Add go-charset and chardet to vendor

vendor/github.com/paulrosania/go-charset/charset/utf16.go

@@ -0,0 +1,110 @@
+package charset
+
+import (
+	"encoding/binary"
+	"errors"
+	"unicode/utf8"
+)
+
+func init() {
+	registerClass("utf16", fromUTF16, toUTF16)
+}
+
+type translateFromUTF16 struct {
+	first   bool
+	endian  binary.ByteOrder
+	scratch []byte
+}
+
+func (p *translateFromUTF16) Translate(data []byte, eof bool) (int, []byte, error) {
+	data = data[0 : len(data)&^1] // round to even number of bytes.
+	if len(data) < 2 {
+		return 0, nil, nil
+	}
+	n := 0
+	if p.first && p.endian == nil {
+		switch binary.BigEndian.Uint16(data) {
+		case 0xfeff:
+			p.endian = binary.BigEndian
+			data = data[2:]
+			n += 2
+		case 0xfffe:
+			p.endian = binary.LittleEndian
+			data = data[2:]
+			n += 2
+		default:
+			p.endian = guessEndian(data)
+		}
+		p.first = false
+	}
+
+	p.scratch = p.scratch[:0]
+	for ; len(data) > 0; data = data[2:] {
+		p.scratch = appendRune(p.scratch, rune(p.endian.Uint16(data)))
+		n += 2
+	}
+	return n, p.scratch, nil
+}
+
+func guessEndian(data []byte) binary.ByteOrder {
+	// XXX TODO
+	return binary.LittleEndian
+}
+
+type translateToUTF16 struct {
+	first   bool
+	endian  binary.ByteOrder
+	scratch []byte
+}
+
+func (p *translateToUTF16) Translate(data []byte, eof bool) (int, []byte, error) {
+	p.scratch = ensureCap(p.scratch[:0], (len(data)+1)*2)
+	if p.first {
+		p.scratch = p.scratch[0:2]
+		p.endian.PutUint16(p.scratch, 0xfeff)
+		p.first = false
+	}
+	n := 0
+	for len(data) > 0 {
+		if !utf8.FullRune(data) && !eof {
+			break
+		}
+		r, size := utf8.DecodeRune(data)
+		// TODO if r > 65535?
+
+		slen := len(p.scratch)
+		p.scratch = p.scratch[0 : slen+2]
+		p.endian.PutUint16(p.scratch[slen:], uint16(r))
+		data = data[size:]
+		n += size
+	}
+	return n, p.scratch, nil
+}
+
+func getEndian(arg string) (binary.ByteOrder, error) {
+	switch arg {
+	case "le":
+		return binary.LittleEndian, nil
+	case "be":
+		return binary.BigEndian, nil
+	case "":
+		return nil, nil
+	}
+	return nil, errors.New("charset: unknown utf16 endianness")
+}
+
+func fromUTF16(arg string) (Translator, error) {
+	endian, err := getEndian(arg)
+	if err != nil {
+		return nil, err
+	}
+	return &translateFromUTF16{first: true, endian: endian}, nil
+}
+
+func toUTF16(arg string) (Translator, error) {
+	endian, err := getEndian(arg)
+	if err != nil {
+		return nil, err
+	}
+	return &translateToUTF16{first: false, endian: endian}, nil
+}