wtf/RandomNumber.cpp

   1 /*
   2  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
   3  *           (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  15  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  17  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  18  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  19  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  20  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  21  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  22  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  24  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "config.h"
  28 #include "RandomNumber.h"
  29
  30 #include "RandomNumberSeed.h"
  31
  32 #include <limits>
  33 #include <limits.h>
  34 #include <stdint.h>
  35 #include <stdlib.h>
  36
  37 #if OS(WINCE)
  38 extern "C" {
  39 #include "wince/mt19937ar.c"
  40 }
  41 #endif
  42
  43 #if PLATFORM(BREWMP)
  44 #include <AEEAppGen.h>
  45 #include <AEESource.h>
  46 #include <AEEStdLib.h>
  47 #endif
  48
  49 namespace WTF {
  50
  51 double weakRandomNumber()
  52 {
  53 #if COMPILER(MSVC) && defined(_CRT_RAND_S)
  54     // rand_s is incredibly slow on windows so we fall back on rand for Math.random
  55     return (rand() + (rand() / (RAND_MAX + 1.0))) / (RAND_MAX + 1.0);
  56 #elif PLATFORM(BREWMP)
  57     uint32_t bits;
  58     GETRAND(reinterpret_cast<byte*>(&bits), sizeof(uint32_t));
  59     return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
  60 #else
  61     return randomNumber();
  62 #endif
  63 }
  64
  65 double randomNumber()
  66 {
  67 #if !ENABLE(JSC_MULTIPLE_THREADS)
  68     static bool s_initialized = false;
  69     if (!s_initialized) {
  70         initializeRandomNumberGenerator();
  71         s_initialized = true;
  72     }
  73 #endif
  74
  75 #if COMPILER(MSVC) && defined(_CRT_RAND_S)
  76     uint32_t bits;
  77     rand_s(&bits);
  78     return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
  79 #elif OS(DARWIN)
  80     uint32_t bits = arc4random();
  81     return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
  82 #elif OS(UNIX)
  83     uint32_t part1 = random() & (RAND_MAX - 1);
  84     uint32_t part2 = random() & (RAND_MAX - 1);
  85     // random only provides 31 bits
  86     uint64_t fullRandom = part1;
  87     fullRandom <<= 31;
  88     fullRandom |= part2;
  89
  90     // Mask off the low 53bits
  91     fullRandom &= (1LL << 53) - 1;
  92     return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
  93 #elif OS(WINCE)
  94     return genrand_res53();
  95 #elif OS(WINDOWS)
  96     uint32_t part1 = rand() & (RAND_MAX - 1);
  97     uint32_t part2 = rand() & (RAND_MAX - 1);
  98     uint32_t part3 = rand() & (RAND_MAX - 1);
  99     uint32_t part4 = rand() & (RAND_MAX - 1);
 100     // rand only provides 15 bits on Win32
 101     uint64_t fullRandom = part1;
 102     fullRandom <<= 15;
 103     fullRandom |= part2;
 104     fullRandom <<= 15;
 105     fullRandom |= part3;
 106     fullRandom <<= 15;
 107     fullRandom |= part4;
 108
 109     // Mask off the low 53bits
 110     fullRandom &= (1LL << 53) - 1;
 111     return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
 112 #elif PLATFORM(BREWMP)
 113     uint32_t bits;
 114     ISource* randomSource;
 115
 116     IShell* shell = reinterpret_cast<AEEApplet*>(GETAPPINSTANCE())->m_pIShell;
 117     ISHELL_CreateInstance(shell, AEECLSID_RANDOM, reinterpret_cast<void**>(&randomSource));
 118     ISOURCE_Read(randomSource, reinterpret_cast<char*>(&bits), 4);
 119     ISOURCE_Release(randomSource);
 120
 121     return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
 122 #else
 123     uint32_t part1 = rand() & (RAND_MAX - 1);
 124     uint32_t part2 = rand() & (RAND_MAX - 1);
 125     // rand only provides 31 bits, and the low order bits of that aren't very random
 126     // so we take the high 26 bits of part 1, and the high 27 bits of part2.
 127     part1 >>= 5; // drop the low 5 bits
 128     part2 >>= 4; // drop the low 4 bits
 129     uint64_t fullRandom = part1;
 130     fullRandom <<= 27;
 131     fullRandom |= part2;
 132
 133     // Mask off the low 53bits
 134     fullRandom &= (1LL << 53) - 1;
 135     return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
 136 #endif
 137 }
 138
 139 }