common/bitutil: using subtle.XORBytes for optimization

Author: cuiweixie

common/bitutil/bitutil.go

@@ -8,6 +8,7 @@
 package bitutil
 
 import (
+	"crypto/subtle"
 	"runtime"
 	"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
 // 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