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common/bitutil: using subtle.XORBytes for optimization

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cuiweixie 2025-11-30 17:33:06 +08:00
parent 5d51208334
commit 6646b42dd4
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1 changed files with 2 additions and 26 deletions
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28
common/bitutil/bitutil.go
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@ -8,6 +8,7 @@
package bitutil package bitutil
import ( import (
"crypto/subtle"
"runtime" "runtime"
"unsafe" "unsafe"
) )
@ -18,32 +19,7 @@ const supportsUnaligned = runtime.GOARCH == "386" || runtime.GOARCH == "amd64" |
// XORBytes xors the bytes in a and b. The destination is assumed to have enough // XORBytes xors the bytes in a and b. The destination is assumed to have enough
// space. Returns the number of bytes xor'd. // space. Returns the number of bytes xor'd.
func XORBytes(dst, a, b []byte) int { func XORBytes(dst, a, b []byte) int {
if supportsUnaligned { return subtle.XORBytes(dst, a, b)
return fastXORBytes(dst, a, b)
}
return safeXORBytes(dst, a, b)
}
// fastXORBytes xors in bulk. It only works on architectures that support
// unaligned read/writes.
func fastXORBytes(dst, a, b []byte) int {
n := len(a)
if len(b) < n {
n = len(b)
}
w := n / wordSize
if w > 0 {
dw := *(*[]uintptr)(unsafe.Pointer(&dst))
aw := *(*[]uintptr)(unsafe.Pointer(&a))
bw := *(*[]uintptr)(unsafe.Pointer(&b))
for i := 0; i < w; i++ {
dw[i] = aw[i] ^ bw[i]
}
}
for i := n - n%wordSize; i < n; i++ {
dst[i] = a[i] ^ b[i]
}
return n
} }
// safeXORBytes xors one by one. It works on all architectures, independent if // safeXORBytes xors one by one. It works on all architectures, independent if