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

src/utils/random-number-generator.h

+// 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.
+
+#ifndef V8_UTILS_RANDOM_NUMBER_GENERATOR_H_
+#define V8_UTILS_RANDOM_NUMBER_GENERATOR_H_
+
+#include "globals.h"
+
+namespace v8 {
+namespace internal {
+
+// -----------------------------------------------------------------------------
+// RandomNumberGenerator
+//
+// This class is used to generate a stream of pseudorandom numbers. The class
+// uses a 48-bit seed, which is modified using a linear congruential formula.
+// (See Donald Knuth, The Art of Computer Programming, Volume 3, Section 3.2.1.)
+// If two instances of RandomNumberGenerator are created with the same seed, and
+// the same sequence of method calls is made for each, they will generate and
+// return identical sequences of numbers.
+// This class is neither reentrant nor threadsafe.
+
+class RandomNumberGenerator V8_FINAL {
+ public:
+  // EntropySource is used as a callback function when V8 needs a source of
+  // entropy.
+  typedef bool (*EntropySource)(unsigned char* buffer, size_t buflen);
+  static void SetEntropySource(EntropySource entropy_source);
+
+  RandomNumberGenerator();
+  explicit RandomNumberGenerator(int64_t seed) { SetSeed(seed); }
+
+  // Returns the next pseudorandom, uniformly distributed int value from this
+  // random number generator's sequence. The general contract of |NextInt()| is
+  // that one int value is pseudorandomly generated and returned.
+  // All 2^32 possible integer values are produced with (approximately) equal
+  // probability.
+  V8_INLINE(int NextInt()) V8_WARN_UNUSED_RESULT {

[Michael Starzinger, 2013/09/10 08:43:31]

nit: Ceterum censeo V8_WARN_UNUSED_RESULT esse delendam.

[Benedikt Meurer, 2013/09/10 10:52:13]

As per offline discussion: This is a valid use.

+    return Next(32);
+  }
+
+  // Returns a pseudorandom, uniformly distributed int value between 0
+  // (inclusive) and the specified max value (exclusive), drawn from this random
+  // number generator's sequence. The general contract of |NextInt(int)| is that
+  // one int value in the specified range is pseudorandomly generated and
+  // returned. All max possible int values are produced with (approximately)
+  // equal probability.
+  int NextInt(int max) V8_WARN_UNUSED_RESULT;

[Michael Starzinger, 2013/09/10 08:43:31]

nit: Ceterum censeo V8_WARN_UNUSED_RESULT esse delendam.

[Benedikt Meurer, 2013/09/10 10:52:13]

As per offline discussion: This is a valid use.

+
+  // Returns the next pseudorandom, uniformly distributed boolean value from
+  // this random number generator's sequence. The general contract of
+  // |NextBoolean()| is that one boolean value is pseudorandomly generated and
+  // returned. The values true and false are produced with (approximately) equal
+  // probability.
+  V8_INLINE(bool NextBool()) V8_WARN_UNUSED_RESULT {

[Michael Starzinger, 2013/09/10 08:43:31]

nit: Ceterum censeo V8_WARN_UNUSED_RESULT esse delendam.

[Benedikt Meurer, 2013/09/10 10:52:13]

As per offline discussion: This is a valid use.

+    return Next(1) != 0;
+  }
+
+  // Returns the next pseudorandom, uniformly distributed double value between
+  // 0.0 and 1.0 from this random number generator's sequence.
+  // The general contract of |NextDouble()| is that one double value, chosen
+  // (approximately) uniformly from the range 0.0 (inclusive) to 1.0
+  // (exclusive), is pseudorandomly generated and returned.
+  double NextDouble() V8_WARN_UNUSED_RESULT;

[Michael Starzinger, 2013/09/10 08:43:31]

nit: Ceterum censeo V8_WARN_UNUSED_RESULT esse delendam.

[Benedikt Meurer, 2013/09/10 10:52:13]

As per offline discussion: This is a valid use.

+
+  // Fills the elements of a specified array of bytes with random numbers.
+  void NextBytes(void* buffer, size_t buflen);
+
+ private:
+  static const int64_t kMultiplier = V8_2PART_UINT64_C(0x5, deece66d);
+  static const int64_t kAddend = 0xb;
+  static const int64_t kMask = V8_2PART_UINT64_C(0xffff, ffffffff);
+
+  int Next(int bits) V8_WARN_UNUSED_RESULT;
+  void SetSeed(int64_t seed);
+
+  int64_t seed_;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_UTILS_RANDOM_NUMBER_GENERATOR_H_