Updating crypto sublte xor overrides

grantnelson-wf · grantnelson-wf · commit 95f4bef561e9 · 2024-04-08T14:24:44.000-06:00
diff --git a/compiler/natives/src/crypto/subtle/xor.go b/compiler/natives/src/crypto/subtle/xor.go
@@ -0,0 +1,78 @@
+//go:build js
+// +build js
+
+package subtle
+
+import "github.com/gopherjs/gopherjs/js"
+
+const wordSize = 4 // bytes for a Uint32Array
+
+func XORBytes(dst, x, y []byte) int {
+	n := len(x)
+	if len(y) < n {
+		n = len(y)
+	}
+	if n == 0 {
+		return 0
+	}
+	if n > len(dst) {
+		panic("subtle.XORBytes: dst too short")
+	}
+
+	// The original uses unsafe and uintptr for specific architecture
+	// to pack registers full instead of doing one byte at a time.
+	// We can't do the unsafe conversions from []byte to []uintptr
+	// but we can convert a Uint8Array into a Uint32Array,
+	// so we'll simply do it four bytes at a time plus any remainder.
+	// The following is similar to xorBytes from xor_generic.go
+
+	dst = dst[:n]
+	x = x[:n]
+	y = y[:n]
+	if wordCount := n / wordSize; wordCount > 0 &&
+		aligned(dst) && aligned(x) && aligned(y) {
+		dstWords := words(dst)
+		xWords := words(x)
+		yWords := words(y)
+		for i := range dstWords {
+			dstWords[i] = xWords[i] ^ yWords[i]
+		}
+		done := n &^ int(wordSize-1)
+		dst = dst[done:]
+		x = x[done:]
+		y = y[done:]
+	}
+	for i := range dst {
+		dst[i] = x[i] ^ y[i]
+	}
+	return n
+}
+
+// aligned determines whether the slice is word-aligned since
+// Uint32Array's require the offset to be multiples of 4.
+func aligned(b []byte) bool {
+	slice := js.InternalObject(b)
+	offset := slice.Get(`$offset`).Int()
+	return offset%wordSize == 0
+}
+
+// words returns a []uint pointing at the same data as b,
+// with any trailing partial word removed.
+// The given b must have a word aligned offset.
+func words(b []byte) []uint {
+	slice := js.InternalObject(b)
+	offset := slice.Get(`$offset`).Int()
+	length := slice.Get(`$length`).Int()
+	byteBuffer := slice.Get(`$array`).Get(`buffer`)
+	wordBuffer := js.Global.Get(`Uint32Array`).New(byteBuffer, offset, length/wordSize)
+	return wordBuffer.Interface().([]uint)
+}
+
+//gopherjs:purge
+const supportsUnaligned = false
+
+//gopherjs:purge
+func xorBytes(dstb, xb, yb *byte, n int)
+
+//gopherjs:purge
+func xorLoop[T byte | uintptr](dst, x, y []T) {}
