111 lines
3.0 KiB
Go
111 lines
3.0 KiB
Go
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// Copyright 2009 The Go Authors.
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// Copyright 2016 Brave New Software Project, Inc.
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// All rights reserved.
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//
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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. It's taken almost
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// verbatim from golang/encoding/hex, however it allows using a different set
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// of encoding characters than the standard 0-F.
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package hex
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import (
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"errors"
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"fmt"
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)
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// DefaultEncoding behaves just like golang/encoding/hex.
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var DefaultEncoding = NewEncoding("0123456789abcdef")
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// An Encoding that uses a specific table of encoding characters.
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type Encoding struct {
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hextable string
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}
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// NewEncoding constructs an Encoding using the given hextable.
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func NewEncoding(hextable string) *Encoding {
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return &Encoding{hextable}
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}
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// EncodedLen returns the length of an encoding of n source bytes.
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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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// 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 (e *Encoding) Encode(dst, src []byte) int {
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for i, v := range src {
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dst[i*2] = e.hextable[v>>4]
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dst[i*2+1] = e.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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func DecodedLen(x int) int { return x / 2 }
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// Decode decodes src into DecodedLen(len(src)) bytes, returning the actual
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// number of bytes written to dst.
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//
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// If Decode encounters invalid input, it returns an error describing the failure.
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func (e *Encoding) 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 := e.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 := e.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 (e *Encoding) fromHexChar(c byte) (byte, bool) {
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for i, ch := range []byte(e.hextable) {
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if ch == c {
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return byte(i), true
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}
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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 (e *Encoding) EncodeToString(src []byte) string {
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dst := make([]byte, EncodedLen(len(src)))
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e.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 (e *Encoding) 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 := e.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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