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 "CryptographicallyRandomNumber.h"
31#include "RandomNumberSeed.h"
32
33#include <limits>
34#include <limits.h>
35#include <stdint.h>
36#include <stdlib.h>
37
38#if USE(MERSENNE_TWISTER_19937)
39extern "C" {
40#include "mt19937ar.c"
41}
42#endif
43
44#if PLATFORM(BREWMP)
45#include <AEEAppGen.h>
46#include <AEESource.h>
47#include <AEEStdLib.h>
48#include <wtf/brew/RefPtrBrew.h>
49#include <wtf/brew/ShellBrew.h>
50#endif
51
52namespace WTF {
53
54double randomNumber()
55{
56#if USE(OS_RANDOMNESS)
57    uint32_t bits = cryptographicallyRandomNumber();
58    return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
59#else
60    // Without OS_RANDOMNESS, we fall back to other random number generators
61    // that might not be cryptographically secure. Ideally, most ports would
62    // define USE(OS_RANDOMNESS).
63
64#if !ENABLE(JSC_MULTIPLE_THREADS)
65    static bool s_initialized = false;
66    if (!s_initialized) {
67        initializeRandomNumberGenerator();
68        s_initialized = true;
69    }
70#endif
71
72#if USE(MERSENNE_TWISTER_19937)
73    return genrand_res53();
74#elif PLATFORM(BREWMP)
75    uint32_t bits;
76    // Is this a cryptographically strong source of random numbers? If so, we
77    // should move this into OSRandomSource.
78    // http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/140sp/140sp851.pdf
79    // is slightly unclear on this point, although it seems to imply that it is
80    // secure.
81    RefPtr<ISource> randomSource = createRefPtrInstance<ISource>(AEECLSID_RANDOM);
82    ISOURCE_Read(randomSource.get(), reinterpret_cast<char*>(&bits), 4);
83
84    return static_cast<double>(bits) / (static_cast<double>(std::numeric_limits<uint32_t>::max()) + 1.0);
85#else
86    uint32_t part1 = rand() & (RAND_MAX - 1);
87    uint32_t part2 = rand() & (RAND_MAX - 1);
88    // rand only provides 31 bits, and the low order bits of that aren't very random
89    // so we take the high 26 bits of part 1, and the high 27 bits of part2.
90    part1 >>= 5; // drop the low 5 bits
91    part2 >>= 4; // drop the low 4 bits
92    uint64_t fullRandom = part1;
93    fullRandom <<= 27;
94    fullRandom |= part2;
95
96    // Mask off the low 53bits
97    fullRandom &= (1LL << 53) - 1;
98    return static_cast<double>(fullRandom)/static_cast<double>(1LL << 53);
99#endif
100#endif
101}
102
103}
104