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: |
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 | |
71 | private: |
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 | |