diff options
Diffstat (limited to 'chromium/v8/src/utils/random-number-generator.cc')
-rw-r--r-- | chromium/v8/src/utils/random-number-generator.cc | 64 |
1 files changed, 21 insertions, 43 deletions
diff --git a/chromium/v8/src/utils/random-number-generator.cc b/chromium/v8/src/utils/random-number-generator.cc index fe273315a7a..3da6a5aa4ac 100644 --- a/chromium/v8/src/utils/random-number-generator.cc +++ b/chromium/v8/src/utils/random-number-generator.cc @@ -1,39 +1,17 @@ // 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 <cstdlib> - -#include "flags.h" -#include "platform/mutex.h" -#include "platform/time.h" -#include "utils.h" +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#include "src/utils/random-number-generator.h" + +#include <stdio.h> +#include <stdlib.h> + +#include <new> + +#include "src/base/macros.h" +#include "src/platform/mutex.h" +#include "src/platform/time.h" namespace v8 { namespace internal { @@ -50,12 +28,6 @@ void RandomNumberGenerator::SetEntropySource(EntropySource 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) { @@ -110,7 +82,7 @@ int RandomNumberGenerator::NextInt(int max) { ASSERT_LE(0, max); // Fast path if max is a power of 2. - if (IsPowerOf2(max)) { + if (IS_POWER_OF_TWO(max)) { return static_cast<int>((max * static_cast<int64_t>(Next(31))) >> 31); } @@ -140,7 +112,13 @@ void RandomNumberGenerator::NextBytes(void* buffer, size_t buflen) { int RandomNumberGenerator::Next(int bits) { ASSERT_LT(0, bits); ASSERT_GE(32, bits); - int64_t seed = (seed_ * kMultiplier + kAddend) & kMask; + // Do unsigned multiplication, which has the intended modulo semantics, while + // signed multiplication would expose undefined behavior. + uint64_t product = static_cast<uint64_t>(seed_) * kMultiplier; + // Assigning a uint64_t to an int64_t is implementation defined, but this + // should be OK. Use a static_cast to explicitly state that we know what we're + // doing. (Famous last words...) + int64_t seed = static_cast<int64_t>((product + kAddend) & kMask); seed_ = seed; return static_cast<int>(seed >> (48 - bits)); } |