1 /*
2 * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
3 * (C) 2008 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 namespace WTF {
38
weakRandomNumber()39 double weakRandomNumber()
40 {
41 #if COMPILER(MSVC) && defined(_CRT_RAND_S)
42 // rand_s is incredibly slow on windows so we fall back on rand for Math.random
43 return (rand() + (rand() / (RAND_MAX + 1.0))) / (RAND_MAX + 1.0);
44 #else
45 return randomNumber();
46 #endif
47 }
48
randomNumber()49 double randomNumber()
50 {
51 #if !ENABLE(JSC_MULTIPLE_THREADS)
52 static bool s_initialized = false;
53 if (!s_initialized) {
54 initializeRandomNumberGenerator();
55 s_initialized = true;
56 }
57 #endif
58
59 #if COMPILER(MSVC) && defined(_CRT_RAND_S)
60 uint32_t bits;
61 rand_s(&bits);
62 return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
63 #elif PLATFORM(DARWIN)
64 uint32_t bits = arc4random();
65 return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
66 #elif PLATFORM(UNIX)
67 uint32_t part1 = random() & (RAND_MAX - 1);
68 uint32_t part2 = random() & (RAND_MAX - 1);
69 // random only provides 31 bits
70 uint64_t fullRandom = part1;
71 fullRandom <<= 31;
72 fullRandom |= part2;
73
74 // Mask off the low 53bits
75 fullRandom &= (1LL << 53) - 1;
76 return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
77 #else
78 uint32_t part1 = rand() & (RAND_MAX - 1);
79 uint32_t part2 = rand() & (RAND_MAX - 1);
80 // rand only provides 31 bits, and the low order bits of that aren't very random
81 // so we take the high 26 bits of part 1, and the high 27 bits of part2.
82 part1 >>= 5; // drop the low 5 bits
83 part2 >>= 4; // drop the low 4 bits
84 uint64_t fullRandom = part1;
85 fullRandom <<= 27;
86 fullRandom |= part2;
87
88 // Mask off the low 53bits
89 fullRandom &= (1LL << 53) - 1;
90 return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
91 #endif
92 }
93
94 }
95