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 

     7 package websocket

     8 

     9 import "unsafe"

    10 

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

    12 

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

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

    15 	if len(b) < 2*wordSize {

    16 		for i := range b {

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

    18 			pos++

    19 		}

    20 		return pos & 3

    21 	}

    22 

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

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

    25 		n = wordSize - n

    26 		for i := range b[:n] {

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

    28 			pos++

    29 		}

    30 		b = b[n:]

    31 	}

    32 

    33 	// Create aligned word size key.

    34 	var k [wordSize]byte

    35 	for i := range k {

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

    37 	}

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

    39 

    40 	// Mask one word at a time.

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

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

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

    44 	}

    45 

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

    47 	b = b[n:]

    48 	for i := range b {

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

    50 		pos++

    51 	}

    52 

    53 	return pos & 3

    54 }