Move platform abstraction to base library

src/utils/random-number-generator.cc

-// Copyright 2013 the V8 project authors. All rights reserved.
-// 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 {
-
-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 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;
-      }
-    }
-  }
-
-#if V8_OS_CYGWIN || V8_OS_WIN
-  // Use rand_s() to gather entropy on Windows. See:
-  // https://code.google.com/p/v8/issues/detail?id=2905
-  unsigned first_half, second_half;
-  errno_t result = rand_s(&first_half);
-  ASSERT_EQ(0, result);
-  result = rand_s(&second_half);
-  ASSERT_EQ(0, result);
-  SetSeed((static_cast<int64_t>(first_half) << 32) + second_half);
-#else
-  // 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.
-  // This is weak entropy, but it's sufficient, because
-  // it is the responsibility of the embedder to install
-  // an entropy source using v8::V8::SetEntropySource(),
-  // which provides reasonable entropy, see:
-  // https://code.google.com/p/v8/issues/detail?id=2905
-  int64_t seed = Time::NowFromSystemTime().ToInternalValue() << 24;
-  seed ^= TimeTicks::HighResolutionNow().ToInternalValue() << 16;
-  seed ^= TimeTicks::Now().ToInternalValue() << 8;
-  SetSeed(seed);
-#endif  // V8_OS_CYGWIN || V8_OS_WIN
-}
-
-
-int RandomNumberGenerator::NextInt(int max) {
-  ASSERT_LE(0, max);
-
-  // Fast path if max is a power of 2.
-  if (IS_POWER_OF_TWO(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);
-  // 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));
-}
-
-
-void RandomNumberGenerator::SetSeed(int64_t seed) {
-  seed_ = (seed ^ kMultiplier) & kMask;
-}
-
-} }  // namespace v8::internal