138 lines
3.4 KiB
Go
138 lines
3.4 KiB
Go
// Copyright 2016 Tom Thorogood. All rights reserved.
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// Use of this source code is governed by a
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// Modified BSD License license that can be found in
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// the LICENSE file.
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//
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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 is an efficient hexadecimal implementation for Golang.
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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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var errLength = errors.New("go-hex: odd length hex string")
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var (
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lower = []byte("0123456789abcdef")
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upper = []byte("0123456789ABCDEF")
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)
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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("go-hex: invalid byte: %#U", rune(e))
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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 {
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return n * 2
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}
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// DecodedLen returns the length of a decoding of n source bytes.
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func DecodedLen(n int) int {
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return n / 2
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}
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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 lowercase hexadecimal encoding.
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func Encode(dst, src []byte) int {
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return RawEncode(dst, src, lower)
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}
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// EncodeUpper 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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// EncodeUpper implements uppercase hexadecimal encoding.
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func EncodeUpper(dst, src []byte) int {
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return RawEncode(dst, src, upper)
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}
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// EncodeToString returns the lowercase hexadecimal encoding of src.
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func EncodeToString(src []byte) string {
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return RawEncodeToString(src, lower)
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}
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// EncodeUpperToString returns the uppercase hexadecimal encoding of src.
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func EncodeUpperToString(src []byte) string {
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return RawEncodeToString(src, upper)
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}
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// RawEncodeToString returns the hexadecimal encoding of src for a given
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// alphabet.
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func RawEncodeToString(src, alpha []byte) string {
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dst := make([]byte, EncodedLen(len(src)))
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RawEncode(dst, src, alpha)
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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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if _, err := Decode(dst, src); 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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// MustDecodeString is like DecodeString but panics if the string cannot be
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// parsed. It simplifies safe initialization of global variables holding
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// binary data.
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func MustDecodeString(str string) []byte {
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dst, err := DecodeString(str)
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if err != nil {
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panic(err)
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}
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return dst
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}
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func encodeGeneric(dst, src, alpha []byte) {
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for i, v := range src {
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dst[i*2] = alpha[v>>4]
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dst[i*2+1] = alpha[v&0x0f]
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}
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}
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func decodeGeneric(dst, src []byte) (uint64, bool) {
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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 uint64(i * 2), false
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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 uint64(i*2 + 1), false
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}
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dst[i] = (a << 4) | b
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}
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return 0, true
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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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