// Copyright 2016 The Gorilla WebSocket Authors. All rights reserved.  Use of

// this source code is governed by a BSD-style license that can be found in the

// LICENSE file.

// +build !appengine

package websocket

import "unsafe"

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

func maskBytes(key [4]byte, pos int, b []byte) int {

	// Mask one byte at a time for small buffers.

	if len(b) < 2*wordSize {

		for i := range b {

			b[i] ^= key[pos&3]

			pos++

		}

		return pos & 3

	}

	// Mask one byte at a time to word boundary.

	if n := int(uintptr(unsafe.Pointer(&b[0]))) % wordSize; n != 0 {

		n = wordSize - n

		for i := range b[:n] {

			b[i] ^= key[pos&3]

			pos++

		}

		b = b[n:]

	}

	// Create aligned word size key.

	var k [wordSize]byte

	for i := range k {

		k[i] = key[(pos+i)&3]

	}

	kw := *(*uintptr)(unsafe.Pointer(&k))

	// Mask one word at a time.

	n := (len(b) / wordSize) * wordSize

	for i := 0; i < n; i += wordSize {

		*(*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&b[0])) + uintptr(i))) ^= kw

	}

	// Mask one byte at a time for remaining bytes.

	b = b[n:]

	for i := range b {

		b[i] ^= key[pos&3]

		pos++

	}

	return pos & 3

}