
+	}
+	runes = append(runes, kelvin, smallLongEss)
+
+	funcs := []struct {
+		name   string
+		fold   func(s, t []byte) bool
+		letter bool // must be ASCII letter
+		simple bool // must be simple ASCII letter (not 'S' or 'K')
+	}{
+		{
+			name: "equalFoldRight",
+			fold: equalFoldRight,
+		},
+		{
+			name:   "asciiEqualFold",
+			fold:   asciiEqualFold,
+			simple: true,
+		},
+		{
+			name:   "simpleLetterEqualFold",
+			fold:   simpleLetterEqualFold,
+			simple: true,
+			letter: true,
+		},
+	}
+
+	for _, ff := range funcs {
+		for _, r := range runes {
+			if r >= utf8.RuneSelf {
+				continue
+			}
+			if ff.letter && !isASCIILetter(byte(r)) {
+				continue
+			}
+			if ff.simple && (r == 's' || r == 'S' || r == 'k' || r == 'K') {
+				continue
+			}
+			for _, r2 := range runes {
+				buf1 = append(utf8.AppendRune(append(buf1[:0], 'x'), r), 'x')
+				buf2 = append(utf8.AppendRune(append(buf2[:0], 'x'), r2), 'x')
+				want := bytes.EqualFold(buf1, buf2)
+				if got := ff.fold(buf1, buf2); got != want {
+					t.Errorf("%s(%q, %q) = %v; want %v", ff.name, buf1, buf2, got, want)
+				}
+			}
+		}
+	}
+}
+
+func isASCIILetter(b byte) bool {
+	return ('A' <= b && b <= 'Z') || ('a' <= b && b <= 'z')
+}

gojson/fuzz.go

@@ -0,0 +1,42 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build gofuzz
+
+package json
+
+import (
+	"fmt"
+)
+
+func Fuzz(data []byte) (score int) {
+	for _, ctor := range []func() any{
+		func() any { return new(any) },
+		func() any { return new(map[string]any) },
+		func() any { return new([]any) },
+	} {
+		v := ctor()
+		err := Unmarshal(data, v)
+		if err != nil {
+			continue
+		}
+		score = 1
+
+		m, err := Marshal(v)
+		if err != nil {
+			fmt.Printf("v=%#v\n", v)
+			panic(err)
+		}
+
+		u := ctor()
+		err = Unmarshal(m, u)
+		if err != nil {
+			fmt.Printf("v=%#v\n", v)
+			fmt.Printf("m=%s\n", m)
+			panic(err)
+		}
+	}
+
+	return
+}

gojson/fuzz_test.go

@@ -0,0 +1,83 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func FuzzUnmarshalJSON(f *testing.F) {
+	f.Add([]byte(`{
+"object": {
+	"slice": [
+		1,
+		2.0,
+		"3",
+		[4],
+		{5: {}}
+	]
+},
+"slice": [[]],
+"string": ":)",
+"int": 1e5,
+"float": 3e-9"
+}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		for _, typ := range []func() interface{}{
+			func() interface{} { return new(interface{}) },
+			func() interface{} { return new(map[string]interface{}) },
+			func() interface{} { return new([]interface{}) },
+		} {
+			i := typ()
+			if err := Unmarshal(b, i); err != nil {
+				return
+			}
+
+			encoded, err := Marshal(i)
+			if err != nil {
+				t.Fatalf("failed to marshal: %s", err)
+			}
+
+			if err := Unmarshal(encoded, i); err != nil {
+				t.Fatalf("failed to roundtrip: %s", err)
+			}
+		}
+	})
+}
+
+func FuzzDecoderToken(f *testing.F) {
+	f.Add([]byte(`{
+"object": {
+	"slice": [
+		1,
+		2.0,
+		"3",
+		[4],
+		{5: {}}
+	]
+},
+"slice": [[]],
+"string": ":)",
+"int": 1e5,
+"float": 3e-9"
+}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		r := bytes.NewReader(b)
+		d := NewDecoder(r)
+		for {
+			_, err := d.Token()
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				return
+			}
+		}
+	})
+}

gojson/gionic.go

@@ -0,0 +1,44 @@
+package json
+
+import (
+	"net/http"
+)
+
+// Render interface is copied from github.com/gin-gonic/gin@v1.8.1/render/render.go
+type Render interface {
+	// Render writes data with custom ContentType.
+	Render(http.ResponseWriter) error
+	// WriteContentType writes custom ContentType.
+	WriteContentType(w http.ResponseWriter)
+}
+
+type GoJsonRender struct {
+	Data          any
+	NilSafeSlices bool
+	NilSafeMaps   bool
+	Indent        *IndentOpt
+}
+
+func (r GoJsonRender) Render(w http.ResponseWriter) error {
+	header := w.Header()
+	if val := header["Content-Type"]; len(val) == 0 {
+		header["Content-Type"] = []string{"application/json; charset=utf-8"}
+	}
+
+	jsonBytes, err := MarshalSafeCollections(r.Data, r.NilSafeSlices, r.NilSafeMaps, r.Indent)
+	if err != nil {
+		panic(err)
+	}
+	_, err = w.Write(jsonBytes)
+	if err != nil {
+		panic(err)
+	}
+	return nil
+}
+
+func (r GoJsonRender) WriteContentType(w http.ResponseWriter) {
+	header := w.Header()
+	if val := header["Content-Type"]; len(val) == 0 {
+		header["Content-Type"] = []string{"application/json; charset=utf-8"}
+	}
+}

gojson/indent.go

@@ -0,0 +1,143 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+)
+
+// Compact appends to dst the JSON-encoded src with
+// insignificant space characters elided.
+func Compact(dst *bytes.Buffer, src []byte) error {
+	return compact(dst, src, false)
+}
+
+func compact(dst *bytes.Buffer, src []byte, escape bool) error {
+	origLen := dst.Len()
+	scan := newScanner()
+	defer freeScanner(scan)
+	start := 0
+	for i, c := range src {
+		if escape && (c == '<' || c == '>' || c == '&') {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u00`)
+			dst.WriteByte(hex[c>>4])
+			dst.WriteByte(hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if escape && c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
+		v := scan.step(scan, c)
+		if v >= scanSkipSpace {
+			if v == scanError {
+				break
+			}
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			start = i + 1
+		}
+	}
+	if scan.eof() == scanError {
+		dst.Truncate(origLen)
+		return scan.err
+	}
+	if start < len(src) {
+		dst.Write(src[start:])
+	}
+	return nil
+}
+
+func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
+	dst.WriteByte('\n')
+	dst.WriteString(prefix)
+	for i := 0; i < depth; i++ {
+		dst.WriteString(indent)
+	}
+}
+
+// Indent appends to dst an indented form of the JSON-encoded src.
+// Each element in a JSON object or array begins on a new,
+// indented line beginning with prefix followed by one or more
+// copies of indent according to the indentation nesting.
+// The data appended to dst does not begin with the prefix nor
+// any indentation, to make it easier to embed inside other formatted JSON data.
+// Although leading space characters (space, tab, carriage return, newline)
+// at the beginning of src are dropped, trailing space characters
+// at the end of src are preserved and copied to dst.
+// For example, if src has no trailing spaces, neither will dst;
+// if src ends in a trailing newline, so will dst.
+func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
+	origLen := dst.Len()
+	scan := newScanner()
+	defer freeScanner(scan)
+	needIndent := false
+	depth := 0
+	for _, c := range src {
+		scan.bytes++
+		v := scan.step(scan, c)
+		if v == scanSkipSpace {
+			continue
+		}
+		if v == scanError {
+			break
+		}
+		if needIndent && v != scanEndObject && v != scanEndArray {
+			needIndent = false
+			depth++
+			newline(dst, prefix, indent, depth)
+		}
+
+		// Emit semantically uninteresting bytes
+		// (in particular, punctuation in strings) unmodified.
+		if v == scanContinue {
+			dst.WriteByte(c)
+			continue
+		}
+
+		// Add spacing around real punctuation.
+		switch c {
+		case '{', '[':
+			// delay indent so that empty object and array are formatted as {} and [].
+			needIndent = true
+			dst.WriteByte(c)
+
+		case ',':
+			dst.WriteByte(c)
+			newline(dst, prefix, indent, depth)
+
+		case ':':
+			dst.WriteByte(c)
+			dst.WriteByte(' ')
+
+		case '}', ']':
+			if needIndent {
+				// suppress indent in empty object/array
+				needIndent = false
+			} else {
+				depth--
+				newline(dst, prefix, indent, depth)
+			}
+			dst.WriteByte(c)
+
+		default:
+			dst.WriteByte(c)
+		}
+	}
+	if scan.eof() == scanError {
+		dst.Truncate(origLen)
+		return scan.err
+	}
+	return nil
+}

gojson/number_test.go

@@ -0,0 +1,118 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"regexp"
+	"testing"
+)
+
+func TestNumberIsValid(t *testing.T) {
+	// From: https://stackoverflow.com/a/13340826
+	var jsonNumberRegexp = regexp.MustCompile(`^-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$`)
+
+	validTests := []string{
+		"0",
+		"-0",
+		"1",
+		"-1",
+		"0.1",
+		"-0.1",
+		"1234",
+		"-1234",
+		"12.34",
+		"-12.34",
+		"12E0",
+		"12E1",
+		"12e34",
+		"12E-0",
+		"12e+1",
+		"12e-34",
+		"-12E0",
+		"-12E1",
+		"-12e34",
+		"-12E-0",
+		"-12e+1",
+		"-12e-34",
+		"1.2E0",
+		"1.2E1",
+		"1.2e34",
+		"1.2E-0",
+		"1.2e+1",
+		"1.2e-34",
+		"-1.2E0",
+		"-1.2E1",
+		"-1.2e34",
+		"-1.2E-0",
+		"-1.2e+1",
+		"-1.2e-34",
+		"0E0",
+		"0E1",
+		"0e34",
+		"0E-0",
+		"0e+1",
+		"0e-34",
+		"-0E0",
+		"-0E1",
+		"-0e34",
+		"-0E-0",
+		"-0e+1",
+		"-0e-34",
+	}
+
+	for _, test := range validTests {
+		if !isValidNumber(test) {
+			t.Errorf("%s should be valid", test)
+		}
+
+		var f float64
+		if err := Unmarshal([]byte(test), &f); err != nil {
+			t.Errorf("%s should be valid but Unmarshal failed: %v", test, err)
+		}
+
+		if !jsonNumberRegexp.MatchString(test) {
+			t.Errorf("%s should be valid but regexp does not match", test)
+		}
+	}
+
+	invalidTests := []string{
+		"",
+		"invalid",
+		"1.0.1",
+		"1..1",
+		"-1-2",
+		"012a42",
+		"01.2",
+		"012",
+		"12E12.12",
+		"1e2e3",
+		"1e+-2",
+		"1e--23",
+		"1e",
+		"e1",
+		"1e+",
+		"1ea",
+		"1a",
+		"1.a",
+		"1.",
+		"01",
+		"1.e1",
+	}
+
+	for _, test := range invalidTests {
+		if isValidNumber(test) {
+			t.Errorf("%s should be invalid", test)
+		}
+
+		var f float64
+		if err := Unmarshal([]byte(test), &f); err == nil {
+			t.Errorf("%s should be invalid but unmarshal wrote %v", test, f)
+		}
+
+		if jsonNumberRegexp.MatchString(test) {
+			t.Errorf("%s should be invalid but matches regexp", test)
+		}
+	}
+}

gojson/scanner.go

@@ -0,0 +1,610 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+// JSON value parser state machine.
+// Just about at the limit of what is reasonable to write by hand.
+// Some parts are a bit tedious, but overall it nicely factors out the
+// otherwise common code from the multiple scanning functions
+// in this package (Compact, Indent, checkValid, etc).
+//
+// This file starts with two simple examples using the scanner
+// before diving into the scanner itself.
+
+import (
+	"strconv"
+	"sync"
+)
+
+// Valid reports whether data is a valid JSON encoding.
+func Valid(data []byte) bool {
+	scan := newScanner()
+	defer freeScanner(scan)
+	return checkValid(data, scan) == nil
+}
+
+// checkValid verifies that data is valid JSON-encoded data.
+// scan is passed in for use by checkValid to avoid an allocation.
+// checkValid returns nil or a SyntaxError.
+func checkValid(data []byte, scan *scanner) error {
+	scan.reset()
+	for _, c := range data {
+		scan.bytes++
+		if scan.step(scan, c) == scanError {
+			return scan.err
+		}
+	}
+	if scan.eof() == scanError {
+		return scan.err
+	}
+	return nil
+}
+
+// A SyntaxError is a description of a JSON syntax error.
+// Unmarshal will return a SyntaxError if the JSON can't be parsed.
+type SyntaxError struct {
+	msg    string // description of error
+	Offset int64  // error occurred after reading Offset bytes
+}
+
+func (e *SyntaxError) Error() string { return e.msg }
+
+// A scanner is a JSON scanning state machine.
+// Callers call scan.reset and then pass bytes in one at a time
+// by calling scan.step(&scan, c) for each byte.
+// The return value, referred to as an opcode, tells the
+// caller about significant parsing events like beginning
+// and ending literals, objects, and arrays, so that the
+// caller can follow along if it wishes.
+// The return value scanEnd indicates that a single top-level
+// JSON value has been completed, *before* the byte that
+// just got passed in.  (The indication must be delayed in order
+// to recognize the end of numbers: is 123 a whole value or
+// the beginning of 12345e+6?).
+type scanner struct {
+	// The step is a func to be called to execute the next transition.
+	// Also tried using an integer constant and a single func
+	// with a switch, but using the func directly was 10% faster
+	// on a 64-bit Mac Mini, and it's nicer to read.
+	step func(*scanner, byte) int
+
+	// Reached end of top-level value.
+	endTop bool
+
+	// Stack of what we're in the middle of - array values, object keys, object values.
+	parseState []int
+
+	// Error that happened, if any.
+	err error
+
+	// total bytes consumed, updated by decoder.Decode (and deliberately
+	// not set to zero by scan.reset)
+	bytes int64
+}
+
+var scannerPool = sync.Pool{
+	New: func() any {
+		return &scanner{}
+	},
+}
+
+func newScanner() *scanner {
+	scan := scannerPool.Get().(*scanner)
+	// scan.reset by design doesn't set bytes to zero
+	scan.bytes = 0
+	scan.reset()
+	return scan
+}
+
+func freeScanner(scan *scanner) {
+	// Avoid hanging on to too much memory in extreme cases.
+	if len(scan.parseState) > 1024 {
+		scan.parseState = nil
+	}
+	scannerPool.Put(scan)
+}
+
+// These values are returned by the state transition functions
+// assigned to scanner.state and the method scanner.eof.
+// They give details about the current state of the scan that
+// callers might be interested to know about.
+// It is okay to ignore the return value of any particular
+// call to scanner.state: if one call returns scanError,
+// every subsequent call will return scanError too.
+const (
+	// Continue.
+	scanContinue     = iota // uninteresting byte
+	scanBeginLiteral        // end implied by next result != scanContinue
+	scanBeginObject         // begin object
+	scanObjectKey           // just finished object key (string)
+	scanObjectValue         // just finished non-last object value
+	scanEndObject           // end object (implies scanObjectValue if possible)
+	scanBeginArray          // begin array
+	scanArrayValue          // just finished array value
+	scanEndArray            // end array (implies scanArrayValue if possible)
+	scanSkipSpace           // space byte; can skip; known to be last "continue" result
+
+	// Stop.
+	scanEnd   // top-level value ended *before* this byte; known to be first "stop" result
+	scanError // hit an error, scanner.err.
+)
+
+// These values are stored in the parseState stack.
+// They give the current state of a composite value
+// being scanned. If the parser is inside a nested value
+// the parseState describes the nested state, outermost at entry 0.
+const (
+	parseObjectKey   = iota // parsing object key (before colon)
+	parseObjectValue        // parsing object value (after colon)
+	parseArrayValue         // parsing array value
+)
+
+// This limits the max nesting depth to prevent stack overflow.
+// This is permitted by https://tools.ietf.org/html/rfc7159#section-9
+const maxNestingDepth = 10000
+
+// reset prepares the scanner for use.
+// It must be called before calling s.step.
+func (s *scanner) reset() {
+	s.step = stateBeginValue
+	s.parseState = s.parseState[0:0]
+	s.err = nil
+	s.endTop = false
+}
+
+// eof tells the scanner that the end of input has been reached.
+// It returns a scan status just as s.step does.
+func (s *scanner) eof() int {
+	if s.err != nil {
+		return scanError
+	}
+	if s.endTop {
+		return scanEnd
+	}
+	s.step(s, ' ')
+	if s.endTop {
+		return scanEnd
+	}
+	if s.err == nil {
+		s.err = &SyntaxError{"unexpected end of JSON input", s.bytes}
+	}
+	return scanError
+}
+
+// pushParseState pushes a new parse state p onto the parse stack.
+// an error state is returned if maxNestingDepth was exceeded, otherwise successState is returned.
+func (s *scanner) pushParseState(c byte, newParseState int, successState int) int {
+	s.parseState = append(s.parseState, newParseState)
+	if len(s.parseState) <= maxNestingDepth {
+		return successState
+	}
+	return s.error(c, "exceeded max depth")
+}
+
+// popParseState pops a parse state (already obtained) off the stack
+// and updates s.step accordingly.
+func (s *scanner) popParseState() {
+	n := len(s.parseState) - 1
+	s.parseState = s.parseState[0:n]
+	if n == 0 {
+		s.step = stateEndTop
+		s.endTop = true
+	} else {
+		s.step = stateEndValue
+	}
+}
+
+func isSpace(c byte) bool {
+	return c <= ' ' && (c == ' ' || c == '\t' || c == '\r' || c == '\n')
+}
+
+// stateBeginValueOrEmpty is the state after reading `[`.
+func stateBeginValueOrEmpty(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == ']' {
+		return stateEndValue(s, c)
+	}
+	return stateBeginValue(s, c)
+}
+
+// stateBeginValue is the state at the beginning of the input.
+func stateBeginValue(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	switch c {
+	case '{':
+		s.step = stateBeginStringOrEmpty
+		return s.pushParseState(c, parseObjectKey, scanBeginObject)
+	case '[':
+		s.step = stateBeginValueOrEmpty
+		return s.pushParseState(c, parseArrayValue, scanBeginArray)
+	case '"':
+		s.step = stateInString
+		return scanBeginLiteral
+	case '-':
+		s.step = stateNeg
+		return scanBeginLiteral
+	case '0': // beginning of 0.123
+		s.step = state0
+		return scanBeginLiteral
+	case 't': // beginning of true
+		s.step = stateT
+		return scanBeginLiteral
+	case 'f': // beginning of false
+		s.step = stateF
+		return scanBeginLiteral
+	case 'n': // beginning of null
+		s.step = stateN
+		return scanBeginLiteral
+	}
+	if '1' <= c && c <= '9' { // beginning of 1234.5
+		s.step = state1
+		return scanBeginLiteral
+	}
+	return s.error(c, "looking for beginning of value")
+}
+
+// stateBeginStringOrEmpty is the state after reading `{`.
+func stateBeginStringOrEmpty(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == '}' {
+		n := len(s.parseState)
+		s.parseState[n-1] = parseObjectValue
+		return stateEndValue(s, c)
+	}
+	return stateBeginString(s, c)
+}
+
+// stateBeginString is the state after reading `{"key": value,`.
+func stateBeginString(s *scanner, c byte) int {
+	if isSpace(c) {
+		return scanSkipSpace
+	}
+	if c == '"' {
+		s.step = stateInString
+		return scanBeginLiteral
+	}
+	return s.error(c, "looking for beginning of object key string")
+}
+
+// stateEndValue is the state after completing a value,
+// such as after reading `{}` or `true` or `["x"`.
+func stateEndValue(s *scanner, c byte) int {
+	n := len(s.parseState)
+	if n == 0 {
+		// Completed top-level before the current byte.
+		s.step = stateEndTop
+		s.endTop = true
+		return stateEndTop(s, c)
+	}
+	if isSpace(c) {
+		s.step = stateEndValue
+		return scanSkipSpace
+	}
+	ps := s.parseState[n-1]
+	switch ps {
+	case parseObjectKey:
+		if c == ':' {
+			s.parseState[n-1] = parseObjectValue
+			s.step = stateBeginValue
+			return scanObjectKey
+		}
+		return s.error(c, "after object key")
+	case parseObjectValue:
+		if c == ',' {
+			s.parseState[n-1] = parseObjectKey
+			s.step = stateBeginString
+			return scanObjectValue
+		}
+		if c == '}' {
+			s.popParseState()
+			return scanEndObject
+		}
+		return s.error(c, "after object key:value pair")
+	case parseArrayValue:
+		if c == ',' {
+			s.step = stateBeginValue
+			return scanArrayValue
+		}
+		if c == ']' {
+			s.popParseState()
+			return scanEndArray
+		}
+		return s.error(c, "after array element")
+	}
+	return s.error(c, "")
+}
+
+// stateEndTop is the state after finishing the top-level value,
+// such as after reading `{}` or `[1,2,3]`.
+// Only space characters should be seen now.
+func stateEndTop(s *scanner, c byte) int {
+	if !isSpace(c) {
+		// Complain about non-space byte on next call.
+		s.error(c, "after top-level value")
+	}
+	return scanEnd
+}
+
+// stateInString is the state after reading `"`.
+func stateInString(s *scanner, c byte) int {
+	if c == '"' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	if c == '\\' {
+		s.step = stateInStringEsc
+		return scanContinue
+	}
+	if c < 0x20 {
+		return s.error(c, "in string literal")
+	}
+	return scanContinue
+}
+
+// stateInStringEsc is the state after reading `"\` during a quoted string.
+func stateInStringEsc(s *scanner, c byte) int {
+	switch c {
+	case 'b', 'f', 'n', 'r', 't', '\\', '/', '"':
+		s.step = stateInString
+		return scanContinue
+	case 'u':
+		s.step = stateInStringEscU
+		return scanContinue
+	}
+	return s.error(c, "in string escape code")
+}
+
+// stateInStringEscU is the state after reading `"\u` during a quoted string.
+func stateInStringEscU(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU1
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU1 is the state after reading `"\u1` during a quoted string.
+func stateInStringEscU1(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU12
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU12 is the state after reading `"\u12` during a quoted string.
+func stateInStringEscU12(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInStringEscU123
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateInStringEscU123 is the state after reading `"\u123` during a quoted string.
+func stateInStringEscU123(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+		s.step = stateInString
+		return scanContinue
+	}
+	// numbers
+	return s.error(c, "in \\u hexadecimal character escape")
+}
+
+// stateNeg is the state after reading `-` during a number.
+func stateNeg(s *scanner, c byte) int {
+	if c == '0' {
+		s.step = state0
+		return scanContinue
+	}
+	if '1' <= c && c <= '9' {
+		s.step = state1
+		return scanContinue
+	}
+	return s.error(c, "in numeric literal")
+}
+
+// state1 is the state after reading a non-zero integer during a number,
+// such as after reading `1` or `100` but not `0`.
+func state1(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = state1
+		return scanContinue
+	}
+	return state0(s, c)
+}
+
+// state0 is the state after reading `0` during a number.
+func state0(s *scanner, c byte) int {
+	if c == '.' {
+		s.step = stateDot
+		return scanContinue
+	}
+	if c == 'e' || c == 'E' {
+		s.step = stateE
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateDot is the state after reading the integer and decimal point in a number,
+// such as after reading `1.`.
+func stateDot(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = stateDot0
+		return scanContinue
+	}
+	return s.error(c, "after decimal point in numeric literal")
+}
+
+// stateDot0 is the state after reading the integer, decimal point, and subsequent
+// digits of a number, such as after reading `3.14`.
+func stateDot0(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		return scanContinue
+	}
+	if c == 'e' || c == 'E' {
+		s.step = stateE
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateE is the state after reading the mantissa and e in a number,
+// such as after reading `314e` or `0.314e`.
+func stateE(s *scanner, c byte) int {
+	if c == '+' || c == '-' {
+		s.step = stateESign
+		return scanContinue
+	}
+	return stateESign(s, c)
+}
+
+// stateESign is the state after reading the mantissa, e, and sign in a number,
+// such as after reading `314e-` or `0.314e+`.
+func stateESign(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		s.step = stateE0
+		return scanContinue
+	}
+	return s.error(c, "in exponent of numeric literal")
+}
+
+// stateE0 is the state after reading the mantissa, e, optional sign,
+// and at least one digit of the exponent in a number,
+// such as after reading `314e-2` or `0.314e+1` or `3.14e0`.
+func stateE0(s *scanner, c byte) int {
+	if '0' <= c && c <= '9' {
+		return scanContinue
+	}
+	return stateEndValue(s, c)
+}
+
+// stateT is the state after reading `t`.
+func stateT(s *scanner, c byte) int {
+	if c == 'r' {
+		s.step = stateTr
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'r')")
+}
+
+// stateTr is the state after reading `tr`.
+func stateTr(s *scanner, c byte) int {
+	if c == 'u' {
+		s.step = stateTru
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'u')")
+}
+
+// stateTru is the state after reading `tru`.
+func stateTru(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal true (expecting 'e')")
+}
+
+// stateF is the state after reading `f`.
+func stateF(s *scanner, c byte) int {
+	if c == 'a' {
+		s.step = stateFa
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'a')")
+}
+
+// stateFa is the state after reading `fa`.
+func stateFa(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateFal
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'l')")
+}
+
+// stateFal is the state after reading `fal`.
+func stateFal(s *scanner, c byte) int {
+	if c == 's' {
+		s.step = stateFals
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 's')")
+}
+
+// stateFals is the state after reading `fals`.
+func stateFals(s *scanner, c byte) int {
+	if c == 'e' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal false (expecting 'e')")
+}
+
+// stateN is the state after reading `n`.
+func stateN(s *scanner, c byte) int {
+	if c == 'u' {
+		s.step = stateNu
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'u')")
+}
+
+// stateNu is the state after reading `nu`.
+func stateNu(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateNul
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'l')")
+}
+
+// stateNul is the state after reading `nul`.
+func stateNul(s *scanner, c byte) int {
+	if c == 'l' {
+		s.step = stateEndValue
+		return scanContinue
+	}
+	return s.error(c, "in literal null (expecting 'l')")
+}
+
+// stateError is the state after reaching a syntax error,
+// such as after reading `[1}` or `5.1.2`.
+func stateError(s *scanner, c byte) int {
+	return scanError
+}
+
+// error records an error and switches to the error state.
+func (s *scanner) error(c byte, context string) int {
+	s.step = stateError
+	s.err = &SyntaxError{"invalid character " + quoteChar(c) + " " + context, s.bytes}
+	return scanError
+}
+
+// quoteChar formats c as a quoted character literal.
+func quoteChar(c byte) string {
+	// special cases - different from quoted strings
+	if c == '\'' {
+		return `'\''`
+	}
+	if c == '"' {
+		return `'"'`
+	}
+
+	// use quoted string with different quotation marks
+	s := strconv.Quote(string(c))
+	return "'" + s[1:len(s)-1] + "'"
+}

gojson/scanner_test.go

@@ -0,0 +1,301 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"math"
+	"math/rand"
+	"reflect"
+	"testing"
+)
+
+var validTests = []struct {
+	data string
+	ok   bool
+}{
+	{`foo`, false},
+	{`}{`, false},
+	{`{]`, false},
+	{`{}`, true},
+	{`{"foo":"bar"}`, true},
+	{`{"foo":"bar","bar":{"baz":["qux"]}}`, true},
+}
+
+func TestValid(t *testing.T) {
+	for _, tt := range validTests {
+		if ok := Valid([]byte(tt.data)); ok != tt.ok {
+			t.Errorf("Valid(%#q) = %v, want %v", tt.data, ok, tt.ok)
+		}
+	}
+}
+
+// Tests of simple examples.
+
+type example struct {
+	compact string
+	indent  string
+}
+
+var examples = []example{
+	{`1`, `1`},
+	{`{}`, `{}`},
+	{`[]`, `[]`},
+	{`{"":2}`, "{\n\t\"\": 2\n}"},
+	{`[3]`, "[\n\t3\n]"},
+	{`[1,2,3]`, "[\n\t1,\n\t2,\n\t3\n]"},
+	{`{"x":1}`, "{\n\t\"x\": 1\n}"},
+	{ex1, ex1i},
+	{"{\"\":\"<>&\u2028\u2029\"}", "{\n\t\"\": \"<>&\u2028\u2029\"\n}"}, // See golang.org/issue/34070
+}
+
+var ex1 = `[true,false,null,"x",1,1.5,0,-5e+2]`
+
+var ex1i = `[
+	true,
+	false,
+	null,
+	"x",
+	1,
+	1.5,
+	0,
+	-5e+2
+]`
+
+func TestCompact(t *testing.T) {
+	var buf bytes.Buffer
+	for _, tt := range examples {
+		buf.Reset()
+		if err := Compact(&buf, []byte(tt.compact)); err != nil {
+			t.Errorf("Compact(%#q): %v", tt.compact, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%#q) = %#q, want original", tt.compact, s)
+		}
+
+		buf.Reset()
+		if err := Compact(&buf, []byte(tt.indent)); err != nil {
+			t.Errorf("Compact(%#q): %v", tt.indent, err)
+			continue
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%#q) = %#q, want %#q", tt.indent, s, tt.compact)
+		}
+	}
+}
+
+func TestCompactSeparators(t *testing.T) {
+	// U+2028 and U+2029 should be escaped inside strings.
+	// They should not appear outside strings.
+	tests := []struct {
+		in, compact string
+	}{
+		{"{\"\u2028\": 1}", "{\"\u2028\":1}"},
+		{"{\"\u2029\" :2}", "{\"\u2029\":2}"},
+	}
+	for _, tt := range tests {
+		var buf bytes.Buffer
+		if err := Compact(&buf, []byte(tt.in)); err != nil {
+			t.Errorf("Compact(%q): %v", tt.in, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%q) = %q, want %q", tt.in, s, tt.compact)
+		}
+	}
+}
+
+func TestIndent(t *testing.T) {
+	var buf bytes.Buffer
+	for _, tt := range examples {
+		buf.Reset()
+		if err := Indent(&buf, []byte(tt.indent), "", "\t"); err != nil {
+			t.Errorf("Indent(%#q): %v", tt.indent, err)
+		} else if s := buf.String(); s != tt.indent {
+			t.Errorf("Indent(%#q) = %#q, want original", tt.indent, s)
+		}
+
+		buf.Reset()
+		if err := Indent(&buf, []byte(tt.compact), "", "\t"); err != nil {
+			t.Errorf("Indent(%#q): %v", tt.compact, err)
+			continue
+		} else if s := buf.String(); s != tt.indent {
+			t.Errorf("Indent(%#q) = %#q, want %#q", tt.compact, s, tt.indent)
+		}
+	}
+}
+
+// Tests of a large random structure.
+
+func TestCompactBig(t *testing.T) {
+	initBig()
+	var buf bytes.Buffer
+	if err := Compact(&buf, jsonBig); err != nil {
+		t.Fatalf("Compact: %v", err)
+	}
+	b := buf.Bytes()
+	if !bytes.Equal(b, jsonBig) {
+		t.Error("Compact(jsonBig) != jsonBig")
+		diff(t, b, jsonBig)
+		return
+	}
+}
+
+func TestIndentBig(t *testing.T) {
+	t.Parallel()
+	initBig()
+	var buf bytes.Buffer
+	if err := Indent(&buf, jsonBig, "", "\t"); err != nil {
+		t.Fatalf("Indent1: %v", err)
+	}
+	b := buf.Bytes()
+	if len(b) == len(jsonBig) {
+		// jsonBig is compact (no unnecessary spaces);
+		// indenting should make it bigger
+		t.Fatalf("Indent(jsonBig) did not get bigger")
+	}
+
+	// should be idempotent
+	var buf1 bytes.Buffer
+	if err := Indent(&buf1, b, "", "\t"); err != nil {
+		t.Fatalf("Indent2: %v", err)
+	}
+	b1 := buf1.Bytes()
+	if !bytes.Equal(b1, b) {
+		t.Error("Indent(Indent(jsonBig)) != Indent(jsonBig)")
+		diff(t, b1, b)
+		return
+	}
+
+	// should get back to original
+	buf1.Reset()
+	if err := Compact(&buf1, b); err != nil {
+		t.Fatalf("Compact: %v", err)
+	}
+	b1 = buf1.Bytes()
+	if !bytes.Equal(b1, jsonBig) {
+		t.Error("Compact(Indent(jsonBig)) != jsonBig")
+		diff(t, b1, jsonBig)
+		return
+	}
+}
+
+type indentErrorTest struct {
+	in  string
+	err error
+}
+
+var indentErrorTests = []indentErrorTest{
+	{`{"X": "foo", "Y"}`, &SyntaxError{"invalid character '}' after object key", 17}},
+	{`{"X": "foo" "Y": "bar"}`, &SyntaxError{"invalid character '\"' after object key:value pair", 13}},
+}
+
+func TestIndentErrors(t *testing.T) {
+	for i, tt := range indentErrorTests {
+		slice := make([]uint8, 0)
+		buf := bytes.NewBuffer(slice)
+		if err := Indent(buf, []uint8(tt.in), "", ""); err != nil {
+			if !reflect.DeepEqual(err, tt.err) {
+				t.Errorf("#%d: Indent: %#v", i, err)
+				continue
+			}
+		}
+	}
+}
+
+func diff(t *testing.T, a, b []byte) {
+	for i := 0; ; i++ {
+		if i >= len(a) || i >= len(b) || a[i] != b[i] {
+			j := i - 10
+			if j < 0 {
+				j = 0
+			}
+			t.Errorf("diverge at %d: «%s» vs «%s»", i, trim(a[j:]), trim(b[j:]))
+			return
+		}
+	}
+}
+
+func trim(b []byte) []byte {
+	if len(b) > 20 {
+		return b[0:20]
+	}
+	return b
+}
+
+// Generate a random JSON object.
+
+var jsonBig []byte
+
+func initBig() {
+	n := 10000
+	if testing.Short() {
+		n = 100
+	}
+	b, err := Marshal(genValue(n))
+	if err != nil {
+		panic(err)
+	}
+	jsonBig = b
+}
+
+func genValue(n int) any {
+	if n > 1 {
+		switch rand.Intn(2) {
+		case 0:
+			return genArray(n)
+		case 1:
+			return genMap(n)
+		}
+	}
+	switch rand.Intn(3) {
+	case 0:
+		return rand.Intn(2) == 0
+	case 1:
+		return rand.NormFloat64()
+	case 2:
+		return genString(30)
+	}
+	panic("unreachable")
+}
+
+func genString(stddev float64) string {
+	n := int(math.Abs(rand.NormFloat64()*stddev + stddev/2))
+	c := make([]rune, n)
+	for i := range c {
+		f := math.Abs(rand.NormFloat64()*64 + 32)
+		if f > 0x10ffff {
+			f = 0x10ffff
+		}
+		c[i] = rune(f)
+	}
+	return string(c)
+}
+
+func genArray(n int) []any {
+	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
+	if f > n {
+		f = n
+	}
+	if f < 1 {
+		f = 1
+	}
+	x := make([]any, f)
+	for i := range x {
+		x[i] = genValue(((i+1)*n)/f - (i*n)/f)
+	}
+	return x
+}
+
+func genMap(n int) map[string]any {
+	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
+	if f > n {
+		f = n
+	}
+	if n > 0 && f == 0 {
+		f = 1
+	}
+	x := make(map[string]any)
+	for i := 0; i < f; i++ {
+		x[genString(10)] = genValue(((i+1)*n)/f - (i*n)/f)
+	}
+	return x
+}

