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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium 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 COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_ | 5 #ifndef COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_ |
6 #define COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_ | 6 #define COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_ |
7 | 7 |
| 8 #include <stddef.h> |
| 9 #include <stdint.h> |
| 10 |
8 #include <functional> | 11 #include <functional> |
9 #include <string> | 12 #include <string> |
10 #include <vector> | 13 #include <vector> |
11 | 14 |
12 #include "base/basictypes.h" | |
13 #include "base/compiler_specific.h" | 15 #include "base/compiler_specific.h" |
| 16 #include "base/macros.h" |
14 #include "base/metrics/field_trial.h" | 17 #include "base/metrics/field_trial.h" |
15 #include "third_party/mt19937ar/mt19937ar.h" | 18 #include "third_party/mt19937ar/mt19937ar.h" |
16 | 19 |
17 namespace metrics { | 20 namespace metrics { |
18 | 21 |
19 // Internals of entropy_provider.cc exposed for testing. | 22 // Internals of entropy_provider.cc exposed for testing. |
20 namespace internal { | 23 namespace internal { |
21 | 24 |
22 // A functor that generates random numbers based on a seed, using the Mersenne | 25 // A functor that generates random numbers based on a seed, using the Mersenne |
23 // Twister algorithm. Suitable for use with std::random_shuffle(). | 26 // Twister algorithm. Suitable for use with std::random_shuffle(). |
24 struct SeededRandGenerator : std::unary_function<uint32, uint32> { | 27 struct SeededRandGenerator : std::unary_function<uint32_t, uint32_t> { |
25 explicit SeededRandGenerator(uint32 seed); | 28 explicit SeededRandGenerator(uint32_t seed); |
26 ~SeededRandGenerator(); | 29 ~SeededRandGenerator(); |
27 | 30 |
28 // Returns a random number in range [0, range). | 31 // Returns a random number in range [0, range). |
29 uint32 operator()(uint32 range); | 32 uint32_t operator()(uint32_t range); |
30 | 33 |
31 MersenneTwister mersenne_twister_; | 34 MersenneTwister mersenne_twister_; |
32 }; | 35 }; |
33 | 36 |
34 // Fills |mapping| to create a bijection of values in the range of | 37 // Fills |mapping| to create a bijection of values in the range of |
35 // [0, |mapping.size()|), permuted based on |randomization_seed|. | 38 // [0, |mapping.size()|), permuted based on |randomization_seed|. |
36 void PermuteMappingUsingRandomizationSeed(uint32 randomization_seed, | 39 void PermuteMappingUsingRandomizationSeed(uint32_t randomization_seed, |
37 std::vector<uint16>* mapping); | 40 std::vector<uint16_t>* mapping); |
38 | 41 |
39 } // namespace internal | 42 } // namespace internal |
40 | 43 |
41 // SHA1EntropyProvider is an entropy provider suitable for high entropy | 44 // SHA1EntropyProvider is an entropy provider suitable for high entropy |
42 // sources. It works by taking the first 64 bits of the SHA1 hash of the | 45 // sources. It works by taking the first 64 bits of the SHA1 hash of the |
43 // entropy source concatenated with the trial name and using that for the | 46 // entropy source concatenated with the trial name and using that for the |
44 // final entropy value. | 47 // final entropy value. |
45 class SHA1EntropyProvider : public base::FieldTrial::EntropyProvider { | 48 class SHA1EntropyProvider : public base::FieldTrial::EntropyProvider { |
46 public: | 49 public: |
47 // Creates a SHA1EntropyProvider with the given |entropy_source|, which | 50 // Creates a SHA1EntropyProvider with the given |entropy_source|, which |
48 // should contain a large amount of entropy - for example, a textual | 51 // should contain a large amount of entropy - for example, a textual |
