clean code and add some comments

bof.go

@@ -1,31 +1,26 @@
 package xls
 
 import (
-	"bytes"
 	"encoding/binary"
 	"io"
 	"unicode/utf16"
 )
 
-type BOF struct {
+//the information unit in xls file
+type bof struct {
 	Id   uint16
 	Size uint16
 }
 
-func (b *BOF) Reader(buf io.ReadSeeker) io.ReadSeeker {
-	rts := make([]byte, b.Size)
-	buf.Read(rts)
-	return bytes.NewReader(rts)
-}
-
-func (b *BOF) Utf16String(buf io.ReadSeeker, count uint32) string {
+//read the utf16 string from reader
+func (b *bof) utf16String(buf io.ReadSeeker, count uint32) string {
 	var bts = make([]uint16, count)
 	binary.Read(buf, binary.LittleEndian, &bts)
 	runes := utf16.Decode(bts[:len(bts)-1])
 	return string(runes)
 }
 
-type BIFFHeader struct {
+type biffHeader struct {
 	Ver     uint16
 	Type    uint16
 	Id_make uint16
@@ -33,16 +28,3 @@ type BIFFHeader struct {
 	Flags   uint32
 	Min_ver uint32
 }
-
-// func parseBofsForWb(bts []byte, wb *WorkBook) {
-// 	bof := new(BOF)
-// 	var bof_pre *BOF
-// 	buf := bytes.NewReader(bts)
-// 	for {
-// 		if err := binary.Read(buf, binary.LittleEndian, bof); err == nil {
-// 			bof_pre = bof.ActForWb(buf, wb, bof_pre)
-// 		} else {
-// 			break
-// 		}
-// 	}
-// }