gojson/stream.go

@@ -0,0 +1,524 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"errors"
+	"io"
+)
+
+// A Decoder reads and decodes JSON values from an input stream.
+type Decoder struct {
+	r       io.Reader
+	buf     []byte
+	d       decodeState
+	scanp   int   // start of unread data in buf
+	scanned int64 // amount of data already scanned
+	scan    scanner
+	err     error
+
+	tokenState int
+	tokenStack []int
+}
+
+// NewDecoder returns a new decoder that reads from r.
+//
+// The decoder introduces its own buffering and may
+// read data from r beyond the JSON values requested.
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: r}
+}
+
+// UseNumber causes the Decoder to unmarshal a number into an interface{} as a
+// Number instead of as a float64.
+func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
+
+// DisallowUnknownFields causes the Decoder to return an error when the destination
+// is a struct and the input contains object keys which do not match any
+// non-ignored, exported fields in the destination.
+func (dec *Decoder) DisallowUnknownFields() { dec.d.disallowUnknownFields = true }
+
+// Decode reads the next JSON-encoded value from its
+// input and stores it in the value pointed to by v.
+//
+// See the documentation for Unmarshal for details about
+// the conversion of JSON into a Go value.
+func (dec *Decoder) Decode(v any) error {
+	if dec.err != nil {
+		return dec.err
+	}
+
+	if err := dec.tokenPrepareForDecode(); err != nil {
+		return err
+	}
+
+	if !dec.tokenValueAllowed() {
+		return &SyntaxError{msg: "not at beginning of value", Offset: dec.InputOffset()}
+	}
+
+	// Read whole value into buffer.
+	n, err := dec.readValue()
+	if err != nil {
+		return err
+	}
+	dec.d.init(dec.buf[dec.scanp : dec.scanp+n])
+	dec.scanp += n
+
+	// Don't save err from unmarshal into dec.err:
+	// the connection is still usable since we read a complete JSON
+	// object from it before the error happened.
+	err = dec.d.unmarshal(v)
+
+	// fixup token streaming state
+	dec.tokenValueEnd()
+
+	return err
+}
+
+// Buffered returns a reader of the data remaining in the Decoder's
+// buffer. The reader is valid until the next call to Decode.
+func (dec *Decoder) Buffered() io.Reader {
+	return bytes.NewReader(dec.buf[dec.scanp:])
+}
+
+// readValue reads a JSON value into dec.buf.
+// It returns the length of the encoding.
+func (dec *Decoder) readValue() (int, error) {
+	dec.scan.reset()
+
+	scanp := dec.scanp
+	var err error
+Input:
+	// help the compiler see that scanp is never negative, so it can remove
+	// some bounds checks below.
+	for scanp >= 0 {
+
+		// Look in the buffer for a new value.
+		for ; scanp < len(dec.buf); scanp++ {
+			c := dec.buf[scanp]
+			dec.scan.bytes++
+			switch dec.scan.step(&dec.scan, c) {
+			case scanEnd:
+				// scanEnd is delayed one byte so we decrement
+				// the scanner bytes count by 1 to ensure that
+				// this value is correct in the next call of Decode.
+				dec.scan.bytes--
+				break Input
+			case scanEndObject, scanEndArray:
+				// scanEnd is delayed one byte.
+				// We might block trying to get that byte from src,
+				// so instead invent a space byte.
+				if stateEndValue(&dec.scan, ' ') == scanEnd {
+					scanp++
+					break Input
+				}
+			case scanError:
+				dec.err = dec.scan.err
+				return 0, dec.scan.err
+			}
+		}
+
+		// Did the last read have an error?
+		// Delayed until now to allow buffer scan.
+		if err != nil {
+			if err == io.EOF {
+				if dec.scan.step(&dec.scan, ' ') == scanEnd {
+					break Input
+				}
+				if nonSpace(dec.buf) {
+					err = io.ErrUnexpectedEOF
+				}
+			}
+			dec.err = err
+			return 0, err
+		}
+
+		n := scanp - dec.scanp
+		err = dec.refill()
+		scanp = dec.scanp + n
+	}
+	return scanp - dec.scanp, nil
+}
+
+func (dec *Decoder) refill() error {
+	// Make room to read more into the buffer.
+	// First slide down data already consumed.
+	if dec.scanp > 0 {
+		dec.scanned += int64(dec.scanp)
+		n := copy(dec.buf, dec.buf[dec.scanp:])
+		dec.buf = dec.buf[:n]
+		dec.scanp = 0
+	}
+
+	// Grow buffer if not large enough.
+	const minRead = 512
+	if cap(dec.buf)-len(dec.buf) < minRead {
+		newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
+		copy(newBuf, dec.buf)
+		dec.buf = newBuf
+	}
+
+	// Read. Delay error for next iteration (after scan).
+	n, err := dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
+	dec.buf = dec.buf[0 : len(dec.buf)+n]
+
+	return err
+}
+
+func nonSpace(b []byte) bool {
+	for _, c := range b {
+		if !isSpace(c) {
+			return true
+		}
+	}
+	return false
+}
+
+// An Encoder writes JSON values to an output stream.
+type Encoder struct {
+	w             io.Writer
+	err           error
+	escapeHTML    bool
+	nilSafeSlices bool
+	nilSafeMaps   bool
+
+	indentBuf    *bytes.Buffer
+	indentPrefix string
+	indentValue  string
+}
+
+// NewEncoder returns a new encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{w: w, escapeHTML: true}
+}
+
+// Encode writes the JSON encoding of v to the stream,
+// followed by a newline character.
+//
+// See the documentation for Marshal for details about the
+// conversion of Go values to JSON.
+func (enc *Encoder) Encode(v any) error {
+	if enc.err != nil {
+		return enc.err
+	}
+
+	e := newEncodeState()
+	defer encodeStatePool.Put(e)
+
+	err := e.marshal(v, encOpts{escapeHTML: enc.escapeHTML, nilSafeMaps: enc.nilSafeMaps, nilSafeSlices: enc.nilSafeSlices})
+	if err != nil {
+		return err
+	}
+
+	// Terminate each value with a newline.
+	// This makes the output look a little nicer
+	// when debugging, and some kind of space
+	// is required if the encoded value was a number,
+	// so that the reader knows there aren't more
+	// digits coming.
+	e.WriteByte('\n')
+
+	b := e.Bytes()
+	if enc.indentPrefix != "" || enc.indentValue != "" {
+		if enc.indentBuf == nil {
+			enc.indentBuf = new(bytes.Buffer)
+		}
+		enc.indentBuf.Reset()
+		err = Indent(enc.indentBuf, b, enc.indentPrefix, enc.indentValue)
+		if err != nil {
+			return err
+		}
+		b = enc.indentBuf.Bytes()
+	}
+	if _, err = enc.w.Write(b); err != nil {
+		enc.err = err
+	}
+	return err
+}
+
+// SetIndent instructs the encoder to format each subsequent encoded
+// value as if indented by the package-level function Indent(dst, src, prefix, indent).
+// Calling SetIndent("", "") disables indentation.
+func (enc *Encoder) SetIndent(prefix, indent string) {
+	enc.indentPrefix = prefix
+	enc.indentValue = indent
+}
+
+// SetNilSafeCollection specifies whether to represent nil slices and maps as
+// '[]' or '{}' respectfully (flag on) instead of 'null' (default) when marshaling json.
+func (enc *Encoder) SetNilSafeCollection(nilSafeSlices bool, nilSafeMaps bool) {
+	enc.nilSafeSlices = nilSafeSlices
+	enc.nilSafeMaps = nilSafeMaps
+}
+
+// SetEscapeHTML specifies whether problematic HTML characters
+// should be escaped inside JSON quoted strings.
+// The default behavior is to escape &, <, and > to \u0026, \u003c, and \u003e
+// to avoid certain safety problems that can arise when embedding JSON in HTML.
+//
+// In non-HTML settings where the escaping interferes with the readability
+// of the output, SetEscapeHTML(false) disables this behavior.
+func (enc *Encoder) SetEscapeHTML(on bool) {
+	enc.escapeHTML = on
+}
+
+// RawMessage is a raw encoded JSON value.
+// It implements Marshaler and Unmarshaler and can
+// be used to delay JSON decoding or precompute a JSON encoding.
+type RawMessage []byte
+
+// MarshalJSON returns m as the JSON encoding of m.
+func (m RawMessage) MarshalJSON() ([]byte, error) {
+	if m == nil {
+		return []byte("null"), nil
+	}
+	return m, nil
+}
+
+// UnmarshalJSON sets *m to a copy of data.
+func (m *RawMessage) UnmarshalJSON(data []byte) error {
+	if m == nil {
+		return errors.New("json.RawMessage: UnmarshalJSON on nil pointer")
+	}
+	*m = append((*m)[0:0], data...)
+	return nil
+}
+
+var _ Marshaler = (*RawMessage)(nil)
+var _ Unmarshaler = (*RawMessage)(nil)
+
+// A Token holds a value of one of these types:
+//
+//	Delim, for the four JSON delimiters [ ] { }
+//	bool, for JSON booleans
+//	float64, for JSON numbers
+//	Number, for JSON numbers
+//	string, for JSON string literals
+//	nil, for JSON null
+type Token any
+
+const (
+	tokenTopValue = iota
+	tokenArrayStart
+	tokenArrayValue
+	tokenArrayComma
+	tokenObjectStart
+	tokenObjectKey
+	tokenObjectColon
+	tokenObjectValue
+	tokenObjectComma
+)
+
+// advance tokenstate from a separator state to a value state
+func (dec *Decoder) tokenPrepareForDecode() error {
+	// Note: Not calling peek before switch, to avoid
+	// putting peek into the standard Decode path.
+	// peek is only called when using the Token API.
+	switch dec.tokenState {
+	case tokenArrayComma:
+		c, err := dec.peek()
+		if err != nil {
+			return err
+		}
+		if c != ',' {
+			return &SyntaxError{"expected comma after array element", dec.InputOffset()}
+		}
+		dec.scanp++
+		dec.tokenState = tokenArrayValue
+	case tokenObjectColon:
+		c, err := dec.peek()
+		if err != nil {
+			return err
+		}
+		if c != ':' {
+			return &SyntaxError{"expected colon after object key", dec.InputOffset()}
+		}
+		dec.scanp++
+		dec.tokenState = tokenObjectValue
+	}
+	return nil
+}
+
+func (dec *Decoder) tokenValueAllowed() bool {
+	switch dec.tokenState {
+	case tokenTopValue, tokenArrayStart, tokenArrayValue, tokenObjectValue:
+		return true
+	}
+	return false
+}
+
+func (dec *Decoder) tokenValueEnd() {
+	switch dec.tokenState {
+	case tokenArrayStart, tokenArrayValue:
+		dec.tokenState = tokenArrayComma
+	case tokenObjectValue:
+		dec.tokenState = tokenObjectComma
+	}
+}
+
+// A Delim is a JSON array or object delimiter, one of [ ] { or }.
+type Delim rune
+
+func (d Delim) String() string {
+	return string(d)
+}
+
+// Token returns the next JSON token in the input stream.
+// At the end of the input stream, Token returns nil, io.EOF.
+//
+// Token guarantees that the delimiters [ ] { } it returns are
+// properly nested and matched: if Token encounters an unexpected
+// delimiter in the input, it will return an error.
+//
+// The input stream consists of basic JSON values—bool, string,
+// number, and null—along with delimiters [ ] { } of type Delim
+// to mark the start and end of arrays and objects.
+// Commas and colons are elided.
+func (dec *Decoder) Token() (Token, error) {
+	for {
+		c, err := dec.peek()
+		if err != nil {
+			return nil, err
+		}
+		switch c {
+		case '[':
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
+			dec.tokenState = tokenArrayStart
+			return Delim('['), nil
+
+		case ']':
+			if dec.tokenState != tokenArrayStart && dec.tokenState != tokenArrayComma {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
+			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
+			dec.tokenValueEnd()
+			return Delim(']'), nil
+
+		case '{':
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
+			dec.tokenState = tokenObjectStart
+			return Delim('{'), nil
+
+		case '}':
+			if dec.tokenState != tokenObjectStart && dec.tokenState != tokenObjectComma {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
+			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
+			dec.tokenValueEnd()
+			return Delim('}'), nil
+
+		case ':':
+			if dec.tokenState != tokenObjectColon {
+				return dec.tokenError(c)
+			}
+			dec.scanp++
+			dec.tokenState = tokenObjectValue
+			continue
+
+		case ',':
+			if dec.tokenState == tokenArrayComma {
+				dec.scanp++
+				dec.tokenState = tokenArrayValue
+				continue
+			}
+			if dec.tokenState == tokenObjectComma {
+				dec.scanp++
+				dec.tokenState = tokenObjectKey
+				continue
+			}
+			return dec.tokenError(c)
+
+		case '"':
+			if dec.tokenState == tokenObjectStart || dec.tokenState == tokenObjectKey {
+				var x string
+				old := dec.tokenState
+				dec.tokenState = tokenTopValue
+				err := dec.Decode(&x)
+				dec.tokenState = old
+				if err != nil {
+					return nil, err
+				}
+				dec.tokenState = tokenObjectColon
+				return x, nil
+			}
+			fallthrough
+
+		default:
+			if !dec.tokenValueAllowed() {
+				return dec.tokenError(c)
+			}
+			var x any
+			if err := dec.Decode(&x); err != nil {
+				return nil, err
+			}
+			return x, nil
+		}
+	}
+}
+
+func (dec *Decoder) tokenError(c byte) (Token, error) {
+	var context string
+	switch dec.tokenState {
+	case tokenTopValue:
+		context = " looking for beginning of value"
+	case tokenArrayStart, tokenArrayValue, tokenObjectValue:
+		context = " looking for beginning of value"
+	case tokenArrayComma:
+		context = " after array element"
+	case tokenObjectKey:
+		context = " looking for beginning of object key string"
+	case tokenObjectColon:
+		context = " after object key"
+	case tokenObjectComma:
+		context = " after object key:value pair"
+	}
+	return nil, &SyntaxError{"invalid character " + quoteChar(c) + context, dec.InputOffset()}
+}
+
+// More reports whether there is another element in the
+// current array or object being parsed.
+func (dec *Decoder) More() bool {
+	c, err := dec.peek()
+	return err == nil && c != ']' && c != '}'
+}
+
+func (dec *Decoder) peek() (byte, error) {
+	var err error
+	for {
+		for i := dec.scanp; i < len(dec.buf); i++ {
+			c := dec.buf[i]
+			if isSpace(c) {
+				continue
+			}
+			dec.scanp = i
+			return c, nil
+		}
+		// buffer has been scanned, now report any error
+		if err != nil {
+			return 0, err
+		}
+		err = dec.refill()
+	}
+}
+
+// InputOffset returns the input stream byte offset of the current decoder position.
+// The offset gives the location of the end of the most recently returned token
+// and the beginning of the next token.
+func (dec *Decoder) InputOffset() int64 {
+	return dec.scanned + int64(dec.scanp)
+}

gojson/stream_test.go

@@ -0,0 +1,539 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"runtime/debug"
+	"strings"
+	"testing"
+)
+
+// Test values for the stream test.
+// One of each JSON kind.
+var streamTest = []any{
+	0.1,
+	"hello",
+	nil,
+	true,
+	false,
+	[]any{"a", "b", "c"},
+	map[string]any{"K": "Kelvin", "ß": "long s"},
+	3.14, // another value to make sure something can follow map
+}
+
+var streamEncoded = `0.1
+"hello"
+null
+true
+false
+["a","b","c"]
+{"ß":"long s","K":"Kelvin"}
+3.14
+`
+
+func TestEncoder(t *testing.T) {
+	for i := 0; i <= len(streamTest); i++ {
+		var buf strings.Builder
+		enc := NewEncoder(&buf)
+		// Check that enc.SetIndent("", "") turns off indentation.
+		enc.SetIndent(">", ".")
+		enc.SetIndent("", "")
+		for j, v := range streamTest[0:i] {
+			if err := enc.Encode(v); err != nil {
+				t.Fatalf("encode #%d: %v", j, err)
+			}
+		}
+		if have, want := buf.String(), nlines(streamEncoded, i); have != want {
+			t.Errorf("encoding %d items: mismatch", i)
+			diff(t, []byte(have), []byte(want))
+			break
+		}
+	}
+}
+
+func TestEncoderErrorAndReuseEncodeState(t *testing.T) {
+	// Disable the GC temporarily to prevent encodeState's in Pool being cleaned away during the test.
+	percent := debug.SetGCPercent(-1)
+	defer debug.SetGCPercent(percent)
+
+	// Trigger an error in Marshal with cyclic data.
+	type Dummy struct {
+		Name string
+		Next *Dummy
+	}
+	dummy := Dummy{Name: "Dummy"}
+	dummy.Next = &dummy
+
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	if err := enc.Encode(dummy); err == nil {
+		t.Errorf("Encode(dummy) == nil; want error")
+	}
+
+	type Data struct {
+		A string
+		I int
+	}
+	data := Data{A: "a", I: 1}
+	if err := enc.Encode(data); err != nil {
+		t.Errorf("Marshal(%v) = %v", data, err)
+	}
+
+	var data2 Data
+	if err := Unmarshal(buf.Bytes(), &data2); err != nil {
+		t.Errorf("Unmarshal(%v) = %v", data2, err)
+	}
+	if data2 != data {
+		t.Errorf("expect: %v, but get: %v", data, data2)
+	}
+}
+
+var streamEncodedIndent = `0.1
+"hello"
+null
+true
+false
+[
+>."a",
+>."b",
+>."c"
+>]
+{
+>."ß": "long s",
+>."K": "Kelvin"
+>}
+3.14
+`
+
+func TestEncoderIndent(t *testing.T) {
+	var buf strings.Builder
+	enc := NewEncoder(&buf)
+	enc.SetIndent(">", ".")
+	for _, v := range streamTest {
+		enc.Encode(v)
+	}
+	if have, want := buf.String(), streamEncodedIndent; have != want {
+		t.Error("indented encoding mismatch")
+		diff(t, []byte(have), []byte(want))
+	}
+}
+
+type strMarshaler string
+
+func (s strMarshaler) MarshalJSON() ([]byte, error) {
+	return []byte(s), nil
+}
+
+type strPtrMarshaler string
+
+func (s *strPtrMarshaler) MarshalJSON() ([]byte, error) {
+	return []byte(*s), nil
+}
+
+func TestEncoderSetEscapeHTML(t *testing.T) {
+	var c C
+	var ct CText
+	var tagStruct struct {
+		Valid   int `json:"<>&#! "`
+		Invalid int `json:"\\"`
+	}
+
+	// This case is particularly interesting, as we force the encoder to
+	// take the address of the Ptr field to use its MarshalJSON method. This
+	// is why the '&' is important.
+	marshalerStruct := &struct {
+		NonPtr strMarshaler
+		Ptr    strPtrMarshaler
+	}{`"<str>"`, `"<str>"`}
+
+	// https://golang.org/issue/34154
+	stringOption := struct {
+		Bar string `json:"bar,string"`
+	}{`<html>foobar</html>`}
+
+	for _, tt := range []struct {
+		name       string
+		v          any
+		wantEscape string
+		want       string
+	}{
+		{"c", c, `"\u003c\u0026\u003e"`, `"<&>"`},
+		{"ct", ct, `"\"\u003c\u0026\u003e\""`, `"\"<&>\""`},
+		{`"<&>"`, "<&>", `"\u003c\u0026\u003e"`, `"<&>"`},
+		{
+			"tagStruct", tagStruct,
+			`{"\u003c\u003e\u0026#! ":0,"Invalid":0}`,
+			`{"<>&#! ":0,"Invalid":0}`,
+		},
+		{
+			`"<str>"`, marshalerStruct,
+			`{"NonPtr":"\u003cstr\u003e","Ptr":"\u003cstr\u003e"}`,
+			`{"NonPtr":"<str>","Ptr":"<str>"}`,
+		},
+		{
+			"stringOption", stringOption,
+			`{"bar":"\"\\u003chtml\\u003efoobar\\u003c/html\\u003e\""}`,
+			`{"bar":"\"<html>foobar</html>\""}`,
+		},
+	} {
+		var buf strings.Builder
+		enc := NewEncoder(&buf)
+		if err := enc.Encode(tt.v); err != nil {
+			t.Errorf("Encode(%s): %s", tt.name, err)
+			continue
+		}
+		if got := strings.TrimSpace(buf.String()); got != tt.wantEscape {
+			t.Errorf("Encode(%s) = %#q, want %#q", tt.name, got, tt.wantEscape)
+		}
+		buf.Reset()
+		enc.SetEscapeHTML(false)
+		if err := enc.Encode(tt.v); err != nil {
+			t.Errorf("SetEscapeHTML(false) Encode(%s): %s", tt.name, err)
+			continue
+		}
+		if got := strings.TrimSpace(buf.String()); got != tt.want {
+			t.Errorf("SetEscapeHTML(false) Encode(%s) = %#q, want %#q",
+				tt.name, got, tt.want)
+		}
+	}
+}
+
+func TestDecoder(t *testing.T) {
+	for i := 0; i <= len(streamTest); i++ {
+		// Use stream without newlines as input,
+		// just to stress the decoder even more.
+		// Our test input does not include back-to-back numbers.
+		// Otherwise stripping the newlines would
+		// merge two adjacent JSON values.
+		var buf bytes.Buffer
+		for _, c := range nlines(streamEncoded, i) {
+			if c != '\n' {
+				buf.WriteRune(c)
+			}
+		}
+		out := make([]any, i)
+		dec := NewDecoder(&buf)
+		for j := range out {
+			if err := dec.Decode(&out[j]); err != nil {
+				t.Fatalf("decode #%d/%d: %v", j, i, err)
+			}
+		}
+		if !reflect.DeepEqual(out, streamTest[0:i]) {
+			t.Errorf("decoding %d items: mismatch", i)
+			for j := range out {
+				if !reflect.DeepEqual(out[j], streamTest[j]) {
+					t.Errorf("#%d: have %v want %v", j, out[j], streamTest[j])
+				}
+			}
+			break
+		}
+	}
+}
+
+func TestDecoderBuffered(t *testing.T) {
+	r := strings.NewReader(`{"Name": "Gopher"} extra `)
+	var m struct {
+		Name string
+	}
+	d := NewDecoder(r)
+	err := d.Decode(&m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if m.Name != "Gopher" {
+		t.Errorf("Name = %q; want Gopher", m.Name)
+	}
+	rest, err := io.ReadAll(d.Buffered())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, w := string(rest), " extra "; g != w {
+		t.Errorf("Remaining = %q; want %q", g, w)
+	}
+}
+
+func nlines(s string, n int) string {
+	if n <= 0 {
+		return ""
+	}
+	for i, c := range s {
+		if c == '\n' {
+			if n--; n == 0 {
+				return s[0 : i+1]
+			}
+		}
+	}
+	return s
+}
+
+func TestRawMessage(t *testing.T) {
+	var data struct {
+		X  float64
+		Id RawMessage
+		Y  float32
+	}
+	const raw = `["\u0056",null]`
+	const msg = `{"X":0.1,"Id":["\u0056",null],"Y":0.2}`
+	err := Unmarshal([]byte(msg), &data)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if string([]byte(data.Id)) != raw {
+		t.Fatalf("Raw mismatch: have %#q want %#q", []byte(data.Id), raw)
+	}
+	b, err := Marshal(&data)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if string(b) != msg {
+		t.Fatalf("Marshal: have %#q want %#q", b, msg)
+	}
+}
+
+func TestNullRawMessage(t *testing.T) {
+	var data struct {
+		X     float64
+		Id    RawMessage
+		IdPtr *RawMessage
+		Y     float32
+	}
+	const msg = `{"X":0.1,"Id":null,"IdPtr":null,"Y":0.2}`
+	err := Unmarshal([]byte(msg), &data)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if want, got := "null", string(data.Id); want != got {
+		t.Fatalf("Raw mismatch: have %q, want %q", got, want)
+	}
+	if data.IdPtr != nil {
+		t.Fatalf("Raw pointer mismatch: have non-nil, want nil")
+	}
+	b, err := Marshal(&data)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if string(b) != msg {
+		t.Fatalf("Marshal: have %#q want %#q", b, msg)
+	}
+}
+
+var blockingTests = []string{
+	`{"x": 1}`,
+	`[1, 2, 3]`,
+}
+
+func TestBlocking(t *testing.T) {
+	for _, enc := range blockingTests {
+		r, w := net.Pipe()
+		go w.Write([]byte(enc))
+		var val any
+
+		// If Decode reads beyond what w.Write writes above,
+		// it will block, and the test will deadlock.
+		if err := NewDecoder(r).Decode(&val); err != nil {
+			t.Errorf("decoding %s: %v", enc, err)
+		}
+		r.Close()
+		w.Close()
+	}
+}
+
+type tokenStreamCase struct {
+	json      string
+	expTokens []any
+}
+
+type decodeThis struct {
+	v any
+}
+
+var tokenStreamCases = []tokenStreamCase{
+	// streaming token cases
+	{json: `10`, expTokens: []any{float64(10)}},
+	{json: ` [10] `, expTokens: []any{
+		Delim('['), float64(10), Delim(']')}},
+	{json: ` [false,10,"b"] `, expTokens: []any{
+		Delim('['), false, float64(10), "b", Delim(']')}},
+	{json: `{ "a": 1 }`, expTokens: []any{
+		Delim('{'), "a", float64(1), Delim('}')}},
+	{json: `{"a": 1, "b":"3"}`, expTokens: []any{
+		Delim('{'), "a", float64(1), "b", "3", Delim('}')}},
+	{json: ` [{"a": 1},{"a": 2}] `, expTokens: []any{
+		Delim('['),
+		Delim('{'), "a", float64(1), Delim('}'),
+		Delim('{'), "a", float64(2), Delim('}'),
+		Delim(']')}},
+	{json: `{"obj": {"a": 1}}`, expTokens: []any{
+		Delim('{'), "obj", Delim('{'), "a", float64(1), Delim('}'),
+		Delim('}')}},
+	{json: `{"obj": [{"a": 1}]}`, expTokens: []any{
+		Delim('{'), "obj", Delim('['),
+		Delim('{'), "a", float64(1), Delim('}'),
+		Delim(']'), Delim('}')}},
+
+	// streaming tokens with intermittent Decode()
+	{json: `{ "a": 1 }`, expTokens: []any{
+		Delim('{'), "a",
+		decodeThis{float64(1)},
+		Delim('}')}},
+	{json: ` [ { "a" : 1 } ] `, expTokens: []any{
+		Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		Delim(']')}},
+	{json: ` [{"a": 1},{"a": 2}] `, expTokens: []any{
+		Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		decodeThis{map[string]any{"a": float64(2)}},
+		Delim(']')}},
+	{json: `{ "obj" : [ { "a" : 1 } ] }`, expTokens: []any{
+		Delim('{'), "obj", Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		Delim(']'), Delim('}')}},
+
+	{json: `{"obj": {"a": 1}}`, expTokens: []any{
+		Delim('{'), "obj",
+		decodeThis{map[string]any{"a": float64(1)}},
+		Delim('}')}},
+	{json: `{"obj": [{"a": 1}]}`, expTokens: []any{
+		Delim('{'), "obj",
+		decodeThis{[]any{
+			map[string]any{"a": float64(1)},
+		}},
+		Delim('}')}},
+	{json: ` [{"a": 1} {"a": 2}] `, expTokens: []any{
+		Delim('['),
+		decodeThis{map[string]any{"a": float64(1)}},
+		decodeThis{&SyntaxError{"expected comma after array element", 11}},
+	}},
+	{json: `{ "` + strings.Repeat("a", 513) + `" 1 }`, expTokens: []any{
+		Delim('{'), strings.Repeat("a", 513),
+		decodeThis{&SyntaxError{"expected colon after object key", 518}},
+	}},
+	{json: `{ "\a" }`, expTokens: []any{
+		Delim('{'),
+		&SyntaxError{"invalid character 'a' in string escape code", 3},
+	}},
+	{json: ` \a`, expTokens: []any{
+		&SyntaxError{"invalid character '\\\\' looking for beginning of value", 1},
+	}},
+}
+
+func TestDecodeInStream(t *testing.T) {
+	for ci, tcase := range tokenStreamCases {
+
+		dec := NewDecoder(strings.NewReader(tcase.json))
+		for i, etk := range tcase.expTokens {
+
+			var tk any
+			var err error
+
+			if dt, ok := etk.(decodeThis); ok {
+				etk = dt.v
+				err = dec.Decode(&tk)
+			} else {
+				tk, err = dec.Token()
+			}
+			if experr, ok := etk.(error); ok {
+				if err == nil || !reflect.DeepEqual(err, experr) {
+					t.Errorf("case %v: Expected error %#v in %q, but was %#v", ci, experr, tcase.json, err)
+				}
+				break
+			} else if err == io.EOF {
+				t.Errorf("case %v: Unexpected EOF in %q", ci, tcase.json)
+				break
+			} else if err != nil {
+				t.Errorf("case %v: Unexpected error '%#v' in %q", ci, err, tcase.json)
+				break
+			}
+			if !reflect.DeepEqual(tk, etk) {
+				t.Errorf(`case %v: %q @ %v expected %T(%v) was %T(%v)`, ci, tcase.json, i, etk, etk, tk, tk)
+				break
+			}
+		}
+	}
+}
+
+// Test from golang.org/issue/11893
+func TestHTTPDecoding(t *testing.T) {
+	const raw = `{ "foo": "bar" }`
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(raw))
+	}))
+	defer ts.Close()
+	res, err := http.Get(ts.URL)
+	if err != nil {
+		log.Fatalf("GET failed: %v", err)
+	}
+	defer res.Body.Close()
+
+	foo := struct {
+		Foo string
+	}{}
+
+	d := NewDecoder(res.Body)
+	err = d.Decode(&foo)
+	if err != nil {
+		t.Fatalf("Decode: %v", err)
+	}
+	if foo.Foo != "bar" {
+		t.Errorf("decoded %q; want \"bar\"", foo.Foo)
+	}
+
+	// make sure we get the EOF the second time
+	err = d.Decode(&foo)
+	if err != io.EOF {
+		t.Errorf("err = %v; want io.EOF", err)
+	}
+}
+
+func TestEncoderSetNilSafeCollection(t *testing.T) {
+	var (
+		nilSlice  []interface{}
+		pNilSlice *[]interface{}
+		nilMap    map[string]interface{}
+		pNilMap   *map[string]interface{}
+	)
+	for _, tt := range []struct {
+		name        string
+		v           interface{}
+		want        string
+		rescuedWant string
+	}{
+		{"nilSlice", nilSlice, "null", "[]"},
+		{"nonNilSlice", []interface{}{}, "[]", "[]"},
+		{"sliceWithValues", []interface{}{1, 2, 3}, "[1,2,3]", "[1,2,3]"},
+		{"pNilSlice", pNilSlice, "null", "null"},
+		{"nilMap", nilMap, "null", "{}"},
+		{"nonNilMap", map[string]interface{}{}, "{}", "{}"},
+		{"mapWithValues", map[string]interface{}{"1": 1, "2": 2, "3": 3}, "{\"1\":1,\"2\":2,\"3\":3}", "{\"1\":1,\"2\":2,\"3\":3}"},
+		{"pNilMap", pNilMap, "null", "null"},
+	} {
+		var buf bytes.Buffer
+		enc := NewEncoder(&buf)
+		if err := enc.Encode(tt.v); err != nil {
+			t.Fatalf("Encode(%s): %s", tt.name, err)
+		}
+		if got := strings.TrimSpace(buf.String()); got != tt.want {
+			t.Errorf("Encode(%s) = %#q, want %#q", tt.name, got, tt.want)
+		}
+		buf.Reset()
+		enc.SetNilSafeCollection(true, true)
+		if err := enc.Encode(tt.v); err != nil {
+			t.Fatalf("SetNilSafeCollection(true) Encode(%s): %s", tt.name, err)
+		}
+		if got := strings.TrimSpace(buf.String()); got != tt.rescuedWant {
+			t.Errorf("SetNilSafeCollection(true) Encode(%s) = %#q, want %#q",
+				tt.name, got, tt.want)
+		}
+	}
+}

gojson/tables.go

@@ -0,0 +1,218 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import "unicode/utf8"
+
+// safeSet holds the value true if the ASCII character with the given array
+// position can be represented inside a JSON string without any further
+// escaping.
+//
+// All values are true except for the ASCII control characters (0-31), the
+// double quote ("), and the backslash character ("\").
+var safeSet = [utf8.RuneSelf]bool{
+	' ':      true,
+	'!':      true,
+	'"':      false,
+	'#':      true,
+	'$':      true,
+	'%':      true,
+	'&':      true,
+	'\'':     true,
+	'(':      true,
+	')':      true,
+	'*':      true,
+	'+':      true,
+	',':      true,
+	'-':      true,
+	'.':      true,
+	'/':      true,
+	'0':      true,
+	'1':      true,
+	'2':      true,
+	'3':      true,
+	'4':      true,
+	'5':      true,
+	'6':      true,
+	'7':      true,
+	'8':      true,
+	'9':      true,
+	':':      true,
+	';':      true,
+	'<':      true,
+	'=':      true,
+	'>':      true,
+	'?':      true,
+	'@':      true,
+	'A':      true,
+	'B':      true,
+	'C':      true,
+	'D':      true,
+	'E':      true,
+	'F':      true,
+	'G':      true,
+	'H':      true,
+	'I':      true,
+	'J':      true,
+	'K':      true,
+	'L':      true,
+	'M':      true,
+	'N':      true,
+	'O':      true,
+	'P':      true,
+	'Q':      true,
+	'R':      true,
+	'S':      true,
+	'T':      true,
+	'U':      true,
+	'V':      true,
+	'W':      true,
+	'X':      true,
+	'Y':      true,
+	'Z':      true,
+	'[':      true,
+	'\\':     false,
+	']':      true,
+	'^':      true,
+	'_':      true,
+	'`':      true,
+	'a':      true,
+	'b':      true,
+	'c':      true,
+	'd':      true,
+	'e':      true,
+	'f':      true,
+	'g':      true,
+	'h':      true,
+	'i':      true,
+	'j':      true,
+	'k':      true,
+	'l':      true,
+	'm':      true,
+	'n':      true,
+	'o':      true,
+	'p':      true,
+	'q':      true,
+	'r':      true,
+	's':      true,
+	't':      true,
+	'u':      true,
+	'v':      true,
+	'w':      true,
+	'x':      true,
+	'y':      true,
+	'z':      true,
+	'{':      true,
+	'|':      true,
+	'}':      true,
+	'~':      true,
+	'\u007f': true,
+}
+
+// htmlSafeSet holds the value true if the ASCII character with the given
+// array position can be safely represented inside a JSON string, embedded
+// inside of HTML <script> tags, without any additional escaping.
+//
+// All values are true except for the ASCII control characters (0-31), the
+// double quote ("), the backslash character ("\"), HTML opening and closing
+// tags ("<" and ">"), and the ampersand ("&").
+var htmlSafeSet = [utf8.RuneSelf]bool{
+	' ':      true,
+	'!':      true,
+	'"':      false,
+	'#':      true,
+	'$':      true,
+	'%':      true,
+	'&':      false,
+	'\'':     true,
+	'(':      true,
+	')':      true,
+	'*':      true,
+	'+':      true,
+	',':      true,
+	'-':      true,
+	'.':      true,
+	'/':      true,
+	'0':      true,
+	'1':      true,
+	'2':      true,
+	'3':      true,
+	'4':      true,
+	'5':      true,
+	'6':      true,
+	'7':      true,
+	'8':      true,
+	'9':      true,
+	':':      true,
+	';':      true,
+	'<':      false,
+	'=':      true,
+	'>':      false,
+	'?':      true,
+	'@':      true,
+	'A':      true,
+	'B':      true,
+	'C':      true,
+	'D':      true,
+	'E':      true,
+	'F':      true,
+	'G':      true,
+	'H':      true,
+	'I':      true,
+	'J':      true,
+	'K':      true,
+	'L':      true,
+	'M':      true,
+	'N':      true,
+	'O':      true,
+	'P':      true,
+	'Q':      true,
+	'R':      true,
+	'S':      true,
+	'T':      true,
+	'U':      true,
+	'V':      true,
+	'W':      true,
+	'X':      true,
+	'Y':      true,
+	'Z':      true,
+	'[':      true,
+	'\\':     false,
+	']':      true,
+	'^':      true,
+	'_':      true,
+	'`':      true,
+	'a':      true,
+	'b':      true,
+	'c':      true,
+	'd':      true,
+	'e':      true,
+	'f':      true,
+	'g':      true,
+	'h':      true,
+	'i':      true,
+	'j':      true,
+	'k':      true,
+	'l':      true,
+	'm':      true,
+	'n':      true,
+	'o':      true,
+	'p':      true,
+	'q':      true,
+	'r':      true,
+	's':      true,
+	't':      true,
+	'u':      true,
+	'v':      true,
+	'w':      true,
+	'x':      true,
+	'y':      true,
+	'z':      true,
+	'{':      true,
+	'|':      true,
+	'}':      true,
+	'~':      true,
+	'\u007f': true,
+}

gojson/tagkey_test.go

@@ -0,0 +1,120 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"testing"
+)
+
+type basicLatin2xTag struct {
+	V string `json:"$%-/"`
+}
+
+type basicLatin3xTag struct {
+	V string `json:"0123456789"`
+}
+
+type basicLatin4xTag struct {
+	V string `json:"ABCDEFGHIJKLMO"`
+}
+
+type basicLatin5xTag struct {
+	V string `json:"PQRSTUVWXYZ_"`
+}
+
+type basicLatin6xTag struct {
+	V string `json:"abcdefghijklmno"`
+}
+
+type basicLatin7xTag struct {
+	V string `json:"pqrstuvwxyz"`
+}
+
+type miscPlaneTag struct {
+	V string `json:"色は匂へど"`
+}
+
+type percentSlashTag struct {
+	V string `json:"text/html%"` // https://golang.org/issue/2718
+}
+
+type punctuationTag struct {
+	V string `json:"!#$%&()*+-./:;<=>?@[]^_{|}~ "` // https://golang.org/issue/3546
+}
+
+type dashTag struct {
+	V string `json:"-,"`
+}
+
+type emptyTag struct {
+	W string
+}
+
+type misnamedTag struct {
+	X string `jsom:"Misnamed"`
+}
+
+type badFormatTag struct {
+	Y string `:"BadFormat"`
+}
+
+type badCodeTag struct {
+	Z string `json:" !\"#&'()*+,."`
+}
+
+type spaceTag struct {
+	Q string `json:"With space"`
+}
+
+type unicodeTag struct {
+	W string `json:"Ελλάδα"`
+}
+
+var structTagObjectKeyTests = []struct {
+	raw   any
+	value string
+	key   string
+}{
+	{basicLatin2xTag{"2x"}, "2x", "$%-/"},
+	{basicLatin3xTag{"3x"}, "3x", "0123456789"},
+	{basicLatin4xTag{"4x"}, "4x", "ABCDEFGHIJKLMO"},
+	{basicLatin5xTag{"5x"}, "5x", "PQRSTUVWXYZ_"},
+	{basicLatin6xTag{"6x"}, "6x", "abcdefghijklmno"},
+	{basicLatin7xTag{"7x"}, "7x", "pqrstuvwxyz"},
+	{miscPlaneTag{"いろはにほへと"}, "いろはにほへと", "色は匂へど"},
+	{dashTag{"foo"}, "foo", "-"},
+	{emptyTag{"Pour Moi"}, "Pour Moi", "W"},
+	{misnamedTag{"Animal Kingdom"}, "Animal Kingdom", "X"},
+	{badFormatTag{"Orfevre"}, "Orfevre", "Y"},
+	{badCodeTag{"Reliable Man"}, "Reliable Man", "Z"},
+	{percentSlashTag{"brut"}, "brut", "text/html%"},
+	{punctuationTag{"Union Rags"}, "Union Rags", "!#$%&()*+-./:;<=>?@[]^_{|}~ "},
+	{spaceTag{"Perreddu"}, "Perreddu", "With space"},
+	{unicodeTag{"Loukanikos"}, "Loukanikos", "Ελλάδα"},
+}
+
+func TestStructTagObjectKey(t *testing.T) {
+	for _, tt := range structTagObjectKeyTests {
+		b, err := Marshal(tt.raw)
+		if err != nil {
+			t.Fatalf("Marshal(%#q) failed: %v", tt.raw, err)
+		}
+		var f any
+		err = Unmarshal(b, &f)
+		if err != nil {
+			t.Fatalf("Unmarshal(%#q) failed: %v", b, err)
+		}
+		for i, v := range f.(map[string]any) {
+			switch i {
+			case tt.key:
+				if s, ok := v.(string); !ok || s != tt.value {
+					t.Fatalf("Unexpected value: %#q, want %v", s, tt.value)
+				}
+			default:
+				t.Fatalf("Unexpected key: %#q, from %#q", i, b)
+			}
+		}
+	}
+}

gojson/tags.go

@@ -0,0 +1,38 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"strings"
+)
+
+// tagOptions is the string following a comma in a struct field's "json"
+// tag, or the empty string. It does not include the leading comma.
+type tagOptions string
+
+// parseTag splits a struct field's json tag into its name and
+// comma-separated options.
+func parseTag(tag string) (string, tagOptions) {
+	tag, opt, _ := strings.Cut(tag, ",")
+	return tag, tagOptions(opt)
+}
+
+// Contains reports whether a comma-separated list of options
+// contains a particular substr flag. substr must be surrounded by a
+// string boundary or commas.
+func (o tagOptions) Contains(optionName string) bool {
+	if len(o) == 0 {
+		return false
+	}
+	s := string(o)
+	for s != "" {
+		var name string
+		name, s, _ = strings.Cut(s, ",")
+		if name == optionName {
+			return true
+		}
+	}
+	return false
+}

gojson/tags_test.go

@@ -0,0 +1,28 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"testing"
+)
+
+func TestTagParsing(t *testing.T) {
+	name, opts := parseTag("field,foobar,foo")
+	if name != "field" {
+		t.Fatalf("name = %q, want field", name)
+	}
+	for _, tt := range []struct {
+		opt  string
+		want bool
+	}{
+		{"foobar", true},
+		{"foo", true},
+		{"bar", false},
+	} {
+		if opts.Contains(tt.opt) != tt.want {
+			t.Errorf("Contains(%q) = %v", tt.opt, !tt.want)
+		}
+	}
+}

langext/array.go

@@ -1,6 +1,8 @@
 package langext
 
 import (
+	"errors"
+	"fmt"
 	"reflect"
 )
 
@@ -217,6 +219,15 @@ func ArrFirst[T any](arr []T, comp func(v T) bool) (T, bool) {
 	return *new(T), false
 }
 
+func ArrFirstOrNil[T any](arr []T, comp func(v T) bool) *T {
+	for _, v := range arr {
+		if comp(v) {
+			return Ptr(v)
+		}
+	}
+	return nil
+}
+
 func ArrLast[T any](arr []T, comp func(v T) bool) (T, bool) {
 	found := false
 	result := *new(T)
@@ -229,6 +240,22 @@ func ArrLast[T any](arr []T, comp func(v T) bool) (T, bool) {
 	return result, found
 }
 
+func ArrLastOrNil[T any](arr []T, comp func(v T) bool) *T {
+	found := false
+	result := *new(T)
+	for _, v := range arr {
+		if comp(v) {
+			found = true
+			result = v
+		}
+	}
+	if found {
+		return Ptr(result)
+	} else {
+		return nil
+	}
+}
+
 func ArrFirstIndex[T comparable](arr []T, needle T) int {
 	for i, v := range arr {
 		if v == needle {
@@ -265,6 +292,26 @@ func ArrMap[T1 any, T2 any](arr []T1, conv func(v T1) T2) []T2 {
 	return r
 }
 
+func MapMap[TK comparable, TV any, TR any](inmap map[TK]TV, conv func(k TK, v TV) TR) []TR {
+	r := make([]TR, 0, len(inmap))
+	for k, v := range inmap {
+		r = append(r, conv(k, v))
+	}
+	return r
+}
+
+func MapMapErr[TK comparable, TV any, TR any](inmap map[TK]TV, conv func(k TK, v TV) (TR, error)) ([]TR, error) {
+	r := make([]TR, 0, len(inmap))
+	for k, v := range inmap {
+		elem, err := conv(k, v)
+		if err != nil {
+			return nil, err
+		}
+		r = append(r, elem)
+	}
+	return r, nil
+}
+
 func ArrMapExt[T1 any, T2 any](arr []T1, conv func(idx int, v T1) T2) []T2 {
 	r := make([]T2, len(arr))
 	for i, v := range arr {
@@ -295,6 +342,16 @@ func ArrFilterMap[T1 any, T2 any](arr []T1, filter func(v T1) bool, conv func(v
 	return r
 }
 
