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 //go:build !appengine
6 // +build !appengine
7 8 package websocket
9 10 import "unsafe"
11 12 const wordSize = int(unsafe.Sizeof(uintptr(0)))
13 14 func maskBytes(key [4]byte, pos int, b []byte) int {
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 }
56