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:
+//
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+//     * Redistributions in binary form must reproduce the above
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+//       with the distribution.
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+//       contributors may be used to endorse or promote products derived
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+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+
+#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 {
+    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;
+
+  // 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 {
+    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;
+
+  // 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_