+func ArrFilter[T any](arr []T, filter func(v T) bool) []T {
+	r := make([]T, 0, len(arr))
+	for _, v := range arr {
+		if filter(v) {
+			r = append(r, v)
+		}
+	}
+	return r
+}
+
 func ArrSum[T NumberConstraint](arr []T) T {
 	var r T = 0
 	for _, v := range arr {
@@ -318,3 +375,68 @@ func ArrFlattenDirect[T1 any](arr [][]T1) []T1 {
 	}
 	return r
 }
+
+func ArrCastToAny[T1 any](arr []T1) []any {
+	r := make([]any, len(arr))
+	for i, v := range arr {
+		r[i] = any(v)
+	}
+	return r
+}
+
+func ArrCastSafe[T1 any, T2 any](arr []T1) []T2 {
+	r := make([]T2, 0, len(arr))
+	for _, v := range arr {
+		if vcast, ok := any(v).(T2); ok {
+			r = append(r, vcast)
+		}
+	}
+	return r
+}
+
+func ArrCastErr[T1 any, T2 any](arr []T1) ([]T2, error) {
+	r := make([]T2, len(arr))
+	for i, v := range arr {
+		if vcast, ok := any(v).(T2); ok {
+			r[i] = vcast
+		} else {
+			return nil, errors.New(fmt.Sprintf("Cannot cast element %d of type %T to type %s", i, v, *new(T2)))
+		}
+	}
+	return r, nil
+}
+
+func ArrCastPanic[T1 any, T2 any](arr []T1) []T2 {
+	r := make([]T2, len(arr))
+	for i, v := range arr {
+		if vcast, ok := any(v).(T2); ok {
+			r[i] = vcast
+		} else {
+			panic(fmt.Sprintf("Cannot cast element %d of type %T to type %s", i, v, *new(T2)))
+		}
+	}
+	return r
+}
+
+func ArrConcat[T any](arr ...[]T) []T {
+	c := 0
+	for _, v := range arr {
+		c += len(v)
+	}
+	r := make([]T, c)
+	i := 0
+	for _, av := range arr {
+		for _, v := range av {
+			r[i] = v
+			i++
+		}
+	}
+	return r
+}
+
+// ArrCopy does a shallow copy of the 'in' array
+func ArrCopy[T any](in []T) []T {
+	out := make([]T, len(in))
+	copy(out, in)
+	return out
+}

langext/base58.go

@@ -0,0 +1,178 @@
+package langext
+
+import (
+	"bytes"
+	"errors"
+	"math/big"
+)
+
+// shamelessly stolen from https://github.com/btcsuite/
+
+type B58Encoding struct {
+	bigRadix     [11]*big.Int
+	bigRadix10   *big.Int
+	alphabet     string
+	alphabetIdx0 byte
+	b58          [256]byte
+}
+
+var Base58DefaultEncoding = newBase58Encoding("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
+var Base58FlickrEncoding = newBase58Encoding("123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ")
+var Base58RippleEncoding = newBase58Encoding("rpshnaf39wBUDNEGHJKLM4PQRST7VWXYZ2bcdeCg65jkm8oFqi1tuvAxyz")
+var Base58BitcoinEncoding = newBase58Encoding("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
+
+func newBase58Encoding(alphabet string) *B58Encoding {
+	bigRadix10 := big.NewInt(58 * 58 * 58 * 58 * 58 * 58 * 58 * 58 * 58 * 58)
+	enc := &B58Encoding{
+		alphabet:     alphabet,
+		alphabetIdx0: '1',
+		bigRadix: [...]*big.Int{
+			big.NewInt(0),
+			big.NewInt(58),
+			big.NewInt(58 * 58),
+			big.NewInt(58 * 58 * 58),
+			big.NewInt(58 * 58 * 58 * 58),
+			big.NewInt(58 * 58 * 58 * 58 * 58),
+			big.NewInt(58 * 58 * 58 * 58 * 58 * 58),
+			big.NewInt(58 * 58 * 58 * 58 * 58 * 58 * 58),
+			big.NewInt(58 * 58 * 58 * 58 * 58 * 58 * 58 * 58),
+			big.NewInt(58 * 58 * 58 * 58 * 58 * 58 * 58 * 58 * 58),
+			bigRadix10,
+		},
+		bigRadix10: bigRadix10,
+	}
+
+	b58 := make([]byte, 0, 256)
+
+	for i := byte(0); i < 32; i++ {
+		for j := byte(0); j < 8; j++ {
+
+			b := i*8 + j
+
+			idx := bytes.IndexByte([]byte(alphabet), b)
+			if idx == -1 {
+				b58 = append(b58, 255)
+			} else {
+				b58 = append(b58, byte(idx))
+			}
+
+		}
+	}
+
+	enc.b58 = *((*[256]byte)(b58))
+
+	return enc
+}
+
+func (enc *B58Encoding) EncodeString(src string) (string, error) {
+	v, err := enc.Encode([]byte(src))
+	if err != nil {
+		return "", err
+	}
+	return string(v), nil
+}
+
+func (enc *B58Encoding) Encode(src []byte) ([]byte, error) {
+	x := new(big.Int)
+	x.SetBytes(src)
+
+	// maximum length of output is log58(2^(8*len(b))) == len(b) * 8 / log(58)
+	maxlen := int(float64(len(src))*1.365658237309761) + 1
+	answer := make([]byte, 0, maxlen)
+	mod := new(big.Int)
+	for x.Sign() > 0 {
+		// Calculating with big.Int is slow for each iteration.
+		//    x, mod = x / 58, x % 58
+		//
+		// Instead we can try to do as much calculations on int64.
+		//    x, mod = x / 58^10, x % 58^10
+		//
+		// Which will give us mod, which is 10 digit base58 number.
+		// We'll loop that 10 times to convert to the answer.
+
+		x.DivMod(x, enc.bigRadix10, mod)
+		if x.Sign() == 0 {
+			// When x = 0, we need to ensure we don't add any extra zeros.
+			m := mod.Int64()
+			for m > 0 {
+				answer = append(answer, enc.alphabet[m%58])
+				m /= 58
+			}
+		} else {
+			m := mod.Int64()
+			for i := 0; i < 10; i++ {
+				answer = append(answer, enc.alphabet[m%58])
+				m /= 58
+			}
+		}
+	}
+
+	// leading zero bytes
+	for _, i := range src {
+		if i != 0 {
+			break
+		}
+		answer = append(answer, enc.alphabetIdx0)
+	}
+
+	// reverse
+	alen := len(answer)
+	for i := 0; i < alen/2; i++ {
+		answer[i], answer[alen-1-i] = answer[alen-1-i], answer[i]
+	}
+
+	return answer, nil
+}
+
+func (enc *B58Encoding) DecodeString(src string) (string, error) {
+	v, err := enc.Decode([]byte(src))
+	if err != nil {
+		return "", err
+	}
+	return string(v), nil
+}
+
+func (enc *B58Encoding) Decode(src []byte) ([]byte, error) {
+	answer := big.NewInt(0)
+	scratch := new(big.Int)
+
+	for t := src; len(t) > 0; {
+		n := len(t)
+		if n > 10 {
+			n = 10
+		}
+
+		total := uint64(0)
+		for _, v := range t[:n] {
+			if v > 255 {
+				return []byte{}, errors.New("invalid char in input")
+			}
+
+			tmp := enc.b58[v]
+			if tmp == 255 {
+				return []byte{}, errors.New("invalid char in input")
+			}
+			total = total*58 + uint64(tmp)
+		}
+
+		answer.Mul(answer, enc.bigRadix[n])
+		scratch.SetUint64(total)
+		answer.Add(answer, scratch)
+
+		t = t[n:]
+	}
+
+	tmpval := answer.Bytes()
+
+	var numZeros int
+	for numZeros = 0; numZeros < len(src); numZeros++ {
+		if src[numZeros] != enc.alphabetIdx0 {
+			break
+		}
+	}
+	flen := numZeros + len(tmpval)
+	val := make([]byte, flen)
+	copy(val[numZeros:], tmpval)
+
+	return val, nil
+}

langext/base58_test.go

@@ -0,0 +1,67 @@
+package langext
+
+import (
+	"testing"
+)
+
+func _encStr(t *testing.T, enc *B58Encoding, v string) string {
+	v, err := enc.EncodeString(v)
+	if err != nil {
+		t.Error(err)
+	}
+	return v
+}
+
+func _decStr(t *testing.T, enc *B58Encoding, v string) string {
+	v, err := enc.DecodeString(v)
+	if err != nil {
+		t.Error(err)
+	}
+	return v
+}
+
+func TestBase58DefaultEncoding(t *testing.T) {
+	tst.AssertEqual(t, _encStr(t, Base58DefaultEncoding, "Hello"), "9Ajdvzr")
+	tst.AssertEqual(t, _encStr(t, Base58DefaultEncoding, "If debugging is the process of removing software bugs, then programming must be the process of putting them in."), "48638SMcJuah5okqPx4kCVf5d8QAdgbdNf28g7ReY13prUENNbMyssjq5GjsrJHF5zeZfqs4uJMUJHr7VbrU4XBUZ2Fw9DVtqtn9N1eXucEWSEZahXV6w4ysGSWqGdpeYTJf1MdDzTg8vfcQViifJjZX")
+}
+
+func TestBase58DefaultDecoding(t *testing.T) {
+	tst.AssertEqual(t, _decStr(t, Base58DefaultEncoding, "9Ajdvzr"), "Hello")
+	tst.AssertEqual(t, _decStr(t, Base58DefaultEncoding, "48638SMcJuah5okqPx4kCVf5d8QAdgbdNf28g7ReY13prUENNbMyssjq5GjsrJHF5zeZfqs4uJMUJHr7VbrU4XBUZ2Fw9DVtqtn9N1eXucEWSEZahXV6w4ysGSWqGdpeYTJf1MdDzTg8vfcQViifJjZX"), "If debugging is the process of removing software bugs, then programming must be the process of putting them in.")
+}
+
+func TestBase58RippleEncoding(t *testing.T) {
+	tst.AssertEqual(t, _encStr(t, Base58RippleEncoding, "Hello"), "9wjdvzi")
+	tst.AssertEqual(t, _encStr(t, Base58RippleEncoding, "If debugging is the process of removing software bugs, then programming must be the process of putting them in."), "h3as3SMcJu26nokqPxhkUVCnd3Qwdgbd4Cp3gfReYrsFi7N44bMy11jqnGj1iJHEnzeZCq1huJM7JHifVbi7hXB7ZpEA9DVtqt894reXucNWSNZ26XVaAhy1GSWqGdFeYTJCrMdDzTg3vCcQV55CJjZX")
+}
+
+func TestBase58RippleDecoding(t *testing.T) {
+	tst.AssertEqual(t, _decStr(t, Base58RippleEncoding, "9wjdvzi"), "Hello")
+	tst.AssertEqual(t, _decStr(t, Base58RippleEncoding, "h3as3SMcJu26nokqPxhkUVCnd3Qwdgbd4Cp3gfReYrsFi7N44bMy11jqnGj1iJHEnzeZCq1huJM7JHifVbi7hXB7ZpEA9DVtqt894reXucNWSNZ26XVaAhy1GSWqGdFeYTJCrMdDzTg3vCcQV55CJjZX"), "If debugging is the process of removing software bugs, then programming must be the process of putting them in.")
+}
+
+func TestBase58BitcoinEncoding(t *testing.T) {
+	tst.AssertEqual(t, _encStr(t, Base58BitcoinEncoding, "Hello"), "9Ajdvzr")
+	tst.AssertEqual(t, _encStr(t, Base58BitcoinEncoding, "If debugging is the process of removing software bugs, then programming must be the process of putting them in."), "48638SMcJuah5okqPx4kCVf5d8QAdgbdNf28g7ReY13prUENNbMyssjq5GjsrJHF5zeZfqs4uJMUJHr7VbrU4XBUZ2Fw9DVtqtn9N1eXucEWSEZahXV6w4ysGSWqGdpeYTJf1MdDzTg8vfcQViifJjZX")
+}
+
+func TestBase58BitcoinDecoding(t *testing.T) {
+	tst.AssertEqual(t, _decStr(t, Base58BitcoinEncoding, "9Ajdvzr"), "Hello")
+	tst.AssertEqual(t, _decStr(t, Base58BitcoinEncoding, "48638SMcJuah5okqPx4kCVf5d8QAdgbdNf28g7ReY13prUENNbMyssjq5GjsrJHF5zeZfqs4uJMUJHr7VbrU4XBUZ2Fw9DVtqtn9N1eXucEWSEZahXV6w4ysGSWqGdpeYTJf1MdDzTg8vfcQViifJjZX"), "If debugging is the process of removing software bugs, then programming must be the process of putting them in.")
+}
+
+func TestBase58FlickrEncoding(t *testing.T) {
+	tst.AssertEqual(t, _encStr(t, Base58FlickrEncoding, "Hello"), "9aJCVZR")
+	tst.AssertEqual(t, _encStr(t, Base58FlickrEncoding, "If debugging is the process of removing software bugs, then programming must be the process of putting them in."), "48638rmBiUzG5NKQoX4KcuE5C8paCFACnE28F7qDx13PRtennAmYSSJQ5gJSRihf5ZDyEQS4UimtihR7uARt4wbty2fW9duTQTM9n1DwUBevreyzGwu6W4YSgrvQgCPDxsiE1mCdZsF8VEBpuHHEiJyw")
+}
+
+func TestBase58FlickrDecoding(t *testing.T) {
+	tst.AssertEqual(t, _decStr(t, Base58FlickrEncoding, "9aJCVZR"), "Hello")
+	tst.AssertEqual(t, _decStr(t, Base58FlickrEncoding, "48638rmBiUzG5NKQoX4KcuE5C8paCFACnE28F7qDx13PRtennAmYSSJQ5gJSRihf5ZDyEQS4UimtihR7uARt4wbty2fW9duTQTM9n1DwUBevreyzGwu6W4YSgrvQgCPDxsiE1mCdZsF8VEBpuHHEiJyw"), "If debugging is the process of removing software bugs, then programming must be the process of putting them in.")
+}
+
+func tst.AssertEqual(t *testing.T, actual string, expected string) {
+	if actual != expected {
+		t.Errorf("values differ: Actual: '%v', Expected: '%v'", actual, expected)
+	}
+}

langext/coalesce.go

@@ -60,3 +60,12 @@ func CoalesceStringer(s fmt.Stringer, def string) string {
 		return s.String()
 	}
 }
+
+func SafeCast[T any](v any, def T) T {
+	switch r := v.(type) {
+	case T:
+		return r
+	default:
+		return def
+	}
+}

langext/compare.go

@@ -31,16 +31,16 @@ func CompareIntArr(arr1 []int, arr2 []int) bool {
 	return false
 }
 
-func CompareArr[T OrderedConstraint](arr1 []T, arr2 []T) bool {
+func CompareArr[T OrderedConstraint](arr1 []T, arr2 []T) int {
 
 	for i := 0; i < len(arr1) || i < len(arr2); i++ {
 
 		if i < len(arr1) && i < len(arr2) {
 
 			if arr1[i] < arr2[i] {
-				return true
+				return -1
 			} else if arr1[i] > arr2[i] {
-				return false
+				return +2
 			} else {
 				continue
 			}
@@ -49,15 +49,55 @@ func CompareArr[T OrderedConstraint](arr1 []T, arr2 []T) bool {
 
 		if i < len(arr1) {
 
-			return true
+			return +1
 
 		} else { // if i < len(arr2)
 
-			return false
+			return -1
 
 		}
 
 	}
 
-	return false
+	return 0
+}
+
+func CompareString(a, b string) int {
+	if a == b {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return +1
+}
+
+func CompareInt(a, b int) int {
+	if a == b {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return +1
+}
+
+func CompareInt64(a, b int64) int {
+	if a == b {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return +1
+}
+
+func Compare[T OrderedConstraint](a, b T) int {
+	if a == b {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return +1
 }

langext/maps.go

@@ -1,5 +1,10 @@
 package langext
 
+type MapEntry[T comparable, V any] struct {
+	Key   T
+	Value V
+}
+
 func MapKeyArr[T comparable, V any](v map[T]V) []T {
 	result := make([]T, 0, len(v))
 	for k := range v {
@@ -8,6 +13,14 @@ func MapKeyArr[T comparable, V any](v map[T]V) []T {
 	return result
 }
 
+func MapValueArr[T comparable, V any](v map[T]V) []V {
+	result := make([]V, 0, len(v))
+	for _, mv := range v {
+		result = append(result, mv)
+	}
+	return result
+}
+
 func ArrToMap[T comparable, V any](a []V, keyfunc func(V) T) map[T]V {
 	result := make(map[T]V, len(a))
 	for _, v := range a {
@@ -15,3 +28,30 @@ func ArrToMap[T comparable, V any](a []V, keyfunc func(V) T) map[T]V {
 	}
 	return result
 }
+
+func MapToArr[T comparable, V any](v map[T]V) []MapEntry[T, V] {
+	result := make([]MapEntry[T, V], 0, len(v))
+	for mk, mv := range v {
+		result = append(result, MapEntry[T, V]{
+			Key:   mk,
+			Value: mv,
+		})
+	}
+	return result
+}
+
+func CopyMap[K comparable, V any](a map[K]V) map[K]V {
+	result := make(map[K]V, len(a))
+	for k, v := range a {
+		result[k] = v
+	}
+	return result
+}
+
+func ForceMap[K comparable, V any](v map[K]V) map[K]V {
+	if v == nil {
+		return make(map[K]V, 0)
+	} else {
+		return v
+	}
+}

langext/panic.go

@@ -0,0 +1,71 @@
+package langext
+
+type PanicWrappedErr struct {
+	panic any
+}
+
+func (p PanicWrappedErr) Error() string {
+	return "A panic occured"
+}
+
+func (p PanicWrappedErr) ReoveredObj() any {
+	return p.panic
+}
+
+func RunPanicSafe(fn func()) (err error) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			err = PanicWrappedErr{panic: rec}
+		}
+	}()
+
+	fn()
+
+	return nil
+}
+
+func RunPanicSafeR1(fn func() error) (err error) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			err = PanicWrappedErr{panic: rec}
+		}
+	}()
+
+	return fn()
+}
+
+func RunPanicSafeR2[T1 any](fn func() (T1, error)) (r1 T1, err error) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			r1 = *new(T1)
+			err = PanicWrappedErr{panic: rec}
+		}
+	}()
+
+	return fn()
+}
+
+func RunPanicSafeR3[T1 any, T2 any](fn func() (T1, T2, error)) (r1 T1, r2 T2, err error) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			r1 = *new(T1)
+			r2 = *new(T2)
+			err = PanicWrappedErr{panic: rec}
+		}
+	}()
+
+	return fn()
+}
+
+func RunPanicSafeR4[T1 any, T2 any, T3 any](fn func() (T1, T2, T3, error)) (r1 T1, r2 T2, r3 T3, err error) {
+	defer func() {
+		if rec := recover(); rec != nil {
+			r1 = *new(T1)
+			r2 = *new(T2)
+			r3 = *new(T3)
+			err = PanicWrappedErr{panic: rec}
+		}
+	}()
+
+	return fn()
+}

langext/pointer.go

@@ -4,6 +4,12 @@ import (
 	"reflect"
 )
 
+// PTrue := &true
+var PTrue = Ptr(true)
+
+// PFalse := &false
+var PFalse = Ptr(false)
+
 func Ptr[T any](v T) *T {
 	return &v
 }

langext/uuid.go

@@ -41,6 +41,14 @@ func NewHexUUID() (string, error) {
 	return string(dst), nil
 }
 
+func MustHexUUID() string {
+	v, err := NewHexUUID()
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
 func NewUpperHexUUID() (string, error) {
 	uuid, err := NewUUID()
 	if err != nil {
@@ -64,6 +72,14 @@ func NewUpperHexUUID() (string, error) {
 	return strings.ToUpper(string(dst)), nil
 }
 
+func MustUpperHexUUID() string {
+	v, err := NewUpperHexUUID()
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
 func NewRawHexUUID() (string, error) {
 	uuid, err := NewUUID()
 	if err != nil {
@@ -83,6 +99,14 @@ func NewRawHexUUID() (string, error) {
 	return strings.ToUpper(string(dst)), nil
 }
 
+func MustRawHexUUID() string {
+	v, err := NewRawHexUUID()
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
 func NewBracesUUID() (string, error) {
 	uuid, err := NewUUID()
 	if err != nil {
@@ -108,6 +132,14 @@ func NewBracesUUID() (string, error) {
 	return strings.ToUpper(string(dst)), nil
 }
 
+func MustBracesUUID() string {
+	v, err := NewBracesUUID()
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
 func NewParensUUID() (string, error) {
 	uuid, err := NewUUID()
 	if err != nil {
@@ -132,3 +164,11 @@ func NewParensUUID() (string, error) {
 
 	return strings.ToUpper(string(dst)), nil
 }
+
+func MustParensUUID() string {
+	v, err := NewParensUUID()
+	if err != nil {
+		panic(err)
+	}
+	return v
+}

mathext/math.go

@@ -22,6 +22,31 @@ func Max[T langext.OrderedConstraint](v1 T, v2 T) T {
 	}
 }
 
+func Max3[T langext.OrderedConstraint](v1 T, v2 T, v3 T) T {
+	result := v1
+	if v2 > result {
+		result = v2
+	}
+	if v3 > result {
+		result = v3
+	}
+	return result
+}
+
+func Max4[T langext.OrderedConstraint](v1 T, v2 T, v3 T, v4 T) T {
+	result := v1
+	if v2 > result {
+		result = v2
+	}
+	if v3 > result {
+		result = v3
+	}
+	if v4 > result {
+		result = v4
+	}
+	return result
+}
+
 func Min[T langext.OrderedConstraint](v1 T, v2 T) T {
 	if v1 < v2 {
 		return v1
@@ -30,6 +55,31 @@ func Min[T langext.OrderedConstraint](v1 T, v2 T) T {
 	}
 }
 
+func Min3[T langext.OrderedConstraint](v1 T, v2 T, v3 T) T {
+	result := v1
+	if v2 < result {
+		result = v2
+	}
+	if v3 < result {
+		result = v3
+	}
+	return result
+}
+
+func Min4[T langext.OrderedConstraint](v1 T, v2 T, v3 T, v4 T) T {
+	result := v1
+	if v2 < result {
+		result = v2
+	}
+	if v3 < result {
+		result = v3
+	}
+	if v4 < result {
+		result = v4
+	}
+	return result
+}
+
 func Abs[T langext.NumberConstraint](v T) T {
 	if v < 0 {
 		return -v

mongo/.errcheck-excludes

@@ -0,0 +1,16 @@
+(go.mongodb.org/mongo-driver/x/mongo/driver.Connection).Close
+(*go.mongodb.org/mongo-driver/x/network/connection.connection).Close
+(go.mongodb.org/mongo-driver/x/network/connection.Connection).Close
+(*go.mongodb.org/mongo-driver/x/mongo/driver/topology.connection).close
+(*go.mongodb.org/mongo-driver/x/mongo/driver/topology.Topology).Unsubscribe
+(*go.mongodb.org/mongo-driver/x/mongo/driver/topology.Server).Close
+(*go.mongodb.org/mongo-driver/x/network/connection.pool).closeConnection
+(*go.mongodb.org/mongo-driver/x/mongo/driver/topology.pool).close
+(go.mongodb.org/mongo-driver/x/network/wiremessage.ReadWriteCloser).Close
+(*go.mongodb.org/mongo-driver/mongo.Cursor).Close
+(*go.mongodb.org/mongo-driver/mongo.ChangeStream).Close
+(*go.mongodb.org/mongo-driver/mongo.Client).Disconnect
+(net.Conn).Close
+encoding/pem.Encode
+fmt.Fprintf
+fmt.Fprint

mongo/.gitignore

@@ -0,0 +1,13 @@
+.vscode
+debug
+.idea
+*.iml
+*.ipr
+*.iws
+.idea
+*.sublime-project
+*.sublime-workspace
+driver-test-data.tar.gz
+perf
+**mongocryptd.pid
+*.test

mongo/.gitmodules

@@ -0,0 +1,3 @@
+[submodule "specifications"]
+	path = specifications
+	url = git@github.com:mongodb/specifications.git

mongo/.golangci.yml

@@ -0,0 +1,123 @@
+run:
+  timeout: 5m
+
+linters:
+  disable-all: true
+  # TODO(GODRIVER-2156): Enable all commented-out linters.
+  enable:
+    - errcheck
+    # - errorlint
+    - gocritic
+    - goimports
+    - gosimple
+    - gosec
+    - govet
+    - ineffassign
+    - makezero
+    - misspell
+    - nakedret
+    - paralleltest
+    - prealloc
+    - revive
+    - staticcheck
+    - typecheck
+    - unused
+    - unconvert
+    - unparam
+
+linters-settings:
+  errcheck:
+    exclude: .errcheck-excludes
+  gocritic:
+    enabled-checks:
+      # Detects suspicious append result assignments. E.g. "b := append(a, 1, 2, 3)"
+      - appendAssign
+  govet:
+    disable:
+      - cgocall
+      - composites
+  paralleltest:
+    # Ignore missing calls to `t.Parallel()` and only report incorrect uses of `t.Parallel()`.
+    ignore-missing: true
+  staticcheck:
+    checks: [
+      "all",
+      "-SA1019", # Disable deprecation warnings for now.
+      "-SA1012", # Disable "do not pass a nil Context" to allow testing nil contexts in tests.
+    ]
+
+issues:
+  exclude-use-default: false
+  exclude:
+    # Add all default excluded issues except issues related to exported types/functions not having
+    # comments; we want those warnings. The defaults are copied from the "--exclude-use-default"
+    # documentation on https://golangci-lint.run/usage/configuration/#command-line-options
+    ## Defaults ##
+    # EXC0001 errcheck: Almost all programs ignore errors on these functions and in most cases it's ok
+    - Error return value of .((os\.)?std(out|err)\..*|.*Close|.*Flush|os\.Remove(All)?|.*print(f|ln)?|os\.(Un)?Setenv). is not checked
+    # EXC0003 golint: False positive when tests are defined in package 'test'
+    - func name will be used as test\.Test.* by other packages, and that stutters; consider calling this
+    # EXC0004 govet: Common false positives
+    - (possible misuse of unsafe.Pointer|should have signature)
+    # EXC0005 staticcheck: Developers tend to write in C-style with an explicit 'break' in a 'switch', so it's ok to ignore
+    - ineffective break statement. Did you mean to break out of the outer loop
+    # EXC0006 gosec: Too many false-positives on 'unsafe' usage
+    - Use of unsafe calls should be audited
+    # EXC0007 gosec: Too many false-positives for parametrized shell calls
+    - Subprocess launch(ed with variable|ing should be audited)
+    # EXC0008 gosec: Duplicated errcheck checks
+    - (G104|G307)
+    # EXC0009 gosec: Too many issues in popular repos
+    - (Expect directory permissions to be 0750 or less|Expect file permissions to be 0600 or less)
+    # EXC0010 gosec: False positive is triggered by 'src, err := ioutil.ReadFile(filename)'
+    - Potential file inclusion via variable
+    ## End Defaults ##
+
+    # Ignore capitalization warning for this weird field name.
+    - "var-naming: struct field CqCssWxW should be CqCSSWxW"
+    # Ignore warnings for common "wiremessage.Read..." usage because the safest way to use that API
+    # is by assigning possibly unused returned byte buffers.
+    - "SA4006: this value of `wm` is never used"
+    - "SA4006: this value of `rem` is never used"
+    - "ineffectual assignment to wm"
+    - "ineffectual assignment to rem"
+
+  skip-dirs-use-default: false
+  skip-dirs:
+    - (^|/)vendor($|/)
+    - (^|/)testdata($|/)
+    - (^|/)etc($|/)
+  exclude-rules:
+    # Ignore some linters for example code that is intentionally simplified.
+    - path: examples/
+      linters:
+        - revive
+        - errcheck
+    # Disable unused code linters for the copy/pasted "awsv4" package.
+    - path: x/mongo/driver/auth/internal/awsv4
+      linters:
+        - unused
+    # Disable "unused" linter for code files that depend on the "mongocrypt.MongoCrypt" type because
+    # the linter build doesn't work correctly with CGO enabled. As a result, all calls to a
+    # "mongocrypt.MongoCrypt" API appear to always panic (see mongocrypt_not_enabled.go), leading
+    # to confusing messages about unused code.
+    - path: x/mongo/driver/crypt.go|mongo/(crypt_retrievers|mongocryptd).go
+      linters:
+        - unused
+    # Ignore "TLS MinVersion too low", "TLS InsecureSkipVerify set true", and "Use of weak random
+    # number generator (math/rand instead of crypto/rand)" in tests.
+    - path: _test\.go
+      text: G401|G402|G404
+      linters:
+        - gosec
+    # Ignore missing comments for exported variable/function/type for code in the "internal" and
+    # "benchmark" directories.
+    - path: (internal\/|benchmark\/)
+      text: exported (.+) should have comment( \(or a comment on this block\))? or be unexported
+    # Ignore missing package comments for directories that aren't frequently used by external users.
+    - path: (internal\/|benchmark\/|x\/|cmd\/|mongo\/integration\/)
+      text: should have a package comment
+    # Disable unused linter for "golang.org/x/exp/rand" package in internal/randutil/rand.
+    - path: internal/randutil/rand
+      linters:
+        - unused

mongo/LICENSE

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
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+          notices within Derivative Works that You distribute, alongside
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+      the conditions stated in this License.
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+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
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+      Contributor provides its Contributions) on an "AS IS" BASIS,
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+      whether in tort (including negligence), contract, or otherwise,
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+      negligent acts) or agreed to in writing, shall any Contributor be
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+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
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+   Copyright [yyyy] [name of copyright owner]
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+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

mongo/Makefile

@@ -0,0 +1,210 @@
+ATLAS_URIS = "$(ATLAS_FREE)" "$(ATLAS_REPLSET)" "$(ATLAS_SHARD)" "$(ATLAS_TLS11)" "$(ATLAS_TLS12)" "$(ATLAS_FREE_SRV)" "$(ATLAS_REPLSET_SRV)" "$(ATLAS_SHARD_SRV)" "$(ATLAS_TLS11_SRV)" "$(ATLAS_TLS12_SRV)" "$(ATLAS_SERVERLESS)" "$(ATLAS_SERVERLESS_SRV)"
+TEST_TIMEOUT = 1800
+
+### Utility targets. ###
+.PHONY: default
+default: build check-license check-fmt check-modules lint test-short
+
+.PHONY: add-license
+add-license:
+	etc/check_license.sh -a
+
+.PHONY: check-license
+check-license:
+	etc/check_license.sh
+
+.PHONY: build
+build: cross-compile build-tests build-compile-check
+	go build ./...
+	go build $(BUILD_TAGS) ./...
+
+# Use ^$ to match no tests so that no tests are actually run but all tests are
+# compiled. Run with -short to ensure none of the TestMain functions try to
+# connect to a server.
+.PHONY: build-tests
+build-tests:
+	go test -short $(BUILD_TAGS) -run ^$$ ./...
+
+.PHONY: build-compile-check
+build-compile-check:
+	etc/compile_check.sh
+
+# Cross-compiling on Linux for architectures 386, arm, arm64, amd64, ppc64le, and s390x.
+# Omit any build tags because we don't expect our build environment to support compiling the C
+# libraries for other architectures.
+.PHONY: cross-compile
+cross-compile:
+	GOOS=linux GOARCH=386 go build ./...
+	GOOS=linux GOARCH=arm go build ./...
+	GOOS=linux GOARCH=arm64 go build ./...
+	GOOS=linux GOARCH=amd64 go build ./...
+	GOOS=linux GOARCH=ppc64le go build ./...
+	GOOS=linux GOARCH=s390x go build ./...
+
+.PHONY: install-lll
+install-lll:
+	go install github.com/walle/lll/...@latest
+
+.PHONY: check-fmt
+check-fmt: install-lll
+	etc/check_fmt.sh
+
+# check-modules runs "go mod tidy" then "go mod vendor" and exits with a non-zero exit code if there
+# are any module or vendored modules changes. The intent is to confirm two properties:
+#
+# 1. Exactly the required modules are declared as dependencies. We should always be able to run
+# "go mod tidy" and expect that no unrelated changes are made to the "go.mod" file.
+#
+# 2. All required modules are copied into the vendor/ directory and are an exact copy of the
+# original module source code (i.e. the vendored modules are not modified from their original code).
+.PHONY: check-modules
+check-modules:
+	go mod tidy -v
+	go mod vendor
+	git diff --exit-code go.mod go.sum ./vendor
+
+.PHONY: doc
+doc:
+	godoc -http=:6060 -index
+
+.PHONY: fmt
+fmt:
+	go fmt ./...
+
+.PHONY: install-golangci-lint
+install-golangci-lint:
+	go install github.com/golangci/golangci-lint/cmd/golangci-lint@v1.51.0
+
+# Lint with various GOOS and GOARCH targets to catch static analysis failures that may only affect
+# specific operating systems or architectures. For example, staticcheck will only check for 64-bit
+# alignment of atomically accessed variables on 32-bit architectures (see
+# https://staticcheck.io/docs/checks#SA1027)
+.PHONY: lint
+lint: install-golangci-lint
+	GOOS=linux GOARCH=386 golangci-lint run --config .golangci.yml ./...
+	GOOS=linux GOARCH=arm golangci-lint run --config .golangci.yml ./...
+	GOOS=linux GOARCH=arm64 golangci-lint run --config .golangci.yml ./...
+	GOOS=linux GOARCH=amd64 golangci-lint run --config .golangci.yml ./...
+	GOOS=linux GOARCH=ppc64le golangci-lint run --config .golangci.yml ./...
+	GOOS=linux GOARCH=s390x golangci-lint run --config .golangci.yml ./...
+
+.PHONY: update-notices
+update-notices:
+	etc/generate_notices.pl > THIRD-PARTY-NOTICES
+
+### Local testing targets. ###
+.PHONY: test
+test:
+	go test $(BUILD_TAGS) -timeout $(TEST_TIMEOUT)s -p 1 ./...
+
+.PHONY: test-cover
+test-cover:
+	go test $(BUILD_TAGS) -timeout $(TEST_TIMEOUT)s -cover $(COVER_ARGS) -p 1 ./...
+
+.PHONY: test-race
+test-race:
+	go test $(BUILD_TAGS) -timeout $(TEST_TIMEOUT)s -race -p 1 ./...
+
+.PHONY: test-short
+test-short:
+	go test $(BUILD_TAGS) -timeout 60s -short ./...
+
+### Evergreen specific targets. ###
+.PHONY: build-aws-ecs-test
+build-aws-ecs-test:
+	go build $(BUILD_TAGS) ./cmd/testaws/main.go
+
+.PHONY: evg-test
+evg-test:
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s -p 1 ./... >> test.suite
+
+.PHONY: evg-test-atlas
+evg-test-atlas:
+	go run ./cmd/testatlas/main.go $(ATLAS_URIS)
+
+.PHONY: evg-test-atlas-data-lake
+evg-test-atlas-data-lake:
+	ATLAS_DATA_LAKE_INTEGRATION_TEST=true go test -v ./mongo/integration -run TestUnifiedSpecs/atlas-data-lake-testing >> spec_test.suite
+	ATLAS_DATA_LAKE_INTEGRATION_TEST=true go test -v ./mongo/integration -run TestAtlasDataLake >> spec_test.suite
+
+.PHONY: evg-test-enterprise-auth
+evg-test-enterprise-auth:
+	go run -tags gssapi ./cmd/testentauth/main.go
+
+.PHONY: evg-test-kmip
+evg-test-kmip:
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionSpec/kmipKMS >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionProse/data_key_and_double_encryption >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionProse/corpus >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionProse/custom_endpoint >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionProse/kms_tls_options_test >> test.suite
+
+.PHONY: evg-test-kms
+evg-test-kms:
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionProse/kms_tls_tests >> test.suite
+
+.PHONY: evg-test-load-balancers
+evg-test-load-balancers:
+	# Load balancer should be tested with all unified tests as well as tests in the following
+	# components: retryable reads, retryable writes, change streams, initial DNS seedlist discovery.
+	go test $(BUILD_TAGS) ./mongo/integration -run TestUnifiedSpecs/retryable-reads -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestRetryableWritesSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestChangeStreamSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestInitialDNSSeedlistDiscoverySpec/load_balanced -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestLoadBalancerSupport -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration/unified -run TestUnifiedSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
+
+.PHONY: evg-test-ocsp
+evg-test-ocsp:
+	go test -v ./mongo -run TestOCSP $(OCSP_TLS_SHOULD_SUCCEED) >> test.suite
+
+.PHONY: evg-test-serverless
+evg-test-serverless:
+	# Serverless should be tested with all unified tests as well as tests in the following components: CRUD, load balancer,
+	# retryable reads, retryable writes, sessions, transactions and cursor behavior.
+	go test $(BUILD_TAGS) ./mongo/integration -run TestCrudSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestWriteErrorsWithLabels -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestWriteErrorsDetails -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestHintErrors -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestWriteConcernError -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestErrorsCodeNamePropagated -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestLoadBalancerSupport -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestUnifiedSpecs/retryable-reads -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestRetryableReadsProse -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestRetryableWritesSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestRetryableWritesProse -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestUnifiedSpecs/sessions -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestSessionsProse -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestUnifiedSpecs/transactions/legacy -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestConvenientTransactions -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration -run TestCursor -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test $(BUILD_TAGS) ./mongo/integration/unified -run TestUnifiedSpec -v -timeout $(TEST_TIMEOUT)s >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionSpec >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration -run TestClientSideEncryptionProse >> test.suite
+
+.PHONY: evg-test-versioned-api
+evg-test-versioned-api:
+	# Versioned API related tests are in the mongo, integration and unified packages.
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration >> test.suite
+	go test -exec "env PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)" $(BUILD_TAGS) -v -timeout $(TEST_TIMEOUT)s ./mongo/integration/unified >> test.suite
+
+.PHONY: build-gcpkms-test
+build-gcpkms-test:
+	go build $(BUILD_TAGS) ./cmd/testgcpkms
+
+### Benchmark specific targets and support. ###
+.PHONY: benchmark
+benchmark:perf
+	go test $(BUILD_TAGS) -benchmem -bench=. ./benchmark
+
+.PHONY: driver-benchmark
+driver-benchmark:perf
+	@go run cmd/godriver-benchmark/main.go | tee perf.suite
+
+perf:driver-test-data.tar.gz
+	tar -zxf $< $(if $(eq $(UNAME_S),Darwin),-s , --transform=s)/testdata/perf/
+	@touch $@
+
+driver-test-data.tar.gz:
+	curl --retry 5 "https://s3.amazonaws.com/boxes.10gen.com/build/driver-test-data.tar.gz" -o driver-test-data.tar.gz --silent --max-time 120

mongo/README.md

@@ -0,0 +1,251 @@
+<p align="center"><img src="etc/assets/mongo-gopher.png" width="250"></p>
+<p align="center">
+  <a href="https://goreportcard.com/report/go.mongodb.org/mongo-driver"><img src="https://goreportcard.com/badge/go.mongodb.org/mongo-driver"></a>
+  <a href="https://pkg.go.dev/go.mongodb.org/mongo-driver/mongo"><img src="etc/assets/godev-mongo-blue.svg" alt="docs"></a>
+  <a href="https://pkg.go.dev/go.mongodb.org/mongo-driver/bson"><img src="etc/assets/godev-bson-blue.svg" alt="docs"></a>
+  <a href="https://www.mongodb.com/docs/drivers/go/current/"><img src="etc/assets/docs-mongodb-green.svg"></a>
+</p>
+
+# MongoDB Go Driver
+
+The MongoDB supported driver for Go.
+
+-------------------------
+- [Requirements](#requirements)
+- [Installation](#installation)
+- [Usage](#usage)
+- [Feedback](#feedback)
+- [Testing / Development](#testing--development)
+- [Continuous Integration](#continuous-integration)
+- [License](#license)
+
+-------------------------
+## Requirements
+
+- Go 1.13 or higher. We aim to support the latest versions of Go.
+  - Go 1.20 or higher is required to run the driver test suite.
+- MongoDB 3.6 and higher.
+
+-------------------------
+## Installation
+
+The recommended way to get started using the MongoDB Go driver is by using Go modules to install the dependency in
+your project. This can be done either by importing packages from `go.mongodb.org/mongo-driver` and having the build
+step install the dependency or by explicitly running
+
+```bash
+go get go.mongodb.org/mongo-driver/mongo
+```
+
+When using a version of Go that does not support modules, the driver can be installed using `dep` by running
+
+```bash
+dep ensure -add "go.mongodb.org/mongo-driver/mongo"
+```
+
+-------------------------
+## Usage
+
+To get started with the driver, import the `mongo` package and create a `mongo.Client` with the `Connect` function:
+
+```go
+import (
+    "context"
+    "time"
+
+    "go.mongodb.org/mongo-driver/mongo"
+    "go.mongodb.org/mongo-driver/mongo/options"
+    "go.mongodb.org/mongo-driver/mongo/readpref"
+)
+
+ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+defer cancel()
+client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://localhost:27017"))
+```
+
+Make sure to defer a call to `Disconnect` after instantiating your client:
+
+```go
+defer func() {
+    if err = client.Disconnect(ctx); err != nil {
+        panic(err)
+    }
+}()
+```
+
+For more advanced configuration and authentication, see the [documentation for mongo.Connect](https://pkg.go.dev/go.mongodb.org/mongo-driver/mongo#Connect).
+
+Calling `Connect` does not block for server discovery. If you wish to know if a MongoDB server has been found and connected to,
+use the `Ping` method:
+
+```go
+ctx, cancel = context.WithTimeout(context.Background(), 2*time.Second)
+defer cancel()
+err = client.Ping(ctx, readpref.Primary())
+```
+
+To insert a document into a collection, first retrieve a `Database` and then `Collection` instance from the `Client`:
+
+```go
+collection := client.Database("testing").Collection("numbers")
+```
+
+The `Collection` instance can then be used to insert documents:
+
+```go
+ctx, cancel = context.WithTimeout(context.Background(), 5*time.Second)
+defer cancel()
+res, err := collection.InsertOne(ctx, bson.D{{"name", "pi"}, {"value", 3.14159}})
+id := res.InsertedID
+```
+
+To use `bson.D`, you will need to add `"go.mongodb.org/mongo-driver/bson"` to your imports.
+
+Your import statement should now look like this:
+
+```go
+import (
+    "context"
+    "log"
+    "time"
+
+    "go.mongodb.org/mongo-driver/bson"
+    "go.mongodb.org/mongo-driver/mongo"
+    "go.mongodb.org/mongo-driver/mongo/options"
+    "go.mongodb.org/mongo-driver/mongo/readpref"
+)
+```
+
+Several query methods return a cursor, which can be used like this:
+
+```go
+ctx, cancel = context.WithTimeout(context.Background(), 30*time.Second)
+defer cancel()
+cur, err := collection.Find(ctx, bson.D{})
+if err != nil { log.Fatal(err) }
+defer cur.Close(ctx)
+for cur.Next(ctx) {
+    var result bson.D
+    err := cur.Decode(&result)
+    if err != nil { log.Fatal(err) }
+    // do something with result....
+}
+if err := cur.Err(); err != nil {
+    log.Fatal(err)
+}
+```
+
+For methods that return a single item, a `SingleResult` instance is returned:
+
+```go
+var result struct {
+    Value float64
+}
+filter := bson.D{{"name", "pi"}}
+ctx, cancel = context.WithTimeout(context.Background(), 5*time.Second)
+defer cancel()
+err = collection.FindOne(ctx, filter).Decode(&result)
+if err == mongo.ErrNoDocuments {
+    // Do something when no record was found
+    fmt.Println("record does not exist")
+} else if err != nil {
+    log.Fatal(err)
+}
+// Do something with result...
+```
+
+Additional examples and documentation can be found under the examples directory and [on the MongoDB Documentation website](https://www.mongodb.com/docs/drivers/go/current/).
+
+-------------------------
+## Feedback
+
+For help with the driver, please post in the [MongoDB Community Forums](https://developer.mongodb.com/community/forums/tag/golang/).
+
+New features and bugs can be reported on jira: https://jira.mongodb.org/browse/GODRIVER
+
+-------------------------
+## Testing / Development
+
+The driver tests can be run against several database configurations. The most simple configuration is a standalone mongod with no auth, no ssl, and no compression. To run these basic driver tests, make sure a standalone MongoDB server instance is running at localhost:27017. To run the tests, you can run `make` (on Windows, run `nmake`). This will run coverage, run go-lint, run go-vet, and build the examples.
+
+### Testing Different Topologies
+
+To test a **replica set** or **sharded cluster**, set `MONGODB_URI="<connection-string>"` for the `make` command.
+For example, for a local replica set named `rs1` comprised of three nodes on ports 27017, 27018, and 27019:
+
+```
+MONGODB_URI="mongodb://localhost:27017,localhost:27018,localhost:27019/?replicaSet=rs1" make
+```
+
+### Testing Auth and TLS
+
+To test authentication and TLS, first set up a MongoDB cluster with auth and TLS configured. Testing authentication requires a user with the `root` role on the `admin` database. Here is an example command that would run a mongod with TLS correctly configured for tests. Either set or replace PATH_TO_SERVER_KEY_FILE and PATH_TO_CA_FILE with paths to their respective files:
+
+```
+mongod \
+--auth \
+--tlsMode requireTLS \
+--tlsCertificateKeyFile $PATH_TO_SERVER_KEY_FILE \
+--tlsCAFile $PATH_TO_CA_FILE \
+--tlsAllowInvalidCertificates
+```
+
+To run the tests with `make`, set:
+- `MONGO_GO_DRIVER_CA_FILE` to the location of the CA file used by the database
+- `MONGO_GO_DRIVER_KEY_FILE` to the location of the client key file
+- `MONGO_GO_DRIVER_PKCS8_ENCRYPTED_KEY_FILE` to the location of the pkcs8 client key file encrypted with the password string: `password`
+- `MONGO_GO_DRIVER_PKCS8_UNENCRYPTED_KEY_FILE` to the location of the unencrypted pkcs8 key file
+- `MONGODB_URI` to the connection string of the server
+- `AUTH=auth`
+- `SSL=ssl`
+
+For example:
+
+```
+AUTH=auth SSL=ssl \
+MONGO_GO_DRIVER_CA_FILE=$PATH_TO_CA_FILE \
+MONGO_GO_DRIVER_KEY_FILE=$PATH_TO_CLIENT_KEY_FILE \
+MONGO_GO_DRIVER_PKCS8_ENCRYPTED_KEY_FILE=$PATH_TO_ENCRYPTED_KEY_FILE \
+MONGO_GO_DRIVER_PKCS8_UNENCRYPTED_KEY_FILE=$PATH_TO_UNENCRYPTED_KEY_FILE \
+MONGODB_URI="mongodb://user:password@localhost:27017/?authSource=admin" \
+make
+```
+
+Notes:
+- The `--tlsAllowInvalidCertificates` flag is required on the server for the test suite to work correctly.
+- The test suite requires the auth database to be set with `?authSource=admin`, not `/admin`.
+
+### Testing Compression
+
+The MongoDB Go Driver supports wire protocol compression using Snappy, zLib, or zstd. To run tests with wire protocol compression, set `MONGO_GO_DRIVER_COMPRESSOR` to `snappy`, `zlib`, or `zstd`.  For example:
+
+```
+MONGO_GO_DRIVER_COMPRESSOR=snappy make
+```
+
+Ensure the [`--networkMessageCompressors` flag](https://www.mongodb.com/docs/manual/reference/program/mongod/#cmdoption-mongod-networkmessagecompressors) on mongod or mongos includes `zlib` if testing zLib compression.
+
+-------------------------
+## Contribution
+
+Check out the [project page](https://jira.mongodb.org/browse/GODRIVER) for tickets that need completing. See our [contribution guidelines](docs/CONTRIBUTING.md) for details.
+
+-------------------------
+## Continuous Integration
+
+Commits to master are run automatically on [evergreen](https://evergreen.mongodb.com/waterfall/mongo-go-driver).
+
+-------------------------
+## Frequently Encountered Issues
+
+See our [common issues](docs/common-issues.md) documentation for troubleshooting frequently encountered issues.
+
+-------------------------
+## Thanks and Acknowledgement
+
+<a href="https://github.com/ashleymcnamara">@ashleymcnamara</a> - Mongo Gopher Artwork
+
+-------------------------
+## License
+
+The MongoDB Go Driver is licensed under the [Apache License](LICENSE).

