Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 1 | // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #include "src/base/utils/random-number-generator.h" |
| 6 | |
| 7 | #include <stdio.h> |
| 8 | #include <stdlib.h> |
| 9 | |
| 10 | #include <new> |
| 11 | |
| 12 | #include "src/base/macros.h" |
| 13 | #include "src/base/platform/mutex.h" |
| 14 | #include "src/base/platform/time.h" |
| 15 | |
| 16 | namespace v8 { |
| 17 | namespace base { |
| 18 | |
| 19 | static LazyMutex entropy_mutex = LAZY_MUTEX_INITIALIZER; |
| 20 | static RandomNumberGenerator::EntropySource entropy_source = NULL; |
| 21 | |
| 22 | |
| 23 | // static |
| 24 | void RandomNumberGenerator::SetEntropySource(EntropySource source) { |
| 25 | LockGuard<Mutex> lock_guard(entropy_mutex.Pointer()); |
| 26 | entropy_source = source; |
| 27 | } |
| 28 | |
| 29 | |
| 30 | RandomNumberGenerator::RandomNumberGenerator() { |
| 31 | // Check if embedder supplied an entropy source. |
| 32 | { LockGuard<Mutex> lock_guard(entropy_mutex.Pointer()); |
| 33 | if (entropy_source != NULL) { |
| 34 | int64_t seed; |
| 35 | if (entropy_source(reinterpret_cast<unsigned char*>(&seed), |
| 36 | sizeof(seed))) { |
| 37 | SetSeed(seed); |
| 38 | return; |
| 39 | } |
| 40 | } |
| 41 | } |
| 42 | |
| 43 | #if V8_OS_CYGWIN || V8_OS_WIN |
| 44 | // Use rand_s() to gather entropy on Windows. See: |
| 45 | // https://code.google.com/p/v8/issues/detail?id=2905 |
| 46 | unsigned first_half, second_half; |
| 47 | errno_t result = rand_s(&first_half); |
| 48 | DCHECK_EQ(0, result); |
| 49 | result = rand_s(&second_half); |
| 50 | DCHECK_EQ(0, result); |
| 51 | SetSeed((static_cast<int64_t>(first_half) << 32) + second_half); |
| 52 | #else |
| 53 | // Gather entropy from /dev/urandom if available. |
| 54 | FILE* fp = fopen("/dev/urandom", "rb"); |
| 55 | if (fp != NULL) { |
| 56 | int64_t seed; |
| 57 | size_t n = fread(&seed, sizeof(seed), 1, fp); |
| 58 | fclose(fp); |
| 59 | if (n == 1) { |
| 60 | SetSeed(seed); |
| 61 | return; |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | // We cannot assume that random() or rand() were seeded |
| 66 | // properly, so instead of relying on random() or rand(), |
| 67 | // we just seed our PRNG using timing data as fallback. |
| 68 | // This is weak entropy, but it's sufficient, because |
| 69 | // it is the responsibility of the embedder to install |
| 70 | // an entropy source using v8::V8::SetEntropySource(), |
| 71 | // which provides reasonable entropy, see: |
| 72 | // https://code.google.com/p/v8/issues/detail?id=2905 |
| 73 | int64_t seed = Time::NowFromSystemTime().ToInternalValue() << 24; |
| 74 | seed ^= TimeTicks::HighResolutionNow().ToInternalValue() << 16; |
| 75 | seed ^= TimeTicks::Now().ToInternalValue() << 8; |
| 76 | SetSeed(seed); |
| 77 | #endif // V8_OS_CYGWIN || V8_OS_WIN |
| 78 | } |
| 79 | |
| 80 | |
| 81 | int RandomNumberGenerator::NextInt(int max) { |
Emily Bernier | d0a1eb7 | 2015-03-24 16:35:39 -0400 | [diff] [blame] | 82 | DCHECK_LT(0, max); |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 83 | |
| 84 | // Fast path if max is a power of 2. |
| 85 | if (IS_POWER_OF_TWO(max)) { |
| 86 | return static_cast<int>((max * static_cast<int64_t>(Next(31))) >> 31); |
| 87 | } |
| 88 | |
| 89 | while (true) { |
| 90 | int rnd = Next(31); |
| 91 | int val = rnd % max; |
| 92 | if (rnd - val + (max - 1) >= 0) { |
| 93 | return val; |
| 94 | } |
| 95 | } |
| 96 | } |
| 97 | |
| 98 | |
| 99 | double RandomNumberGenerator::NextDouble() { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 100 | XorShift128(&state0_, &state1_); |
| 101 | return ToDouble(state0_, state1_); |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 102 | } |
| 103 | |
| 104 | |
Emily Bernier | d0a1eb7 | 2015-03-24 16:35:39 -0400 | [diff] [blame] | 105 | int64_t RandomNumberGenerator::NextInt64() { |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 106 | XorShift128(&state0_, &state1_); |
| 107 | return bit_cast<int64_t>(state0_ + state1_); |
Emily Bernier | d0a1eb7 | 2015-03-24 16:35:39 -0400 | [diff] [blame] | 108 | } |
| 109 | |
| 110 | |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 111 | void RandomNumberGenerator::NextBytes(void* buffer, size_t buflen) { |
| 112 | for (size_t n = 0; n < buflen; ++n) { |
| 113 | static_cast<uint8_t*>(buffer)[n] = static_cast<uint8_t>(Next(8)); |
| 114 | } |
| 115 | } |
| 116 | |
| 117 | |
| 118 | int RandomNumberGenerator::Next(int bits) { |
| 119 | DCHECK_LT(0, bits); |
| 120 | DCHECK_GE(32, bits); |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 121 | XorShift128(&state0_, &state1_); |
| 122 | return static_cast<int>((state0_ + state1_) >> (64 - bits)); |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 123 | } |
| 124 | |
| 125 | |
| 126 | void RandomNumberGenerator::SetSeed(int64_t seed) { |
| 127 | initial_seed_ = seed; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 128 | state0_ = MurmurHash3(bit_cast<uint64_t>(seed)); |
Ben Murdoch | 61f157c | 2016-09-16 13:49:30 +0100 | [diff] [blame] | 129 | state1_ = MurmurHash3(~state0_); |
| 130 | CHECK(state0_ != 0 || state1_ != 0); |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 131 | } |
| 132 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 133 | |
| 134 | uint64_t RandomNumberGenerator::MurmurHash3(uint64_t h) { |
| 135 | h ^= h >> 33; |
| 136 | h *= V8_UINT64_C(0xFF51AFD7ED558CCD); |
| 137 | h ^= h >> 33; |
| 138 | h *= V8_UINT64_C(0xC4CEB9FE1A85EC53); |
| 139 | h ^= h >> 33; |
| 140 | return h; |
| 141 | } |
| 142 | |
| 143 | } // namespace base |
| 144 | } // namespace v8 |