Introduce a RandonNumberGenerator class. Refactor the random/private_random uses in Isolate/Context.

src/utils/random-number-generator.cc

+// 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