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Side by Side Diff: src/base/utils/random-number-generator.h

Issue 2381273002: Turn libbase into a component (Closed)
Patch Set: updates Created 4 years, 2 months ago
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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"
8 #include "src/base/macros.h" 9 #include "src/base/macros.h"
9 10
10 namespace v8 { 11 namespace v8 {
11 namespace base { 12 namespace base {
12 13
13 // ----------------------------------------------------------------------------- 14 // -----------------------------------------------------------------------------
14 // RandomNumberGenerator 15 // RandomNumberGenerator
15 16
16 // This class is used to generate a stream of pseudo-random numbers. The class 17 // This class is used to generate a stream of pseudo-random numbers. The class
17 // uses a 64-bit seed, which is passed through MurmurHash3 to create two 64-bit 18 // uses a 64-bit seed, which is passed through MurmurHash3 to create two 64-bit
18 // state values. This pair of state values is then used in xorshift128+. 19 // state values. This pair of state values is then used in xorshift128+.
19 // The resulting stream of pseudo-random numbers has a period length of 2^128-1. 20 // The resulting stream of pseudo-random numbers has a period length of 2^128-1.
20 // See Marsaglia: http://www.jstatsoft.org/v08/i14/paper 21 // See Marsaglia: http://www.jstatsoft.org/v08/i14/paper
21 // And Vigna: http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf 22 // And Vigna: http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf
22 // NOTE: Any changes to the algorithm must be tested against TestU01. 23 // NOTE: Any changes to the algorithm must be tested against TestU01.
23 // Please find instructions for this in the internal repository. 24 // Please find instructions for this in the internal repository.
24 25
25 // If two instances of RandomNumberGenerator are created with the same seed, and 26 // If two instances of RandomNumberGenerator are created with the same seed, and
26 // the same sequence of method calls is made for each, they will generate and 27 // the same sequence of method calls is made for each, they will generate and
27 // return identical sequences of numbers. 28 // return identical sequences of numbers.
28 // This class uses (probably) weak entropy by default, but it's sufficient, 29 // This class uses (probably) weak entropy by default, but it's sufficient,
29 // because it is the responsibility of the embedder to install an entropy source 30 // because it is the responsibility of the embedder to install an entropy source
30 // using v8::V8::SetEntropySource(), which provides reasonable entropy, see: 31 // using v8::V8::SetEntropySource(), which provides reasonable entropy, see:
31 // https://code.google.com/p/v8/issues/detail?id=2905 32 // https://code.google.com/p/v8/issues/detail?id=2905
32 // This class is neither reentrant nor threadsafe. 33 // This class is neither reentrant nor threadsafe.
33 34
34 class RandomNumberGenerator final { 35 class V8_BASE_EXPORT RandomNumberGenerator final {
35 public: 36 public:
36 // EntropySource is used as a callback function when V8 needs a source of 37 // EntropySource is used as a callback function when V8 needs a source of
37 // entropy. 38 // entropy.
38 typedef bool (*EntropySource)(unsigned char* buffer, size_t buflen); 39 typedef bool (*EntropySource)(unsigned char* buffer, size_t buflen);
39 static void SetEntropySource(EntropySource entropy_source); 40 static void SetEntropySource(EntropySource entropy_source);
40 41
41 RandomNumberGenerator(); 42 RandomNumberGenerator();
42 explicit RandomNumberGenerator(int64_t seed) { SetSeed(seed); } 43 explicit RandomNumberGenerator(int64_t seed) { SetSeed(seed); }
43 44
44 // Returns the next pseudorandom, uniformly distributed int value from this 45 // Returns the next pseudorandom, uniformly distributed int value from this
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121 122
122 int64_t initial_seed_; 123 int64_t initial_seed_;
123 uint64_t state0_; 124 uint64_t state0_;
124 uint64_t state1_; 125 uint64_t state1_;
125 }; 126 };
126 127
127 } // namespace base 128 } // namespace base
128 } // namespace v8 129 } // namespace v8
129 130
130 #endif // V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_ 131 #endif // V8_BASE_UTILS_RANDOM_NUMBER_GENERATOR_H_
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