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Diffstat (limited to 'deps/v8/src/utils/random-number-generator.cc')
-rw-r--r-- | deps/v8/src/utils/random-number-generator.cc | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/deps/v8/src/utils/random-number-generator.cc b/deps/v8/src/utils/random-number-generator.cc new file mode 100644 index 0000000000..1e03ee2449 --- /dev/null +++ b/deps/v8/src/utils/random-number-generator.cc @@ -0,0 +1,136 @@ +// Copyright 2013 the V8 project authors. All rights reserved. +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following +// disclaimer in the documentation and/or other materials provided +// with the distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived +// from this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +#include "utils/random-number-generator.h" + +#include <cstdio> + +#include "flags.h" +#include "platform/mutex.h" +#include "platform/time.h" +#include "utils.h" + +namespace v8 { +namespace internal { + +static LazyMutex entropy_mutex = LAZY_MUTEX_INITIALIZER; +static RandomNumberGenerator::EntropySource entropy_source = NULL; + + +// static +void RandomNumberGenerator::SetEntropySource(EntropySource source) { + LockGuard<Mutex> lock_guard(entropy_mutex.Pointer()); + entropy_source = source; +} + + +RandomNumberGenerator::RandomNumberGenerator() { + // Check --random-seed flag first. + if (FLAG_random_seed != 0) { + SetSeed(FLAG_random_seed); + return; + } + + // Check if embedder supplied an entropy source. + { LockGuard<Mutex> lock_guard(entropy_mutex.Pointer()); + if (entropy_source != NULL) { + int64_t seed; + if (entropy_source(reinterpret_cast<unsigned char*>(&seed), + sizeof(seed))) { + SetSeed(seed); + return; + } + } + } + + // Gather entropy from /dev/urandom if available. + FILE* fp = fopen("/dev/urandom", "rb"); + if (fp != NULL) { + int64_t seed; + size_t n = fread(&seed, sizeof(seed), 1, fp); + fclose(fp); + if (n == 1) { + SetSeed(seed); + return; + } + } + + // We cannot assume that random() or rand() were seeded + // properly, so instead of relying on random() or rand(), + // we just seed our PRNG using timing data as fallback. + int64_t seed = Time::NowFromSystemTime().ToInternalValue() << 24; + seed ^= TimeTicks::HighResNow().ToInternalValue() << 16; + seed ^= TimeTicks::Now().ToInternalValue() << 8; + SetSeed(seed); +} + + +int RandomNumberGenerator::NextInt(int max) { + ASSERT_LE(0, max); + + // Fast path if max is a power of 2. + if (IsPowerOf2(max)) { + return static_cast<int>((max * static_cast<int64_t>(Next(31))) >> 31); + } + + while (true) { + int rnd = Next(31); + int val = rnd % max; + if (rnd - val + (max - 1) >= 0) { + return val; + } + } +} + + +double RandomNumberGenerator::NextDouble() { + return ((static_cast<int64_t>(Next(26)) << 27) + Next(27)) / + static_cast<double>(static_cast<int64_t>(1) << 53); +} + + +void RandomNumberGenerator::NextBytes(void* buffer, size_t buflen) { + for (size_t n = 0; n < buflen; ++n) { + static_cast<uint8_t*>(buffer)[n] = static_cast<uint8_t>(Next(8)); + } +} + + +int RandomNumberGenerator::Next(int bits) { + ASSERT_LT(0, bits); + ASSERT_GE(32, bits); + int64_t seed = (seed_ * kMultiplier + kAddend) & kMask; + seed_ = seed; + return static_cast<int>(seed >> (48 - bits)); +} + + +void RandomNumberGenerator::SetSeed(int64_t seed) { + seed_ = (seed ^ kMultiplier) & kMask; +} + +} } // namespace v8::internal |