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adf16b3 Dec 31, 2016
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// 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
}