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)
38extern "C" {
39#include "wince/mt19937ar.c"
40}
41#endif
42
43namespace WTF {
44
45double weakRandomNumber()
46{
47#if COMPILER(MSVC) && defined(_CRT_RAND_S)
48 // rand_s is incredibly slow on windows so we fall back on rand for Math.random
49 return (rand() + (rand() / (RAND_MAX + 1.0))) / (RAND_MAX + 1.0);
50#else
51 return randomNumber();
52#endif
53}
54
55double randomNumber()
56{
57#if !ENABLE(JSC_MULTIPLE_THREADS)
58 static bool s_initialized = false;
59 if (!s_initialized) {
60 initializeRandomNumberGenerator();
61 s_initialized = true;
62 }
63#endif
64
65#if COMPILER(MSVC) && defined(_CRT_RAND_S)
66 uint32_t bits;
67 rand_s(&bits);
68 return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
69#elif OS(DARWIN)
70 uint32_t bits = arc4random();
71 return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
72#elif OS(UNIX)
73 uint32_t part1 = random() & (RAND_MAX - 1);
74 uint32_t part2 = random() & (RAND_MAX - 1);
75 // random only provides 31 bits
76 uint64_t fullRandom = part1;
77 fullRandom <<= 31;
78 fullRandom |= part2;
79
80 // Mask off the low 53bits
81 fullRandom &= (1LL << 53) - 1;
82 return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
83#elif OS(WINCE)
84 return genrand_res53();
85#elif OS(WINDOWS)
86 uint32_t part1 = rand() & (RAND_MAX - 1);
87 uint32_t part2 = rand() & (RAND_MAX - 1);
88 uint32_t part3 = rand() & (RAND_MAX - 1);
89 uint32_t part4 = rand() & (RAND_MAX - 1);
90 // rand only provides 15 bits on Win32
91 uint64_t fullRandom = part1;
92 fullRandom <<= 15;
93 fullRandom |= part2;
94 fullRandom <<= 15;
95 fullRandom |= part3;
96 fullRandom <<= 15;
97 fullRandom |= part4;
98
99 // Mask off the low 53bits
100 fullRandom &= (1LL << 53) - 1;
101 return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
102#else
103 uint32_t part1 = rand() & (RAND_MAX - 1);
104 uint32_t part2 = rand() & (RAND_MAX - 1);
105 // rand only provides 31 bits, and the low order bits of that aren't very random
106 // so we take the high 26 bits of part 1, and the high 27 bits of part2.
107 part1 >>= 5; // drop the low 5 bits
108 part2 >>= 4; // drop the low 4 bits
109 uint64_t fullRandom = part1;
110 fullRandom <<= 27;
111 fullRandom |= part2;
112
113 // Mask off the low 53bits
114 fullRandom &= (1LL << 53) - 1;
115 return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
116#endif
117}
118
119}
120

source code of qtscript/src/3rdparty/javascriptcore/JavaScriptCore/wtf/RandomNumber.cpp