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| 1 // Copyright 2013 the V8 project authors. All rights reserved. | 1 // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
| 4 | 4 |
| 5 #ifndef V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ | 5 #ifndef V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ |
| 6 #define V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ | 6 #define V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ |
| 7 | 7 |
| 8 #include "src/base/base-export.h" | |
| 9 #include "src/base/macros.h" | 8 #include "src/base/macros.h" |
| 10 | 9 |
| 11 namespace v8 { | 10 namespace v8 { |
| 12 namespace base { | 11 namespace base { |
| 13 | 12 |
| 14 // ----------------------------------------------------------------------------- | 13 // ----------------------------------------------------------------------------- |
| 15 // RandomNumberGenerator | 14 // RandomNumberGenerator |
| 16 | 15 |
| 17 // This class is used to generate a stream of pseudo-random numbers. The class | 16 // This class is used to generate a stream of pseudo-random numbers. The class |
| 18 // uses a 64-bit seed, which is passed through MurmurHash3 to create two 64-bit | 17 // uses a 64-bit seed, which is passed through MurmurHash3 to create two 64-bit |
| 19 // state values. This pair of state values is then used in xorshift128+. | 18 // state values. This pair of state values is then used in xorshift128+. |
| 20 // The resulting stream of pseudo-random numbers has a period length of 2^128-1. | 19 // The resulting stream of pseudo-random numbers has a period length of 2^128-1. |
| 21 // See Marsaglia: http://www.jstatsoft.org/v08/i14/paper | 20 // See Marsaglia: http://www.jstatsoft.org/v08/i14/paper |
| 22 // And Vigna: http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf | 21 // And Vigna: http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf |
| 23 // NOTE: Any changes to the algorithm must be tested against TestU01. | 22 // NOTE: Any changes to the algorithm must be tested against TestU01. |
| 24 // Please find instructions for this in the internal repository. | 23 // Please find instructions for this in the internal repository. |
| 25 | 24 |
| 26 // If two instances of RandomNumberGenerator are created with the same seed, and | 25 // If two instances of RandomNumberGenerator are created with the same seed, and |
| 27 // the same sequence of method calls is made for each, they will generate and | 26 // the same sequence of method calls is made for each, they will generate and |
| 28 // return identical sequences of numbers. | 27 // return identical sequences of numbers. |
| 29 // This class uses (probably) weak entropy by default, but it's sufficient, | 28 // This class uses (probably) weak entropy by default, but it's sufficient, |
| 30 // because it is the responsibility of the embedder to install an entropy source | 29 // because it is the responsibility of the embedder to install an entropy source |
| 31 // using v8::V8::SetEntropySource(), which provides reasonable entropy, see: | 30 // using v8::V8::SetEntropySource(), which provides reasonable entropy, see: |
| 32 // https://code.google.com/p/v8/issues/detail?id=2905 | 31 // https://code.google.com/p/v8/issues/detail?id=2905 |
| 33 // This class is neither reentrant nor threadsafe. | 32 // This class is neither reentrant nor threadsafe. |
| 34 | 33 |
| 35 class V8_BASE_EXPORT RandomNumberGenerator final { | 34 class RandomNumberGenerator final { |
| 36 public: | 35 public: |
| 37 // EntropySource is used as a callback function when V8 needs a source of | 36 // EntropySource is used as a callback function when V8 needs a source of |
| 38 // entropy. | 37 // entropy. |
| 39 typedef bool (*EntropySource)(unsigned char* buffer, size_t buflen); | 38 typedef bool (*EntropySource)(unsigned char* buffer, size_t buflen); |
| 40 static void SetEntropySource(EntropySource entropy_source); | 39 static void SetEntropySource(EntropySource entropy_source); |
| 41 | 40 |
| 42 RandomNumberGenerator(); | 41 RandomNumberGenerator(); |
| 43 explicit RandomNumberGenerator(int64_t seed) { SetSeed(seed); } | 42 explicit RandomNumberGenerator(int64_t seed) { SetSeed(seed); } |
| 44 | 43 |
| 45 // Returns the next pseudorandom, uniformly distributed int value from this | 44 // Returns the next pseudorandom, uniformly distributed int value from this |
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| 122 | 121 |
| 123 int64_t initial_seed_; | 122 int64_t initial_seed_; |
| 124 uint64_t state0_; | 123 uint64_t state0_; |
| 125 uint64_t state1_; | 124 uint64_t state1_; |
| 126 }; | 125 }; |
| 127 | 126 |
| 128 } // namespace base | 127 } // namespace base |
| 129 } // namespace v8 | 128 } // namespace v8 |
| 130 | 129 |
| 131 #endif // V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ | 130 #endif // V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ |
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