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common/bitutil: using subtle.XORBytes for optimization #33331

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common/bitutil: using subtle.XORBytes for optimization #33331

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28 changes: 2 additions & 26 deletions common/bitutil/bitutil.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
package bitutil

import (
"crypto/subtle"
"runtime"
"unsafe"
)
Expand All @@ -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
// space. Returns the number of bytes xor'd.
func XORBytes(dst, a, b []byte) int {
if supportsUnaligned {
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
return subtle.XORBytes(dst, a, b)
}

// safeXORBytes xors one by one. It works on all architectures, independent if
Expand Down