• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
56 namespace JSC {
57 
58 class WeakRandom {
59 public:
WeakRandom(unsigned seed)60     WeakRandom(unsigned seed)
61         : m_low(seed ^ 0x49616E42)
62         , m_high(seed)
63     {
64     }
65 
get()66     double get()
67     {
68         return advance() / (UINT_MAX + 1.0);
69     }
70 
71 private:
advance()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