2012-03-27 23:13:14 +00:00
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package hex implements hexadecimal encoding and decoding.
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package hex
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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)
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2017-10-07 00:16:47 +00:00
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var hextable = [16]byte{
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'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
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'a', 'b', 'c', 'd', 'e', 'f',
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}
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2012-03-27 23:13:14 +00:00
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// EncodedLen returns the length of an encoding of n source bytes.
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// Specifically, it returns n * 2.
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2012-03-27 23:13:14 +00:00
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func EncodedLen(n int) int { return n * 2 }
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// Encode encodes src into EncodedLen(len(src))
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// bytes of dst. As a convenience, it returns the number
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2012-03-27 23:13:14 +00:00
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// of bytes written to dst, but this value is always EncodedLen(len(src)).
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// Encode implements hexadecimal encoding.
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func Encode(dst, src []byte) int {
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for i, v := range src {
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dst[i*2] = hextable[v>>4]
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dst[i*2+1] = hextable[v&0x0f]
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}
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return len(src) * 2
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}
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// ErrLength results from decoding an odd length slice.
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var ErrLength = errors.New("encoding/hex: odd length hex string")
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// InvalidByteError values describe errors resulting from an invalid byte in a hex string.
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type InvalidByteError byte
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func (e InvalidByteError) Error() string {
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return fmt.Sprintf("encoding/hex: invalid byte: %#U", rune(e))
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}
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// DecodedLen returns the length of a decoding of x source bytes.
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// Specifically, it returns x / 2.
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2012-03-27 23:13:14 +00:00
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func DecodedLen(x int) int { return x / 2 }
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// Decode decodes src into DecodedLen(len(src)) bytes,
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// returning the actual number of bytes written to dst.
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//
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// Decode expects that src contain only hexadecimal
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// characters and that src should have an even length.
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2012-03-27 23:13:14 +00:00
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func Decode(dst, src []byte) (int, error) {
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if len(src)%2 == 1 {
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return 0, ErrLength
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}
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for i := 0; i < len(src)/2; i++ {
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a, ok := fromHexChar(src[i*2])
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if !ok {
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return 0, InvalidByteError(src[i*2])
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}
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b, ok := fromHexChar(src[i*2+1])
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if !ok {
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return 0, InvalidByteError(src[i*2+1])
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}
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dst[i] = (a << 4) | b
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}
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return len(src) / 2, nil
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}
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// fromHexChar converts a hex character into its value and a success flag.
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func fromHexChar(c byte) (byte, bool) {
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switch {
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case '0' <= c && c <= '9':
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return c - '0', true
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case 'a' <= c && c <= 'f':
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return c - 'a' + 10, true
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case 'A' <= c && c <= 'F':
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return c - 'A' + 10, true
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}
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return 0, false
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}
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// EncodeToString returns the hexadecimal encoding of src.
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func EncodeToString(src []byte) string {
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dst := make([]byte, EncodedLen(len(src)))
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Encode(dst, src)
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return string(dst)
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}
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// DecodeString returns the bytes represented by the hexadecimal string s.
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func DecodeString(s string) ([]byte, error) {
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src := []byte(s)
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dst := make([]byte, DecodedLen(len(src)))
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_, err := Decode(dst, src)
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if err != nil {
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return nil, err
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}
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return dst, nil
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}
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// Dump returns a string that contains a hex dump of the given data. The format
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// of the hex dump matches the output of `hexdump -C` on the command line.
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func Dump(data []byte) string {
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var buf bytes.Buffer
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dumper := Dumper(&buf)
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dumper.Write(data)
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dumper.Close()
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return buf.String()
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2012-03-27 23:13:14 +00:00
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}
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// Dumper returns a WriteCloser that writes a hex dump of all written data to
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// w. The format of the dump matches the output of `hexdump -C` on the command
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// line.
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func Dumper(w io.Writer) io.WriteCloser {
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return &dumper{w: w}
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}
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type dumper struct {
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w io.Writer
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rightChars [18]byte
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buf [14]byte
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used int // number of bytes in the current line
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n uint // number of bytes, total
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}
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func toChar(b byte) byte {
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if b < 32 || b > 126 {
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return '.'
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}
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return b
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}
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func (h *dumper) Write(data []byte) (n int, err error) {
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// Output lines look like:
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// 00000010 2e 2f 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d |./0123456789:;<=|
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// ^ offset ^ extra space ^ ASCII of line.
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for i := range data {
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if h.used == 0 {
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// At the beginning of a line we print the current
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// offset in hex.
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h.buf[0] = byte(h.n >> 24)
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h.buf[1] = byte(h.n >> 16)
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h.buf[2] = byte(h.n >> 8)
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h.buf[3] = byte(h.n)
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Encode(h.buf[4:], h.buf[:4])
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h.buf[12] = ' '
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h.buf[13] = ' '
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_, err = h.w.Write(h.buf[4:])
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2015-08-28 15:33:40 +00:00
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if err != nil {
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return
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}
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2012-03-27 23:13:14 +00:00
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}
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Encode(h.buf[:], data[i:i+1])
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h.buf[2] = ' '
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l := 3
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if h.used == 7 {
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// There's an additional space after the 8th byte.
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h.buf[3] = ' '
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l = 4
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} else if h.used == 15 {
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// At the end of the line there's an extra space and
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// the bar for the right column.
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h.buf[3] = ' '
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h.buf[4] = '|'
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l = 5
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}
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_, err = h.w.Write(h.buf[:l])
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if err != nil {
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return
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}
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n++
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h.rightChars[h.used] = toChar(data[i])
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h.used++
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h.n++
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if h.used == 16 {
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h.rightChars[16] = '|'
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h.rightChars[17] = '\n'
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_, err = h.w.Write(h.rightChars[:])
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if err != nil {
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return
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}
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h.used = 0
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}
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}
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return
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}
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func (h *dumper) Close() (err error) {
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// See the comments in Write() for the details of this format.
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if h.used == 0 {
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return
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}
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h.buf[0] = ' '
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h.buf[1] = ' '
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h.buf[2] = ' '
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h.buf[3] = ' '
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h.buf[4] = '|'
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nBytes := h.used
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for h.used < 16 {
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l := 3
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if h.used == 7 {
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l = 4
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} else if h.used == 15 {
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l = 5
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}
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_, err = h.w.Write(h.buf[:l])
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if err != nil {
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return
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}
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h.used++
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}
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h.rightChars[nBytes] = '|'
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h.rightChars[nBytes+1] = '\n'
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_, err = h.w.Write(h.rightChars[:nBytes+2])
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return
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}
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