mongo/bson/benchmark_test.go

@@ -0,0 +1,307 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bson
+
+import (
+	"compress/gzip"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+	"testing"
+)
+
+type encodetest struct {
+	Field1String  string
+	Field1Int64   int64
+	Field1Float64 float64
+	Field2String  string
+	Field2Int64   int64
+	Field2Float64 float64
+	Field3String  string
+	Field3Int64   int64
+	Field3Float64 float64
+	Field4String  string
+	Field4Int64   int64
+	Field4Float64 float64
+}
+
+type nestedtest1 struct {
+	Nested nestedtest2
+}
+
+type nestedtest2 struct {
+	Nested nestedtest3
+}
+
+type nestedtest3 struct {
+	Nested nestedtest4
+}
+
+type nestedtest4 struct {
+	Nested nestedtest5
+}
+
+type nestedtest5 struct {
+	Nested nestedtest6
+}
+
+type nestedtest6 struct {
+	Nested nestedtest7
+}
+
+type nestedtest7 struct {
+	Nested nestedtest8
+}
+
+type nestedtest8 struct {
+	Nested nestedtest9
+}
+
+type nestedtest9 struct {
+	Nested nestedtest10
+}
+
+type nestedtest10 struct {
+	Nested nestedtest11
+}
+
+type nestedtest11 struct {
+	Nested encodetest
+}
+
+var encodetestInstance = encodetest{
+	Field1String:  "foo",
+	Field1Int64:   1,
+	Field1Float64: 3.0,
+	Field2String:  "bar",
+	Field2Int64:   2,
+	Field2Float64: 3.1,
+	Field3String:  "baz",
+	Field3Int64:   3,
+	Field3Float64: 3.14,
+	Field4String:  "qux",
+	Field4Int64:   4,
+	Field4Float64: 3.141,
+}
+
+var nestedInstance = nestedtest1{
+	nestedtest2{
+		nestedtest3{
+			nestedtest4{
+				nestedtest5{
+					nestedtest6{
+						nestedtest7{
+							nestedtest8{
+								nestedtest9{
+									nestedtest10{
+										nestedtest11{
+											encodetest{
+												Field1String:  "foo",
+												Field1Int64:   1,
+												Field1Float64: 3.0,
+												Field2String:  "bar",
+												Field2Int64:   2,
+												Field2Float64: 3.1,
+												Field3String:  "baz",
+												Field3Int64:   3,
+												Field3Float64: 3.14,
+												Field4String:  "qux",
+												Field4Int64:   4,
+												Field4Float64: 3.141,
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	},
+}
+
+const extendedBSONDir = "../testdata/extended_bson"
+
+// readExtJSONFile reads the GZIP-compressed extended JSON document from the given filename in the
+// "extended BSON" test data directory (../testdata/extended_bson) and returns it as a
+// map[string]interface{}. It panics on any errors.
+func readExtJSONFile(filename string) map[string]interface{} {
+	filePath := path.Join(extendedBSONDir, filename)
+	file, err := os.Open(filePath)
+	if err != nil {
+		panic(fmt.Sprintf("error opening file %q: %s", filePath, err))
+	}
+	defer func() {
+		_ = file.Close()
+	}()
+
+	gz, err := gzip.NewReader(file)
+	if err != nil {
+		panic(fmt.Sprintf("error creating GZIP reader: %s", err))
+	}
+	defer func() {
+		_ = gz.Close()
+	}()
+
+	data, err := ioutil.ReadAll(gz)
+	if err != nil {
+		panic(fmt.Sprintf("error reading GZIP contents of file: %s", err))
+	}
+
+	var v map[string]interface{}
+	err = UnmarshalExtJSON(data, false, &v)
+	if err != nil {
+		panic(fmt.Sprintf("error unmarshalling extended JSON: %s", err))
+	}
+
+	return v
+}
+
+func BenchmarkMarshal(b *testing.B) {
+	cases := []struct {
+		desc  string
+		value interface{}
+	}{
+		{
+			desc:  "simple struct",
+			value: encodetestInstance,
+		},
+		{
+			desc:  "nested struct",
+			value: nestedInstance,
+		},
+		{
+			desc:  "deep_bson.json.gz",
+			value: readExtJSONFile("deep_bson.json.gz"),
+		},
+		{
+			desc:  "flat_bson.json.gz",
+			value: readExtJSONFile("flat_bson.json.gz"),
+		},
+		{
+			desc:  "full_bson.json.gz",
+			value: readExtJSONFile("full_bson.json.gz"),
+		},
+	}
+
+	for _, tc := range cases {
+		b.Run(tc.desc, func(b *testing.B) {
+			b.Run("BSON", func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					_, err := Marshal(tc.value)
+					if err != nil {
+						b.Errorf("error marshalling BSON: %s", err)
+					}
+				}
+			})
+
+			b.Run("extJSON", func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					_, err := MarshalExtJSON(tc.value, true, false)
+					if err != nil {
+						b.Errorf("error marshalling extended JSON: %s", err)
+					}
+				}
+			})
+
+			b.Run("JSON", func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					_, err := json.Marshal(tc.value)
+					if err != nil {
+						b.Errorf("error marshalling JSON: %s", err)
+					}
+				}
+			})
+		})
+	}
+}
+
+func BenchmarkUnmarshal(b *testing.B) {
+	cases := []struct {
+		desc  string
+		value interface{}
+	}{
+		{
+			desc:  "simple struct",
+			value: encodetestInstance,
+		},
+		{
+			desc:  "nested struct",
+			value: nestedInstance,
+		},
+		{
+			desc:  "deep_bson.json.gz",
+			value: readExtJSONFile("deep_bson.json.gz"),
+		},
+		{
+			desc:  "flat_bson.json.gz",
+			value: readExtJSONFile("flat_bson.json.gz"),
+		},
+		{
+			desc:  "full_bson.json.gz",
+			value: readExtJSONFile("full_bson.json.gz"),
+		},
+	}
+
+	for _, tc := range cases {
+		b.Run(tc.desc, func(b *testing.B) {
+			b.Run("BSON", func(b *testing.B) {
+				data, err := Marshal(tc.value)
+				if err != nil {
+					b.Errorf("error marshalling BSON: %s", err)
+					return
+				}
+
+				b.ResetTimer()
+				var v2 map[string]interface{}
+				for i := 0; i < b.N; i++ {
+					err := Unmarshal(data, &v2)
+					if err != nil {
+						b.Errorf("error unmarshalling BSON: %s", err)
+					}
+				}
+			})
+
+			b.Run("extJSON", func(b *testing.B) {
+				data, err := MarshalExtJSON(tc.value, true, false)
+				if err != nil {
+					b.Errorf("error marshalling extended JSON: %s", err)
+					return
+				}
+
+				b.ResetTimer()
+				var v2 map[string]interface{}
+				for i := 0; i < b.N; i++ {
+					err := UnmarshalExtJSON(data, true, &v2)
+					if err != nil {
+						b.Errorf("error unmarshalling extended JSON: %s", err)
+					}
+				}
+			})
+
+			b.Run("JSON", func(b *testing.B) {
+				data, err := json.Marshal(tc.value)
+				if err != nil {
+					b.Errorf("error marshalling JSON: %s", err)
+					return
+				}
+
+				b.ResetTimer()
+				var v2 map[string]interface{}
+				for i := 0; i < b.N; i++ {
+					err := json.Unmarshal(data, &v2)
+					if err != nil {
+						b.Errorf("error unmarshalling JSON: %s", err)
+					}
+				}
+			})
+		})
+	}
+}

mongo/bson/bson.go

@@ -0,0 +1,50 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+//
+// Based on gopkg.in/mgo.v2/bson by Gustavo Niemeyer
+// See THIRD-PARTY-NOTICES for original license terms.
+
+package bson // import "go.mongodb.org/mongo-driver/bson"
+
+import (
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+// Zeroer allows custom struct types to implement a report of zero
+// state. All struct types that don't implement Zeroer or where IsZero
+// returns false are considered to be not zero.
+type Zeroer interface {
+	IsZero() bool
+}
+
+// D is an ordered representation of a BSON document. This type should be used when the order of the elements matters,
+// such as MongoDB command documents. If the order of the elements does not matter, an M should be used instead.
+//
+// A D should not be constructed with duplicate key names, as that can cause undefined server behavior.
+//
+// Example usage:
+//
+//	bson.D{{"foo", "bar"}, {"hello", "world"}, {"pi", 3.14159}}
+type D = primitive.D
+
+// E represents a BSON element for a D. It is usually used inside a D.
+type E = primitive.E
+
+// M is an unordered representation of a BSON document. This type should be used when the order of the elements does not
+// matter. This type is handled as a regular map[string]interface{} when encoding and decoding. Elements will be
+// serialized in an undefined, random order. If the order of the elements matters, a D should be used instead.
+//
+// Example usage:
+//
+//	bson.M{"foo": "bar", "hello": "world", "pi": 3.14159}
+type M = primitive.M
+
+// An A is an ordered representation of a BSON array.
+//
+// Example usage:
+//
+//	bson.A{"bar", "world", 3.14159, bson.D{{"qux", 12345}}}
+type A = primitive.A

mongo/bson/bson_corpus_spec_test.go

@@ -0,0 +1,530 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bson
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"math"
+	"os"
+	"path"
+	"strconv"
+	"strings"
+	"testing"
+	"unicode"
+	"unicode/utf8"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
+	"github.com/tidwall/pretty"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/internal/testutil/assert"
+)
+
+type testCase struct {
+	Description  string                `json:"description"`
+	BsonType     string                `json:"bson_type"`
+	TestKey      *string               `json:"test_key"`
+	Valid        []validityTestCase    `json:"valid"`
+	DecodeErrors []decodeErrorTestCase `json:"decodeErrors"`
+	ParseErrors  []parseErrorTestCase  `json:"parseErrors"`
+	Deprecated   *bool                 `json:"deprecated"`
+}
+
+type validityTestCase struct {
+	Description       string  `json:"description"`
+	CanonicalBson     string  `json:"canonical_bson"`
+	CanonicalExtJSON  string  `json:"canonical_extjson"`
+	RelaxedExtJSON    *string `json:"relaxed_extjson"`
+	DegenerateBSON    *string `json:"degenerate_bson"`
+	DegenerateExtJSON *string `json:"degenerate_extjson"`
+	ConvertedBSON     *string `json:"converted_bson"`
+	ConvertedExtJSON  *string `json:"converted_extjson"`
+	Lossy             *bool   `json:"lossy"`
+}
+
+type decodeErrorTestCase struct {
+	Description string `json:"description"`
+	Bson        string `json:"bson"`
+}
+
+type parseErrorTestCase struct {
+	Description string `json:"description"`
+	String      string `json:"string"`
+}
+
+const dataDir = "../testdata/bson-corpus/"
+
+func findJSONFilesInDir(dir string) ([]string, error) {
+	files := make([]string, 0)
+
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() || path.Ext(entry.Name()) != ".json" {
+			continue
+		}
+
+		files = append(files, entry.Name())
+	}
+
+	return files, nil
+}
+
+// seedExtJSON will add the byte representation of the "extJSON" string to the fuzzer's coprus.
+func seedExtJSON(f *testing.F, extJSON string, extJSONType string, desc string) {
+	jbytes, err := jsonToBytes(extJSON, extJSONType, desc)
+	if err != nil {
+		f.Fatalf("failed to convert JSON to bytes: %v", err)
+	}
+
+	f.Add(jbytes)
+}
+
+// seedTestCase will add the byte representation for each "extJSON" string of each valid test case to the fuzzer's
+// corpus.
+func seedTestCase(f *testing.F, tcase *testCase) {
+	for _, vtc := range tcase.Valid {
+		seedExtJSON(f, vtc.CanonicalExtJSON, "canonical", vtc.Description)
+
+		// Seed the relaxed extended JSON.
+		if vtc.RelaxedExtJSON != nil {
+			seedExtJSON(f, *vtc.RelaxedExtJSON, "relaxed", vtc.Description)
+		}
+
+		// Seed the degenerate extended JSON.
+		if vtc.DegenerateExtJSON != nil {
+			seedExtJSON(f, *vtc.DegenerateExtJSON, "degenerate", vtc.Description)
+		}
+
+		// Seed the converted extended JSON.
+		if vtc.ConvertedExtJSON != nil {
+			seedExtJSON(f, *vtc.ConvertedExtJSON, "converted", vtc.Description)
+		}
+	}
+}
+
+// seedBSONCorpus will unmarshal the data from "testdata/bson-corpus" into a slice of "testCase" structs and then
+// marshal the "*_extjson" field of each "validityTestCase" into a slice of bytes to seed the fuzz corpus.
+func seedBSONCorpus(f *testing.F) {
+	fileNames, err := findJSONFilesInDir(dataDir)
+	if err != nil {
+		f.Fatalf("failed to find JSON files in directory %q: %v", dataDir, err)
+	}
+
+	for _, fileName := range fileNames {
+		filePath := path.Join(dataDir, fileName)
+
+		file, err := os.Open(filePath)
+		if err != nil {
+			f.Fatalf("failed to open file %q: %v", filePath, err)
+		}
+
+		var tcase testCase
+		if err := json.NewDecoder(file).Decode(&tcase); err != nil {
+			f.Fatal(err)
+		}
+
+		seedTestCase(f, &tcase)
+	}
+}
+
+func needsEscapedUnicode(bsonType string) bool {
+	return bsonType == "0x02" || bsonType == "0x0D" || bsonType == "0x0E" || bsonType == "0x0F"
+}
+
+func unescapeUnicode(s, bsonType string) string {
+	if !needsEscapedUnicode(bsonType) {
+		return s
+	}
+
+	newS := ""
+
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		switch c {
+		case '\\':
+			switch s[i+1] {
+			case 'u':
+				us := s[i : i+6]
+				u, err := strconv.Unquote(strings.Replace(strconv.Quote(us), `\\u`, `\u`, 1))
+				if err != nil {
+					return ""
+				}
+				for _, r := range u {
+					if r < ' ' {
+						newS += fmt.Sprintf(`\u%04x`, r)
+					} else {
+						newS += string(r)
+					}
+				}
+				i += 5
+			default:
+				newS += string(c)
+			}
+		default:
+			if c > unicode.MaxASCII {
+				r, size := utf8.DecodeRune([]byte(s[i:]))
+				newS += string(r)
+				i += size - 1
+			} else {
+				newS += string(c)
+			}
+		}
+	}
+
+	return newS
+}
+
+func formatDouble(f float64) string {
+	var s string
+	if math.IsInf(f, 1) {
+		s = "Infinity"
+	} else if math.IsInf(f, -1) {
+		s = "-Infinity"
+	} else if math.IsNaN(f) {
+		s = "NaN"
+	} else {
+		// Print exactly one decimalType place for integers; otherwise, print as many are necessary to
+		// perfectly represent it.
+		s = strconv.FormatFloat(f, 'G', -1, 64)
+		if !strings.ContainsRune(s, 'E') && !strings.ContainsRune(s, '.') {
+			s += ".0"
+		}
+	}
+
+	return s
+}
+
+func normalizeCanonicalDouble(t *testing.T, key string, cEJ string) string {
+	// Unmarshal string into map
+	cEJMap := make(map[string]map[string]string)
+	err := json.Unmarshal([]byte(cEJ), &cEJMap)
+	require.NoError(t, err)
+
+	// Parse the float contained by the map.
+	expectedString := cEJMap[key]["$numberDouble"]
+	expectedFloat, err := strconv.ParseFloat(expectedString, 64)
+	require.NoError(t, err)
+
+	// Normalize the string
+	return fmt.Sprintf(`{"%s":{"$numberDouble":"%s"}}`, key, formatDouble(expectedFloat))
+}
+
+func normalizeRelaxedDouble(t *testing.T, key string, rEJ string) string {
+	// Unmarshal string into map
+	rEJMap := make(map[string]float64)
+	err := json.Unmarshal([]byte(rEJ), &rEJMap)
+	if err != nil {
+		return normalizeCanonicalDouble(t, key, rEJ)
+	}
+
+	// Parse the float contained by the map.
+	expectedFloat := rEJMap[key]
+
+	// Normalize the string
+	return fmt.Sprintf(`{"%s":%s}`, key, formatDouble(expectedFloat))
+}
+
+// bsonToNative decodes the BSON bytes (b) into a native Document
+func bsonToNative(t *testing.T, b []byte, bType, testDesc string) D {
+	var doc D
+	err := Unmarshal(b, &doc)
+	expectNoError(t, err, fmt.Sprintf("%s: decoding %s BSON", testDesc, bType))
+	return doc
+}
+
+// nativeToBSON encodes the native Document (doc) into canonical BSON and compares it to the expected
+// canonical BSON (cB)
+func nativeToBSON(t *testing.T, cB []byte, doc D, testDesc, bType, docSrcDesc string) {
+	actual, err := Marshal(doc)
+	expectNoError(t, err, fmt.Sprintf("%s: encoding %s BSON", testDesc, bType))
+
+	if diff := cmp.Diff(cB, actual); diff != "" {
+		t.Errorf("%s: 'native_to_bson(%s) = cB' failed (-want, +got):\n-%v\n+%v\n",
+			testDesc, docSrcDesc, cB, actual)
+		t.FailNow()
+	}
+}
+
+// jsonToNative decodes the extended JSON string (ej) into a native Document
+func jsonToNative(ej, ejType, testDesc string) (D, error) {
+	var doc D
+	if err := UnmarshalExtJSON([]byte(ej), ejType != "relaxed", &doc); err != nil {
+		return nil, fmt.Errorf("%s: decoding %s extended JSON: %w", testDesc, ejType, err)
+	}
+	return doc, nil
+}
+
+// jsonToBytes decodes the extended JSON string (ej) into canonical BSON and then encodes it into a byte slice.
+func jsonToBytes(ej, ejType, testDesc string) ([]byte, error) {
+	native, err := jsonToNative(ej, ejType, testDesc)
+	if err != nil {
+		return nil, err
+	}
+
+	b, err := Marshal(native)
+	if err != nil {
+		return nil, fmt.Errorf("%s: encoding %s BSON: %w", testDesc, ejType, err)
+	}
+
+	return b, nil
+}
+
+// nativeToJSON encodes the native Document (doc) into an extended JSON string
+func nativeToJSON(t *testing.T, ej string, doc D, testDesc, ejType, ejShortName, docSrcDesc string) {
+	actualEJ, err := MarshalExtJSON(doc, ejType != "relaxed", true)
+	expectNoError(t, err, fmt.Sprintf("%s: encoding %s extended JSON", testDesc, ejType))
+
+	if diff := cmp.Diff(ej, string(actualEJ)); diff != "" {
+		t.Errorf("%s: 'native_to_%s_extended_json(%s) = %s' failed (-want, +got):\n%s\n",
+			testDesc, ejType, docSrcDesc, ejShortName, diff)
+		t.FailNow()
+	}
+}
+
+func runTest(t *testing.T, file string) {
+	filepath := path.Join(dataDir, file)
+	content, err := os.ReadFile(filepath)
+	require.NoError(t, err)
+
+	// Remove ".json" from filename.
+	file = file[:len(file)-5]
+	testName := "bson_corpus--" + file
+
+	t.Run(testName, func(t *testing.T) {
+		var test testCase
+		require.NoError(t, json.Unmarshal(content, &test))
+
+		t.Run("valid", func(t *testing.T) {
+			for _, v := range test.Valid {
+				t.Run(v.Description, func(t *testing.T) {
+					// get canonical BSON
+					cB, err := hex.DecodeString(v.CanonicalBson)
+					expectNoError(t, err, fmt.Sprintf("%s: reading canonical BSON", v.Description))
+
+					// get canonical extended JSON
+					cEJ := unescapeUnicode(string(pretty.Ugly([]byte(v.CanonicalExtJSON))), test.BsonType)
+					if test.BsonType == "0x01" {
+						cEJ = normalizeCanonicalDouble(t, *test.TestKey, cEJ)
+					}
+
+					/*** canonical BSON round-trip tests ***/
+					doc := bsonToNative(t, cB, "canonical", v.Description)
+
+					// native_to_bson(bson_to_native(cB)) = cB
+					nativeToBSON(t, cB, doc, v.Description, "canonical", "bson_to_native(cB)")
+
+					// native_to_canonical_extended_json(bson_to_native(cB)) = cEJ
+					nativeToJSON(t, cEJ, doc, v.Description, "canonical", "cEJ", "bson_to_native(cB)")
+
+					// native_to_relaxed_extended_json(bson_to_native(cB)) = rEJ (if rEJ exists)
+					if v.RelaxedExtJSON != nil {
+						rEJ := unescapeUnicode(string(pretty.Ugly([]byte(*v.RelaxedExtJSON))), test.BsonType)
+						if test.BsonType == "0x01" {
+							rEJ = normalizeRelaxedDouble(t, *test.TestKey, rEJ)
+						}
+
+						nativeToJSON(t, rEJ, doc, v.Description, "relaxed", "rEJ", "bson_to_native(cB)")
+
+						/*** relaxed extended JSON round-trip tests (if exists) ***/
+						doc, err = jsonToNative(rEJ, "relaxed", v.Description)
+						require.NoError(t, err)
+
+						// native_to_relaxed_extended_json(json_to_native(rEJ)) = rEJ
+						nativeToJSON(t, rEJ, doc, v.Description, "relaxed", "eJR", "json_to_native(rEJ)")
+					}
+
+					/*** canonical extended JSON round-trip tests ***/
+					doc, err = jsonToNative(cEJ, "canonical", v.Description)
+					require.NoError(t, err)
+
+					// native_to_canonical_extended_json(json_to_native(cEJ)) = cEJ
+					nativeToJSON(t, cEJ, doc, v.Description, "canonical", "cEJ", "json_to_native(cEJ)")
+
+					// native_to_bson(json_to_native(cEJ)) = cb (unless lossy)
+					if v.Lossy == nil || !*v.Lossy {
+						nativeToBSON(t, cB, doc, v.Description, "canonical", "json_to_native(cEJ)")
+					}
+
+					/*** degenerate BSON round-trip tests (if exists) ***/
+					if v.DegenerateBSON != nil {
+						dB, err := hex.DecodeString(*v.DegenerateBSON)
+						expectNoError(t, err, fmt.Sprintf("%s: reading degenerate BSON", v.Description))
+
+						doc = bsonToNative(t, dB, "degenerate", v.Description)
+
+						// native_to_bson(bson_to_native(dB)) = cB
+						nativeToBSON(t, cB, doc, v.Description, "degenerate", "bson_to_native(dB)")
+					}
+
+					/*** degenerate JSON round-trip tests (if exists) ***/
+					if v.DegenerateExtJSON != nil {
+						dEJ := unescapeUnicode(string(pretty.Ugly([]byte(*v.DegenerateExtJSON))), test.BsonType)
+						if test.BsonType == "0x01" {
+							dEJ = normalizeCanonicalDouble(t, *test.TestKey, dEJ)
+						}
+
+						doc, err = jsonToNative(dEJ, "degenerate canonical", v.Description)
+						require.NoError(t, err)
+
+						// native_to_canonical_extended_json(json_to_native(dEJ)) = cEJ
+						nativeToJSON(t, cEJ, doc, v.Description, "degenerate canonical", "cEJ", "json_to_native(dEJ)")
+
+						// native_to_bson(json_to_native(dEJ)) = cB (unless lossy)
+						if v.Lossy == nil || !*v.Lossy {
+							nativeToBSON(t, cB, doc, v.Description, "canonical", "json_to_native(dEJ)")
+						}
+					}
+				})
+			}
+		})
+
+		t.Run("decode error", func(t *testing.T) {
+			for _, d := range test.DecodeErrors {
+				t.Run(d.Description, func(t *testing.T) {
+					b, err := hex.DecodeString(d.Bson)
+					expectNoError(t, err, d.Description)
+
+					var doc D
+					err = Unmarshal(b, &doc)
+
+					// The driver unmarshals invalid UTF-8 strings without error. Loop over the unmarshalled elements
+					// and assert that there was no error if any of the string or DBPointer values contain invalid UTF-8
+					// characters.
+					for _, elem := range doc {
+						str, ok := elem.Value.(string)
+						invalidString := ok && !utf8.ValidString(str)
+						dbPtr, ok := elem.Value.(primitive.DBPointer)
+						invalidDBPtr := ok && !utf8.ValidString(dbPtr.DB)
+
+						if invalidString || invalidDBPtr {
+							expectNoError(t, err, d.Description)
+							return
+						}
+					}
+
+					expectError(t, err, fmt.Sprintf("%s: expected decode error", d.Description))
+				})
+			}
+		})
+
+		t.Run("parse error", func(t *testing.T) {
+			for _, p := range test.ParseErrors {
+				t.Run(p.Description, func(t *testing.T) {
+					s := unescapeUnicode(p.String, test.BsonType)
+					if test.BsonType == "0x13" {
+						s = fmt.Sprintf(`{"decimal128": {"$numberDecimal": "%s"}}`, s)
+					}
+
+					switch test.BsonType {
+					case "0x00", "0x05", "0x13":
+						var doc D
+						err := UnmarshalExtJSON([]byte(s), true, &doc)
+						// Null bytes are validated when marshaling to BSON
+						if strings.Contains(p.Description, "Null") {
+							_, err = Marshal(doc)
+						}
+						expectError(t, err, fmt.Sprintf("%s: expected parse error", p.Description))
+					default:
+						t.Errorf("Update test to check for parse errors for type %s", test.BsonType)
+						t.Fail()
+					}
+				})
+			}
+		})
+	})
+}
+
+func Test_BsonCorpus(t *testing.T) {
+	jsonFiles, err := findJSONFilesInDir(dataDir)
+	if err != nil {
+		t.Fatalf("error finding JSON files in %s: %v", dataDir, err)
+	}
+
+	for _, file := range jsonFiles {
+		runTest(t, file)
+	}
+}
+
+func expectNoError(t *testing.T, err error, desc string) {
+	if err != nil {
+		t.Helper()
+		t.Errorf("%s: Unepexted error: %v", desc, err)
+		t.FailNow()
+	}
+}
+
+func expectError(t *testing.T, err error, desc string) {
+	if err == nil {
+		t.Helper()
+		t.Errorf("%s: Expected error", desc)
+		t.FailNow()
+	}
+}
+
+func TestRelaxedUUIDValidation(t *testing.T) {
+	testCases := []struct {
+		description       string
+		canonicalExtJSON  string
+		degenerateExtJSON string
+		expectedErr       string
+	}{
+		{
+			"valid uuid",
+			"{\"x\" : { \"$binary\" : {\"base64\" : \"c//SZESzTGmQ6OfR38A11A==\", \"subType\" : \"04\"}}}",
+			"{\"x\" : { \"$uuid\" : \"73ffd264-44b3-4c69-90e8-e7d1dfc035d4\"}}",
+			"",
+		},
+		{
+			"invalid uuid--no hyphens",
+			"",
+			"{\"x\" : { \"$uuid\" : \"73ffd26444b34c6990e8e7d1dfc035d4\"}}",
+			"$uuid value does not follow RFC 4122 format regarding length and hyphens",
+		},
+		{
+			"invalid uuid--trailing hyphens",
+			"",
+			"{\"x\" : { \"$uuid\" : \"73ffd264-44b3-4c69-90e8-e7d1dfc035--\"}}",
+			"$uuid value does not follow RFC 4122 format regarding length and hyphens",
+		},
+		{
+			"invalid uuid--malformed hex",
+			"",
+			"{\"x\" : { \"$uuid\" : \"q3@fd26l-44b3-4c69-90e8-e7d1dfc035d4\"}}",
+			"$uuid value does not follow RFC 4122 format regarding hex bytes: encoding/hex: invalid byte: U+0071 'q'",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			// get canonical extended JSON
+			cEJ := unescapeUnicode(string(pretty.Ugly([]byte(tc.canonicalExtJSON))), "0x05")
+
+			// get degenerate extended JSON
+			dEJ := unescapeUnicode(string(pretty.Ugly([]byte(tc.degenerateExtJSON))), "0x05")
+
+			// convert dEJ to native doc
+			var doc D
+			err := UnmarshalExtJSON([]byte(dEJ), true, &doc)
+
+			if tc.expectedErr != "" {
+				assert.Equal(t, tc.expectedErr, err.Error(), "expected error %v, got %v", tc.expectedErr, err)
+			} else {
+				assert.Nil(t, err, "expected no error, got error: %v", err)
+
+				// Marshal doc into extended JSON and compare with cEJ
+				nativeToJSON(t, cEJ, doc, tc.description, "degenerate canonical", "cEJ", "json_to_native(dEJ)")
+			}
+		})
+	}
+
+}

mongo/bson/bson_test.go

@@ -0,0 +1,279 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bson
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"go.mongodb.org/mongo-driver/bson/bsoncodec"
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/internal/testutil/assert"
+	"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
+)
+
+func noerr(t *testing.T, err error) {
+	if err != nil {
+		t.Helper()
+		t.Errorf("Unexpected error: (%T)%v", err, err)
+		t.FailNow()
+	}
+}
+
+func TestTimeRoundTrip(t *testing.T) {
+	val := struct {
+		Value time.Time
+		ID    string
+	}{
+		ID: "time-rt-test",
+	}
+
+	if !val.Value.IsZero() {
+		t.Errorf("Did not get zero time as expected.")
+	}
+
+	bsonOut, err := Marshal(val)
+	noerr(t, err)
+	rtval := struct {
+		Value time.Time
+		ID    string
+	}{}
+
+	err = Unmarshal(bsonOut, &rtval)
+	noerr(t, err)
+	if !cmp.Equal(val, rtval) {
+		t.Errorf("Did not round trip properly. got %v; want %v", val, rtval)
+	}
+	if !rtval.Value.IsZero() {
+		t.Errorf("Did not get zero time as expected.")
+	}
+}
+
+func TestNonNullTimeRoundTrip(t *testing.T) {
+	now := time.Now()
+	now = time.Unix(now.Unix(), 0)
+	val := struct {
+		Value time.Time
+		ID    string
+	}{
+		ID:    "time-rt-test",
+		Value: now,
+	}
+
+	bsonOut, err := Marshal(val)
+	noerr(t, err)
+	rtval := struct {
+		Value time.Time
+		ID    string
+	}{}
+
+	err = Unmarshal(bsonOut, &rtval)
+	noerr(t, err)
+	if !cmp.Equal(val, rtval) {
+		t.Errorf("Did not round trip properly. got %v; want %v", val, rtval)
+	}
+}
+
+func TestD(t *testing.T) {
+	t.Run("can marshal", func(t *testing.T) {
+		d := D{{"foo", "bar"}, {"hello", "world"}, {"pi", 3.14159}}
+		idx, want := bsoncore.AppendDocumentStart(nil)
+		want = bsoncore.AppendStringElement(want, "foo", "bar")
+		want = bsoncore.AppendStringElement(want, "hello", "world")
+		want = bsoncore.AppendDoubleElement(want, "pi", 3.14159)
+		want, err := bsoncore.AppendDocumentEnd(want, idx)
+		noerr(t, err)
+		got, err := Marshal(d)
+		noerr(t, err)
+		if !bytes.Equal(got, want) {
+			t.Errorf("Marshaled documents do not match. got %v; want %v", Raw(got), Raw(want))
+		}
+	})
+	t.Run("can unmarshal", func(t *testing.T) {
+		want := D{{"foo", "bar"}, {"hello", "world"}, {"pi", 3.14159}}
+		idx, doc := bsoncore.AppendDocumentStart(nil)
+		doc = bsoncore.AppendStringElement(doc, "foo", "bar")
+		doc = bsoncore.AppendStringElement(doc, "hello", "world")
+		doc = bsoncore.AppendDoubleElement(doc, "pi", 3.14159)
+		doc, err := bsoncore.AppendDocumentEnd(doc, idx)
+		noerr(t, err)
+		var got D
+		err = Unmarshal(doc, &got)
+		noerr(t, err)
+		if !cmp.Equal(got, want) {
+			t.Errorf("Unmarshaled documents do not match. got %v; want %v", got, want)
+		}
+	})
+}
+
+type stringerString string
+
+func (ss stringerString) String() string {
+	return "bar"
+}
+
+type keyBool bool
+
+func (kb keyBool) MarshalKey() (string, error) {
+	return fmt.Sprintf("%v", kb), nil
+}
+
+func (kb *keyBool) UnmarshalKey(key string) error {
+	switch key {
+	case "true":
+		*kb = true
+	case "false":
+		*kb = false
+	default:
+		return fmt.Errorf("invalid bool value %v", key)
+	}
+	return nil
+}
+
+type keyStruct struct {
+	val int64
+}
+
+func (k keyStruct) MarshalText() (text []byte, err error) {
+	str := strconv.FormatInt(k.val, 10)
+
+	return []byte(str), nil
+}
+
+func (k *keyStruct) UnmarshalText(text []byte) error {
+	val, err := strconv.ParseInt(string(text), 10, 64)
+	if err != nil {
+		return err
+	}
+
+	*k = keyStruct{
+		val: val,
+	}
+
+	return nil
+}
+
+func TestMapCodec(t *testing.T) {
+	t.Run("EncodeKeysWithStringer", func(t *testing.T) {
+		strstr := stringerString("foo")
+		mapObj := map[stringerString]int{strstr: 1}
+		testCases := []struct {
+			name string
+			opts *bsonoptions.MapCodecOptions
+			key  string
+		}{
+			{"default", bsonoptions.MapCodec(), "foo"},
+			{"true", bsonoptions.MapCodec().SetEncodeKeysWithStringer(true), "bar"},
+			{"false", bsonoptions.MapCodec().SetEncodeKeysWithStringer(false), "foo"},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				mapCodec := bsoncodec.NewMapCodec(tc.opts)
+				mapRegistry := NewRegistryBuilder().RegisterDefaultEncoder(reflect.Map, mapCodec).Build()
+				val, err := MarshalWithRegistry(mapRegistry, mapObj)
+				assert.Nil(t, err, "Marshal error: %v", err)
+				assert.True(t, strings.Contains(string(val), tc.key), "expected result to contain %v, got: %v", tc.key, string(val))
+			})
+		}
+	})
+
+	t.Run("keys implements keyMarshaler and keyUnmarshaler", func(t *testing.T) {
+		mapObj := map[keyBool]int{keyBool(true): 1}
+
+		doc, err := Marshal(mapObj)
+		assert.Nil(t, err, "Marshal error: %v", err)
+		idx, want := bsoncore.AppendDocumentStart(nil)
+		want = bsoncore.AppendInt32Element(want, "true", 1)
+		want, _ = bsoncore.AppendDocumentEnd(want, idx)
+		assert.Equal(t, want, doc, "expected result %v, got %v", string(want), string(doc))
+
+		var got map[keyBool]int
+		err = Unmarshal(doc, &got)
+		assert.Nil(t, err, "Unmarshal error: %v", err)
+		assert.Equal(t, mapObj, got, "expected result %v, got %v", mapObj, got)
+
+	})
+
+	t.Run("keys implements encoding.TextMarshaler and encoding.TextUnmarshaler", func(t *testing.T) {
+		mapObj := map[keyStruct]int{
+			{val: 10}: 100,
+		}
+
+		doc, err := Marshal(mapObj)
+		assert.Nil(t, err, "Marshal error: %v", err)
+		idx, want := bsoncore.AppendDocumentStart(nil)
+		want = bsoncore.AppendInt32Element(want, "10", 100)
+		want, _ = bsoncore.AppendDocumentEnd(want, idx)
+		assert.Equal(t, want, doc, "expected result %v, got %v", string(want), string(doc))
+
+		var got map[keyStruct]int
+		err = Unmarshal(doc, &got)
+		assert.Nil(t, err, "Unmarshal error: %v", err)
+		assert.Equal(t, mapObj, got, "expected result %v, got %v", mapObj, got)
+
+	})
+}
+
+func TestExtJSONEscapeKey(t *testing.T) {
+	doc := D{{Key: "\\usb#", Value: int32(1)}}
+	b, err := MarshalExtJSON(&doc, false, false)
+	noerr(t, err)
+
+	want := "{\"\\\\usb#\":1}"
+	if diff := cmp.Diff(want, string(b)); diff != "" {
+		t.Errorf("Marshaled documents do not match. got %v, want %v", string(b), want)
+	}
+
+	var got D
+	err = UnmarshalExtJSON(b, false, &got)
+	noerr(t, err)
+	if !cmp.Equal(got, doc) {
+		t.Errorf("Unmarshaled documents do not match. got %v; want %v", got, doc)
+	}
+}
+
+func TestBsoncoreArray(t *testing.T) {
+	type BSONDocumentArray struct {
+		Array []D `bson:"array"`
+	}
+
+	type BSONArray struct {
+		Array bsoncore.Array `bson:"array"`
+	}
+
+	bda := BSONDocumentArray{
+		Array: []D{
+			{{"x", 1}},
+			{{"x", 2}},
+			{{"x", 3}},
+		},
+	}
+
+	expectedBSON, err := Marshal(bda)
+	assert.Nil(t, err, "Marshal bsoncore.Document array error: %v", err)
+
+	var ba BSONArray
+	err = Unmarshal(expectedBSON, &ba)
+	assert.Nil(t, err, "Unmarshal error: %v", err)
+
+	actualBSON, err := Marshal(ba)
+	assert.Nil(t, err, "Marshal bsoncore.Array error: %v", err)
+
+	assert.Equal(t, expectedBSON, actualBSON,
+		"expected BSON to be %v after Marshalling again; got %v", expectedBSON, actualBSON)
+
+	doc := bsoncore.Document(actualBSON)
+	v := doc.Lookup("array")
+	assert.Equal(t, bsontype.Array, v.Type, "expected type array, got %v", v.Type)
+}

mongo/bson/bsoncodec/array_codec.go

@@ -0,0 +1,50 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
+)
+
+// ArrayCodec is the Codec used for bsoncore.Array values.
+type ArrayCodec struct{}
+
+var defaultArrayCodec = NewArrayCodec()
+
+// NewArrayCodec returns an ArrayCodec.
+func NewArrayCodec() *ArrayCodec {
+	return &ArrayCodec{}
+}
+
+// EncodeValue is the ValueEncoder for bsoncore.Array values.
+func (ac *ArrayCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tCoreArray {
+		return ValueEncoderError{Name: "CoreArrayEncodeValue", Types: []reflect.Type{tCoreArray}, Received: val}
+	}
+
+	arr := val.Interface().(bsoncore.Array)
+	return bsonrw.Copier{}.CopyArrayFromBytes(vw, arr)
+}
+
+// DecodeValue is the ValueDecoder for bsoncore.Array values.
+func (ac *ArrayCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Type() != tCoreArray {
+		return ValueDecoderError{Name: "CoreArrayDecodeValue", Types: []reflect.Type{tCoreArray}, Received: val}
+	}
+
+	if val.IsNil() {
+		val.Set(reflect.MakeSlice(val.Type(), 0, 0))
+	}
+
+	val.SetLen(0)
+	arr, err := bsonrw.Copier{}.AppendArrayBytes(val.Interface().(bsoncore.Array), vr)
+	val.Set(reflect.ValueOf(arr))
+	return err
+}