49 // representation of a persistent randomly-generated 128-bit value. | 52 // representation of a persistent randomly-generated 128-bit value. |
50 explicit SHA1EntropyProvider(const std::string& entropy_source); | 53 explicit SHA1EntropyProvider(const std::string& entropy_source); |
51 ~SHA1EntropyProvider() override; | 54 ~SHA1EntropyProvider() override; |
52 | 55 |
53 // base::FieldTrial::EntropyProvider implementation: | 56 // base::FieldTrial::EntropyProvider implementation: |
54 double GetEntropyForTrial(const std::string& trial_name, | 57 double GetEntropyForTrial(const std::string& trial_name, |
55 uint32 randomization_seed) const override; | 58 uint32_t randomization_seed) const override; |
56 | 59 |
57 private: | 60 private: |
58 std::string entropy_source_; | 61 std::string entropy_source_; |
59 | 62 |
60 DISALLOW_COPY_AND_ASSIGN(SHA1EntropyProvider); | 63 DISALLOW_COPY_AND_ASSIGN(SHA1EntropyProvider); |
61 }; | 64 }; |
62 | 65 |
63 // PermutedEntropyProvider is an entropy provider suitable for low entropy | 66 // PermutedEntropyProvider is an entropy provider suitable for low entropy |
64 // sources (below 16 bits). It uses the field trial name to generate a | 67 // sources (below 16 bits). It uses the field trial name to generate a |
65 // permutation of a mapping array from an initial entropy value to a new value. | 68 // permutation of a mapping array from an initial entropy value to a new value. |
66 // Note: This provider's performance is O(2^n), where n is the number of bits | 69 // Note: This provider's performance is O(2^n), where n is the number of bits |
67 // in the entropy source. | 70 // in the entropy source. |
68 class PermutedEntropyProvider : public base::FieldTrial::EntropyProvider { | 71 class PermutedEntropyProvider : public base::FieldTrial::EntropyProvider { |
69 public: | 72 public: |
70 // Creates a PermutedEntropyProvider with the given |low_entropy_source|, | 73 // Creates a PermutedEntropyProvider with the given |low_entropy_source|, |
71 // which should have a value in the range of [0, low_entropy_source_max). | 74 // which should have a value in the range of [0, low_entropy_source_max). |
72 PermutedEntropyProvider(uint16 low_entropy_source, | 75 PermutedEntropyProvider(uint16_t low_entropy_source, |
73 size_t low_entropy_source_max); | 76 size_t low_entropy_source_max); |
74 ~PermutedEntropyProvider() override; | 77 ~PermutedEntropyProvider() override; |
75 | 78 |
76 // base::FieldTrial::EntropyProvider implementation: | 79 // base::FieldTrial::EntropyProvider implementation: |
77 double GetEntropyForTrial(const std::string& trial_name, | 80 double GetEntropyForTrial(const std::string& trial_name, |
78 uint32 randomization_seed) const override; | 81 uint32_t randomization_seed) const override; |
79 | 82 |
80 protected: | 83 protected: |
81 // Performs the permutation algorithm and returns the permuted value that | 84 // Performs the permutation algorithm and returns the permuted value that |
82 // corresponds to |low_entropy_source_|. | 85 // corresponds to |low_entropy_source_|. |
83 virtual uint16 GetPermutedValue(uint32 randomization_seed) const; | 86 virtual uint16_t GetPermutedValue(uint32_t randomization_seed) const; |
84 | 87 |
85 private: | 88 private: |
86 uint16 low_entropy_source_; | 89 uint16_t low_entropy_source_; |
87 size_t low_entropy_source_max_; | 90 size_t low_entropy_source_max_; |
88 | 91 |
89 DISALLOW_COPY_AND_ASSIGN(PermutedEntropyProvider); | 92 DISALLOW_COPY_AND_ASSIGN(PermutedEntropyProvider); |
90 }; | 93 }; |
91 | 94 |
92 } // namespace metrics | 95 } // namespace metrics |
93 | 96 |
94 #endif // COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_ | 97 #endif // COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_ |
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