1/*
2 * Copyright (C) 2009 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 *
26 * Copyright (c) 2009 Ian C. Bullard
27 *
28 * Permission is hereby granted, free of charge, to any person
29 * obtaining a copy of this software and associated documentation
30 * files (the "Software"), to deal in the Software without
31 * restriction, including without limitation the rights to use,
32 * copy, modify, merge, publish, distribute, sublicense, and/or sell
33 * copies of the Software, and to permit persons to whom the
34 * Software is furnished to do so, subject to the following
35 * conditions:
36 *
37 * The above copyright notice and this permission notice shall be
38 * included in all copies or substantial portions of the Software.
39 *
40 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
41 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
42 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
43 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
44 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
45 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
46 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
47 * OTHER DEALINGS IN THE SOFTWARE.
48 */
49
50#ifndef WeakRandom_h
51#define WeakRandom_h
52
53#include <limits.h>
54#include <wtf/StdLibExtras.h>
55
56namespace JSC {
57
58class WeakRandom {
59public:
60 WeakRandom(unsigned seed)
61 : m_low(seed ^ 0x49616E42)
62 , m_high(seed)
63 {
64 }
65
66 double get()
67 {
68 return advance() / (UINT_MAX + 1.0);
69 }
70
71private:
72 unsigned advance()
73 {
74 m_high = (m_high << 16) + (m_high >> 16);
75 m_high += m_low;
76 m_low += m_high;
77 return m_high;
78 }
79
80 unsigned m_low;
81 unsigned m_high;
82};
83
84} // namespace JSC
85
86#endif // WeakRandom_h
87

source code of qtscript/src/3rdparty/javascriptcore/JavaScriptCore/runtime/WeakRandom.h