mongo/bson/bsoncodec/bsoncodec.go

@@ -0,0 +1,238 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec // import "go.mongodb.org/mongo-driver/bson/bsoncodec"
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+var (
+	emptyValue = reflect.Value{}
+)
+
+// Marshaler is an interface implemented by types that can marshal themselves
+// into a BSON document represented as bytes. The bytes returned must be a valid
+// BSON document if the error is nil.
+type Marshaler interface {
+	MarshalBSON() ([]byte, error)
+}
+
+// ValueMarshaler is an interface implemented by types that can marshal
+// themselves into a BSON value as bytes. The type must be the valid type for
+// the bytes returned. The bytes and byte type together must be valid if the
+// error is nil.
+type ValueMarshaler interface {
+	MarshalBSONValue() (bsontype.Type, []byte, error)
+}
+
+// Unmarshaler is an interface implemented by types that can unmarshal a BSON
+// document representation of themselves. The BSON bytes can be assumed to be
+// valid. UnmarshalBSON must copy the BSON bytes if it wishes to retain the data
+// after returning.
+type Unmarshaler interface {
+	UnmarshalBSON([]byte) error
+}
+
+// ValueUnmarshaler is an interface implemented by types that can unmarshal a
+// BSON value representation of themselves. The BSON bytes and type can be
+// assumed to be valid. UnmarshalBSONValue must copy the BSON value bytes if it
+// wishes to retain the data after returning.
+type ValueUnmarshaler interface {
+	UnmarshalBSONValue(bsontype.Type, []byte) error
+}
+
+// ValueEncoderError is an error returned from a ValueEncoder when the provided value can't be
+// encoded by the ValueEncoder.
+type ValueEncoderError struct {
+	Name     string
+	Types    []reflect.Type
+	Kinds    []reflect.Kind
+	Received reflect.Value
+}
+
+func (vee ValueEncoderError) Error() string {
+	typeKinds := make([]string, 0, len(vee.Types)+len(vee.Kinds))
+	for _, t := range vee.Types {
+		typeKinds = append(typeKinds, t.String())
+	}
+	for _, k := range vee.Kinds {
+		if k == reflect.Map {
+			typeKinds = append(typeKinds, "map[string]*")
+			continue
+		}
+		typeKinds = append(typeKinds, k.String())
+	}
+	received := vee.Received.Kind().String()
+	if vee.Received.IsValid() {
+		received = vee.Received.Type().String()
+	}
+	return fmt.Sprintf("%s can only encode valid %s, but got %s", vee.Name, strings.Join(typeKinds, ", "), received)
+}
+
+// ValueDecoderError is an error returned from a ValueDecoder when the provided value can't be
+// decoded by the ValueDecoder.
+type ValueDecoderError struct {
+	Name     string
+	Types    []reflect.Type
+	Kinds    []reflect.Kind
+	Received reflect.Value
+}
+
+func (vde ValueDecoderError) Error() string {
+	typeKinds := make([]string, 0, len(vde.Types)+len(vde.Kinds))
+	for _, t := range vde.Types {
+		typeKinds = append(typeKinds, t.String())
+	}
+	for _, k := range vde.Kinds {
+		if k == reflect.Map {
+			typeKinds = append(typeKinds, "map[string]*")
+			continue
+		}
+		typeKinds = append(typeKinds, k.String())
+	}
+	received := vde.Received.Kind().String()
+	if vde.Received.IsValid() {
+		received = vde.Received.Type().String()
+	}
+	return fmt.Sprintf("%s can only decode valid and settable %s, but got %s", vde.Name, strings.Join(typeKinds, ", "), received)
+}
+
+// EncodeContext is the contextual information required for a Codec to encode a
+// value.
+type EncodeContext struct {
+	*Registry
+	MinSize bool
+}
+
+// DecodeContext is the contextual information required for a Codec to decode a
+// value.
+type DecodeContext struct {
+	*Registry
+	Truncate bool
+
+	// Ancestor is the type of a containing document. This is mainly used to determine what type
+	// should be used when decoding an embedded document into an empty interface. For example, if
+	// Ancestor is a bson.M, BSON embedded document values being decoded into an empty interface
+	// will be decoded into a bson.M.
+	//
+	// Deprecated: Use DefaultDocumentM or DefaultDocumentD instead.
+	Ancestor reflect.Type
+
+	// defaultDocumentType specifies the Go type to decode top-level and nested BSON documents into. In particular, the
+	// usage for this field is restricted to data typed as "interface{}" or "map[string]interface{}". If DocumentType is
+	// set to a type that a BSON document cannot be unmarshaled into (e.g. "string"), unmarshalling will result in an
+	// error. DocumentType overrides the Ancestor field.
+	defaultDocumentType reflect.Type
+}
+
+// DefaultDocumentM will decode empty documents using the primitive.M type. This behavior is restricted to data typed as
+// "interface{}" or "map[string]interface{}".
+func (dc *DecodeContext) DefaultDocumentM() {
+	dc.defaultDocumentType = reflect.TypeOf(primitive.M{})
+}
+
+// DefaultDocumentD will decode empty documents using the primitive.D type. This behavior is restricted to data typed as
+// "interface{}" or "map[string]interface{}".
+func (dc *DecodeContext) DefaultDocumentD() {
+	dc.defaultDocumentType = reflect.TypeOf(primitive.D{})
+}
+
+// ValueCodec is the interface that groups the methods to encode and decode
+// values.
+type ValueCodec interface {
+	ValueEncoder
+	ValueDecoder
+}
+
+// ValueEncoder is the interface implemented by types that can handle the encoding of a value.
+type ValueEncoder interface {
+	EncodeValue(EncodeContext, bsonrw.ValueWriter, reflect.Value) error
+}
+
+// ValueEncoderFunc is an adapter function that allows a function with the correct signature to be
+// used as a ValueEncoder.
+type ValueEncoderFunc func(EncodeContext, bsonrw.ValueWriter, reflect.Value) error
+
+// EncodeValue implements the ValueEncoder interface.
+func (fn ValueEncoderFunc) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	return fn(ec, vw, val)
+}
+
+// ValueDecoder is the interface implemented by types that can handle the decoding of a value.
+type ValueDecoder interface {
+	DecodeValue(DecodeContext, bsonrw.ValueReader, reflect.Value) error
+}
+
+// ValueDecoderFunc is an adapter function that allows a function with the correct signature to be
+// used as a ValueDecoder.
+type ValueDecoderFunc func(DecodeContext, bsonrw.ValueReader, reflect.Value) error
+
+// DecodeValue implements the ValueDecoder interface.
+func (fn ValueDecoderFunc) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	return fn(dc, vr, val)
+}
+
+// typeDecoder is the interface implemented by types that can handle the decoding of a value given its type.
+type typeDecoder interface {
+	decodeType(DecodeContext, bsonrw.ValueReader, reflect.Type) (reflect.Value, error)
+}
+
+// typeDecoderFunc is an adapter function that allows a function with the correct signature to be used as a typeDecoder.
+type typeDecoderFunc func(DecodeContext, bsonrw.ValueReader, reflect.Type) (reflect.Value, error)
+
+func (fn typeDecoderFunc) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	return fn(dc, vr, t)
+}
+
+// decodeAdapter allows two functions with the correct signatures to be used as both a ValueDecoder and typeDecoder.
+type decodeAdapter struct {
+	ValueDecoderFunc
+	typeDecoderFunc
+}
+
+var _ ValueDecoder = decodeAdapter{}
+var _ typeDecoder = decodeAdapter{}
+
+// decodeTypeOrValue calls decoder.decodeType is decoder is a typeDecoder. Otherwise, it allocates a new element of type
+// t and calls decoder.DecodeValue on it.
+func decodeTypeOrValue(decoder ValueDecoder, dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	td, _ := decoder.(typeDecoder)
+	return decodeTypeOrValueWithInfo(decoder, td, dc, vr, t, true)
+}
+
+func decodeTypeOrValueWithInfo(vd ValueDecoder, td typeDecoder, dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type, convert bool) (reflect.Value, error) {
+	if td != nil {
+		val, err := td.decodeType(dc, vr, t)
+		if err == nil && convert && val.Type() != t {
+			// This conversion step is necessary for slices and maps. If a user declares variables like:
+			//
+			// type myBool bool
+			// var m map[string]myBool
+			//
+			// and tries to decode BSON bytes into the map, the decoding will fail if this conversion is not present
+			// because we'll try to assign a value of type bool to one of type myBool.
+			val = val.Convert(t)
+		}
+		return val, err
+	}
+
+	val := reflect.New(t).Elem()
+	err := vd.DecodeValue(dc, vr, val)
+	return val, err
+}
+
+// CodecZeroer is the interface implemented by Codecs that can also determine if
+// a value of the type that would be encoded is zero.
+type CodecZeroer interface {
+	IsTypeZero(interface{}) bool
+}

mongo/bson/bsoncodec/bsoncodec_test.go

@@ -0,0 +1,143 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+func ExampleValueEncoder() {
+	var _ ValueEncoderFunc = func(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+		if val.Kind() != reflect.String {
+			return ValueEncoderError{Name: "StringEncodeValue", Kinds: []reflect.Kind{reflect.String}, Received: val}
+		}
+
+		return vw.WriteString(val.String())
+	}
+}
+
+func ExampleValueDecoder() {
+	var _ ValueDecoderFunc = func(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+		if !val.CanSet() || val.Kind() != reflect.String {
+			return ValueDecoderError{Name: "StringDecodeValue", Kinds: []reflect.Kind{reflect.String}, Received: val}
+		}
+
+		if vr.Type() != bsontype.String {
+			return fmt.Errorf("cannot decode %v into a string type", vr.Type())
+		}
+
+		str, err := vr.ReadString()
+		if err != nil {
+			return err
+		}
+		val.SetString(str)
+		return nil
+	}
+}
+
+func noerr(t *testing.T, err error) {
+	if err != nil {
+		t.Helper()
+		t.Errorf("Unexpected error: (%T)%v", err, err)
+		t.FailNow()
+	}
+}
+
+func compareTime(t1, t2 time.Time) bool {
+	if t1.Location() != t2.Location() {
+		return false
+	}
+	return t1.Equal(t2)
+}
+
+func compareErrors(err1, err2 error) bool {
+	if err1 == nil && err2 == nil {
+		return true
+	}
+
+	if err1 == nil || err2 == nil {
+		return false
+	}
+
+	if err1.Error() != err2.Error() {
+		return false
+	}
+
+	return true
+}
+
+func compareDecimal128(d1, d2 primitive.Decimal128) bool {
+	d1H, d1L := d1.GetBytes()
+	d2H, d2L := d2.GetBytes()
+
+	if d1H != d2H {
+		return false
+	}
+
+	if d1L != d2L {
+		return false
+	}
+
+	return true
+}
+
+type noPrivateFields struct {
+	a string
+}
+
+func compareNoPrivateFields(npf1, npf2 noPrivateFields) bool {
+	return npf1.a != npf2.a // We don't want these to be equal
+}
+
+type zeroTest struct {
+	reportZero bool
+}
+
+func (z zeroTest) IsZero() bool { return z.reportZero }
+
+func compareZeroTest(_, _ zeroTest) bool { return true }
+
+type nonZeroer struct {
+	value bool
+}
+
+type llCodec struct {
+	t         *testing.T
+	decodeval interface{}
+	encodeval interface{}
+	err       error
+}
+
+func (llc *llCodec) EncodeValue(_ EncodeContext, _ bsonrw.ValueWriter, i interface{}) error {
+	if llc.err != nil {
+		return llc.err
+	}
+
+	llc.encodeval = i
+	return nil
+}
+
+func (llc *llCodec) DecodeValue(_ DecodeContext, _ bsonrw.ValueReader, val reflect.Value) error {
+	if llc.err != nil {
+		return llc.err
+	}
+
+	if !reflect.TypeOf(llc.decodeval).AssignableTo(val.Type()) {
+		llc.t.Errorf("decodeval must be assignable to val provided to DecodeValue, but is not. decodeval %T; val %T", llc.decodeval, val)
+		return nil
+	}
+
+	val.Set(reflect.ValueOf(llc.decodeval))
+	return nil
+}

mongo/bson/bsoncodec/byte_slice_codec.go

@@ -0,0 +1,111 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"fmt"
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+// ByteSliceCodec is the Codec used for []byte values.
+type ByteSliceCodec struct {
+	EncodeNilAsEmpty bool
+}
+
+var (
+	defaultByteSliceCodec = NewByteSliceCodec()
+
+	_ ValueCodec  = defaultByteSliceCodec
+	_ typeDecoder = defaultByteSliceCodec
+)
+
+// NewByteSliceCodec returns a StringCodec with options opts.
+func NewByteSliceCodec(opts ...*bsonoptions.ByteSliceCodecOptions) *ByteSliceCodec {
+	byteSliceOpt := bsonoptions.MergeByteSliceCodecOptions(opts...)
+	codec := ByteSliceCodec{}
+	if byteSliceOpt.EncodeNilAsEmpty != nil {
+		codec.EncodeNilAsEmpty = *byteSliceOpt.EncodeNilAsEmpty
+	}
+	return &codec
+}
+
+// EncodeValue is the ValueEncoder for []byte.
+func (bsc *ByteSliceCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tByteSlice {
+		return ValueEncoderError{Name: "ByteSliceEncodeValue", Types: []reflect.Type{tByteSlice}, Received: val}
+	}
+	if val.IsNil() && !bsc.EncodeNilAsEmpty {
+		return vw.WriteNull()
+	}
+	return vw.WriteBinary(val.Interface().([]byte))
+}
+
+func (bsc *ByteSliceCodec) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	if t != tByteSlice {
+		return emptyValue, ValueDecoderError{
+			Name:     "ByteSliceDecodeValue",
+			Types:    []reflect.Type{tByteSlice},
+			Received: reflect.Zero(t),
+		}
+	}
+
+	var data []byte
+	var err error
+	switch vrType := vr.Type(); vrType {
+	case bsontype.String:
+		str, err := vr.ReadString()
+		if err != nil {
+			return emptyValue, err
+		}
+		data = []byte(str)
+	case bsontype.Symbol:
+		sym, err := vr.ReadSymbol()
+		if err != nil {
+			return emptyValue, err
+		}
+		data = []byte(sym)
+	case bsontype.Binary:
+		var subtype byte
+		data, subtype, err = vr.ReadBinary()
+		if err != nil {
+			return emptyValue, err
+		}
+		if subtype != bsontype.BinaryGeneric && subtype != bsontype.BinaryBinaryOld {
+			return emptyValue, decodeBinaryError{subtype: subtype, typeName: "[]byte"}
+		}
+	case bsontype.Null:
+		err = vr.ReadNull()
+	case bsontype.Undefined:
+		err = vr.ReadUndefined()
+	default:
+		return emptyValue, fmt.Errorf("cannot decode %v into a []byte", vrType)
+	}
+	if err != nil {
+		return emptyValue, err
+	}
+
+	return reflect.ValueOf(data), nil
+}
+
+// DecodeValue is the ValueDecoder for []byte.
+func (bsc *ByteSliceCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Type() != tByteSlice {
+		return ValueDecoderError{Name: "ByteSliceDecodeValue", Types: []reflect.Type{tByteSlice}, Received: val}
+	}
+
+	elem, err := bsc.decodeType(dc, vr, tByteSlice)
+	if err != nil {
+		return err
+	}
+
+	val.Set(elem)
+	return nil
+}

mongo/bson/bsoncodec/cond_addr_codec.go

@@ -0,0 +1,63 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+)
+
+// condAddrEncoder is the encoder used when a pointer to the encoding value has an encoder.
+type condAddrEncoder struct {
+	canAddrEnc ValueEncoder
+	elseEnc    ValueEncoder
+}
+
+var _ ValueEncoder = (*condAddrEncoder)(nil)
+
+// newCondAddrEncoder returns an condAddrEncoder.
+func newCondAddrEncoder(canAddrEnc, elseEnc ValueEncoder) *condAddrEncoder {
+	encoder := condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
+	return &encoder
+}
+
+// EncodeValue is the ValueEncoderFunc for a value that may be addressable.
+func (cae *condAddrEncoder) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if val.CanAddr() {
+		return cae.canAddrEnc.EncodeValue(ec, vw, val)
+	}
+	if cae.elseEnc != nil {
+		return cae.elseEnc.EncodeValue(ec, vw, val)
+	}
+	return ErrNoEncoder{Type: val.Type()}
+}
+
+// condAddrDecoder is the decoder used when a pointer to the value has a decoder.
+type condAddrDecoder struct {
+	canAddrDec ValueDecoder
+	elseDec    ValueDecoder
+}
+
+var _ ValueDecoder = (*condAddrDecoder)(nil)
+
+// newCondAddrDecoder returns an CondAddrDecoder.
+func newCondAddrDecoder(canAddrDec, elseDec ValueDecoder) *condAddrDecoder {
+	decoder := condAddrDecoder{canAddrDec: canAddrDec, elseDec: elseDec}
+	return &decoder
+}
+
+// DecodeValue is the ValueDecoderFunc for a value that may be addressable.
+func (cad *condAddrDecoder) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if val.CanAddr() {
+		return cad.canAddrDec.DecodeValue(dc, vr, val)
+	}
+	if cad.elseDec != nil {
+		return cad.elseDec.DecodeValue(dc, vr, val)
+	}
+	return ErrNoDecoder{Type: val.Type()}
+}

mongo/bson/bsoncodec/cond_addr_codec_test.go

@@ -0,0 +1,97 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"testing"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsonrw/bsonrwtest"
+	"go.mongodb.org/mongo-driver/internal/testutil/assert"
+)
+
+func TestCondAddrCodec(t *testing.T) {
+	var inner int
+	canAddrVal := reflect.ValueOf(&inner)
+	addressable := canAddrVal.Elem()
+	unaddressable := reflect.ValueOf(inner)
+	rw := &bsonrwtest.ValueReaderWriter{}
+
+	t.Run("addressEncode", func(t *testing.T) {
+		invoked := 0
+		encode1 := ValueEncoderFunc(func(EncodeContext, bsonrw.ValueWriter, reflect.Value) error {
+			invoked = 1
+			return nil
+		})
+		encode2 := ValueEncoderFunc(func(EncodeContext, bsonrw.ValueWriter, reflect.Value) error {
+			invoked = 2
+			return nil
+		})
+		condEncoder := newCondAddrEncoder(encode1, encode2)
+
+		testCases := []struct {
+			name    string
+			val     reflect.Value
+			invoked int
+		}{
+			{"canAddr", addressable, 1},
+			{"else", unaddressable, 2},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				err := condEncoder.EncodeValue(EncodeContext{}, rw, tc.val)
+				assert.Nil(t, err, "CondAddrEncoder error: %v", err)
+
+				assert.Equal(t, invoked, tc.invoked, "Expected function %v to be called, called %v", tc.invoked, invoked)
+			})
+		}
+
+		t.Run("error", func(t *testing.T) {
+			errEncoder := newCondAddrEncoder(encode1, nil)
+			err := errEncoder.EncodeValue(EncodeContext{}, rw, unaddressable)
+			want := ErrNoEncoder{Type: unaddressable.Type()}
+			assert.Equal(t, err, want, "expected error %v, got %v", want, err)
+		})
+	})
+	t.Run("addressDecode", func(t *testing.T) {
+		invoked := 0
+		decode1 := ValueDecoderFunc(func(DecodeContext, bsonrw.ValueReader, reflect.Value) error {
+			invoked = 1
+			return nil
+		})
+		decode2 := ValueDecoderFunc(func(DecodeContext, bsonrw.ValueReader, reflect.Value) error {
+			invoked = 2
+			return nil
+		})
+		condDecoder := newCondAddrDecoder(decode1, decode2)
+
+		testCases := []struct {
+			name    string
+			val     reflect.Value
+			invoked int
+		}{
+			{"canAddr", addressable, 1},
+			{"else", unaddressable, 2},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				err := condDecoder.DecodeValue(DecodeContext{}, rw, tc.val)
+				assert.Nil(t, err, "CondAddrDecoder error: %v", err)
+
+				assert.Equal(t, invoked, tc.invoked, "Expected function %v to be called, called %v", tc.invoked, invoked)
+			})
+		}
+
+		t.Run("error", func(t *testing.T) {
+			errDecoder := newCondAddrDecoder(decode1, nil)
+			err := errDecoder.DecodeValue(DecodeContext{}, rw, unaddressable)
+			want := ErrNoDecoder{Type: unaddressable.Type()}
+			assert.Equal(t, err, want, "expected error %v, got %v", want, err)
+		})
+	})
+}

mongo/bson/bsoncodec/default_value_encoders.go

@@ -0,0 +1,766 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"math"
+	"net/url"
+	"reflect"
+	"sync"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
+)
+
+var defaultValueEncoders DefaultValueEncoders
+
+var bvwPool = bsonrw.NewBSONValueWriterPool()
+
+var errInvalidValue = errors.New("cannot encode invalid element")
+
+var sliceWriterPool = sync.Pool{
+	New: func() interface{} {
+		sw := make(bsonrw.SliceWriter, 0)
+		return &sw
+	},
+}
+
+func encodeElement(ec EncodeContext, dw bsonrw.DocumentWriter, e primitive.E) error {
+	vw, err := dw.WriteDocumentElement(e.Key)
+	if err != nil {
+		return err
+	}
+
+	if e.Value == nil {
+		return vw.WriteNull()
+	}
+	encoder, err := ec.LookupEncoder(reflect.TypeOf(e.Value))
+	if err != nil {
+		return err
+	}
+
+	err = encoder.EncodeValue(ec, vw, reflect.ValueOf(e.Value))
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// DefaultValueEncoders is a namespace type for the default ValueEncoders used
+// when creating a registry.
+type DefaultValueEncoders struct{}
+
+// RegisterDefaultEncoders will register the encoder methods attached to DefaultValueEncoders with
+// the provided RegistryBuilder.
+func (dve DefaultValueEncoders) RegisterDefaultEncoders(rb *RegistryBuilder) {
+	if rb == nil {
+		panic(errors.New("argument to RegisterDefaultEncoders must not be nil"))
+	}
+	rb.
+		RegisterTypeEncoder(tByteSlice, defaultByteSliceCodec).
+		RegisterTypeEncoder(tTime, defaultTimeCodec).
+		RegisterTypeEncoder(tEmpty, defaultEmptyInterfaceCodec).
+		RegisterTypeEncoder(tCoreArray, defaultArrayCodec).
+		RegisterTypeEncoder(tOID, ValueEncoderFunc(dve.ObjectIDEncodeValue)).
+		RegisterTypeEncoder(tDecimal, ValueEncoderFunc(dve.Decimal128EncodeValue)).
+		RegisterTypeEncoder(tJSONNumber, ValueEncoderFunc(dve.JSONNumberEncodeValue)).
+		RegisterTypeEncoder(tURL, ValueEncoderFunc(dve.URLEncodeValue)).
+		RegisterTypeEncoder(tJavaScript, ValueEncoderFunc(dve.JavaScriptEncodeValue)).
+		RegisterTypeEncoder(tSymbol, ValueEncoderFunc(dve.SymbolEncodeValue)).
+		RegisterTypeEncoder(tBinary, ValueEncoderFunc(dve.BinaryEncodeValue)).
+		RegisterTypeEncoder(tUndefined, ValueEncoderFunc(dve.UndefinedEncodeValue)).
+		RegisterTypeEncoder(tDateTime, ValueEncoderFunc(dve.DateTimeEncodeValue)).
+		RegisterTypeEncoder(tNull, ValueEncoderFunc(dve.NullEncodeValue)).
+		RegisterTypeEncoder(tRegex, ValueEncoderFunc(dve.RegexEncodeValue)).
+		RegisterTypeEncoder(tDBPointer, ValueEncoderFunc(dve.DBPointerEncodeValue)).
+		RegisterTypeEncoder(tTimestamp, ValueEncoderFunc(dve.TimestampEncodeValue)).
+		RegisterTypeEncoder(tMinKey, ValueEncoderFunc(dve.MinKeyEncodeValue)).
+		RegisterTypeEncoder(tMaxKey, ValueEncoderFunc(dve.MaxKeyEncodeValue)).
+		RegisterTypeEncoder(tCoreDocument, ValueEncoderFunc(dve.CoreDocumentEncodeValue)).
+		RegisterTypeEncoder(tCodeWithScope, ValueEncoderFunc(dve.CodeWithScopeEncodeValue)).
+		RegisterDefaultEncoder(reflect.Bool, ValueEncoderFunc(dve.BooleanEncodeValue)).
+		RegisterDefaultEncoder(reflect.Int, ValueEncoderFunc(dve.IntEncodeValue)).
+		RegisterDefaultEncoder(reflect.Int8, ValueEncoderFunc(dve.IntEncodeValue)).
+		RegisterDefaultEncoder(reflect.Int16, ValueEncoderFunc(dve.IntEncodeValue)).
+		RegisterDefaultEncoder(reflect.Int32, ValueEncoderFunc(dve.IntEncodeValue)).
+		RegisterDefaultEncoder(reflect.Int64, ValueEncoderFunc(dve.IntEncodeValue)).
+		RegisterDefaultEncoder(reflect.Uint, defaultUIntCodec).
+		RegisterDefaultEncoder(reflect.Uint8, defaultUIntCodec).
+		RegisterDefaultEncoder(reflect.Uint16, defaultUIntCodec).
+		RegisterDefaultEncoder(reflect.Uint32, defaultUIntCodec).
+		RegisterDefaultEncoder(reflect.Uint64, defaultUIntCodec).
+		RegisterDefaultEncoder(reflect.Float32, ValueEncoderFunc(dve.FloatEncodeValue)).
+		RegisterDefaultEncoder(reflect.Float64, ValueEncoderFunc(dve.FloatEncodeValue)).
+		RegisterDefaultEncoder(reflect.Array, ValueEncoderFunc(dve.ArrayEncodeValue)).
+		RegisterDefaultEncoder(reflect.Map, defaultMapCodec).
+		RegisterDefaultEncoder(reflect.Slice, defaultSliceCodec).
+		RegisterDefaultEncoder(reflect.String, defaultStringCodec).
+		RegisterDefaultEncoder(reflect.Struct, newDefaultStructCodec()).
+		RegisterDefaultEncoder(reflect.Ptr, NewPointerCodec()).
+		RegisterHookEncoder(tValueMarshaler, ValueEncoderFunc(dve.ValueMarshalerEncodeValue)).
+		RegisterHookEncoder(tMarshaler, ValueEncoderFunc(dve.MarshalerEncodeValue)).
+		RegisterHookEncoder(tProxy, ValueEncoderFunc(dve.ProxyEncodeValue))
+}
+
+// BooleanEncodeValue is the ValueEncoderFunc for bool types.
+func (dve DefaultValueEncoders) BooleanEncodeValue(ectx EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Bool {
+		return ValueEncoderError{Name: "BooleanEncodeValue", Kinds: []reflect.Kind{reflect.Bool}, Received: val}
+	}
+	return vw.WriteBoolean(val.Bool())
+}
+
+func fitsIn32Bits(i int64) bool {
+	return math.MinInt32 <= i && i <= math.MaxInt32
+}
+
+// IntEncodeValue is the ValueEncoderFunc for int types.
+func (dve DefaultValueEncoders) IntEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	switch val.Kind() {
+	case reflect.Int8, reflect.Int16, reflect.Int32:
+		return vw.WriteInt32(int32(val.Int()))
+	case reflect.Int:
+		i64 := val.Int()
+		if fitsIn32Bits(i64) {
+			return vw.WriteInt32(int32(i64))
+		}
+		return vw.WriteInt64(i64)
+	case reflect.Int64:
+		i64 := val.Int()
+		if ec.MinSize && fitsIn32Bits(i64) {
+			return vw.WriteInt32(int32(i64))
+		}
+		return vw.WriteInt64(i64)
+	}
+
+	return ValueEncoderError{
+		Name:     "IntEncodeValue",
+		Kinds:    []reflect.Kind{reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int},
+		Received: val,
+	}
+}
+
+// UintEncodeValue is the ValueEncoderFunc for uint types.
+//
+// Deprecated: UintEncodeValue is not registered by default. Use UintCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) UintEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	switch val.Kind() {
+	case reflect.Uint8, reflect.Uint16:
+		return vw.WriteInt32(int32(val.Uint()))
+	case reflect.Uint, reflect.Uint32, reflect.Uint64:
+		u64 := val.Uint()
+		if ec.MinSize && u64 <= math.MaxInt32 {
+			return vw.WriteInt32(int32(u64))
+		}
+		if u64 > math.MaxInt64 {
+			return fmt.Errorf("%d overflows int64", u64)
+		}
+		return vw.WriteInt64(int64(u64))
+	}
+
+	return ValueEncoderError{
+		Name:     "UintEncodeValue",
+		Kinds:    []reflect.Kind{reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint},
+		Received: val,
+	}
+}
+
+// FloatEncodeValue is the ValueEncoderFunc for float types.
+func (dve DefaultValueEncoders) FloatEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	switch val.Kind() {
+	case reflect.Float32, reflect.Float64:
+		return vw.WriteDouble(val.Float())
+	}
+
+	return ValueEncoderError{Name: "FloatEncodeValue", Kinds: []reflect.Kind{reflect.Float32, reflect.Float64}, Received: val}
+}
+
+// StringEncodeValue is the ValueEncoderFunc for string types.
+//
+// Deprecated: StringEncodeValue is not registered by default. Use StringCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) StringEncodeValue(ectx EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if val.Kind() != reflect.String {
+		return ValueEncoderError{
+			Name:     "StringEncodeValue",
+			Kinds:    []reflect.Kind{reflect.String},
+			Received: val,
+		}
+	}
+
+	return vw.WriteString(val.String())
+}
+
+// ObjectIDEncodeValue is the ValueEncoderFunc for primitive.ObjectID.
+func (dve DefaultValueEncoders) ObjectIDEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tOID {
+		return ValueEncoderError{Name: "ObjectIDEncodeValue", Types: []reflect.Type{tOID}, Received: val}
+	}
+	return vw.WriteObjectID(val.Interface().(primitive.ObjectID))
+}
+
+// Decimal128EncodeValue is the ValueEncoderFunc for primitive.Decimal128.
+func (dve DefaultValueEncoders) Decimal128EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tDecimal {
+		return ValueEncoderError{Name: "Decimal128EncodeValue", Types: []reflect.Type{tDecimal}, Received: val}
+	}
+	return vw.WriteDecimal128(val.Interface().(primitive.Decimal128))
+}
+
+// JSONNumberEncodeValue is the ValueEncoderFunc for json.Number.
+func (dve DefaultValueEncoders) JSONNumberEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tJSONNumber {
+		return ValueEncoderError{Name: "JSONNumberEncodeValue", Types: []reflect.Type{tJSONNumber}, Received: val}
+	}
+	jsnum := val.Interface().(json.Number)
+
+	// Attempt int first, then float64
+	if i64, err := jsnum.Int64(); err == nil {
+		return dve.IntEncodeValue(ec, vw, reflect.ValueOf(i64))
+	}
+
+	f64, err := jsnum.Float64()
+	if err != nil {
+		return err
+	}
+
+	return dve.FloatEncodeValue(ec, vw, reflect.ValueOf(f64))
+}
+
+// URLEncodeValue is the ValueEncoderFunc for url.URL.
+func (dve DefaultValueEncoders) URLEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tURL {
+		return ValueEncoderError{Name: "URLEncodeValue", Types: []reflect.Type{tURL}, Received: val}
+	}
+	u := val.Interface().(url.URL)
+	return vw.WriteString(u.String())
+}
+
+// TimeEncodeValue is the ValueEncoderFunc for time.TIme.
+//
+// Deprecated: TimeEncodeValue is not registered by default. Use TimeCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) TimeEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tTime {
+		return ValueEncoderError{Name: "TimeEncodeValue", Types: []reflect.Type{tTime}, Received: val}
+	}
+	tt := val.Interface().(time.Time)
+	dt := primitive.NewDateTimeFromTime(tt)
+	return vw.WriteDateTime(int64(dt))
+}
+
+// ByteSliceEncodeValue is the ValueEncoderFunc for []byte.
+//
+// Deprecated: ByteSliceEncodeValue is not registered by default. Use ByteSliceCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) ByteSliceEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tByteSlice {
+		return ValueEncoderError{Name: "ByteSliceEncodeValue", Types: []reflect.Type{tByteSlice}, Received: val}
+	}
+	if val.IsNil() {
+		return vw.WriteNull()
+	}
+	return vw.WriteBinary(val.Interface().([]byte))
+}
+
+// MapEncodeValue is the ValueEncoderFunc for map[string]* types.
+//
+// Deprecated: MapEncodeValue is not registered by default. Use MapCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) MapEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Map || val.Type().Key().Kind() != reflect.String {
+		return ValueEncoderError{Name: "MapEncodeValue", Kinds: []reflect.Kind{reflect.Map}, Received: val}
+	}
+
+	if val.IsNil() {
+		// If we have a nill map but we can't WriteNull, that means we're probably trying to encode
+		// to a TopLevel document. We can't currently tell if this is what actually happened, but if
+		// there's a deeper underlying problem, the error will also be returned from WriteDocument,
+		// so just continue. The operations on a map reflection value are valid, so we can call
+		// MapKeys within mapEncodeValue without a problem.
+		err := vw.WriteNull()
+		if err == nil {
+			return nil
+		}
+	}
+
+	dw, err := vw.WriteDocument()
+	if err != nil {
+		return err
+	}
+
+	return dve.mapEncodeValue(ec, dw, val, nil)
+}
+
+// mapEncodeValue handles encoding of the values of a map. The collisionFn returns
+// true if the provided key exists, this is mainly used for inline maps in the
+// struct codec.
+func (dve DefaultValueEncoders) mapEncodeValue(ec EncodeContext, dw bsonrw.DocumentWriter, val reflect.Value, collisionFn func(string) bool) error {
+
+	elemType := val.Type().Elem()
+	encoder, err := ec.LookupEncoder(elemType)
+	if err != nil && elemType.Kind() != reflect.Interface {
+		return err
+	}
+
+	keys := val.MapKeys()
+	for _, key := range keys {
+		if collisionFn != nil && collisionFn(key.String()) {
+			return fmt.Errorf("Key %s of inlined map conflicts with a struct field name", key)
+		}
+
+		currEncoder, currVal, lookupErr := dve.lookupElementEncoder(ec, encoder, val.MapIndex(key))
+		if lookupErr != nil && lookupErr != errInvalidValue {
+			return lookupErr
+		}
+
+		vw, err := dw.WriteDocumentElement(key.String())
+		if err != nil {
+			return err
+		}
+
+		if lookupErr == errInvalidValue {
+			err = vw.WriteNull()
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		err = currEncoder.EncodeValue(ec, vw, currVal)
+		if err != nil {
+			return err
+		}
+	}
+
+	return dw.WriteDocumentEnd()
+}
+
+// ArrayEncodeValue is the ValueEncoderFunc for array types.
+func (dve DefaultValueEncoders) ArrayEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Array {
+		return ValueEncoderError{Name: "ArrayEncodeValue", Kinds: []reflect.Kind{reflect.Array}, Received: val}
+	}
+
+	// If we have a []primitive.E we want to treat it as a document instead of as an array.
+	if val.Type().Elem() == tE {
+		dw, err := vw.WriteDocument()
+		if err != nil {
+			return err
+		}
+
+		for idx := 0; idx < val.Len(); idx++ {
+			e := val.Index(idx).Interface().(primitive.E)
+			err = encodeElement(ec, dw, e)
+			if err != nil {
+				return err
+			}
+		}
+
+		return dw.WriteDocumentEnd()
+	}
+
+	// If we have a []byte we want to treat it as a binary instead of as an array.
+	if val.Type().Elem() == tByte {
+		var byteSlice []byte
+		for idx := 0; idx < val.Len(); idx++ {
+			byteSlice = append(byteSlice, val.Index(idx).Interface().(byte))
+		}
+		return vw.WriteBinary(byteSlice)
+	}
+
+	aw, err := vw.WriteArray()
+	if err != nil {
+		return err
+	}
+
+	elemType := val.Type().Elem()
+	encoder, err := ec.LookupEncoder(elemType)
+	if err != nil && elemType.Kind() != reflect.Interface {
+		return err
+	}
+
+	for idx := 0; idx < val.Len(); idx++ {
+		currEncoder, currVal, lookupErr := dve.lookupElementEncoder(ec, encoder, val.Index(idx))
+		if lookupErr != nil && lookupErr != errInvalidValue {
+			return lookupErr
+		}
+
+		vw, err := aw.WriteArrayElement()
+		if err != nil {
+			return err
+		}
+
+		if lookupErr == errInvalidValue {
+			err = vw.WriteNull()
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		err = currEncoder.EncodeValue(ec, vw, currVal)
+		if err != nil {
+			return err
+		}
+	}
+	return aw.WriteArrayEnd()
+}
+
+// SliceEncodeValue is the ValueEncoderFunc for slice types.
+//
+// Deprecated: SliceEncodeValue is not registered by default. Use SliceCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) SliceEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Slice {
+		return ValueEncoderError{Name: "SliceEncodeValue", Kinds: []reflect.Kind{reflect.Slice}, Received: val}
+	}
+
+	if val.IsNil() {
+		return vw.WriteNull()
+	}
+
+	// If we have a []primitive.E we want to treat it as a document instead of as an array.
+	if val.Type().ConvertibleTo(tD) {
+		d := val.Convert(tD).Interface().(primitive.D)
+
+		dw, err := vw.WriteDocument()
+		if err != nil {
+			return err
+		}
+
+		for _, e := range d {
+			err = encodeElement(ec, dw, e)
+			if err != nil {
+				return err
+			}
+		}
+
+		return dw.WriteDocumentEnd()
+	}
+
+	aw, err := vw.WriteArray()
+	if err != nil {
+		return err
+	}
+
+	elemType := val.Type().Elem()
+	encoder, err := ec.LookupEncoder(elemType)
+	if err != nil && elemType.Kind() != reflect.Interface {
+		return err
+	}
+
+	for idx := 0; idx < val.Len(); idx++ {
+		currEncoder, currVal, lookupErr := dve.lookupElementEncoder(ec, encoder, val.Index(idx))
+		if lookupErr != nil && lookupErr != errInvalidValue {
+			return lookupErr
+		}
+
+		vw, err := aw.WriteArrayElement()
+		if err != nil {
+			return err
+		}
+
+		if lookupErr == errInvalidValue {
+			err = vw.WriteNull()
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		err = currEncoder.EncodeValue(ec, vw, currVal)
+		if err != nil {
+			return err
+		}
+	}
+	return aw.WriteArrayEnd()
+}
+
+func (dve DefaultValueEncoders) lookupElementEncoder(ec EncodeContext, origEncoder ValueEncoder, currVal reflect.Value) (ValueEncoder, reflect.Value, error) {
+	if origEncoder != nil || (currVal.Kind() != reflect.Interface) {
+		return origEncoder, currVal, nil
+	}
+	currVal = currVal.Elem()
+	if !currVal.IsValid() {
+		return nil, currVal, errInvalidValue
+	}
+	currEncoder, err := ec.LookupEncoder(currVal.Type())
+
+	return currEncoder, currVal, err
+}
+
+// EmptyInterfaceEncodeValue is the ValueEncoderFunc for interface{}.
+//
+// Deprecated: EmptyInterfaceEncodeValue is not registered by default. Use EmptyInterfaceCodec.EncodeValue instead.
+func (dve DefaultValueEncoders) EmptyInterfaceEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tEmpty {
+		return ValueEncoderError{Name: "EmptyInterfaceEncodeValue", Types: []reflect.Type{tEmpty}, Received: val}
+	}
+
+	if val.IsNil() {
+		return vw.WriteNull()
+	}
+	encoder, err := ec.LookupEncoder(val.Elem().Type())
+	if err != nil {
+		return err
+	}
+
+	return encoder.EncodeValue(ec, vw, val.Elem())
+}
+
+// ValueMarshalerEncodeValue is the ValueEncoderFunc for ValueMarshaler implementations.
+func (dve DefaultValueEncoders) ValueMarshalerEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	// Either val or a pointer to val must implement ValueMarshaler
+	switch {
+	case !val.IsValid():
+		return ValueEncoderError{Name: "ValueMarshalerEncodeValue", Types: []reflect.Type{tValueMarshaler}, Received: val}
+	case val.Type().Implements(tValueMarshaler):
+		// If ValueMarshaler is implemented on a concrete type, make sure that val isn't a nil pointer
+		if isImplementationNil(val, tValueMarshaler) {
+			return vw.WriteNull()
+		}
+	case reflect.PtrTo(val.Type()).Implements(tValueMarshaler) && val.CanAddr():
+		val = val.Addr()
+	default:
+		return ValueEncoderError{Name: "ValueMarshalerEncodeValue", Types: []reflect.Type{tValueMarshaler}, Received: val}
+	}
+
+	fn := val.Convert(tValueMarshaler).MethodByName("MarshalBSONValue")
+	returns := fn.Call(nil)
+	if !returns[2].IsNil() {
+		return returns[2].Interface().(error)
+	}
+	t, data := returns[0].Interface().(bsontype.Type), returns[1].Interface().([]byte)
+	return bsonrw.Copier{}.CopyValueFromBytes(vw, t, data)
+}
+
+// MarshalerEncodeValue is the ValueEncoderFunc for Marshaler implementations.
+func (dve DefaultValueEncoders) MarshalerEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	// Either val or a pointer to val must implement Marshaler
+	switch {
+	case !val.IsValid():
+		return ValueEncoderError{Name: "MarshalerEncodeValue", Types: []reflect.Type{tMarshaler}, Received: val}
+	case val.Type().Implements(tMarshaler):
+		// If Marshaler is implemented on a concrete type, make sure that val isn't a nil pointer
+		if isImplementationNil(val, tMarshaler) {
+			return vw.WriteNull()
+		}
+	case reflect.PtrTo(val.Type()).Implements(tMarshaler) && val.CanAddr():
+		val = val.Addr()
+	default:
+		return ValueEncoderError{Name: "MarshalerEncodeValue", Types: []reflect.Type{tMarshaler}, Received: val}
+	}
+
+	fn := val.Convert(tMarshaler).MethodByName("MarshalBSON")
+	returns := fn.Call(nil)
+	if !returns[1].IsNil() {
+		return returns[1].Interface().(error)
+	}
+	data := returns[0].Interface().([]byte)
+	return bsonrw.Copier{}.CopyValueFromBytes(vw, bsontype.EmbeddedDocument, data)
+}
+
+// ProxyEncodeValue is the ValueEncoderFunc for Proxy implementations.
+func (dve DefaultValueEncoders) ProxyEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	// Either val or a pointer to val must implement Proxy
+	switch {
+	case !val.IsValid():
+		return ValueEncoderError{Name: "ProxyEncodeValue", Types: []reflect.Type{tProxy}, Received: val}
+	case val.Type().Implements(tProxy):
+		// If Proxy is implemented on a concrete type, make sure that val isn't a nil pointer
+		if isImplementationNil(val, tProxy) {
+			return vw.WriteNull()
+		}
+	case reflect.PtrTo(val.Type()).Implements(tProxy) && val.CanAddr():
+		val = val.Addr()
+	default:
+		return ValueEncoderError{Name: "ProxyEncodeValue", Types: []reflect.Type{tProxy}, Received: val}
+	}
+
+	fn := val.Convert(tProxy).MethodByName("ProxyBSON")
+	returns := fn.Call(nil)
+	if !returns[1].IsNil() {
+		return returns[1].Interface().(error)
+	}
+	data := returns[0]
+	var encoder ValueEncoder
+	var err error
+	if data.Elem().IsValid() {
+		encoder, err = ec.LookupEncoder(data.Elem().Type())
+	} else {
+		encoder, err = ec.LookupEncoder(nil)
+	}
+	if err != nil {
+		return err
+	}
+	return encoder.EncodeValue(ec, vw, data.Elem())
+}
+
+// JavaScriptEncodeValue is the ValueEncoderFunc for the primitive.JavaScript type.
+func (DefaultValueEncoders) JavaScriptEncodeValue(ectx EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tJavaScript {
+		return ValueEncoderError{Name: "JavaScriptEncodeValue", Types: []reflect.Type{tJavaScript}, Received: val}
+	}
+
+	return vw.WriteJavascript(val.String())
+}
+
+// SymbolEncodeValue is the ValueEncoderFunc for the primitive.Symbol type.
+func (DefaultValueEncoders) SymbolEncodeValue(ectx EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tSymbol {
+		return ValueEncoderError{Name: "SymbolEncodeValue", Types: []reflect.Type{tSymbol}, Received: val}
+	}
+
+	return vw.WriteSymbol(val.String())
+}
+
+// BinaryEncodeValue is the ValueEncoderFunc for Binary.
+func (DefaultValueEncoders) BinaryEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tBinary {
+		return ValueEncoderError{Name: "BinaryEncodeValue", Types: []reflect.Type{tBinary}, Received: val}
+	}
+	b := val.Interface().(primitive.Binary)
+
+	return vw.WriteBinaryWithSubtype(b.Data, b.Subtype)
+}
+
+// UndefinedEncodeValue is the ValueEncoderFunc for Undefined.
+func (DefaultValueEncoders) UndefinedEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tUndefined {
+		return ValueEncoderError{Name: "UndefinedEncodeValue", Types: []reflect.Type{tUndefined}, Received: val}
+	}
+
+	return vw.WriteUndefined()
+}
+
+// DateTimeEncodeValue is the ValueEncoderFunc for DateTime.
+func (DefaultValueEncoders) DateTimeEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tDateTime {
+		return ValueEncoderError{Name: "DateTimeEncodeValue", Types: []reflect.Type{tDateTime}, Received: val}
+	}
+
+	return vw.WriteDateTime(val.Int())
+}
+
+// NullEncodeValue is the ValueEncoderFunc for Null.
+func (DefaultValueEncoders) NullEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tNull {
+		return ValueEncoderError{Name: "NullEncodeValue", Types: []reflect.Type{tNull}, Received: val}
+	}
+
+	return vw.WriteNull()
+}
+
+// RegexEncodeValue is the ValueEncoderFunc for Regex.
+func (DefaultValueEncoders) RegexEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tRegex {
+		return ValueEncoderError{Name: "RegexEncodeValue", Types: []reflect.Type{tRegex}, Received: val}
+	}
+
+	regex := val.Interface().(primitive.Regex)
+
+	return vw.WriteRegex(regex.Pattern, regex.Options)
+}
+
+// DBPointerEncodeValue is the ValueEncoderFunc for DBPointer.
+func (DefaultValueEncoders) DBPointerEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tDBPointer {
+		return ValueEncoderError{Name: "DBPointerEncodeValue", Types: []reflect.Type{tDBPointer}, Received: val}
+	}
+
+	dbp := val.Interface().(primitive.DBPointer)
+
+	return vw.WriteDBPointer(dbp.DB, dbp.Pointer)
+}
+
+// TimestampEncodeValue is the ValueEncoderFunc for Timestamp.
+func (DefaultValueEncoders) TimestampEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tTimestamp {
+		return ValueEncoderError{Name: "TimestampEncodeValue", Types: []reflect.Type{tTimestamp}, Received: val}
+	}
+
+	ts := val.Interface().(primitive.Timestamp)
+
+	return vw.WriteTimestamp(ts.T, ts.I)
+}
+
+// MinKeyEncodeValue is the ValueEncoderFunc for MinKey.
+func (DefaultValueEncoders) MinKeyEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tMinKey {
+		return ValueEncoderError{Name: "MinKeyEncodeValue", Types: []reflect.Type{tMinKey}, Received: val}
+	}
+
+	return vw.WriteMinKey()
+}
+
+// MaxKeyEncodeValue is the ValueEncoderFunc for MaxKey.
+func (DefaultValueEncoders) MaxKeyEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tMaxKey {
+		return ValueEncoderError{Name: "MaxKeyEncodeValue", Types: []reflect.Type{tMaxKey}, Received: val}
+	}
+
+	return vw.WriteMaxKey()
+}
+
+// CoreDocumentEncodeValue is the ValueEncoderFunc for bsoncore.Document.
+func (DefaultValueEncoders) CoreDocumentEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tCoreDocument {
+		return ValueEncoderError{Name: "CoreDocumentEncodeValue", Types: []reflect.Type{tCoreDocument}, Received: val}
+	}
+
+	cdoc := val.Interface().(bsoncore.Document)
+
+	return bsonrw.Copier{}.CopyDocumentFromBytes(vw, cdoc)
+}
+
+// CodeWithScopeEncodeValue is the ValueEncoderFunc for CodeWithScope.
+func (dve DefaultValueEncoders) CodeWithScopeEncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tCodeWithScope {
+		return ValueEncoderError{Name: "CodeWithScopeEncodeValue", Types: []reflect.Type{tCodeWithScope}, Received: val}
+	}
+
+	cws := val.Interface().(primitive.CodeWithScope)
+
+	dw, err := vw.WriteCodeWithScope(string(cws.Code))
+	if err != nil {
+		return err
+	}
+
+	sw := sliceWriterPool.Get().(*bsonrw.SliceWriter)
+	defer sliceWriterPool.Put(sw)
+	*sw = (*sw)[:0]
+
+	scopeVW := bvwPool.Get(sw)
+	defer bvwPool.Put(scopeVW)
+
+	encoder, err := ec.LookupEncoder(reflect.TypeOf(cws.Scope))
+	if err != nil {
+		return err
+	}
+
+	err = encoder.EncodeValue(ec, scopeVW, reflect.ValueOf(cws.Scope))
+	if err != nil {
+		return err
+	}
+
+	err = bsonrw.Copier{}.CopyBytesToDocumentWriter(dw, *sw)
+	if err != nil {
+		return err
+	}
+	return dw.WriteDocumentEnd()
+}
+
+// isImplementationNil returns if val is a nil pointer and inter is implemented on a concrete type
+func isImplementationNil(val reflect.Value, inter reflect.Type) bool {
+	vt := val.Type()
+	for vt.Kind() == reflect.Ptr {
+		vt = vt.Elem()
+	}
+	return vt.Implements(inter) && val.Kind() == reflect.Ptr && val.IsNil()
+}

