GoToSocial/vendor/github.com/tmthrgd/go-hex/hex.go

138 lines
3.4 KiB
Go

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