base64_arm64.go

//go:build arm64 && !purego

package base64

var dencodeStdLut = [128]byte{
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 255, 255, 255,
	255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
	15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255,
	255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
	41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 255, 255, 255, 255, 255,
}

var dencodeUrlLut = [128]byte{
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255,
	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 255, 255, 255,
	255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 
	15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255,	63, 
	255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 
	41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 255, 255, 255, 255, 255,
}

//go:noescape
func encodeAsm(dst, src []byte, lut *[64]byte) int

//go:noescape
func decodeAsm(dst, src []byte, lut *[128]byte) int

func encode(enc *Encoding, dst, src []byte) {
	if len(src) >= 16 {
		encoded := encodeAsm(dst, src, &enc.encode)
		src = src[(encoded/4)*3:]
		dst = dst[encoded:]
	}
	encodeGeneric(enc, dst, src)
}

func decode(enc *Encoding, dst, src []byte) (int, error) {
	srcLen := len(src)
	if srcLen >= 24 {
		remain := srcLen
		if enc.lut == &encodeStdLut {
			remain = decodeAsm(dst, src, &dencodeStdLut)
		} else if enc.lut == &encodeURLLut {
			remain = decodeAsm(dst, src, &dencodeUrlLut)
		}

		if remain < srcLen {
			// decoded by SIMD
			remain = srcLen - remain // remain is decoded length now
			src = src[remain:]
			dstStart := (remain / 4) * 3
			dst = dst[dstStart:]
			n, err := decodeGeneric(enc, dst, src)
			if cerr, ok := err.(CorruptInputError); ok {
				return n + dstStart, CorruptInputError(int(cerr) + remain)
			}
			return n + dstStart, err
		}
	}
	return decodeGeneric(enc, dst, src)
}