mongo/bson/bsoncodec/doc.go

@@ -0,0 +1,90 @@
+// Copyright (C) MongoDB, Inc. 2022-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+// Package bsoncodec provides a system for encoding values to BSON representations and decoding
+// values from BSON representations. This package considers both binary BSON and ExtendedJSON as
+// BSON representations. The types in this package enable a flexible system for handling this
+// encoding and decoding.
+//
+// The codec system is composed of two parts:
+//
+// 1) ValueEncoders and ValueDecoders that handle encoding and decoding Go values to and from BSON
+// representations.
+//
+// 2) A Registry that holds these ValueEncoders and ValueDecoders and provides methods for
+// retrieving them.
+//
+// # ValueEncoders and ValueDecoders
+//
+// The ValueEncoder interface is implemented by types that can encode a provided Go type to BSON.
+// The value to encode is provided as a reflect.Value and a bsonrw.ValueWriter is used within the
+// EncodeValue method to actually create the BSON representation. For convenience, ValueEncoderFunc
+// is provided to allow use of a function with the correct signature as a ValueEncoder. An
+// EncodeContext instance is provided to allow implementations to lookup further ValueEncoders and
+// to provide configuration information.
+//
+// The ValueDecoder interface is the inverse of the ValueEncoder. Implementations should ensure that
+// the value they receive is settable. Similar to ValueEncoderFunc, ValueDecoderFunc is provided to
+// allow the use of a function with the correct signature as a ValueDecoder. A DecodeContext
+// instance is provided and serves similar functionality to the EncodeContext.
+//
+// # Registry and RegistryBuilder
+//
+// A Registry is an immutable store for ValueEncoders, ValueDecoders, and a type map. See the Registry type
+// documentation for examples of registering various custom encoders and decoders. A Registry can be constructed using a
+// RegistryBuilder, which handles three main types of codecs:
+//
+// 1. Type encoders/decoders - These can be registered using the RegisterTypeEncoder and RegisterTypeDecoder methods.
+// The registered codec will be invoked when encoding/decoding a value whose type matches the registered type exactly.
+// If the registered type is an interface, the codec will be invoked when encoding or decoding values whose type is the
+// interface, but not for values with concrete types that implement the interface.
+//
+// 2. Hook encoders/decoders - These can be registered using the RegisterHookEncoder and RegisterHookDecoder methods.
+// These methods only accept interface types and the registered codecs will be invoked when encoding or decoding values
+// whose types implement the interface. An example of a hook defined by the driver is bson.Marshaler. The driver will
+// call the MarshalBSON method for any value whose type implements bson.Marshaler, regardless of the value's concrete
+// type.
+//
+// 3. Type map entries - This can be used to associate a BSON type with a Go type. These type associations are used when
+// decoding into a bson.D/bson.M or a struct field of type interface{}. For example, by default, BSON int32 and int64
+// values decode as Go int32 and int64 instances, respectively, when decoding into a bson.D. The following code would
+// change the behavior so these values decode as Go int instances instead:
+//
+//	intType := reflect.TypeOf(int(0))
+//	registryBuilder.RegisterTypeMapEntry(bsontype.Int32, intType).RegisterTypeMapEntry(bsontype.Int64, intType)
+//
+// 4. Kind encoder/decoders - These can be registered using the RegisterDefaultEncoder and RegisterDefaultDecoder
+// methods. The registered codec will be invoked when encoding or decoding values whose reflect.Kind matches the
+// registered reflect.Kind as long as the value's type doesn't match a registered type or hook encoder/decoder first.
+// These methods should be used to change the behavior for all values for a specific kind.
+//
+// # Registry Lookup Procedure
+//
+// When looking up an encoder in a Registry, the precedence rules are as follows:
+//
+// 1. A type encoder registered for the exact type of the value.
+//
+// 2. A hook encoder registered for an interface that is implemented by the value or by a pointer to the value. If the
+// value matches multiple hooks (e.g. the type implements bsoncodec.Marshaler and bsoncodec.ValueMarshaler), the first
+// one registered will be selected. Note that registries constructed using bson.NewRegistryBuilder have driver-defined
+// hooks registered for the bsoncodec.Marshaler, bsoncodec.ValueMarshaler, and bsoncodec.Proxy interfaces, so those
+// will take precedence over any new hooks.
+//
+// 3. A kind encoder registered for the value's kind.
+//
+// If all of these lookups fail to find an encoder, an error of type ErrNoEncoder is returned. The same precedence
+// rules apply for decoders, with the exception that an error of type ErrNoDecoder will be returned if no decoder is
+// found.
+//
+// # DefaultValueEncoders and DefaultValueDecoders
+//
+// The DefaultValueEncoders and DefaultValueDecoders types provide a full set of ValueEncoders and
+// ValueDecoders for handling a wide range of Go types, including all of the types within the
+// primitive package. To make registering these codecs easier, a helper method on each type is
+// provided. For the DefaultValueEncoders type the method is called RegisterDefaultEncoders and for
+// the DefaultValueDecoders type the method is called RegisterDefaultDecoders, this method also
+// handles registering type map entries for each BSON type.
+package bsoncodec

mongo/bson/bsoncodec/empty_interface_codec.go

@@ -0,0 +1,147 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+// EmptyInterfaceCodec is the Codec used for interface{} values.
+type EmptyInterfaceCodec struct {
+	DecodeBinaryAsSlice bool
+}
+
+var (
+	defaultEmptyInterfaceCodec = NewEmptyInterfaceCodec()
+
+	_ ValueCodec  = defaultEmptyInterfaceCodec
+	_ typeDecoder = defaultEmptyInterfaceCodec
+)
+
+// NewEmptyInterfaceCodec returns a EmptyInterfaceCodec with options opts.
+func NewEmptyInterfaceCodec(opts ...*bsonoptions.EmptyInterfaceCodecOptions) *EmptyInterfaceCodec {
+	interfaceOpt := bsonoptions.MergeEmptyInterfaceCodecOptions(opts...)
+
+	codec := EmptyInterfaceCodec{}
+	if interfaceOpt.DecodeBinaryAsSlice != nil {
+		codec.DecodeBinaryAsSlice = *interfaceOpt.DecodeBinaryAsSlice
+	}
+	return &codec
+}
+
+// EncodeValue is the ValueEncoderFunc for interface{}.
+func (eic EmptyInterfaceCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tEmpty {
+		return ValueEncoderError{Name: "EmptyInterfaceEncodeValue", Types: []reflect.Type{tEmpty}, Received: val}
+	}
+
+	if val.IsNil() {
+		return vw.WriteNull()
+	}
+	encoder, err := ec.LookupEncoder(val.Elem().Type())
+	if err != nil {
+		return err
+	}
+
+	return encoder.EncodeValue(ec, vw, val.Elem())
+}
+
+func (eic EmptyInterfaceCodec) getEmptyInterfaceDecodeType(dc DecodeContext, valueType bsontype.Type) (reflect.Type, error) {
+	isDocument := valueType == bsontype.Type(0) || valueType == bsontype.EmbeddedDocument
+	if isDocument {
+		if dc.defaultDocumentType != nil {
+			// If the bsontype is an embedded document and the DocumentType is set on the DecodeContext, then return
+			// that type.
+			return dc.defaultDocumentType, nil
+		}
+		if dc.Ancestor != nil {
+			// Using ancestor information rather than looking up the type map entry forces consistent decoding.
+			// If we're decoding into a bson.D, subdocuments should also be decoded as bson.D, even if a type map entry
+			// has been registered.
+			return dc.Ancestor, nil
+		}
+	}
+
+	rtype, err := dc.LookupTypeMapEntry(valueType)
+	if err == nil {
+		return rtype, nil
+	}
+
+	if isDocument {
+		// For documents, fallback to looking up a type map entry for bsontype.Type(0) or bsontype.EmbeddedDocument,
+		// depending on the original valueType.
+		var lookupType bsontype.Type
+		switch valueType {
+		case bsontype.Type(0):
+			lookupType = bsontype.EmbeddedDocument
+		case bsontype.EmbeddedDocument:
+			lookupType = bsontype.Type(0)
+		}
+
+		rtype, err = dc.LookupTypeMapEntry(lookupType)
+		if err == nil {
+			return rtype, nil
+		}
+	}
+
+	return nil, err
+}
+
+func (eic EmptyInterfaceCodec) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	if t != tEmpty {
+		return emptyValue, ValueDecoderError{Name: "EmptyInterfaceDecodeValue", Types: []reflect.Type{tEmpty}, Received: reflect.Zero(t)}
+	}
+
+	rtype, err := eic.getEmptyInterfaceDecodeType(dc, vr.Type())
+	if err != nil {
+		switch vr.Type() {
+		case bsontype.Null:
+			return reflect.Zero(t), vr.ReadNull()
+		default:
+			return emptyValue, err
+		}
+	}
+
+	decoder, err := dc.LookupDecoder(rtype)
+	if err != nil {
+		return emptyValue, err
+	}
+
+	elem, err := decodeTypeOrValue(decoder, dc, vr, rtype)
+	if err != nil {
+		return emptyValue, err
+	}
+
+	if eic.DecodeBinaryAsSlice && rtype == tBinary {
+		binElem := elem.Interface().(primitive.Binary)
+		if binElem.Subtype == bsontype.BinaryGeneric || binElem.Subtype == bsontype.BinaryBinaryOld {
+			elem = reflect.ValueOf(binElem.Data)
+		}
+	}
+
+	return elem, nil
+}
+
+// DecodeValue is the ValueDecoderFunc for interface{}.
+func (eic EmptyInterfaceCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Type() != tEmpty {
+		return ValueDecoderError{Name: "EmptyInterfaceDecodeValue", Types: []reflect.Type{tEmpty}, Received: val}
+	}
+
+	elem, err := eic.decodeType(dc, vr, val.Type())
+	if err != nil {
+		return err
+	}
+
+	val.Set(elem)
+	return nil
+}

mongo/bson/bsoncodec/map_codec.go

@@ -0,0 +1,309 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"encoding"
+	"fmt"
+	"reflect"
+	"strconv"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+var defaultMapCodec = NewMapCodec()
+
+// MapCodec is the Codec used for map values.
+type MapCodec struct {
+	DecodeZerosMap         bool
+	EncodeNilAsEmpty       bool
+	EncodeKeysWithStringer bool
+}
+
+var _ ValueCodec = &MapCodec{}
+
+// KeyMarshaler is the interface implemented by an object that can marshal itself into a string key.
+// This applies to types used as map keys and is similar to encoding.TextMarshaler.
+type KeyMarshaler interface {
+	MarshalKey() (key string, err error)
+}
+
+// KeyUnmarshaler is the interface implemented by an object that can unmarshal a string representation
+// of itself. This applies to types used as map keys and is similar to encoding.TextUnmarshaler.
+//
+// UnmarshalKey must be able to decode the form generated by MarshalKey.
+// UnmarshalKey must copy the text if it wishes to retain the text
+// after returning.
+type KeyUnmarshaler interface {
+	UnmarshalKey(key string) error
+}
+
+// NewMapCodec returns a MapCodec with options opts.
+func NewMapCodec(opts ...*bsonoptions.MapCodecOptions) *MapCodec {
+	mapOpt := bsonoptions.MergeMapCodecOptions(opts...)
+
+	codec := MapCodec{}
+	if mapOpt.DecodeZerosMap != nil {
+		codec.DecodeZerosMap = *mapOpt.DecodeZerosMap
+	}
+	if mapOpt.EncodeNilAsEmpty != nil {
+		codec.EncodeNilAsEmpty = *mapOpt.EncodeNilAsEmpty
+	}
+	if mapOpt.EncodeKeysWithStringer != nil {
+		codec.EncodeKeysWithStringer = *mapOpt.EncodeKeysWithStringer
+	}
+	return &codec
+}
+
+// EncodeValue is the ValueEncoder for map[*]* types.
+func (mc *MapCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Map {
+		return ValueEncoderError{Name: "MapEncodeValue", Kinds: []reflect.Kind{reflect.Map}, Received: val}
+	}
+
+	if val.IsNil() && !mc.EncodeNilAsEmpty {
+		// If we have a nil map but we can't WriteNull, that means we're probably trying to encode
+		// to a TopLevel document. We can't currently tell if this is what actually happened, but if
+		// there's a deeper underlying problem, the error will also be returned from WriteDocument,
+		// so just continue. The operations on a map reflection value are valid, so we can call
+		// MapKeys within mapEncodeValue without a problem.
+		err := vw.WriteNull()
+		if err == nil {
+			return nil
+		}
+	}
+
+	dw, err := vw.WriteDocument()
+	if err != nil {
+		return err
+	}
+
+	return mc.mapEncodeValue(ec, dw, val, nil)
+}
+
+// mapEncodeValue handles encoding of the values of a map. The collisionFn returns
+// true if the provided key exists, this is mainly used for inline maps in the
+// struct codec.
+func (mc *MapCodec) mapEncodeValue(ec EncodeContext, dw bsonrw.DocumentWriter, val reflect.Value, collisionFn func(string) bool) error {
+
+	elemType := val.Type().Elem()
+	encoder, err := ec.LookupEncoder(elemType)
+	if err != nil && elemType.Kind() != reflect.Interface {
+		return err
+	}
+
+	keys := val.MapKeys()
+	for _, key := range keys {
+		keyStr, err := mc.encodeKey(key)
+		if err != nil {
+			return err
+		}
+
+		if collisionFn != nil && collisionFn(keyStr) {
+			return fmt.Errorf("Key %s of inlined map conflicts with a struct field name", key)
+		}
+
+		currEncoder, currVal, lookupErr := defaultValueEncoders.lookupElementEncoder(ec, encoder, val.MapIndex(key))
+		if lookupErr != nil && lookupErr != errInvalidValue {
+			return lookupErr
+		}
+
+		vw, err := dw.WriteDocumentElement(keyStr)
+		if err != nil {
+			return err
+		}
+
+		if lookupErr == errInvalidValue {
+			err = vw.WriteNull()
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		err = currEncoder.EncodeValue(ec, vw, currVal)
+		if err != nil {
+			return err
+		}
+	}
+
+	return dw.WriteDocumentEnd()
+}
+
+// DecodeValue is the ValueDecoder for map[string/decimal]* types.
+func (mc *MapCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if val.Kind() != reflect.Map || (!val.CanSet() && val.IsNil()) {
+		return ValueDecoderError{Name: "MapDecodeValue", Kinds: []reflect.Kind{reflect.Map}, Received: val}
+	}
+
+	switch vrType := vr.Type(); vrType {
+	case bsontype.Type(0), bsontype.EmbeddedDocument:
+	case bsontype.Null:
+		val.Set(reflect.Zero(val.Type()))
+		return vr.ReadNull()
+	case bsontype.Undefined:
+		val.Set(reflect.Zero(val.Type()))
+		return vr.ReadUndefined()
+	default:
+		return fmt.Errorf("cannot decode %v into a %s", vrType, val.Type())
+	}
+
+	dr, err := vr.ReadDocument()
+	if err != nil {
+		return err
+	}
+
+	if val.IsNil() {
+		val.Set(reflect.MakeMap(val.Type()))
+	}
+
+	if val.Len() > 0 && mc.DecodeZerosMap {
+		clearMap(val)
+	}
+
+	eType := val.Type().Elem()
+	decoder, err := dc.LookupDecoder(eType)
+	if err != nil {
+		return err
+	}
+	eTypeDecoder, _ := decoder.(typeDecoder)
+
+	if eType == tEmpty {
+		dc.Ancestor = val.Type()
+	}
+
+	keyType := val.Type().Key()
+
+	for {
+		key, vr, err := dr.ReadElement()
+		if err == bsonrw.ErrEOD {
+			break
+		}
+		if err != nil {
+			return err
+		}
+
+		k, err := mc.decodeKey(key, keyType)
+		if err != nil {
+			return err
+		}
+
+		elem, err := decodeTypeOrValueWithInfo(decoder, eTypeDecoder, dc, vr, eType, true)
+		if err != nil {
+			return newDecodeError(key, err)
+		}
+
+		val.SetMapIndex(k, elem)
+	}
+	return nil
+}
+
+func clearMap(m reflect.Value) {
+	var none reflect.Value
+	for _, k := range m.MapKeys() {
+		m.SetMapIndex(k, none)
+	}
+}
+
+func (mc *MapCodec) encodeKey(val reflect.Value) (string, error) {
+	if mc.EncodeKeysWithStringer {
+		return fmt.Sprint(val), nil
+	}
+
+	// keys of any string type are used directly
+	if val.Kind() == reflect.String {
+		return val.String(), nil
+	}
+	// KeyMarshalers are marshaled
+	if km, ok := val.Interface().(KeyMarshaler); ok {
+		if val.Kind() == reflect.Ptr && val.IsNil() {
+			return "", nil
+		}
+		buf, err := km.MarshalKey()
+		if err == nil {
+			return buf, nil
+		}
+		return "", err
+	}
+	// keys implement encoding.TextMarshaler are marshaled.
+	if km, ok := val.Interface().(encoding.TextMarshaler); ok {
+		if val.Kind() == reflect.Ptr && val.IsNil() {
+			return "", nil
+		}
+
+		buf, err := km.MarshalText()
+		if err != nil {
+			return "", err
+		}
+
+		return string(buf), nil
+	}
+
+	switch val.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.FormatInt(val.Int(), 10), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return strconv.FormatUint(val.Uint(), 10), nil
+	}
+	return "", fmt.Errorf("unsupported key type: %v", val.Type())
+}
+
+var keyUnmarshalerType = reflect.TypeOf((*KeyUnmarshaler)(nil)).Elem()
+var textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+
+func (mc *MapCodec) decodeKey(key string, keyType reflect.Type) (reflect.Value, error) {
+	keyVal := reflect.ValueOf(key)
+	var err error
+	switch {
+	// First, if EncodeKeysWithStringer is not enabled, try to decode withKeyUnmarshaler
+	case !mc.EncodeKeysWithStringer && reflect.PtrTo(keyType).Implements(keyUnmarshalerType):
+		keyVal = reflect.New(keyType)
+		v := keyVal.Interface().(KeyUnmarshaler)
+		err = v.UnmarshalKey(key)
+		keyVal = keyVal.Elem()
+	// Try to decode encoding.TextUnmarshalers.
+	case reflect.PtrTo(keyType).Implements(textUnmarshalerType):
+		keyVal = reflect.New(keyType)
+		v := keyVal.Interface().(encoding.TextUnmarshaler)
+		err = v.UnmarshalText([]byte(key))
+		keyVal = keyVal.Elem()
+	// Otherwise, go to type specific behavior
+	default:
+		switch keyType.Kind() {
+		case reflect.String:
+			keyVal = reflect.ValueOf(key).Convert(keyType)
+		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+			n, parseErr := strconv.ParseInt(key, 10, 64)
+			if parseErr != nil || reflect.Zero(keyType).OverflowInt(n) {
+				err = fmt.Errorf("failed to unmarshal number key %v", key)
+			}
+			keyVal = reflect.ValueOf(n).Convert(keyType)
+		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+			n, parseErr := strconv.ParseUint(key, 10, 64)
+			if parseErr != nil || reflect.Zero(keyType).OverflowUint(n) {
+				err = fmt.Errorf("failed to unmarshal number key %v", key)
+				break
+			}
+			keyVal = reflect.ValueOf(n).Convert(keyType)
+		case reflect.Float32, reflect.Float64:
+			if mc.EncodeKeysWithStringer {
+				parsed, err := strconv.ParseFloat(key, 64)
+				if err != nil {
+					return keyVal, fmt.Errorf("Map key is defined to be a decimal type (%v) but got error %v", keyType.Kind(), err)
+				}
+				keyVal = reflect.ValueOf(parsed)
+				break
+			}
+			fallthrough
+		default:
+			return keyVal, fmt.Errorf("unsupported key type: %v", keyType)
+		}
+	}
+	return keyVal, err
+}

mongo/bson/bsoncodec/mode.go

@@ -0,0 +1,65 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import "fmt"
+
+type mode int
+
+const (
+	_ mode = iota
+	mTopLevel
+	mDocument
+	mArray
+	mValue
+	mElement
+	mCodeWithScope
+	mSpacer
+)
+
+func (m mode) String() string {
+	var str string
+
+	switch m {
+	case mTopLevel:
+		str = "TopLevel"
+	case mDocument:
+		str = "DocumentMode"
+	case mArray:
+		str = "ArrayMode"
+	case mValue:
+		str = "ValueMode"
+	case mElement:
+		str = "ElementMode"
+	case mCodeWithScope:
+		str = "CodeWithScopeMode"
+	case mSpacer:
+		str = "CodeWithScopeSpacerFrame"
+	default:
+		str = "UnknownMode"
+	}
+
+	return str
+}
+
+// TransitionError is an error returned when an invalid progressing a
+// ValueReader or ValueWriter state machine occurs.
+type TransitionError struct {
+	parent      mode
+	current     mode
+	destination mode
+}
+
+func (te TransitionError) Error() string {
+	if te.destination == mode(0) {
+		return fmt.Sprintf("invalid state transition: cannot read/write value while in %s", te.current)
+	}
+	if te.parent == mode(0) {
+		return fmt.Sprintf("invalid state transition: %s -> %s", te.current, te.destination)
+	}
+	return fmt.Sprintf("invalid state transition: %s -> %s; parent %s", te.current, te.destination, te.parent)
+}

mongo/bson/bsoncodec/pointer_codec.go

@@ -0,0 +1,109 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"sync"
+
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+var _ ValueEncoder = &PointerCodec{}
+var _ ValueDecoder = &PointerCodec{}
+
+// PointerCodec is the Codec used for pointers.
+type PointerCodec struct {
+	ecache map[reflect.Type]ValueEncoder
+	dcache map[reflect.Type]ValueDecoder
+	l      sync.RWMutex
+}
+
+// NewPointerCodec returns a PointerCodec that has been initialized.
+func NewPointerCodec() *PointerCodec {
+	return &PointerCodec{
+		ecache: make(map[reflect.Type]ValueEncoder),
+		dcache: make(map[reflect.Type]ValueDecoder),
+	}
+}
+
+// EncodeValue handles encoding a pointer by either encoding it to BSON Null if the pointer is nil
+// or looking up an encoder for the type of value the pointer points to.
+func (pc *PointerCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if val.Kind() != reflect.Ptr {
+		if !val.IsValid() {
+			return vw.WriteNull()
+		}
+		return ValueEncoderError{Name: "PointerCodec.EncodeValue", Kinds: []reflect.Kind{reflect.Ptr}, Received: val}
+	}
+
+	if val.IsNil() {
+		return vw.WriteNull()
+	}
+
+	pc.l.RLock()
+	enc, ok := pc.ecache[val.Type()]
+	pc.l.RUnlock()
+	if ok {
+		if enc == nil {
+			return ErrNoEncoder{Type: val.Type()}
+		}
+		return enc.EncodeValue(ec, vw, val.Elem())
+	}
+
+	enc, err := ec.LookupEncoder(val.Type().Elem())
+	pc.l.Lock()
+	pc.ecache[val.Type()] = enc
+	pc.l.Unlock()
+	if err != nil {
+		return err
+	}
+
+	return enc.EncodeValue(ec, vw, val.Elem())
+}
+
+// DecodeValue handles decoding a pointer by looking up a decoder for the type it points to and
+// using that to decode. If the BSON value is Null, this method will set the pointer to nil.
+func (pc *PointerCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Kind() != reflect.Ptr {
+		return ValueDecoderError{Name: "PointerCodec.DecodeValue", Kinds: []reflect.Kind{reflect.Ptr}, Received: val}
+	}
+
+	if vr.Type() == bsontype.Null {
+		val.Set(reflect.Zero(val.Type()))
+		return vr.ReadNull()
+	}
+	if vr.Type() == bsontype.Undefined {
+		val.Set(reflect.Zero(val.Type()))
+		return vr.ReadUndefined()
+	}
+
+	if val.IsNil() {
+		val.Set(reflect.New(val.Type().Elem()))
+	}
+
+	pc.l.RLock()
+	dec, ok := pc.dcache[val.Type()]
+	pc.l.RUnlock()
+	if ok {
+		if dec == nil {
+			return ErrNoDecoder{Type: val.Type()}
+		}
+		return dec.DecodeValue(dc, vr, val.Elem())
+	}
+
+	dec, err := dc.LookupDecoder(val.Type().Elem())
+	pc.l.Lock()
+	pc.dcache[val.Type()] = dec
+	pc.l.Unlock()
+	if err != nil {
+		return err
+	}
+
+	return dec.DecodeValue(dc, vr, val.Elem())
+}

mongo/bson/bsoncodec/proxy.go

@@ -0,0 +1,14 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+// Proxy is an interface implemented by types that cannot themselves be directly encoded. Types
+// that implement this interface with have ProxyBSON called during the encoding process and that
+// value will be encoded in place for the implementer.
+type Proxy interface {
+	ProxyBSON() (interface{}, error)
+}

mongo/bson/bsoncodec/registry.go

@@ -0,0 +1,469 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"sync"
+
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+// ErrNilType is returned when nil is passed to either LookupEncoder or LookupDecoder.
+var ErrNilType = errors.New("cannot perform a decoder lookup on <nil>")
+
+// ErrNotPointer is returned when a non-pointer type is provided to LookupDecoder.
+var ErrNotPointer = errors.New("non-pointer provided to LookupDecoder")
+
+// ErrNoEncoder is returned when there wasn't an encoder available for a type.
+type ErrNoEncoder struct {
+	Type reflect.Type
+}
+
+func (ene ErrNoEncoder) Error() string {
+	if ene.Type == nil {
+		return "no encoder found for <nil>"
+	}
+	return "no encoder found for " + ene.Type.String()
+}
+
+// ErrNoDecoder is returned when there wasn't a decoder available for a type.
+type ErrNoDecoder struct {
+	Type reflect.Type
+}
+
+func (end ErrNoDecoder) Error() string {
+	return "no decoder found for " + end.Type.String()
+}
+
+// ErrNoTypeMapEntry is returned when there wasn't a type available for the provided BSON type.
+type ErrNoTypeMapEntry struct {
+	Type bsontype.Type
+}
+
+func (entme ErrNoTypeMapEntry) Error() string {
+	return "no type map entry found for " + entme.Type.String()
+}
+
+// ErrNotInterface is returned when the provided type is not an interface.
+var ErrNotInterface = errors.New("The provided type is not an interface")
+
+// A RegistryBuilder is used to build a Registry. This type is not goroutine
+// safe.
+type RegistryBuilder struct {
+	typeEncoders      map[reflect.Type]ValueEncoder
+	interfaceEncoders []interfaceValueEncoder
+	kindEncoders      map[reflect.Kind]ValueEncoder
+
+	typeDecoders      map[reflect.Type]ValueDecoder
+	interfaceDecoders []interfaceValueDecoder
+	kindDecoders      map[reflect.Kind]ValueDecoder
+
+	typeMap map[bsontype.Type]reflect.Type
+}
+
+// A Registry is used to store and retrieve codecs for types and interfaces. This type is the main
+// typed passed around and Encoders and Decoders are constructed from it.
+type Registry struct {
+	typeEncoders map[reflect.Type]ValueEncoder
+	typeDecoders map[reflect.Type]ValueDecoder
+
+	interfaceEncoders []interfaceValueEncoder
+	interfaceDecoders []interfaceValueDecoder
+
+	kindEncoders map[reflect.Kind]ValueEncoder
+	kindDecoders map[reflect.Kind]ValueDecoder
+
+	typeMap map[bsontype.Type]reflect.Type
+
+	mu sync.RWMutex
+}
+
+// NewRegistryBuilder creates a new empty RegistryBuilder.
+func NewRegistryBuilder() *RegistryBuilder {
+	return &RegistryBuilder{
+		typeEncoders: make(map[reflect.Type]ValueEncoder),
+		typeDecoders: make(map[reflect.Type]ValueDecoder),
+
+		interfaceEncoders: make([]interfaceValueEncoder, 0),
+		interfaceDecoders: make([]interfaceValueDecoder, 0),
+
+		kindEncoders: make(map[reflect.Kind]ValueEncoder),
+		kindDecoders: make(map[reflect.Kind]ValueDecoder),
+
+		typeMap: make(map[bsontype.Type]reflect.Type),
+	}
+}
+
+func buildDefaultRegistry() *Registry {
+	rb := NewRegistryBuilder()
+	defaultValueEncoders.RegisterDefaultEncoders(rb)
+	defaultValueDecoders.RegisterDefaultDecoders(rb)
+	return rb.Build()
+}
+
+// RegisterCodec will register the provided ValueCodec for the provided type.
+func (rb *RegistryBuilder) RegisterCodec(t reflect.Type, codec ValueCodec) *RegistryBuilder {
+	rb.RegisterTypeEncoder(t, codec)
+	rb.RegisterTypeDecoder(t, codec)
+	return rb
+}
+
+// RegisterTypeEncoder will register the provided ValueEncoder for the provided type.
+//
+// The type will be used directly, so an encoder can be registered for a type and a different encoder can be registered
+// for a pointer to that type.
+//
+// If the given type is an interface, the encoder will be called when marshalling a type that is that interface. It
+// will not be called when marshalling a non-interface type that implements the interface.
+func (rb *RegistryBuilder) RegisterTypeEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
+	rb.typeEncoders[t] = enc
+	return rb
+}
+
+// RegisterHookEncoder will register an encoder for the provided interface type t. This encoder will be called when
+// marshalling a type if the type implements t or a pointer to the type implements t. If the provided type is not
+// an interface (i.e. t.Kind() != reflect.Interface), this method will panic.
+func (rb *RegistryBuilder) RegisterHookEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
+	if t.Kind() != reflect.Interface {
+		panicStr := fmt.Sprintf("RegisterHookEncoder expects a type with kind reflect.Interface, "+
+			"got type %s with kind %s", t, t.Kind())
+		panic(panicStr)
+	}
+
+	for idx, encoder := range rb.interfaceEncoders {
+		if encoder.i == t {
+			rb.interfaceEncoders[idx].ve = enc
+			return rb
+		}
+	}
+
+	rb.interfaceEncoders = append(rb.interfaceEncoders, interfaceValueEncoder{i: t, ve: enc})
+	return rb
+}
+
+// RegisterTypeDecoder will register the provided ValueDecoder for the provided type.
+//
+// The type will be used directly, so a decoder can be registered for a type and a different decoder can be registered
+// for a pointer to that type.
+//
+// If the given type is an interface, the decoder will be called when unmarshalling into a type that is that interface.
+// It will not be called when unmarshalling into a non-interface type that implements the interface.
+func (rb *RegistryBuilder) RegisterTypeDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
+	rb.typeDecoders[t] = dec
+	return rb
+}
+
+// RegisterHookDecoder will register an decoder for the provided interface type t. This decoder will be called when
+// unmarshalling into a type if the type implements t or a pointer to the type implements t. If the provided type is not
+// an interface (i.e. t.Kind() != reflect.Interface), this method will panic.
+func (rb *RegistryBuilder) RegisterHookDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
+	if t.Kind() != reflect.Interface {
+		panicStr := fmt.Sprintf("RegisterHookDecoder expects a type with kind reflect.Interface, "+
+			"got type %s with kind %s", t, t.Kind())
+		panic(panicStr)
+	}
+
+	for idx, decoder := range rb.interfaceDecoders {
+		if decoder.i == t {
+			rb.interfaceDecoders[idx].vd = dec
+			return rb
+		}
+	}
+
+	rb.interfaceDecoders = append(rb.interfaceDecoders, interfaceValueDecoder{i: t, vd: dec})
+	return rb
+}
+
+// RegisterEncoder registers the provided type and encoder pair.
+//
+// Deprecated: Use RegisterTypeEncoder or RegisterHookEncoder instead.
+func (rb *RegistryBuilder) RegisterEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
+	if t == tEmpty {
+		rb.typeEncoders[t] = enc
+		return rb
+	}
+	switch t.Kind() {
+	case reflect.Interface:
+		for idx, ir := range rb.interfaceEncoders {
+			if ir.i == t {
+				rb.interfaceEncoders[idx].ve = enc
+				return rb
+			}
+		}
+
+		rb.interfaceEncoders = append(rb.interfaceEncoders, interfaceValueEncoder{i: t, ve: enc})
+	default:
+		rb.typeEncoders[t] = enc
+	}
+	return rb
+}
+
+// RegisterDecoder registers the provided type and decoder pair.
+//
+// Deprecated: Use RegisterTypeDecoder or RegisterHookDecoder instead.
+func (rb *RegistryBuilder) RegisterDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
+	if t == nil {
+		rb.typeDecoders[nil] = dec
+		return rb
+	}
+	if t == tEmpty {
+		rb.typeDecoders[t] = dec
+		return rb
+	}
+	switch t.Kind() {
+	case reflect.Interface:
+		for idx, ir := range rb.interfaceDecoders {
+			if ir.i == t {
+				rb.interfaceDecoders[idx].vd = dec
+				return rb
+			}
+		}
+
+		rb.interfaceDecoders = append(rb.interfaceDecoders, interfaceValueDecoder{i: t, vd: dec})
+	default:
+		rb.typeDecoders[t] = dec
+	}
+	return rb
+}
+
+// RegisterDefaultEncoder will registr the provided ValueEncoder to the provided
+// kind.
+func (rb *RegistryBuilder) RegisterDefaultEncoder(kind reflect.Kind, enc ValueEncoder) *RegistryBuilder {
+	rb.kindEncoders[kind] = enc
+	return rb
+}
+
+// RegisterDefaultDecoder will register the provided ValueDecoder to the
+// provided kind.
+func (rb *RegistryBuilder) RegisterDefaultDecoder(kind reflect.Kind, dec ValueDecoder) *RegistryBuilder {
+	rb.kindDecoders[kind] = dec
+	return rb
+}
+
+// RegisterTypeMapEntry will register the provided type to the BSON type. The primary usage for this
+// mapping is decoding situations where an empty interface is used and a default type needs to be
+// created and decoded into.
+//
+// By default, BSON documents will decode into interface{} values as bson.D. To change the default type for BSON
+// documents, a type map entry for bsontype.EmbeddedDocument should be registered. For example, to force BSON documents
+// to decode to bson.Raw, use the following code:
+//
+//	rb.RegisterTypeMapEntry(bsontype.EmbeddedDocument, reflect.TypeOf(bson.Raw{}))
+func (rb *RegistryBuilder) RegisterTypeMapEntry(bt bsontype.Type, rt reflect.Type) *RegistryBuilder {
+	rb.typeMap[bt] = rt
+	return rb
+}
+
+// Build creates a Registry from the current state of this RegistryBuilder.
+func (rb *RegistryBuilder) Build() *Registry {
+	registry := new(Registry)
+
+	registry.typeEncoders = make(map[reflect.Type]ValueEncoder)
+	for t, enc := range rb.typeEncoders {
+		registry.typeEncoders[t] = enc
+	}
+
+	registry.typeDecoders = make(map[reflect.Type]ValueDecoder)
+	for t, dec := range rb.typeDecoders {
+		registry.typeDecoders[t] = dec
+	}
+
+	registry.interfaceEncoders = make([]interfaceValueEncoder, len(rb.interfaceEncoders))
+	copy(registry.interfaceEncoders, rb.interfaceEncoders)
+
+	registry.interfaceDecoders = make([]interfaceValueDecoder, len(rb.interfaceDecoders))
+	copy(registry.interfaceDecoders, rb.interfaceDecoders)
+
+	registry.kindEncoders = make(map[reflect.Kind]ValueEncoder)
+	for kind, enc := range rb.kindEncoders {
+		registry.kindEncoders[kind] = enc
+	}
+
+	registry.kindDecoders = make(map[reflect.Kind]ValueDecoder)
+	for kind, dec := range rb.kindDecoders {
+		registry.kindDecoders[kind] = dec
+	}
+
+	registry.typeMap = make(map[bsontype.Type]reflect.Type)
+	for bt, rt := range rb.typeMap {
+		registry.typeMap[bt] = rt
+	}
+
+	return registry
+}
+
+// LookupEncoder inspects the registry for an encoder for the given type. The lookup precedence works as follows:
+//
+// 1. An encoder registered for the exact type. If the given type represents an interface, an encoder registered using
+// RegisterTypeEncoder for the interface will be selected.
+//
+// 2. An encoder registered using RegisterHookEncoder for an interface implemented by the type or by a pointer to the
+// type.
+//
+// 3. An encoder registered for the reflect.Kind of the value.
+//
+// If no encoder is found, an error of type ErrNoEncoder is returned.
+func (r *Registry) LookupEncoder(t reflect.Type) (ValueEncoder, error) {
+	encodererr := ErrNoEncoder{Type: t}
+	r.mu.RLock()
+	enc, found := r.lookupTypeEncoder(t)
+	r.mu.RUnlock()
+	if found {
+		if enc == nil {
+			return nil, ErrNoEncoder{Type: t}
+		}
+		return enc, nil
+	}
+
+	enc, found = r.lookupInterfaceEncoder(t, true)
+	if found {
+		r.mu.Lock()
+		r.typeEncoders[t] = enc
+		r.mu.Unlock()
+		return enc, nil
+	}
+
+	if t == nil {
+		r.mu.Lock()
+		r.typeEncoders[t] = nil
+		r.mu.Unlock()
+		return nil, encodererr
+	}
+
+	enc, found = r.kindEncoders[t.Kind()]
+	if !found {
+		r.mu.Lock()
+		r.typeEncoders[t] = nil
+		r.mu.Unlock()
+		return nil, encodererr
+	}
+
+	r.mu.Lock()
+	r.typeEncoders[t] = enc
+	r.mu.Unlock()
+	return enc, nil
+}
+
+func (r *Registry) lookupTypeEncoder(t reflect.Type) (ValueEncoder, bool) {
+	enc, found := r.typeEncoders[t]
+	return enc, found
+}
+
+func (r *Registry) lookupInterfaceEncoder(t reflect.Type, allowAddr bool) (ValueEncoder, bool) {
+	if t == nil {
+		return nil, false
+	}
+	for _, ienc := range r.interfaceEncoders {
+		if t.Implements(ienc.i) {
+			return ienc.ve, true
+		}
+		if allowAddr && t.Kind() != reflect.Ptr && reflect.PtrTo(t).Implements(ienc.i) {
+			// if *t implements an interface, this will catch if t implements an interface further ahead
+			// in interfaceEncoders
+			defaultEnc, found := r.lookupInterfaceEncoder(t, false)
+			if !found {
+				defaultEnc = r.kindEncoders[t.Kind()]
+			}
+			return newCondAddrEncoder(ienc.ve, defaultEnc), true
+		}
+	}
+	return nil, false
+}
+
+// LookupDecoder inspects the registry for an decoder for the given type. The lookup precedence works as follows:
+//
+// 1. A decoder registered for the exact type. If the given type represents an interface, a decoder registered using
+// RegisterTypeDecoder for the interface will be selected.
+//
+// 2. A decoder registered using RegisterHookDecoder for an interface implemented by the type or by a pointer to the
+// type.
+//
+// 3. A decoder registered for the reflect.Kind of the value.
+//
+// If no decoder is found, an error of type ErrNoDecoder is returned.
+func (r *Registry) LookupDecoder(t reflect.Type) (ValueDecoder, error) {
+	if t == nil {
+		return nil, ErrNilType
+	}
+	decodererr := ErrNoDecoder{Type: t}
+	r.mu.RLock()
+	dec, found := r.lookupTypeDecoder(t)
+	r.mu.RUnlock()
+	if found {
+		if dec == nil {
+			return nil, ErrNoDecoder{Type: t}
+		}
+		return dec, nil
+	}
+
+	dec, found = r.lookupInterfaceDecoder(t, true)
+	if found {
+		r.mu.Lock()
+		r.typeDecoders[t] = dec
+		r.mu.Unlock()
+		return dec, nil
+	}
+
+	dec, found = r.kindDecoders[t.Kind()]
+	if !found {
+		r.mu.Lock()
+		r.typeDecoders[t] = nil
+		r.mu.Unlock()
+		return nil, decodererr
+	}
+
+	r.mu.Lock()
+	r.typeDecoders[t] = dec
+	r.mu.Unlock()
+	return dec, nil
+}
+
+func (r *Registry) lookupTypeDecoder(t reflect.Type) (ValueDecoder, bool) {
+	dec, found := r.typeDecoders[t]
+	return dec, found
+}
+
+func (r *Registry) lookupInterfaceDecoder(t reflect.Type, allowAddr bool) (ValueDecoder, bool) {
+	for _, idec := range r.interfaceDecoders {
+		if t.Implements(idec.i) {
+			return idec.vd, true
+		}
+		if allowAddr && t.Kind() != reflect.Ptr && reflect.PtrTo(t).Implements(idec.i) {
+			// if *t implements an interface, this will catch if t implements an interface further ahead
+			// in interfaceDecoders
+			defaultDec, found := r.lookupInterfaceDecoder(t, false)
+			if !found {
+				defaultDec = r.kindDecoders[t.Kind()]
+			}
+			return newCondAddrDecoder(idec.vd, defaultDec), true
+		}
+	}
+	return nil, false
+}
+
+// LookupTypeMapEntry inspects the registry's type map for a Go type for the corresponding BSON
+// type. If no type is found, ErrNoTypeMapEntry is returned.
+func (r *Registry) LookupTypeMapEntry(bt bsontype.Type) (reflect.Type, error) {
+	t, ok := r.typeMap[bt]
+	if !ok || t == nil {
+		return nil, ErrNoTypeMapEntry{Type: bt}
+	}
+	return t, nil
+}
+
+type interfaceValueEncoder struct {
+	i  reflect.Type
+	ve ValueEncoder
+}
+
+type interfaceValueDecoder struct {
+	i  reflect.Type
+	vd ValueDecoder
+}

