96 lines
3.2 KiB
Go
96 lines
3.2 KiB
Go
package inline
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import (
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"errors"
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)
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const (
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hextable = "0123456789abcdef"
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reverseHexTable = "" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\xff\xff\xff\xff\xff\xff" +
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"\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\x0a\x0b\x0c\x0d\x0e\x0f\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
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"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
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)
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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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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 Encode(dst, src []byte) int {
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j := 0
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for _, v := range src {
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dst[j] = hextable[v>>4]
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dst[j+1] = hextable[v&0x0f]
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j += 2
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}
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return len(src) * 2
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}
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// ErrLength reports an attempt to decode an odd-length input
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// using [Decode] or [DecodeString].
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// The stream-based Decoder returns [io.ErrUnexpectedEOF] instead of ErrLength.
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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 "encoding/hex: invalid byte"
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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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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 contains only hexadecimal
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// characters and that src has even length.
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// If the input is malformed, Decode returns the number
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// of bytes decoded before the error.
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func Decode(dst, src []byte) (int, error) {
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i, j := 0, 1
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for ; j < len(src); j += 2 {
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p := src[j-1]
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q := src[j]
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a := reverseHexTable[p]
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b := reverseHexTable[q]
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if a > 0x0f {
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return i, InvalidByteError(p)
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}
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if b > 0x0f {
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return i, InvalidByteError(q)
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}
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dst[i] = (a << 4) | b
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i++
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}
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if len(src)%2 == 1 {
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// Check for invalid char before reporting bad length,
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// since the invalid char (if present) is an earlier problem.
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if reverseHexTable[src[j-1]] > 0x0f {
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return i, InvalidByteError(src[j-1])
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}
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return i, ErrLength
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}
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return i, nil
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}
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