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