mongo/bson/bsoncodec/registry_examples_test.go

@@ -0,0 +1,125 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec_test
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsoncodec"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+func ExampleRegistry_customEncoder() {
+	// Write a custom encoder for an integer type that is multiplied by -1 when
+	// encoding.
+
+	// To register the default encoders and decoders in addition to this custom
+	// one, use bson.NewRegistryBuilder instead.
+	rb := bsoncodec.NewRegistryBuilder()
+	type negatedInt int
+
+	niType := reflect.TypeOf(negatedInt(0))
+	encoder := func(
+		ec bsoncodec.EncodeContext,
+		vw bsonrw.ValueWriter,
+		val reflect.Value,
+	) error {
+		// All encoder implementations should check that val is valid and is of
+		// the correct type before proceeding.
+		if !val.IsValid() || val.Type() != niType {
+			return bsoncodec.ValueEncoderError{
+				Name:     "negatedIntEncodeValue",
+				Types:    []reflect.Type{niType},
+				Received: val,
+			}
+		}
+
+		// Negate val and encode as a BSON int32 if it can fit in 32 bits and a
+		// BSON int64 otherwise.
+		negatedVal := val.Int() * -1
+		if math.MinInt32 <= negatedVal && negatedVal <= math.MaxInt32 {
+			return vw.WriteInt32(int32(negatedVal))
+		}
+		return vw.WriteInt64(negatedVal)
+	}
+
+	rb.RegisterTypeEncoder(niType, bsoncodec.ValueEncoderFunc(encoder))
+}
+
+func ExampleRegistry_customDecoder() {
+	// Write a custom decoder for a boolean type that can be stored in the
+	// database as a BSON boolean, int32, int64, double, or null. BSON int32,
+	// int64, and double values are considered "true" in this decoder if they
+	// are non-zero. BSON null values are always considered false.
+
+	// To register the default encoders and decoders in addition to this custom
+	// one, use bson.NewRegistryBuilder instead.
+	rb := bsoncodec.NewRegistryBuilder()
+	type lenientBool bool
+
+	decoder := func(
+		dc bsoncodec.DecodeContext,
+		vr bsonrw.ValueReader,
+		val reflect.Value,
+	) error {
+		// All decoder implementations should check that val is valid, settable,
+		// and is of the correct kind before proceeding.
+		if !val.IsValid() || !val.CanSet() || val.Kind() != reflect.Bool {
+			return bsoncodec.ValueDecoderError{
+				Name:     "lenientBoolDecodeValue",
+				Kinds:    []reflect.Kind{reflect.Bool},
+				Received: val,
+			}
+		}
+
+		var result bool
+		switch vr.Type() {
+		case bsontype.Boolean:
+			b, err := vr.ReadBoolean()
+			if err != nil {
+				return err
+			}
+			result = b
+		case bsontype.Int32:
+			i32, err := vr.ReadInt32()
+			if err != nil {
+				return err
+			}
+			result = i32 != 0
+		case bsontype.Int64:
+			i64, err := vr.ReadInt64()
+			if err != nil {
+				return err
+			}
+			result = i64 != 0
+		case bsontype.Double:
+			f64, err := vr.ReadDouble()
+			if err != nil {
+				return err
+			}
+			result = f64 != 0
+		case bsontype.Null:
+			if err := vr.ReadNull(); err != nil {
+				return err
+			}
+			result = false
+		default:
+			return fmt.Errorf(
+				"received invalid BSON type to decode into lenientBool: %s",
+				vr.Type())
+		}
+
+		val.SetBool(result)
+		return nil
+	}
+
+	lbType := reflect.TypeOf(lenientBool(true))
+	rb.RegisterTypeDecoder(lbType, bsoncodec.ValueDecoderFunc(decoder))
+}

mongo/bson/bsoncodec/registry_test.go

@@ -0,0 +1,452 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/internal/testutil/assert"
+)
+
+func TestRegistry(t *testing.T) {
+	t.Run("Register", func(t *testing.T) {
+		fc1, fc2, fc3, fc4 := new(fakeCodec), new(fakeCodec), new(fakeCodec), new(fakeCodec)
+		t.Run("interface", func(t *testing.T) {
+			var t1f *testInterface1
+			var t2f *testInterface2
+			var t4f *testInterface4
+			ips := []interfaceValueEncoder{
+				{i: reflect.TypeOf(t1f).Elem(), ve: fc1},
+				{i: reflect.TypeOf(t2f).Elem(), ve: fc2},
+				{i: reflect.TypeOf(t1f).Elem(), ve: fc3},
+				{i: reflect.TypeOf(t4f).Elem(), ve: fc4},
+			}
+			want := []interfaceValueEncoder{
+				{i: reflect.TypeOf(t1f).Elem(), ve: fc3},
+				{i: reflect.TypeOf(t2f).Elem(), ve: fc2},
+				{i: reflect.TypeOf(t4f).Elem(), ve: fc4},
+			}
+			rb := NewRegistryBuilder()
+			for _, ip := range ips {
+				rb.RegisterHookEncoder(ip.i, ip.ve)
+			}
+			got := rb.interfaceEncoders
+			if !cmp.Equal(got, want, cmp.AllowUnexported(interfaceValueEncoder{}, fakeCodec{}), cmp.Comparer(typeComparer)) {
+				t.Errorf("The registered interfaces are not correct. got %v; want %v", got, want)
+			}
+		})
+		t.Run("type", func(t *testing.T) {
+			ft1, ft2, ft4 := fakeType1{}, fakeType2{}, fakeType4{}
+			rb := NewRegistryBuilder().
+				RegisterTypeEncoder(reflect.TypeOf(ft1), fc1).
+				RegisterTypeEncoder(reflect.TypeOf(ft2), fc2).
+				RegisterTypeEncoder(reflect.TypeOf(ft1), fc3).
+				RegisterTypeEncoder(reflect.TypeOf(ft4), fc4)
+			want := []struct {
+				t reflect.Type
+				c ValueEncoder
+			}{
+				{reflect.TypeOf(ft1), fc3},
+				{reflect.TypeOf(ft2), fc2},
+				{reflect.TypeOf(ft4), fc4},
+			}
+			got := rb.typeEncoders
+			for _, s := range want {
+				wantT, wantC := s.t, s.c
+				gotC, exists := got[wantT]
+				if !exists {
+					t.Errorf("Did not find type in the type registry: %v", wantT)
+				}
+				if !cmp.Equal(gotC, wantC, cmp.AllowUnexported(fakeCodec{})) {
+					t.Errorf("Codecs did not match. got %#v; want %#v", gotC, wantC)
+				}
+			}
+		})
+		t.Run("kind", func(t *testing.T) {
+			k1, k2, k4 := reflect.Struct, reflect.Slice, reflect.Map
+			rb := NewRegistryBuilder().
+				RegisterDefaultEncoder(k1, fc1).
+				RegisterDefaultEncoder(k2, fc2).
+				RegisterDefaultEncoder(k1, fc3).
+				RegisterDefaultEncoder(k4, fc4)
+			want := []struct {
+				k reflect.Kind
+				c ValueEncoder
+			}{
+				{k1, fc3},
+				{k2, fc2},
+				{k4, fc4},
+			}
+			got := rb.kindEncoders
+			for _, s := range want {
+				wantK, wantC := s.k, s.c
+				gotC, exists := got[wantK]
+				if !exists {
+					t.Errorf("Did not find kind in the kind registry: %v", wantK)
+				}
+				if !cmp.Equal(gotC, wantC, cmp.AllowUnexported(fakeCodec{})) {
+					t.Errorf("Codecs did not match. got %#v; want %#v", gotC, wantC)
+				}
+			}
+		})
+		t.Run("RegisterDefault", func(t *testing.T) {
+			t.Run("MapCodec", func(t *testing.T) {
+				codec := fakeCodec{num: 1}
+				codec2 := fakeCodec{num: 2}
+				rb := NewRegistryBuilder()
+				rb.RegisterDefaultEncoder(reflect.Map, codec)
+				if rb.kindEncoders[reflect.Map] != codec {
+					t.Errorf("Did not properly set the map codec. got %v; want %v", rb.kindEncoders[reflect.Map], codec)
+				}
+				rb.RegisterDefaultEncoder(reflect.Map, codec2)
+				if rb.kindEncoders[reflect.Map] != codec2 {
+					t.Errorf("Did not properly set the map codec. got %v; want %v", rb.kindEncoders[reflect.Map], codec2)
+				}
+			})
+			t.Run("StructCodec", func(t *testing.T) {
+				codec := fakeCodec{num: 1}
+				codec2 := fakeCodec{num: 2}
+				rb := NewRegistryBuilder()
+				rb.RegisterDefaultEncoder(reflect.Struct, codec)
+				if rb.kindEncoders[reflect.Struct] != codec {
+					t.Errorf("Did not properly set the struct codec. got %v; want %v", rb.kindEncoders[reflect.Struct], codec)
+				}
+				rb.RegisterDefaultEncoder(reflect.Struct, codec2)
+				if rb.kindEncoders[reflect.Struct] != codec2 {
+					t.Errorf("Did not properly set the struct codec. got %v; want %v", rb.kindEncoders[reflect.Struct], codec2)
+				}
+			})
+			t.Run("SliceCodec", func(t *testing.T) {
+				codec := fakeCodec{num: 1}
+				codec2 := fakeCodec{num: 2}
+				rb := NewRegistryBuilder()
+				rb.RegisterDefaultEncoder(reflect.Slice, codec)
+				if rb.kindEncoders[reflect.Slice] != codec {
+					t.Errorf("Did not properly set the slice codec. got %v; want %v", rb.kindEncoders[reflect.Slice], codec)
+				}
+				rb.RegisterDefaultEncoder(reflect.Slice, codec2)
+				if rb.kindEncoders[reflect.Slice] != codec2 {
+					t.Errorf("Did not properly set the slice codec. got %v; want %v", rb.kindEncoders[reflect.Slice], codec2)
+				}
+			})
+			t.Run("ArrayCodec", func(t *testing.T) {
+				codec := fakeCodec{num: 1}
+				codec2 := fakeCodec{num: 2}
+				rb := NewRegistryBuilder()
+				rb.RegisterDefaultEncoder(reflect.Array, codec)
+				if rb.kindEncoders[reflect.Array] != codec {
+					t.Errorf("Did not properly set the slice codec. got %v; want %v", rb.kindEncoders[reflect.Array], codec)
+				}
+				rb.RegisterDefaultEncoder(reflect.Array, codec2)
+				if rb.kindEncoders[reflect.Array] != codec2 {
+					t.Errorf("Did not properly set the slice codec. got %v; want %v", rb.kindEncoders[reflect.Array], codec2)
+				}
+			})
+		})
+		t.Run("Lookup", func(t *testing.T) {
+			type Codec interface {
+				ValueEncoder
+				ValueDecoder
+			}
+
+			var arrinstance [12]int
+			arr := reflect.TypeOf(arrinstance)
+			slc := reflect.TypeOf(make([]int, 12))
+			m := reflect.TypeOf(make(map[string]int))
+			strct := reflect.TypeOf(struct{ Foo string }{})
+			ft1 := reflect.PtrTo(reflect.TypeOf(fakeType1{}))
+			ft2 := reflect.TypeOf(fakeType2{})
+			ft3 := reflect.TypeOf(fakeType5(func(string, string) string { return "fakeType5" }))
+			ti1 := reflect.TypeOf((*testInterface1)(nil)).Elem()
+			ti2 := reflect.TypeOf((*testInterface2)(nil)).Elem()
+			ti1Impl := reflect.TypeOf(testInterface1Impl{})
+			ti2Impl := reflect.TypeOf(testInterface2Impl{})
+			ti3 := reflect.TypeOf((*testInterface3)(nil)).Elem()
+			ti3Impl := reflect.TypeOf(testInterface3Impl{})
+			ti3ImplPtr := reflect.TypeOf((*testInterface3Impl)(nil))
+			fc1, fc2 := fakeCodec{num: 1}, fakeCodec{num: 2}
+			fsc, fslcc, fmc := new(fakeStructCodec), new(fakeSliceCodec), new(fakeMapCodec)
+			pc := NewPointerCodec()
+
+			reg := NewRegistryBuilder().
+				RegisterTypeEncoder(ft1, fc1).
+				RegisterTypeEncoder(ft2, fc2).
+				RegisterTypeEncoder(ti1, fc1).
+				RegisterDefaultEncoder(reflect.Struct, fsc).
+				RegisterDefaultEncoder(reflect.Slice, fslcc).
+				RegisterDefaultEncoder(reflect.Array, fslcc).
+				RegisterDefaultEncoder(reflect.Map, fmc).
+				RegisterDefaultEncoder(reflect.Ptr, pc).
+				RegisterTypeDecoder(ft1, fc1).
+				RegisterTypeDecoder(ft2, fc2).
+				RegisterTypeDecoder(ti1, fc1). // values whose exact type is testInterface1 will use fc1 encoder
+				RegisterDefaultDecoder(reflect.Struct, fsc).
+				RegisterDefaultDecoder(reflect.Slice, fslcc).
+				RegisterDefaultDecoder(reflect.Array, fslcc).
+				RegisterDefaultDecoder(reflect.Map, fmc).
+				RegisterDefaultDecoder(reflect.Ptr, pc).
+				RegisterHookEncoder(ti2, fc2).
+				RegisterHookDecoder(ti2, fc2).
+				RegisterHookEncoder(ti3, fc3).
+				RegisterHookDecoder(ti3, fc3).
+				Build()
+
+			testCases := []struct {
+				name      string
+				t         reflect.Type
+				wantcodec Codec
+				wanterr   error
+				testcache bool
+			}{
+				{
+					"type registry (pointer)",
+					ft1,
+					fc1,
+					nil,
+					false,
+				},
+				{
+					"type registry (non-pointer)",
+					ft2,
+					fc2,
+					nil,
+					false,
+				},
+				{
+					// lookup an interface type and expect that the registered encoder is returned
+					"interface with type encoder",
+					ti1,
+					fc1,
+					nil,
+					true,
+				},
+				{
+					// lookup a type that implements an interface and expect that the default struct codec is returned
+					"interface implementation with type encoder",
+					ti1Impl,
+					fsc,
+					nil,
+					false,
+				},
+				{
+					// lookup an interface type and expect that the registered hook is returned
+					"interface with hook",
+					ti2,
+					fc2,
+					nil,
+					false,
+				},
+				{
+					// lookup a type that implements an interface and expect that the registered hook is returned
+					"interface implementation with hook",
+					ti2Impl,
+					fc2,
+					nil,
+					false,
+				},
+				{
+					// lookup a pointer to a type where the pointer implements an interface and expect that the
+					// registered hook is returned
+					"interface pointer to implementation with hook (pointer)",
+					ti3ImplPtr,
+					fc3,
+					nil,
+					false,
+				},
+				{
+					"default struct codec (pointer)",
+					reflect.PtrTo(strct),
+					pc,
+					nil,
+					false,
+				},
+				{
+					"default struct codec (non-pointer)",
+					strct,
+					fsc,
+					nil,
+					false,
+				},
+				{
+					"default array codec",
+					arr,
+					fslcc,
+					nil,
+					false,
+				},
+				{
+					"default slice codec",
+					slc,
+					fslcc,
+					nil,
+					false,
+				},
+				{
+					"default map",
+					m,
+					fmc,
+					nil,
+					false,
+				},
+				{
+					"map non-string key",
+					reflect.TypeOf(map[int]int{}),
+					fmc,
+					nil,
+					false,
+				},
+				{
+					"No Codec Registered",
+					ft3,
+					nil,
+					ErrNoEncoder{Type: ft3},
+					false,
+				},
+			}
+
+			allowunexported := cmp.AllowUnexported(fakeCodec{}, fakeStructCodec{}, fakeSliceCodec{}, fakeMapCodec{})
+			comparepc := func(pc1, pc2 *PointerCodec) bool { return true }
+			for _, tc := range testCases {
+				t.Run(tc.name, func(t *testing.T) {
+					t.Run("Encoder", func(t *testing.T) {
+						gotcodec, goterr := reg.LookupEncoder(tc.t)
+						if !cmp.Equal(goterr, tc.wanterr, cmp.Comparer(compareErrors)) {
+							t.Errorf("Errors did not match. got %v; want %v", goterr, tc.wanterr)
+						}
+						if !cmp.Equal(gotcodec, tc.wantcodec, allowunexported, cmp.Comparer(comparepc)) {
+							t.Errorf("Codecs did not match. got %v; want %v", gotcodec, tc.wantcodec)
+						}
+					})
+					t.Run("Decoder", func(t *testing.T) {
+						var wanterr error
+						if ene, ok := tc.wanterr.(ErrNoEncoder); ok {
+							wanterr = ErrNoDecoder(ene)
+						} else {
+							wanterr = tc.wanterr
+						}
+						gotcodec, goterr := reg.LookupDecoder(tc.t)
+						if !cmp.Equal(goterr, wanterr, cmp.Comparer(compareErrors)) {
+							t.Errorf("Errors did not match. got %v; want %v", goterr, wanterr)
+						}
+						if !cmp.Equal(gotcodec, tc.wantcodec, allowunexported, cmp.Comparer(comparepc)) {
+							t.Errorf("Codecs did not match. got %v; want %v", gotcodec, tc.wantcodec)
+							t.Errorf("Codecs did not match. got %T; want %T", gotcodec, tc.wantcodec)
+						}
+					})
+				})
+			}
+			// lookup a type whose pointer implements an interface and expect that the registered hook is
+			// returned
+			t.Run("interface implementation with hook (pointer)", func(t *testing.T) {
+				t.Run("Encoder", func(t *testing.T) {
+					gotEnc, err := reg.LookupEncoder(ti3Impl)
+					assert.Nil(t, err, "LookupEncoder error: %v", err)
+
+					cae, ok := gotEnc.(*condAddrEncoder)
+					assert.True(t, ok, "Expected CondAddrEncoder, got %T", gotEnc)
+					if !cmp.Equal(cae.canAddrEnc, fc3, allowunexported, cmp.Comparer(comparepc)) {
+						t.Errorf("expected canAddrEnc %v, got %v", cae.canAddrEnc, fc3)
+					}
+					if !cmp.Equal(cae.elseEnc, fsc, allowunexported, cmp.Comparer(comparepc)) {
+						t.Errorf("expected elseEnc %v, got %v", cae.elseEnc, fsc)
+					}
+				})
+				t.Run("Decoder", func(t *testing.T) {
+					gotDec, err := reg.LookupDecoder(ti3Impl)
+					assert.Nil(t, err, "LookupDecoder error: %v", err)
+
+					cad, ok := gotDec.(*condAddrDecoder)
+					assert.True(t, ok, "Expected CondAddrDecoder, got %T", gotDec)
+					if !cmp.Equal(cad.canAddrDec, fc3, allowunexported, cmp.Comparer(comparepc)) {
+						t.Errorf("expected canAddrDec %v, got %v", cad.canAddrDec, fc3)
+					}
+					if !cmp.Equal(cad.elseDec, fsc, allowunexported, cmp.Comparer(comparepc)) {
+						t.Errorf("expected elseDec %v, got %v", cad.elseDec, fsc)
+					}
+				})
+			})
+		})
+	})
+	t.Run("Type Map", func(t *testing.T) {
+		reg := NewRegistryBuilder().
+			RegisterTypeMapEntry(bsontype.String, reflect.TypeOf("")).
+			RegisterTypeMapEntry(bsontype.Int32, reflect.TypeOf(int(0))).
+			Build()
+
+		var got, want reflect.Type
+
+		want = reflect.TypeOf("")
+		got, err := reg.LookupTypeMapEntry(bsontype.String)
+		noerr(t, err)
+		if got != want {
+			t.Errorf("Did not get expected type. got %v; want %v", got, want)
+		}
+
+		want = reflect.TypeOf(int(0))
+		got, err = reg.LookupTypeMapEntry(bsontype.Int32)
+		noerr(t, err)
+		if got != want {
+			t.Errorf("Did not get expected type. got %v; want %v", got, want)
+		}
+
+		want = nil
+		wanterr := ErrNoTypeMapEntry{Type: bsontype.ObjectID}
+		got, err = reg.LookupTypeMapEntry(bsontype.ObjectID)
+		if err != wanterr {
+			t.Errorf("Did not get expected error. got %v; want %v", err, wanterr)
+		}
+		if got != want {
+			t.Errorf("Did not get expected type. got %v; want %v", got, want)
+		}
+	})
+}
+
+type fakeType1 struct{}
+type fakeType2 struct{}
+type fakeType4 struct{}
+type fakeType5 func(string, string) string
+type fakeStructCodec struct{ fakeCodec }
+type fakeSliceCodec struct{ fakeCodec }
+type fakeMapCodec struct{ fakeCodec }
+
+type fakeCodec struct{ num int }
+
+func (fc fakeCodec) EncodeValue(EncodeContext, bsonrw.ValueWriter, reflect.Value) error {
+	return nil
+}
+func (fc fakeCodec) DecodeValue(DecodeContext, bsonrw.ValueReader, reflect.Value) error {
+	return nil
+}
+
+type testInterface1 interface{ test1() }
+type testInterface2 interface{ test2() }
+type testInterface3 interface{ test3() }
+type testInterface4 interface{ test4() }
+
+type testInterface1Impl struct{}
+
+var _ testInterface1 = testInterface1Impl{}
+
+func (testInterface1Impl) test1() {}
+
+type testInterface2Impl struct{}
+
+var _ testInterface2 = testInterface2Impl{}
+
+func (testInterface2Impl) test2() {}
+
+type testInterface3Impl struct{}
+
+var _ testInterface3 = (*testInterface3Impl)(nil)
+
+func (*testInterface3Impl) test3() {}
+
+func typeComparer(i1, i2 reflect.Type) bool { return i1 == i2 }

mongo/bson/bsoncodec/slice_codec.go

@@ -0,0 +1,199 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"fmt"
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+var defaultSliceCodec = NewSliceCodec()
+
+// SliceCodec is the Codec used for slice values.
+type SliceCodec struct {
+	EncodeNilAsEmpty bool
+}
+
+var _ ValueCodec = &MapCodec{}
+
+// NewSliceCodec returns a MapCodec with options opts.
+func NewSliceCodec(opts ...*bsonoptions.SliceCodecOptions) *SliceCodec {
+	sliceOpt := bsonoptions.MergeSliceCodecOptions(opts...)
+
+	codec := SliceCodec{}
+	if sliceOpt.EncodeNilAsEmpty != nil {
+		codec.EncodeNilAsEmpty = *sliceOpt.EncodeNilAsEmpty
+	}
+	return &codec
+}
+
+// EncodeValue is the ValueEncoder for slice types.
+func (sc SliceCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Slice {
+		return ValueEncoderError{Name: "SliceEncodeValue", Kinds: []reflect.Kind{reflect.Slice}, Received: val}
+	}
+
+	if val.IsNil() && !sc.EncodeNilAsEmpty {
+		return vw.WriteNull()
+	}
+
+	// If we have a []byte we want to treat it as a binary instead of as an array.
+	if val.Type().Elem() == tByte {
+		var byteSlice []byte
+		for idx := 0; idx < val.Len(); idx++ {
+			byteSlice = append(byteSlice, val.Index(idx).Interface().(byte))
+		}
+		return vw.WriteBinary(byteSlice)
+	}
+
+	// If we have a []primitive.E we want to treat it as a document instead of as an array.
+	if val.Type().ConvertibleTo(tD) {
+		d := val.Convert(tD).Interface().(primitive.D)
+
+		dw, err := vw.WriteDocument()
+		if err != nil {
+			return err
+		}
+
+		for _, e := range d {
+			err = encodeElement(ec, dw, e)
+			if err != nil {
+				return err
+			}
+		}
+
+		return dw.WriteDocumentEnd()
+	}
+
+	aw, err := vw.WriteArray()
+	if err != nil {
+		return err
+	}
+
+	elemType := val.Type().Elem()
+	encoder, err := ec.LookupEncoder(elemType)
+	if err != nil && elemType.Kind() != reflect.Interface {
+		return err
+	}
+
+	for idx := 0; idx < val.Len(); idx++ {
+		currEncoder, currVal, lookupErr := defaultValueEncoders.lookupElementEncoder(ec, encoder, val.Index(idx))
+		if lookupErr != nil && lookupErr != errInvalidValue {
+			return lookupErr
+		}
+
+		vw, err := aw.WriteArrayElement()
+		if err != nil {
+			return err
+		}
+
+		if lookupErr == errInvalidValue {
+			err = vw.WriteNull()
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		err = currEncoder.EncodeValue(ec, vw, currVal)
+		if err != nil {
+			return err
+		}
+	}
+	return aw.WriteArrayEnd()
+}
+
+// DecodeValue is the ValueDecoder for slice types.
+func (sc *SliceCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Kind() != reflect.Slice {
+		return ValueDecoderError{Name: "SliceDecodeValue", Kinds: []reflect.Kind{reflect.Slice}, Received: val}
+	}
+
+	switch vrType := vr.Type(); vrType {
+	case bsontype.Array:
+	case bsontype.Null:
+		val.Set(reflect.Zero(val.Type()))
+		return vr.ReadNull()
+	case bsontype.Undefined:
+		val.Set(reflect.Zero(val.Type()))
+		return vr.ReadUndefined()
+	case bsontype.Type(0), bsontype.EmbeddedDocument:
+		if val.Type().Elem() != tE {
+			return fmt.Errorf("cannot decode document into %s", val.Type())
+		}
+	case bsontype.Binary:
+		if val.Type().Elem() != tByte {
+			return fmt.Errorf("SliceDecodeValue can only decode a binary into a byte array, got %v", vrType)
+		}
+		data, subtype, err := vr.ReadBinary()
+		if err != nil {
+			return err
+		}
+		if subtype != bsontype.BinaryGeneric && subtype != bsontype.BinaryBinaryOld {
+			return fmt.Errorf("SliceDecodeValue can only be used to decode subtype 0x00 or 0x02 for %s, got %v", bsontype.Binary, subtype)
+		}
+
+		if val.IsNil() {
+			val.Set(reflect.MakeSlice(val.Type(), 0, len(data)))
+		}
+
+		val.SetLen(0)
+		for _, elem := range data {
+			val.Set(reflect.Append(val, reflect.ValueOf(elem)))
+		}
+		return nil
+	case bsontype.String:
+		if sliceType := val.Type().Elem(); sliceType != tByte {
+			return fmt.Errorf("SliceDecodeValue can only decode a string into a byte array, got %v", sliceType)
+		}
+		str, err := vr.ReadString()
+		if err != nil {
+			return err
+		}
+		byteStr := []byte(str)
+
+		if val.IsNil() {
+			val.Set(reflect.MakeSlice(val.Type(), 0, len(byteStr)))
+		}
+
+		val.SetLen(0)
+		for _, elem := range byteStr {
+			val.Set(reflect.Append(val, reflect.ValueOf(elem)))
+		}
+		return nil
+	default:
+		return fmt.Errorf("cannot decode %v into a slice", vrType)
+	}
+
+	var elemsFunc func(DecodeContext, bsonrw.ValueReader, reflect.Value) ([]reflect.Value, error)
+	switch val.Type().Elem() {
+	case tE:
+		dc.Ancestor = val.Type()
+		elemsFunc = defaultValueDecoders.decodeD
+	default:
+		elemsFunc = defaultValueDecoders.decodeDefault
+	}
+
+	elems, err := elemsFunc(dc, vr, val)
+	if err != nil {
+		return err
+	}
+
+	if val.IsNil() {
+		val.Set(reflect.MakeSlice(val.Type(), 0, len(elems)))
+	}
+
+	val.SetLen(0)
+	val.Set(reflect.Append(val, elems...))
+
+	return nil
+}

mongo/bson/bsoncodec/string_codec.go

@@ -0,0 +1,119 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"fmt"
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+// StringCodec is the Codec used for struct values.
+type StringCodec struct {
+	DecodeObjectIDAsHex bool
+}
+
+var (
+	defaultStringCodec = NewStringCodec()
+
+	_ ValueCodec  = defaultStringCodec
+	_ typeDecoder = defaultStringCodec
+)
+
+// NewStringCodec returns a StringCodec with options opts.
+func NewStringCodec(opts ...*bsonoptions.StringCodecOptions) *StringCodec {
+	stringOpt := bsonoptions.MergeStringCodecOptions(opts...)
+	return &StringCodec{*stringOpt.DecodeObjectIDAsHex}
+}
+
+// EncodeValue is the ValueEncoder for string types.
+func (sc *StringCodec) EncodeValue(ectx EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if val.Kind() != reflect.String {
+		return ValueEncoderError{
+			Name:     "StringEncodeValue",
+			Kinds:    []reflect.Kind{reflect.String},
+			Received: val,
+		}
+	}
+
+	return vw.WriteString(val.String())
+}
+
+func (sc *StringCodec) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	if t.Kind() != reflect.String {
+		return emptyValue, ValueDecoderError{
+			Name:     "StringDecodeValue",
+			Kinds:    []reflect.Kind{reflect.String},
+			Received: reflect.Zero(t),
+		}
+	}
+
+	var str string
+	var err error
+	switch vr.Type() {
+	case bsontype.String:
+		str, err = vr.ReadString()
+		if err != nil {
+			return emptyValue, err
+		}
+	case bsontype.ObjectID:
+		oid, err := vr.ReadObjectID()
+		if err != nil {
+			return emptyValue, err
+		}
+		if sc.DecodeObjectIDAsHex {
+			str = oid.Hex()
+		} else {
+			byteArray := [12]byte(oid)
+			str = string(byteArray[:])
+		}
+	case bsontype.Symbol:
+		str, err = vr.ReadSymbol()
+		if err != nil {
+			return emptyValue, err
+		}
+	case bsontype.Binary:
+		data, subtype, err := vr.ReadBinary()
+		if err != nil {
+			return emptyValue, err
+		}
+		if subtype != bsontype.BinaryGeneric && subtype != bsontype.BinaryBinaryOld {
+			return emptyValue, decodeBinaryError{subtype: subtype, typeName: "string"}
+		}
+		str = string(data)
+	case bsontype.Null:
+		if err = vr.ReadNull(); err != nil {
+			return emptyValue, err
+		}
+	case bsontype.Undefined:
+		if err = vr.ReadUndefined(); err != nil {
+			return emptyValue, err
+		}
+	default:
+		return emptyValue, fmt.Errorf("cannot decode %v into a string type", vr.Type())
+	}
+
+	return reflect.ValueOf(str), nil
+}
+
+// DecodeValue is the ValueDecoder for string types.
+func (sc *StringCodec) DecodeValue(dctx DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Kind() != reflect.String {
+		return ValueDecoderError{Name: "StringDecodeValue", Kinds: []reflect.Kind{reflect.String}, Received: val}
+	}
+
+	elem, err := sc.decodeType(dctx, vr, val.Type())
+	if err != nil {
+		return err
+	}
+
+	val.SetString(elem.String())
+	return nil
+}

mongo/bson/bsoncodec/string_codec_test.go

@@ -0,0 +1,48 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"testing"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw/bsonrwtest"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/internal/testutil/assert"
+)
+
+func TestStringCodec(t *testing.T) {
+	t.Run("ObjectIDAsHex", func(t *testing.T) {
+		oid := primitive.NewObjectID()
+		byteArray := [12]byte(oid)
+		reader := &bsonrwtest.ValueReaderWriter{BSONType: bsontype.ObjectID, Return: oid}
+		testCases := []struct {
+			name   string
+			opts   *bsonoptions.StringCodecOptions
+			hex    bool
+			result string
+		}{
+			{"default", bsonoptions.StringCodec(), true, oid.Hex()},
+			{"true", bsonoptions.StringCodec().SetDecodeObjectIDAsHex(true), true, oid.Hex()},
+			{"false", bsonoptions.StringCodec().SetDecodeObjectIDAsHex(false), false, string(byteArray[:])},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				stringCodec := NewStringCodec(tc.opts)
+
+				actual := reflect.New(reflect.TypeOf("")).Elem()
+				err := stringCodec.DecodeValue(DecodeContext{}, reader, actual)
+				assert.Nil(t, err, "StringCodec.DecodeValue error: %v", err)
+
+				actualString := actual.Interface().(string)
+				assert.Equal(t, tc.result, actualString, "Expected string %v, got %v", tc.result, actualString)
+			})
+		}
+	})
+}

