1// Copyright 2016 The Gorilla WebSocket Authors. All rights reserved.  Use of
 2// this source code is governed by a BSD-style license that can be found in the
 3// LICENSE file.
 4
 5// +build !appengine
 6
 7package websocket
 8
 9import "unsafe"
10
11const wordSize = int(unsafe.Sizeof(uintptr(0)))
12
13func maskBytes(key [4]byte, pos int, b []byte) int {
14
15	// Mask one byte at a time for small buffers.
16	if len(b) < 2*wordSize {
17		for i := range b {
18			b[i] ^= key[pos&3]
19			pos++
20		}
21		return pos & 3
22	}
23
24	// Mask one byte at a time to word boundary.
25	if n := int(uintptr(unsafe.Pointer(&b[0]))) % wordSize; n != 0 {
26		n = wordSize - n
27		for i := range b[:n] {
28			b[i] ^= key[pos&3]
29			pos++
30		}
31		b = b[n:]
32	}
33
34	// Create aligned word size key.
35	var k [wordSize]byte
36	for i := range k {
37		k[i] = key[(pos+i)&3]
38	}
39	kw := *(*uintptr)(unsafe.Pointer(&k))
40
41	// Mask one word at a time.
42	n := (len(b) / wordSize) * wordSize
43	for i := 0; i < n; i += wordSize {
44		*(*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&b[0])) + uintptr(i))) ^= kw
45	}
46
47	// Mask one byte at a time for remaining bytes.
48	b = b[n:]
49	for i := range b {
50		b[i] ^= key[pos&3]
51		pos++
52	}
53
54	return pos & 3
55}