fix: review comment

Author: cuiweixie

common/bitutil/bitutil.go

@@ -105,7 +105,14 @@ func safeANDBytes(dst, a, b []byte) int {
 
 // ORBytes ors the bytes in a and b. The destination is assumed to have enough
 // space. Returns the number of bytes or'd.
+//
+// dst and x or y may overlap exactly or not at all,
+// otherwise ORBytes may panic.
 func ORBytes(dst, a, b []byte) int {
+	n := min(len(a), len(b))
+	if inexactOverlap(dst[:n], a[:n]) || inexactOverlap(dst[:n], b[:n]) {
+		panic("ORBytes: invalid overlap")
+	}
 	return orBytes(dst, a, b)
 }
 
@@ -161,3 +168,26 @@ func safeTestBytes(p []byte) bool {
 	}
 	return false
 }
+
+// anyOverlap reports whether x and y share memory at any (not necessarily
+// corresponding) index. The memory beyond the slice length is ignored.
+// from: https://github.com/golang/go/blob/4a3cef2036097d323b6cc0bbe90fc4d8c7588660/src/crypto/internal/fips140/alias/alias.go#L13-L17
+func anyOverlap(x, y []byte) bool {
+	return len(x) > 0 && len(y) > 0 &&
+		uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) &&
+		uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1]))
+}
+
+// inexactOverlap reports whether x and y share memory at any non-corresponding
+// index. The memory beyond the slice length is ignored. Note that x and y can
+// have different lengths and still not have any inexact overlap.
+//
+// inexactOverlap can be used to implement the requirements of the crypto/cipher
+// AEAD, Block, BlockMode and Stream interfaces.
+// from: https://github.com/golang/go/blob/4a3cef2036097d323b6cc0bbe90fc4d8c7588660/src/crypto/internal/fips140/alias/alias.go#L25-L30
+func inexactOverlap(x, y []byte) bool {
+	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
+		return false
+	}
+	return anyOverlap(x, y)
+}

common/bitutil/or_asm.go

@@ -8,12 +8,8 @@
 package bitutil
 
 func orBytes(dst, a, b []byte) int {
-	n := min(len(a), len(b))
-	if n == 0 {
-		return 0
-	}
-	orBytesASM(&dst[0], &a[0], &b[0], n)
-	return n
+	orBytesASM(&dst[0], &a[0], &b[0], len(a))
+	return len(a)
 }
 
 //go:noescape