mongo/bson/bsoncodec/struct_codec.go

@@ -0,0 +1,675 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+// DecodeError represents an error that occurs when unmarshalling BSON bytes into a native Go type.
+type DecodeError struct {
+	keys    []string
+	wrapped error
+}
+
+// Unwrap returns the underlying error
+func (de *DecodeError) Unwrap() error {
+	return de.wrapped
+}
+
+// Error implements the error interface.
+func (de *DecodeError) Error() string {
+	// The keys are stored in reverse order because the de.keys slice is builtup while propagating the error up the
+	// stack of BSON keys, so we call de.Keys(), which reverses them.
+	keyPath := strings.Join(de.Keys(), ".")
+	return fmt.Sprintf("error decoding key %s: %v", keyPath, de.wrapped)
+}
+
+// Keys returns the BSON key path that caused an error as a slice of strings. The keys in the slice are in top-down
+// order. For example, if the document being unmarshalled was {a: {b: {c: 1}}} and the value for c was supposed to be
+// a string, the keys slice will be ["a", "b", "c"].
+func (de *DecodeError) Keys() []string {
+	reversedKeys := make([]string, 0, len(de.keys))
+	for idx := len(de.keys) - 1; idx >= 0; idx-- {
+		reversedKeys = append(reversedKeys, de.keys[idx])
+	}
+
+	return reversedKeys
+}
+
+// Zeroer allows custom struct types to implement a report of zero
+// state. All struct types that don't implement Zeroer or where IsZero
+// returns false are considered to be not zero.
+type Zeroer interface {
+	IsZero() bool
+}
+
+// StructCodec is the Codec used for struct values.
+type StructCodec struct {
+	cache                            map[reflect.Type]*structDescription
+	l                                sync.RWMutex
+	parser                           StructTagParser
+	DecodeZeroStruct                 bool
+	DecodeDeepZeroInline             bool
+	EncodeOmitDefaultStruct          bool
+	AllowUnexportedFields            bool
+	OverwriteDuplicatedInlinedFields bool
+}
+
+var _ ValueEncoder = &StructCodec{}
+var _ ValueDecoder = &StructCodec{}
+
+// NewStructCodec returns a StructCodec that uses p for struct tag parsing.
+func NewStructCodec(p StructTagParser, opts ...*bsonoptions.StructCodecOptions) (*StructCodec, error) {
+	if p == nil {
+		return nil, errors.New("a StructTagParser must be provided to NewStructCodec")
+	}
+
+	structOpt := bsonoptions.MergeStructCodecOptions(opts...)
+
+	codec := &StructCodec{
+		cache:  make(map[reflect.Type]*structDescription),
+		parser: p,
+	}
+
+	if structOpt.DecodeZeroStruct != nil {
+		codec.DecodeZeroStruct = *structOpt.DecodeZeroStruct
+	}
+	if structOpt.DecodeDeepZeroInline != nil {
+		codec.DecodeDeepZeroInline = *structOpt.DecodeDeepZeroInline
+	}
+	if structOpt.EncodeOmitDefaultStruct != nil {
+		codec.EncodeOmitDefaultStruct = *structOpt.EncodeOmitDefaultStruct
+	}
+	if structOpt.OverwriteDuplicatedInlinedFields != nil {
+		codec.OverwriteDuplicatedInlinedFields = *structOpt.OverwriteDuplicatedInlinedFields
+	}
+	if structOpt.AllowUnexportedFields != nil {
+		codec.AllowUnexportedFields = *structOpt.AllowUnexportedFields
+	}
+
+	return codec, nil
+}
+
+// EncodeValue handles encoding generic struct types.
+func (sc *StructCodec) EncodeValue(r EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Kind() != reflect.Struct {
+		return ValueEncoderError{Name: "StructCodec.EncodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
+	}
+
+	sd, err := sc.describeStruct(r.Registry, val.Type())
+	if err != nil {
+		return err
+	}
+
+	dw, err := vw.WriteDocument()
+	if err != nil {
+		return err
+	}
+	var rv reflect.Value
+	for _, desc := range sd.fl {
+		if desc.omitAlways {
+			continue
+		}
+
+		if desc.inline == nil {
+			rv = val.Field(desc.idx)
+		} else {
+			rv, err = fieldByIndexErr(val, desc.inline)
+			if err != nil {
+				continue
+			}
+		}
+
+		desc.encoder, rv, err = defaultValueEncoders.lookupElementEncoder(r, desc.encoder, rv)
+
+		if err != nil && err != errInvalidValue {
+			return err
+		}
+
+		if err == errInvalidValue {
+			if desc.omitEmpty {
+				continue
+			}
+			vw2, err := dw.WriteDocumentElement(desc.name)
+			if err != nil {
+				return err
+			}
+			err = vw2.WriteNull()
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		if desc.encoder == nil {
+			return ErrNoEncoder{Type: rv.Type()}
+		}
+
+		encoder := desc.encoder
+
+		var isZero bool
+		rvInterface := rv.Interface()
+		if cz, ok := encoder.(CodecZeroer); ok {
+			isZero = cz.IsTypeZero(rvInterface)
+		} else if rv.Kind() == reflect.Interface {
+			// sc.isZero will not treat an interface rv as an interface, so we need to check for the zero interface separately.
+			isZero = rv.IsNil()
+		} else {
+			isZero = sc.isZero(rvInterface)
+		}
+		if desc.omitEmpty && isZero {
+			continue
+		}
+
+		vw2, err := dw.WriteDocumentElement(desc.name)
+		if err != nil {
+			return err
+		}
+
+		ectx := EncodeContext{Registry: r.Registry, MinSize: desc.minSize}
+		err = encoder.EncodeValue(ectx, vw2, rv)
+		if err != nil {
+			return err
+		}
+	}
+
+	if sd.inlineMap >= 0 {
+		rv := val.Field(sd.inlineMap)
+		collisionFn := func(key string) bool {
+			_, exists := sd.fm[key]
+			return exists
+		}
+
+		return defaultMapCodec.mapEncodeValue(r, dw, rv, collisionFn)
+	}
+
+	return dw.WriteDocumentEnd()
+}
+
+func newDecodeError(key string, original error) error {
+	de, ok := original.(*DecodeError)
+	if !ok {
+		return &DecodeError{
+			keys:    []string{key},
+			wrapped: original,
+		}
+	}
+
+	de.keys = append(de.keys, key)
+	return de
+}
+
+// DecodeValue implements the Codec interface.
+// By default, map types in val will not be cleared. If a map has existing key/value pairs, it will be extended with the new ones from vr.
+// For slices, the decoder will set the length of the slice to zero and append all elements. The underlying array will not be cleared.
+func (sc *StructCodec) DecodeValue(r DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Kind() != reflect.Struct {
+		return ValueDecoderError{Name: "StructCodec.DecodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
+	}
+
+	switch vrType := vr.Type(); vrType {
+	case bsontype.Type(0), bsontype.EmbeddedDocument:
+	case bsontype.Null:
+		if err := vr.ReadNull(); err != nil {
+			return err
+		}
+
+		val.Set(reflect.Zero(val.Type()))
+		return nil
+	case bsontype.Undefined:
+		if err := vr.ReadUndefined(); err != nil {
+			return err
+		}
+
+		val.Set(reflect.Zero(val.Type()))
+		return nil
+	default:
+		return fmt.Errorf("cannot decode %v into a %s", vrType, val.Type())
+	}
+
+	sd, err := sc.describeStruct(r.Registry, val.Type())
+	if err != nil {
+		return err
+	}
+
+	if sc.DecodeZeroStruct {
+		val.Set(reflect.Zero(val.Type()))
+	}
+	if sc.DecodeDeepZeroInline && sd.inline {
+		val.Set(deepZero(val.Type()))
+	}
+
+	var decoder ValueDecoder
+	var inlineMap reflect.Value
+	if sd.inlineMap >= 0 {
+		inlineMap = val.Field(sd.inlineMap)
+		decoder, err = r.LookupDecoder(inlineMap.Type().Elem())
+		if err != nil {
+			return err
+		}
+	}
+
+	dr, err := vr.ReadDocument()
+	if err != nil {
+		return err
+	}
+
+	for {
+		name, vr, err := dr.ReadElement()
+		if err == bsonrw.ErrEOD {
+			break
+		}
+		if err != nil {
+			return err
+		}
+
+		fd, exists := sd.fm[name]
+		if !exists {
+			// if the original name isn't found in the struct description, try again with the name in lowercase
+			// this could match if a BSON tag isn't specified because by default, describeStruct lowercases all field
+			// names
+			fd, exists = sd.fm[strings.ToLower(name)]
+		}
+
+		if !exists {
+			if sd.inlineMap < 0 {
+				// The encoding/json package requires a flag to return on error for non-existent fields.
+				// This functionality seems appropriate for the struct codec.
+				err = vr.Skip()
+				if err != nil {
+					return err
+				}
+				continue
+			}
+
+			if inlineMap.IsNil() {
+				inlineMap.Set(reflect.MakeMap(inlineMap.Type()))
+			}
+
+			elem := reflect.New(inlineMap.Type().Elem()).Elem()
+			r.Ancestor = inlineMap.Type()
+			err = decoder.DecodeValue(r, vr, elem)
+			if err != nil {
+				return err
+			}
+			inlineMap.SetMapIndex(reflect.ValueOf(name), elem)
+			continue
+		}
+
+		var field reflect.Value
+		if fd.inline == nil {
+			field = val.Field(fd.idx)
+		} else {
+			field, err = getInlineField(val, fd.inline)
+			if err != nil {
+				return err
+			}
+		}
+
+		if !field.CanSet() { // Being settable is a super set of being addressable.
+			innerErr := fmt.Errorf("field %v is not settable", field)
+			return newDecodeError(fd.name, innerErr)
+		}
+		if field.Kind() == reflect.Ptr && field.IsNil() {
+			field.Set(reflect.New(field.Type().Elem()))
+		}
+		field = field.Addr()
+
+		dctx := DecodeContext{
+			Registry:            r.Registry,
+			Truncate:            fd.truncate || r.Truncate,
+			defaultDocumentType: r.defaultDocumentType,
+		}
+
+		if fd.decoder == nil {
+			return newDecodeError(fd.name, ErrNoDecoder{Type: field.Elem().Type()})
+		}
+
+		err = fd.decoder.DecodeValue(dctx, vr, field.Elem())
+		if err != nil {
+			return newDecodeError(fd.name, err)
+		}
+	}
+
+	return nil
+}
+
+func (sc *StructCodec) isZero(i interface{}) bool {
+	v := reflect.ValueOf(i)
+
+	// check the value validity
+	if !v.IsValid() {
+		return true
+	}
+
+	if z, ok := v.Interface().(Zeroer); ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
+		return z.IsZero()
+	}
+
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	case reflect.Struct:
+		if sc.EncodeOmitDefaultStruct {
+			vt := v.Type()
+			if vt == tTime {
+				return v.Interface().(time.Time).IsZero()
+			}
+			for i := 0; i < v.NumField(); i++ {
+				if vt.Field(i).PkgPath != "" && !vt.Field(i).Anonymous {
+					continue // Private field
+				}
+				fld := v.Field(i)
+				if !sc.isZero(fld.Interface()) {
+					return false
+				}
+			}
+			return true
+		}
+	}
+
+	return false
+}
+
+type structDescription struct {
+	fm        map[string]fieldDescription
+	fl        []fieldDescription
+	inlineMap int
+	inline    bool
+}
+
+type fieldDescription struct {
+	name       string // BSON key name
+	fieldName  string // struct field name
+	idx        int
+	omitEmpty  bool
+	omitAlways bool
+	minSize    bool
+	truncate   bool
+	inline     []int
+	encoder    ValueEncoder
+	decoder    ValueDecoder
+}
+
+type byIndex []fieldDescription
+
+func (bi byIndex) Len() int { return len(bi) }
+
+func (bi byIndex) Swap(i, j int) { bi[i], bi[j] = bi[j], bi[i] }
+
+func (bi byIndex) Less(i, j int) bool {
+	// If a field is inlined, its index in the top level struct is stored at inline[0]
+	iIdx, jIdx := bi[i].idx, bi[j].idx
+	if len(bi[i].inline) > 0 {
+		iIdx = bi[i].inline[0]
+	}
+	if len(bi[j].inline) > 0 {
+		jIdx = bi[j].inline[0]
+	}
+	if iIdx != jIdx {
+		return iIdx < jIdx
+	}
+	for k, biik := range bi[i].inline {
+		if k >= len(bi[j].inline) {
+			return false
+		}
+		if biik != bi[j].inline[k] {
+			return biik < bi[j].inline[k]
+		}
+	}
+	return len(bi[i].inline) < len(bi[j].inline)
+}
+
+func (sc *StructCodec) describeStruct(r *Registry, t reflect.Type) (*structDescription, error) {
+	// We need to analyze the struct, including getting the tags, collecting
+	// information about inlining, and create a map of the field name to the field.
+	sc.l.RLock()
+	ds, exists := sc.cache[t]
+	sc.l.RUnlock()
+	if exists {
+		return ds, nil
+	}
+
+	numFields := t.NumField()
+	sd := &structDescription{
+		fm:        make(map[string]fieldDescription, numFields),
+		fl:        make([]fieldDescription, 0, numFields),
+		inlineMap: -1,
+	}
+
+	var fields []fieldDescription
+	for i := 0; i < numFields; i++ {
+		sf := t.Field(i)
+		if sf.PkgPath != "" && (!sc.AllowUnexportedFields || !sf.Anonymous) {
+			// field is private or unexported fields aren't allowed, ignore
+			continue
+		}
+
+		sfType := sf.Type
+		encoder, err := r.LookupEncoder(sfType)
+		if err != nil {
+			encoder = nil
+		}
+		decoder, err := r.LookupDecoder(sfType)
+		if err != nil {
+			decoder = nil
+		}
+
+		description := fieldDescription{
+			fieldName: sf.Name,
+			idx:       i,
+			encoder:   encoder,
+			decoder:   decoder,
+		}
+
+		stags, err := sc.parser.ParseStructTags(sf)
+		if err != nil {
+			return nil, err
+		}
+		if stags.Skip {
+			continue
+		}
+		description.name = stags.Name
+		description.omitEmpty = stags.OmitEmpty
+		description.omitAlways = stags.OmitAlways
+		description.minSize = stags.MinSize
+		description.truncate = stags.Truncate
+
+		if stags.Inline {
+			sd.inline = true
+			switch sfType.Kind() {
+			case reflect.Map:
+				if sd.inlineMap >= 0 {
+					return nil, errors.New("(struct " + t.String() + ") multiple inline maps")
+				}
+				if sfType.Key() != tString {
+					return nil, errors.New("(struct " + t.String() + ") inline map must have a string keys")
+				}
+				sd.inlineMap = description.idx
+			case reflect.Ptr:
+				sfType = sfType.Elem()
+				if sfType.Kind() != reflect.Struct {
+					return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
+				}
+				fallthrough
+			case reflect.Struct:
+				inlinesf, err := sc.describeStruct(r, sfType)
+				if err != nil {
+					return nil, err
+				}
+				for _, fd := range inlinesf.fl {
+					if fd.inline == nil {
+						fd.inline = []int{i, fd.idx}
+					} else {
+						fd.inline = append([]int{i}, fd.inline...)
+					}
+					fields = append(fields, fd)
+
+				}
+			default:
+				return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
+			}
+			continue
+		}
+		fields = append(fields, description)
+	}
+
+	// Sort fieldDescriptions by name and use dominance rules to determine which should be added for each name
+	sort.Slice(fields, func(i, j int) bool {
+		x := fields
+		// sort field by name, breaking ties with depth, then
+		// breaking ties with index sequence.
+		if x[i].name != x[j].name {
+			return x[i].name < x[j].name
+		}
+		if len(x[i].inline) != len(x[j].inline) {
+			return len(x[i].inline) < len(x[j].inline)
+		}
+		return byIndex(x).Less(i, j)
+	})
+
+	for advance, i := 0, 0; i < len(fields); i += advance {
+		// One iteration per name.
+		// Find the sequence of fields with the name of this first field.
+		fi := fields[i]
+		name := fi.name
+		for advance = 1; i+advance < len(fields); advance++ {
+			fj := fields[i+advance]
+			if fj.name != name {
+				break
+			}
+		}
+		if advance == 1 { // Only one field with this name
+			sd.fl = append(sd.fl, fi)
+			sd.fm[name] = fi
+			continue
+		}
+		dominant, ok := dominantField(fields[i : i+advance])
+		if !ok || !sc.OverwriteDuplicatedInlinedFields {
+			return nil, fmt.Errorf("struct %s has duplicated key %s", t.String(), name)
+		}
+		sd.fl = append(sd.fl, dominant)
+		sd.fm[name] = dominant
+	}
+
+	sort.Sort(byIndex(sd.fl))
+
+	sc.l.Lock()
+	sc.cache[t] = sd
+	sc.l.Unlock()
+
+	return sd, nil
+}
+
+// dominantField looks through the fields, all of which are known to
+// have the same name, to find the single field that dominates the
+// others using Go's inlining rules. If there are multiple top-level
+// fields, the boolean will be false: This condition is an error in Go
+// and we skip all the fields.
+func dominantField(fields []fieldDescription) (fieldDescription, bool) {
+	// The fields are sorted in increasing index-length order, then by presence of tag.
+	// That means that the first field is the dominant one. We need only check
+	// for error cases: two fields at top level.
+	if len(fields) > 1 &&
+		len(fields[0].inline) == len(fields[1].inline) {
+		return fieldDescription{}, false
+	}
+	return fields[0], true
+}
+
+func fieldByIndexErr(v reflect.Value, index []int) (result reflect.Value, err error) {
+	defer func() {
+		if recovered := recover(); recovered != nil {
+			switch r := recovered.(type) {
+			case string:
+				err = fmt.Errorf("%s", r)
+			case error:
+				err = r
+			}
+		}
+	}()
+
+	result = v.FieldByIndex(index)
+	return
+}
+
+func getInlineField(val reflect.Value, index []int) (reflect.Value, error) {
+	field, err := fieldByIndexErr(val, index)
+	if err == nil {
+		return field, nil
+	}
+
+	// if parent of this element doesn't exist, fix its parent
+	inlineParent := index[:len(index)-1]
+	var fParent reflect.Value
+	if fParent, err = fieldByIndexErr(val, inlineParent); err != nil {
+		fParent, err = getInlineField(val, inlineParent)
+		if err != nil {
+			return fParent, err
+		}
+	}
+	fParent.Set(reflect.New(fParent.Type().Elem()))
+
+	return fieldByIndexErr(val, index)
+}
+
+// DeepZero returns recursive zero object
+func deepZero(st reflect.Type) (result reflect.Value) {
+	result = reflect.Indirect(reflect.New(st))
+
+	if result.Kind() == reflect.Struct {
+		for i := 0; i < result.NumField(); i++ {
+			if f := result.Field(i); f.Kind() == reflect.Ptr {
+				if f.CanInterface() {
+					if ft := reflect.TypeOf(f.Interface()); ft.Elem().Kind() == reflect.Struct {
+						result.Field(i).Set(recursivePointerTo(deepZero(ft.Elem())))
+					}
+				}
+			}
+		}
+	}
+
+	return
+}
+
+// recursivePointerTo calls reflect.New(v.Type) but recursively for its fields inside
+func recursivePointerTo(v reflect.Value) reflect.Value {
+	v = reflect.Indirect(v)
+	result := reflect.New(v.Type())
+	if v.Kind() == reflect.Struct {
+		for i := 0; i < v.NumField(); i++ {
+			if f := v.Field(i); f.Kind() == reflect.Ptr {
+				if f.Elem().Kind() == reflect.Struct {
+					result.Elem().Field(i).Set(recursivePointerTo(f))
+				}
+			}
+		}
+	}
+
+	return result
+}

mongo/bson/bsoncodec/struct_codec_test.go

@@ -0,0 +1,47 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestZeoerInterfaceUsedByDecoder(t *testing.T) {
+	enc := &StructCodec{}
+
+	// cases that are zero, because they are known types or pointers
+	var st *nonZeroer
+	assert.True(t, enc.isZero(st))
+	assert.True(t, enc.isZero(0))
+	assert.True(t, enc.isZero(false))
+
+	// cases that shouldn't be zero
+	st = &nonZeroer{value: false}
+	assert.False(t, enc.isZero(struct{ val bool }{val: true}))
+	assert.False(t, enc.isZero(struct{ val bool }{val: false}))
+	assert.False(t, enc.isZero(st))
+	st.value = true
+	assert.False(t, enc.isZero(st))
+
+	// a test to see if the interface impacts the outcome
+	z := zeroTest{}
+	assert.False(t, enc.isZero(z))
+
+	z.reportZero = true
+	assert.True(t, enc.isZero(z))
+
+	// *time.Time with nil should be zero
+	var tp *time.Time
+	assert.True(t, enc.isZero(tp))
+
+	// actually all zeroer if nil should also be zero
+	var zp *zeroTest
+	assert.True(t, enc.isZero(zp))
+}

mongo/bson/bsoncodec/struct_tag_parser.go

@@ -0,0 +1,142 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"strings"
+)
+
+// StructTagParser returns the struct tags for a given struct field.
+type StructTagParser interface {
+	ParseStructTags(reflect.StructField) (StructTags, error)
+}
+
+// StructTagParserFunc is an adapter that allows a generic function to be used
+// as a StructTagParser.
+type StructTagParserFunc func(reflect.StructField) (StructTags, error)
+
+// ParseStructTags implements the StructTagParser interface.
+func (stpf StructTagParserFunc) ParseStructTags(sf reflect.StructField) (StructTags, error) {
+	return stpf(sf)
+}
+
+// StructTags represents the struct tag fields that the StructCodec uses during
+// the encoding and decoding process.
+//
+// In the case of a struct, the lowercased field name is used as the key for each exported
+// field but this behavior may be changed using a struct tag. The tag may also contain flags to
+// adjust the marshalling behavior for the field.
+//
+// The properties are defined below:
+//
+//	OmitEmpty  Only include the field if it's not set to the zero value for the type or to
+//	           empty slices or maps.
+//
+//	MinSize    Marshal an integer of a type larger than 32 bits value as an int32, if that's
+//	           feasible while preserving the numeric value.
+//
+//	Truncate   When unmarshaling a BSON double, it is permitted to lose precision to fit within
+//	           a float32.
+//
+//	Inline     Inline the field, which must be a struct or a map, causing all of its fields
+//	           or keys to be processed as if they were part of the outer struct. For maps,
+//	           keys must not conflict with the bson keys of other struct fields.
+//
+//	Skip       This struct field should be skipped. This is usually denoted by parsing a "-"
+//	           for the name.
+//
+// TODO(skriptble): Add tags for undefined as nil and for null as nil.
+type StructTags struct {
+	Name       string
+	OmitEmpty  bool
+	OmitAlways bool
+	MinSize    bool
+	Truncate   bool
+	Inline     bool
+	Skip       bool
+}
+
+// DefaultStructTagParser is the StructTagParser used by the StructCodec by default.
+// It will handle the bson struct tag. See the documentation for StructTags to see
+// what each of the returned fields means.
+//
+// If there is no name in the struct tag fields, the struct field name is lowercased.
+// The tag formats accepted are:
+//
+//	"[<key>][,<flag1>[,<flag2>]]"
+//
+//	`(...) bson:"[<key>][,<flag1>[,<flag2>]]" (...)`
+//
+// An example:
+//
+//	type T struct {
+//	    A bool
+//	    B int    "myb"
+//	    C string "myc,omitempty"
+//	    D string `bson:",omitempty" json:"jsonkey"`
+//	    E int64  ",minsize"
+//	    F int64  "myf,omitempty,minsize"
+//	}
+//
+// A struct tag either consisting entirely of '-' or with a bson key with a
+// value consisting entirely of '-' will return a StructTags with Skip true and
+// the remaining fields will be their default values.
+var DefaultStructTagParser StructTagParserFunc = func(sf reflect.StructField) (StructTags, error) {
+	key := strings.ToLower(sf.Name)
+	tag, ok := sf.Tag.Lookup("bson")
+	if !ok && !strings.Contains(string(sf.Tag), ":") && len(sf.Tag) > 0 {
+		tag = string(sf.Tag)
+	}
+	return parseTags(key, tag)
+}
+
+func parseTags(key string, tag string) (StructTags, error) {
+	var st StructTags
+	if tag == "-" {
+		st.Skip = true
+		return st, nil
+	}
+
+	for idx, str := range strings.Split(tag, ",") {
+		if idx == 0 && str != "" {
+			key = str
+		}
+		switch str {
+		case "omitempty":
+			st.OmitEmpty = true
+		case "omitalways":
+			st.OmitAlways = true
+		case "minsize":
+			st.MinSize = true
+		case "truncate":
+			st.Truncate = true
+		case "inline":
+			st.Inline = true
+		}
+	}
+
+	st.Name = key
+
+	return st, nil
+}
+
+// JSONFallbackStructTagParser has the same behavior as DefaultStructTagParser
+// but will also fallback to parsing the json tag instead on a field where the
+// bson tag isn't available.
+var JSONFallbackStructTagParser StructTagParserFunc = func(sf reflect.StructField) (StructTags, error) {
+	key := strings.ToLower(sf.Name)
+	tag, ok := sf.Tag.Lookup("bson")
+	if !ok {
+		tag, ok = sf.Tag.Lookup("json")
+	}
+	if !ok && !strings.Contains(string(sf.Tag), ":") && len(sf.Tag) > 0 {
+		tag = string(sf.Tag)
+	}
+
+	return parseTags(key, tag)
+}

mongo/bson/bsoncodec/struct_tag_parser_test.go

@@ -0,0 +1,160 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestStructTagParsers(t *testing.T) {
+	testCases := []struct {
+		name   string
+		sf     reflect.StructField
+		want   StructTags
+		parser StructTagParserFunc
+	}{
+		{
+			"default no bson tag",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag("bar")},
+			StructTags{Name: "bar"},
+			DefaultStructTagParser,
+		},
+		{
+			"default empty",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag("")},
+			StructTags{Name: "foo"},
+			DefaultStructTagParser,
+		},
+		{
+			"default tag only dash",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag("-")},
+			StructTags{Skip: true},
+			DefaultStructTagParser,
+		},
+		{
+			"default bson tag only dash",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:"-"`)},
+			StructTags{Skip: true},
+			DefaultStructTagParser,
+		},
+		{
+			"default all options",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bar,omitempty,minsize,truncate,inline`)},
+			StructTags{Name: "bar", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			DefaultStructTagParser,
+		},
+		{
+			"default all options default name",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`,omitempty,minsize,truncate,inline`)},
+			StructTags{Name: "foo", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			DefaultStructTagParser,
+		},
+		{
+			"default bson tag all options",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:"bar,omitempty,minsize,truncate,inline"`)},
+			StructTags{Name: "bar", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			DefaultStructTagParser,
+		},
+		{
+			"default bson tag all options default name",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:",omitempty,minsize,truncate,inline"`)},
+			StructTags{Name: "foo", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			DefaultStructTagParser,
+		},
+		{
+			"default ignore xml",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`xml:"bar"`)},
+			StructTags{Name: "foo"},
+			DefaultStructTagParser,
+		},
+		{
+			"JSONFallback no bson tag",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag("bar")},
+			StructTags{Name: "bar"},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback empty",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag("")},
+			StructTags{Name: "foo"},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback tag only dash",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag("-")},
+			StructTags{Skip: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback bson tag only dash",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:"-"`)},
+			StructTags{Skip: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback all options",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bar,omitempty,minsize,truncate,inline`)},
+			StructTags{Name: "bar", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback all options default name",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`,omitempty,minsize,truncate,inline`)},
+			StructTags{Name: "foo", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback bson tag all options",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:"bar,omitempty,minsize,truncate,inline"`)},
+			StructTags{Name: "bar", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback bson tag all options default name",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:",omitempty,minsize,truncate,inline"`)},
+			StructTags{Name: "foo", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback json tag all options",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`json:"bar,omitempty,minsize,truncate,inline"`)},
+			StructTags{Name: "bar", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback json tag all options default name",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`json:",omitempty,minsize,truncate,inline"`)},
+			StructTags{Name: "foo", OmitEmpty: true, MinSize: true, Truncate: true, Inline: true},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback bson tag overrides other tags",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`bson:"bar" json:"qux,truncate"`)},
+			StructTags{Name: "bar"},
+			JSONFallbackStructTagParser,
+		},
+		{
+			"JSONFallback ignore xml",
+			reflect.StructField{Name: "foo", Tag: reflect.StructTag(`xml:"bar"`)},
+			StructTags{Name: "foo"},
+			JSONFallbackStructTagParser,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := tc.parser(tc.sf)
+			noerr(t, err)
+			if !cmp.Equal(got, tc.want) {
+				t.Errorf("Returned struct tags do not match. got %#v; want %#v", got, tc.want)
+			}
+		})
+	}
+}

mongo/bson/bsoncodec/time_codec.go

@@ -0,0 +1,127 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"fmt"
+	"reflect"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+)
+
+const (
+	timeFormatString = "2006-01-02T15:04:05.999Z07:00"
+)
+
+// TimeCodec is the Codec used for time.Time values.
+type TimeCodec struct {
+	UseLocalTimeZone bool
+}
+
+var (
+	defaultTimeCodec = NewTimeCodec()
+
+	_ ValueCodec  = defaultTimeCodec
+	_ typeDecoder = defaultTimeCodec
+)
+
+// NewTimeCodec returns a TimeCodec with options opts.
+func NewTimeCodec(opts ...*bsonoptions.TimeCodecOptions) *TimeCodec {
+	timeOpt := bsonoptions.MergeTimeCodecOptions(opts...)
+
+	codec := TimeCodec{}
+	if timeOpt.UseLocalTimeZone != nil {
+		codec.UseLocalTimeZone = *timeOpt.UseLocalTimeZone
+	}
+	return &codec
+}
+
+func (tc *TimeCodec) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	if t != tTime {
+		return emptyValue, ValueDecoderError{
+			Name:     "TimeDecodeValue",
+			Types:    []reflect.Type{tTime},
+			Received: reflect.Zero(t),
+		}
+	}
+
+	var timeVal time.Time
+	switch vrType := vr.Type(); vrType {
+	case bsontype.DateTime:
+		dt, err := vr.ReadDateTime()
+		if err != nil {
+			return emptyValue, err
+		}
+		timeVal = time.Unix(dt/1000, dt%1000*1000000)
+	case bsontype.String:
+		// assume strings are in the isoTimeFormat
+		timeStr, err := vr.ReadString()
+		if err != nil {
+			return emptyValue, err
+		}
+		timeVal, err = time.Parse(timeFormatString, timeStr)
+		if err != nil {
+			return emptyValue, err
+		}
+	case bsontype.Int64:
+		i64, err := vr.ReadInt64()
+		if err != nil {
+			return emptyValue, err
+		}
+		timeVal = time.Unix(i64/1000, i64%1000*1000000)
+	case bsontype.Timestamp:
+		t, _, err := vr.ReadTimestamp()
+		if err != nil {
+			return emptyValue, err
+		}
+		timeVal = time.Unix(int64(t), 0)
+	case bsontype.Null:
+		if err := vr.ReadNull(); err != nil {
+			return emptyValue, err
+		}
+	case bsontype.Undefined:
+		if err := vr.ReadUndefined(); err != nil {
+			return emptyValue, err
+		}
+	default:
+		return emptyValue, fmt.Errorf("cannot decode %v into a time.Time", vrType)
+	}
+
+	if !tc.UseLocalTimeZone {
+		timeVal = timeVal.UTC()
+	}
+	return reflect.ValueOf(timeVal), nil
+}
+
+// DecodeValue is the ValueDecoderFunc for time.Time.
+func (tc *TimeCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() || val.Type() != tTime {
+		return ValueDecoderError{Name: "TimeDecodeValue", Types: []reflect.Type{tTime}, Received: val}
+	}
+
+	elem, err := tc.decodeType(dc, vr, tTime)
+	if err != nil {
+		return err
+	}
+
+	val.Set(elem)
+	return nil
+}
+
+// EncodeValue is the ValueEncoderFunc for time.TIme.
+func (tc *TimeCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	if !val.IsValid() || val.Type() != tTime {
+		return ValueEncoderError{Name: "TimeEncodeValue", Types: []reflect.Type{tTime}, Received: val}
+	}
+	tt := val.Interface().(time.Time)
+	dt := primitive.NewDateTimeFromTime(tt)
+	return vw.WriteDateTime(int64(dt))
+}

mongo/bson/bsoncodec/time_codec_test.go

@@ -0,0 +1,79 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"reflect"
+	"testing"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw/bsonrwtest"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+	"go.mongodb.org/mongo-driver/internal/testutil/assert"
+	"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
+)
+
+func TestTimeCodec(t *testing.T) {
+	now := time.Now().Truncate(time.Millisecond)
+
+	t.Run("UseLocalTimeZone", func(t *testing.T) {
+		reader := &bsonrwtest.ValueReaderWriter{BSONType: bsontype.DateTime, Return: now.UnixNano() / int64(time.Millisecond)}
+		testCases := []struct {
+			name string
+			opts *bsonoptions.TimeCodecOptions
+			utc  bool
+		}{
+			{"default", bsonoptions.TimeCodec(), true},
+			{"false", bsonoptions.TimeCodec().SetUseLocalTimeZone(false), true},
+			{"true", bsonoptions.TimeCodec().SetUseLocalTimeZone(true), false},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				timeCodec := NewTimeCodec(tc.opts)
+
+				actual := reflect.New(reflect.TypeOf(now)).Elem()
+				err := timeCodec.DecodeValue(DecodeContext{}, reader, actual)
+				assert.Nil(t, err, "TimeCodec.DecodeValue error: %v", err)
+
+				actualTime := actual.Interface().(time.Time)
+				assert.Equal(t, actualTime.Location().String() == "UTC", tc.utc,
+					"Expected UTC: %v, got %v", tc.utc, actualTime.Location())
+				assert.Equal(t, now, actualTime, "expected time %v, got %v", now, actualTime)
+			})
+		}
+	})
+
+	t.Run("DecodeFromBsontype", func(t *testing.T) {
+		testCases := []struct {
+			name   string
+			reader *bsonrwtest.ValueReaderWriter
+		}{
+			{"string", &bsonrwtest.ValueReaderWriter{BSONType: bsontype.String, Return: now.Format(timeFormatString)}},
+			{"int64", &bsonrwtest.ValueReaderWriter{BSONType: bsontype.Int64, Return: now.Unix()*1000 + int64(now.Nanosecond()/1e6)}},
+			{"timestamp", &bsonrwtest.ValueReaderWriter{BSONType: bsontype.Timestamp,
+				Return: bsoncore.Value{
+					Type: bsontype.Timestamp,
+					Data: bsoncore.AppendTimestamp(nil, uint32(now.Unix()), 0),
+				}},
+			},
+		}
+		for _, tc := range testCases {
+			t.Run(tc.name, func(t *testing.T) {
+				actual := reflect.New(reflect.TypeOf(now)).Elem()
+				err := defaultTimeCodec.DecodeValue(DecodeContext{}, tc.reader, actual)
+				assert.Nil(t, err, "DecodeValue error: %v", err)
+
+				actualTime := actual.Interface().(time.Time)
+				if tc.name == "timestamp" {
+					now = time.Unix(now.Unix(), 0)
+				}
+				assert.Equal(t, now, actualTime, "expected time %v, got %v", now, actualTime)
+			})
+		}
+	})
+}

mongo/bson/bsoncodec/types.go

@@ -0,0 +1,57 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"encoding/json"
+	"net/url"
+	"reflect"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
+)
+
+var tBool = reflect.TypeOf(false)
+var tFloat64 = reflect.TypeOf(float64(0))
+var tInt32 = reflect.TypeOf(int32(0))
+var tInt64 = reflect.TypeOf(int64(0))
+var tString = reflect.TypeOf("")
+var tTime = reflect.TypeOf(time.Time{})
+
+var tEmpty = reflect.TypeOf((*interface{})(nil)).Elem()
+var tByteSlice = reflect.TypeOf([]byte(nil))
+var tByte = reflect.TypeOf(byte(0x00))
+var tURL = reflect.TypeOf(url.URL{})
+var tJSONNumber = reflect.TypeOf(json.Number(""))
+
+var tValueMarshaler = reflect.TypeOf((*ValueMarshaler)(nil)).Elem()
+var tValueUnmarshaler = reflect.TypeOf((*ValueUnmarshaler)(nil)).Elem()
+var tMarshaler = reflect.TypeOf((*Marshaler)(nil)).Elem()
+var tUnmarshaler = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
+var tProxy = reflect.TypeOf((*Proxy)(nil)).Elem()
+
+var tBinary = reflect.TypeOf(primitive.Binary{})
+var tUndefined = reflect.TypeOf(primitive.Undefined{})
+var tOID = reflect.TypeOf(primitive.ObjectID{})
+var tDateTime = reflect.TypeOf(primitive.DateTime(0))
+var tNull = reflect.TypeOf(primitive.Null{})
+var tRegex = reflect.TypeOf(primitive.Regex{})
+var tCodeWithScope = reflect.TypeOf(primitive.CodeWithScope{})
+var tDBPointer = reflect.TypeOf(primitive.DBPointer{})
+var tJavaScript = reflect.TypeOf(primitive.JavaScript(""))
+var tSymbol = reflect.TypeOf(primitive.Symbol(""))
+var tTimestamp = reflect.TypeOf(primitive.Timestamp{})
+var tDecimal = reflect.TypeOf(primitive.Decimal128{})
+var tMinKey = reflect.TypeOf(primitive.MinKey{})
+var tMaxKey = reflect.TypeOf(primitive.MaxKey{})
+var tD = reflect.TypeOf(primitive.D{})
+var tA = reflect.TypeOf(primitive.A{})
+var tE = reflect.TypeOf(primitive.E{})
+
+var tCoreDocument = reflect.TypeOf(bsoncore.Document{})
+var tCoreArray = reflect.TypeOf(bsoncore.Array{})

mongo/bson/bsoncodec/uint_codec.go

@@ -0,0 +1,173 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsoncodec
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+
+	"go.mongodb.org/mongo-driver/bson/bsonoptions"
+	"go.mongodb.org/mongo-driver/bson/bsonrw"
+	"go.mongodb.org/mongo-driver/bson/bsontype"
+)
+
+// UIntCodec is the Codec used for uint values.
+type UIntCodec struct {
+	EncodeToMinSize bool
+}
+
+var (
+	defaultUIntCodec = NewUIntCodec()
+
+	_ ValueCodec  = defaultUIntCodec
+	_ typeDecoder = defaultUIntCodec
+)
+
+// NewUIntCodec returns a UIntCodec with options opts.
+func NewUIntCodec(opts ...*bsonoptions.UIntCodecOptions) *UIntCodec {
+	uintOpt := bsonoptions.MergeUIntCodecOptions(opts...)
+
+	codec := UIntCodec{}
+	if uintOpt.EncodeToMinSize != nil {
+		codec.EncodeToMinSize = *uintOpt.EncodeToMinSize
+	}
+	return &codec
+}
+
+// EncodeValue is the ValueEncoder for uint types.
+func (uic *UIntCodec) EncodeValue(ec EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
+	switch val.Kind() {
+	case reflect.Uint8, reflect.Uint16:
+		return vw.WriteInt32(int32(val.Uint()))
+	case reflect.Uint, reflect.Uint32, reflect.Uint64:
+		u64 := val.Uint()
+
+		// If ec.MinSize or if encodeToMinSize is true for a non-uint64 value we should write val as an int32
+		useMinSize := ec.MinSize || (uic.EncodeToMinSize && val.Kind() != reflect.Uint64)
+
+		if u64 <= math.MaxInt32 && useMinSize {
+			return vw.WriteInt32(int32(u64))
+		}
+		if u64 > math.MaxInt64 {
+			return fmt.Errorf("%d overflows int64", u64)
+		}
+		return vw.WriteInt64(int64(u64))
+	}
+
+	return ValueEncoderError{
+		Name:     "UintEncodeValue",
+		Kinds:    []reflect.Kind{reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint},
+		Received: val,
+	}
+}
+
+func (uic *UIntCodec) decodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
+	var i64 int64
+	var err error
+	switch vrType := vr.Type(); vrType {
+	case bsontype.Int32:
+		i32, err := vr.ReadInt32()
+		if err != nil {
+			return emptyValue, err
+		}
+		i64 = int64(i32)
+	case bsontype.Int64:
+		i64, err = vr.ReadInt64()
+		if err != nil {
+			return emptyValue, err
+		}
+	case bsontype.Double:
+		f64, err := vr.ReadDouble()
+		if err != nil {
+			return emptyValue, err
+		}
+		if !dc.Truncate && math.Floor(f64) != f64 {
+			return emptyValue, errCannotTruncate
+		}
+		if f64 > float64(math.MaxInt64) {
+			return emptyValue, fmt.Errorf("%g overflows int64", f64)
+		}
+		i64 = int64(f64)
+	case bsontype.Boolean:
+		b, err := vr.ReadBoolean()
+		if err != nil {
+			return emptyValue, err
+		}
+		if b {
+			i64 = 1
+		}
+	case bsontype.Null:
+		if err = vr.ReadNull(); err != nil {
+			return emptyValue, err
+		}
+	case bsontype.Undefined:
+		if err = vr.ReadUndefined(); err != nil {
+			return emptyValue, err
+		}
+	default:
+		return emptyValue, fmt.Errorf("cannot decode %v into an integer type", vrType)
+	}
+
+	switch t.Kind() {
+	case reflect.Uint8:
+		if i64 < 0 || i64 > math.MaxUint8 {
+			return emptyValue, fmt.Errorf("%d overflows uint8", i64)
+		}
+
+		return reflect.ValueOf(uint8(i64)), nil
+	case reflect.Uint16:
+		if i64 < 0 || i64 > math.MaxUint16 {
+			return emptyValue, fmt.Errorf("%d overflows uint16", i64)
+		}
+
+		return reflect.ValueOf(uint16(i64)), nil
+	case reflect.Uint32:
+		if i64 < 0 || i64 > math.MaxUint32 {
+			return emptyValue, fmt.Errorf("%d overflows uint32", i64)
+		}
+
+		return reflect.ValueOf(uint32(i64)), nil
+	case reflect.Uint64:
+		if i64 < 0 {
+			return emptyValue, fmt.Errorf("%d overflows uint64", i64)
+		}
+
+		return reflect.ValueOf(uint64(i64)), nil
+	case reflect.Uint:
+		if i64 < 0 || int64(uint(i64)) != i64 { // Can we fit this inside of an uint
+			return emptyValue, fmt.Errorf("%d overflows uint", i64)
+		}
+
+		return reflect.ValueOf(uint(i64)), nil
+	default:
+		return emptyValue, ValueDecoderError{
+			Name:     "UintDecodeValue",
+			Kinds:    []reflect.Kind{reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint},
+			Received: reflect.Zero(t),
+		}
+	}
+}
+
+// DecodeValue is the ValueDecoder for uint types.
+func (uic *UIntCodec) DecodeValue(dc DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
+	if !val.CanSet() {
+		return ValueDecoderError{
+			Name:     "UintDecodeValue",
+			Kinds:    []reflect.Kind{reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint},
+			Received: val,
+		}
+	}
+
+	elem, err := uic.decodeType(dc, vr, val.Type())
+	if err != nil {
+		return err
+	}
+
+	val.SetUint(elem.Uint())
+	return nil
+}

mongo/bson/bsonoptions/byte_slice_codec_options.go

@@ -0,0 +1,38 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package bsonoptions
+
+// ByteSliceCodecOptions represents all possible options for byte slice encoding and decoding.
+type ByteSliceCodecOptions struct {
+	EncodeNilAsEmpty *bool // Specifies if a nil byte slice should encode as an empty binary instead of null. Defaults to false.
+}
+
+// ByteSliceCodec creates a new *ByteSliceCodecOptions
+func ByteSliceCodec() *ByteSliceCodecOptions {
+	return &ByteSliceCodecOptions{}
+}
+
+// SetEncodeNilAsEmpty specifies  if a nil byte slice should encode as an empty binary instead of null. Defaults to false.
+func (bs *ByteSliceCodecOptions) SetEncodeNilAsEmpty(b bool) *ByteSliceCodecOptions {
+	bs.EncodeNilAsEmpty = &b
+	return bs
+}
+
+// MergeByteSliceCodecOptions combines the given *ByteSliceCodecOptions into a single *ByteSliceCodecOptions in a last one wins fashion.
+func MergeByteSliceCodecOptions(opts ...*ByteSliceCodecOptions) *ByteSliceCodecOptions {
+	bs := ByteSliceCodec()
+	for _, opt := range opts {
+		if opt == nil {
+			continue
+		}
+		if opt.EncodeNilAsEmpty != nil {
+			bs.EncodeNilAsEmpty = opt.EncodeNilAsEmpty
+		}
+	}
+
+	return bs
+}

mongo/bson/bsonoptions/doc.go

@@ -0,0 +1,8 @@
+// Copyright (C) MongoDB, Inc. 2022-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+// Package bsonoptions defines the optional configurations for the BSON codecs.
+package bsonoptions