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
