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

Issue 2396933002: Revert of Reland "Turn libbase into a component" (Closed)
Patch Set: 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"
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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