golang, convert UTF-16 to UTF-8 string

gistfile1.go

package main

import "fmt"
import "unicode/utf16"
import "unicode/utf8"
import "bytes"

func main() {

	b := []byte{
		0xff, // BOM
		0xfe, // BOM
		'T',
		0x00,
		'E',
		0x00,
		'S',
		0x00,
		'T',
		0x00,
		0x6C,
		0x34,
		'\n',
		0x00,
	}

	s, err := DecodeUTF16(b)
	if err != nil {
		panic(err)
	}
	fmt.Println(s)
}

// EncodeUTF16 get a utf8 string and translate it into a slice of bytes of ucs2
func EncodeUTF16(s string, add_bom bool) []byte {
        r := []rune(s)
        iresult := utf16.Encode(r)
        var bytes []byte
        if add_bom {
                bytes = make([]byte, 2)
                bytes = []byte{254, 255}
        }
        for _, i := range iresult {
                temp := make([]byte, 2)
                binary.BigEndian.PutUint16(temp, i)
                bytes = append(bytes, temp...)
        }
        return bytes
}

// DecodeUTF16 get a slice of bytes and decode it to UTF-8
func DecodeUTF16(b []byte) (string, error) {

        if len(b)%2 != 0 {
                return "", fmt.Errorf("Must have even length byte slice")
        }

        bom := UTF16Bom(b)
        if bom < 0 {
                return "", fmt.Errorf("Buffer is too small")
        }

        u16s := make([]uint16, 1)
        ret := &bytes.Buffer{}
        b8buf := make([]byte, 4)
        lb := len(b)

        for i := 0; i < lb; i += 2 {
                //assuming bom is big endian if 0 returned
                if bom == 0 || bom == 1 {
                        u16s[0] = uint16(b[i+1]) + (uint16(b[i]) << 8)
                }
                if bom == 2 {
                        u16s[0] = uint16(b[i]) + (uint16(b[i+1]) << 8)
                }
                r := utf16.Decode(u16s)
                n := utf8.EncodeRune(b8buf, r[0])
                ret.Write([]byte(string(b8buf[:n])))
        }

        return ret.String(), nil
}

// UTF16Bom returns 0 for no BOM, 1 for Big Endian and 2 for little endian
// it will return -1 if b is too small for having BOM
func UTF16Bom(b []byte) int8 {
        if len(b) < 2 {
                return -1
        }

        if b[0] == 0xFE && b[1] == 0xFF {
                return 1
        }

        if b[0] == 0xFF && b[1] == 0xFE {
                return 2
        }

        return 0
}