projects / apple / javascriptcore.git / blame
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|---|---|---|
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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 |