// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file was split out from Go's crypto/cipher/xor.go

// +build 386 amd64 ppc64 ppc64le s390x appengine

package sasl

import (
	"unsafe"
)

const wordSize = int(unsafe.Sizeof(uintptr(0)))

// xorBytes xors in bulk. It only works on architectures that support unaligned
// read/writes.
func xorBytes(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
}

// xorWords XORs multiples of 4 or 8 bytes (depending on architecture.) The
// arguments are assumed to be of equal length.
func xorWords(dst, a, b []byte) {
	dw := *(*[]uintptr)(unsafe.Pointer(&dst))
	aw := *(*[]uintptr)(unsafe.Pointer(&a))
	bw := *(*[]uintptr)(unsafe.Pointer(&b))
	n := len(b) / wordSize
	for i := 0; i < n; i++ {
		dw[i] = aw[i] ^ bw[i]
	}
}