Ruben Vermeersch
116 lines
2.2 KiB
Go
116 lines
2.2 KiB
Go
// +build go1.7,amd64,!gccgo,!appengine,!nacl
|
|
|
|
package fastxor
|
|
|
|
import (
|
|
"unsafe"
|
|
|
|
"golang.org/x/sys/cpu"
|
|
)
|
|
|
|
//go:noescape
|
|
func xorBytesSSE(dst, a, b []byte, n int)
|
|
|
|
//go:noescape
|
|
func xorBytesAVX2(dst, a, b []byte, n int)
|
|
|
|
func min(a, b, c int) int {
|
|
if a < b {
|
|
b = a
|
|
}
|
|
if b < c {
|
|
c = b
|
|
}
|
|
return c
|
|
}
|
|
|
|
// Bytes stores (a xor b) in dst, stopping when the end of any slice is
|
|
// reached. It returns the number of bytes xor'd.
|
|
func Bytes(dst, a, b []byte) int {
|
|
n := min(len(dst), len(a), len(b))
|
|
if n == 0 {
|
|
return 0
|
|
}
|
|
switch {
|
|
case cpu.X86.HasAVX2:
|
|
xorBytesAVX2(dst, a, b, n)
|
|
case cpu.X86.HasSSE2:
|
|
xorBytesSSE(dst, a, b, n)
|
|
default:
|
|
xorBytesGeneric(dst, a, b, n)
|
|
}
|
|
return n
|
|
}
|
|
|
|
const wordSize = int(unsafe.Sizeof(uintptr(0)))
|
|
|
|
func xorBytesGeneric(dst, a, b []byte, n int) {
|
|
// Assert dst has enough space
|
|
_ = dst[n-1]
|
|
|
|
w := n / wordSize
|
|
if w > 0 {
|
|
dw := *(*[]uintptr)(unsafe.Pointer(&dst))
|
|
aw := *(*[]uintptr)(unsafe.Pointer(&a))
|
|
bw := *(*[]uintptr)(unsafe.Pointer(&b))
|
|
_ = aw[w-1]
|
|
_ = bw[w-1]
|
|
_ = dw[w-1]
|
|
for i := 0; i < w; i++ {
|
|
dw[i] = aw[i] ^ bw[i]
|
|
}
|
|
}
|
|
|
|
_ = dst[n-1]
|
|
_ = a[n-1]
|
|
_ = b[n-1]
|
|
for i := (n - n%wordSize); i < n; i++ {
|
|
dst[i] = a[i] ^ b[i]
|
|
}
|
|
}
|
|
|
|
// Byte xors each byte in a with b and stores the result in dst, stopping when
|
|
// the end of either dst or a is reached. It returns the number of bytes
|
|
// xor'd.
|
|
func Byte(dst, a []byte, b byte) int {
|
|
n := len(a)
|
|
if len(dst) < n {
|
|
n = len(dst)
|
|
}
|
|
|
|
var bw uintptr
|
|
for i := 0; i < wordSize; i += 1 {
|
|
bw |= uintptr(b) << uint(i*8)
|
|
}
|
|
|
|
w := n / wordSize
|
|
if w > 0 {
|
|
dw := *(*[]uintptr)(unsafe.Pointer(&dst))
|
|
aw := *(*[]uintptr)(unsafe.Pointer(&a))
|
|
_ = aw[w-1]
|
|
_ = dw[w-1]
|
|
for i := 0; i < w; i++ {
|
|
dw[i] = aw[i] ^ bw
|
|
}
|
|
}
|
|
|
|
_ = dst[n-1]
|
|
_ = a[n-1]
|
|
for i := (n - n%wordSize); i < n; i++ {
|
|
dst[i] = a[i] ^ b
|
|
}
|
|
|
|
return n
|
|
}
|
|
|
|
// Block stores (a xor b) in dst, where a, b, and dst all have length 16.
|
|
func Block(dst, a, b []byte) {
|
|
// profiling indicates that for 16-byte blocks, the cost of a function
|
|
// call outweighs the SSE/AVX speedup
|
|
dw := (*[2]uintptr)(unsafe.Pointer(&dst[0]))
|
|
aw := (*[2]uintptr)(unsafe.Pointer(&a[0]))
|
|
bw := (*[2]uintptr)(unsafe.Pointer(&b[0]))
|
|
dw[0] = aw[0] ^ bw[0]
|
|
dw[1] = aw[1] ^ bw[1]
|
|
}
|