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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 #include "components/variations/entropy_provider.h" | 5 #include "components/variations/entropy_provider.h" |
6 | 6 |
7 #include <cmath> | 7 #include <cmath> |
8 #include <limits> | 8 #include <limits> |
9 #include <numeric> | 9 #include <numeric> |
10 | 10 |
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76 // entropy corresponding to a low entropy source). | 76 // entropy corresponding to a low entropy source). |
77 class SHA1EntropyGenerator : public TrialEntropyGenerator { | 77 class SHA1EntropyGenerator : public TrialEntropyGenerator { |
78 public: | 78 public: |
79 explicit SHA1EntropyGenerator(const std::string& trial_name) | 79 explicit SHA1EntropyGenerator(const std::string& trial_name) |
80 : trial_name_(trial_name) { | 80 : trial_name_(trial_name) { |
81 } | 81 } |
82 | 82 |
83 virtual ~SHA1EntropyGenerator() { | 83 virtual ~SHA1EntropyGenerator() { |
84 } | 84 } |
85 | 85 |
86 virtual double GenerateEntropyValue() const OVERRIDE { | 86 virtual double GenerateEntropyValue() const override { |
87 // Use a random GUID + 13 additional bits of entropy to match how the | 87 // Use a random GUID + 13 additional bits of entropy to match how the |
88 // SHA1EntropyProvider is used in metrics_service.cc. | 88 // SHA1EntropyProvider is used in metrics_service.cc. |
89 const int low_entropy_source = | 89 const int low_entropy_source = |
90 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); | 90 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); |
91 const std::string high_entropy_source = | 91 const std::string high_entropy_source = |
92 base::GenerateGUID() + base::IntToString(low_entropy_source); | 92 base::GenerateGUID() + base::IntToString(low_entropy_source); |
93 return GenerateSHA1Entropy(high_entropy_source, trial_name_); | 93 return GenerateSHA1Entropy(high_entropy_source, trial_name_); |
94 } | 94 } |
95 | 95 |
96 private: | 96 private: |
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109 // As a performance optimization, pre-compute the mapping once per trial | 109 // As a performance optimization, pre-compute the mapping once per trial |
110 // name and index into it for each entropy value. | 110 // name and index into it for each entropy value. |
111 const uint32 randomization_seed = HashName(trial_name); | 111 const uint32 randomization_seed = HashName(trial_name); |
112 internal::PermuteMappingUsingRandomizationSeed(randomization_seed, | 112 internal::PermuteMappingUsingRandomizationSeed(randomization_seed, |
113 &mapping_); | 113 &mapping_); |
114 } | 114 } |
115 | 115 |
116 virtual ~PermutedEntropyGenerator() { | 116 virtual ~PermutedEntropyGenerator() { |
117 } | 117 } |
118 | 118 |
119 virtual double GenerateEntropyValue() const OVERRIDE { | 119 virtual double GenerateEntropyValue() const override { |
120 const int low_entropy_source = | 120 const int low_entropy_source = |
121 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); | 121 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); |
122 return mapping_[low_entropy_source] / | 122 return mapping_[low_entropy_source] / |
123 static_cast<double>(kMaxLowEntropySize); | 123 static_cast<double>(kMaxLowEntropySize); |
124 } | 124 } |
125 | 125 |
126 private: | 126 private: |
127 std::vector<uint16> mapping_; | 127 std::vector<uint16> mapping_; |
128 | 128 |
129 DISALLOW_COPY_AND_ASSIGN(PermutedEntropyGenerator); | 129 DISALLOW_COPY_AND_ASSIGN(PermutedEntropyGenerator); |
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360 ++count; | 360 ++count; |
361 } | 361 } |
362 | 362 |
363 ASSERT_LT(count, kMaxAttempts) << "Expected average was " << | 363 ASSERT_LT(count, kMaxAttempts) << "Expected average was " << |
364 kExpectedAverage << ", average ended at " << cumulative_average << | 364 kExpectedAverage << ", average ended at " << cumulative_average << |
365 ", for trial " << kTestTrialNames[i]; | 365 ", for trial " << kTestTrialNames[i]; |
366 } | 366 } |
367 } | 367 } |
368 | 368 |
369 } // namespace metrics | 369 } // namespace metrics |
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