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//go:build amd64 && !purego
// +build amd64,!purego
package base64
import (
"encoding/base64"
"github.com/segmentio/asm/cpu"
"github.com/segmentio/asm/cpu/x86"
)
const (
encLutSize = 32
decLutSize = 48
minEncodeLen = 28
minDecodeLen = 45
)
func newEncoding(encoder string) *Encoding {
e := &Encoding{base: base64.NewEncoding(encoder)}
if cpu.X86.Has(x86.AVX2) {
e.enableEncodeAVX2(encoder)
e.enableDecodeAVX2(encoder)
}
return e
}
func (e *Encoding) enableEncodeAVX2(encoder string) {
// Translate values 0..63 to the Base64 alphabet. There are five sets:
//
// From To Add Index Example
// [0..25] [65..90] +65 0 ABCDEFGHIJKLMNOPQRSTUVWXYZ
// [26..51] [97..122] +71 1 abcdefghijklmnopqrstuvwxyz
// [52..61] [48..57] -4 [2..11] 0123456789
// [62] [43] -19 12 +
// [63] [47] -16 13 /
tab := [encLutSize]int8{int8(encoder[0]), int8(encoder[letterRange]) - letterRange}
for i, ch := range encoder[2*letterRange:] {
tab[2+i] = int8(ch) - 2*letterRange - int8(i)
}
e.enc = encodeAVX2
e.enclut = tab
}
func (e *Encoding) enableDecodeAVX2(encoder string) {
c62, c63 := int8(encoder[62]), int8(encoder[63])
url := c63 == '_'
if url {
c63 = '/'
}
// Translate values from the Base64 alphabet using five sets. Values outside
// of these ranges are considered invalid:
//
// From To Add Index Example
// [47] [63] +16 1 /
// [43] [62] +19 2 +
// [48..57] [52..61] +4 3 0123456789
// [65..90] [0..25] -65 4,5 ABCDEFGHIJKLMNOPQRSTUVWXYZ
// [97..122] [26..51] -71 6,7 abcdefghijklmnopqrstuvwxyz
tab := [decLutSize]int8{
0, 63 - c63, 62 - c62, 4, -65, -65, -71, -71,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x15, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
0x11, 0x11, 0x13, 0x1B, 0x1B, 0x1B, 0x1B, 0x1B,
}
tab[(c62&15)+16] = 0x1A
tab[(c63&15)+16] = 0x1A
if url {
e.dec = decodeAVX2URI
} else {
e.dec = decodeAVX2
}
e.declut = tab
}
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