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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 <cmath> | 5 #include <cmath> |
| 6 #include <limits> | 6 #include <limits> |
| 7 #include <numeric> | 7 #include <numeric> |
| 8 | 8 |
| 9 #include "base/basictypes.h" | 9 #include "base/basictypes.h" |
| 10 #include "base/guid.h" | 10 #include "base/guid.h" |
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| 72 | 72 |
| 73 // An TrialEntropyGenerator that uses the SHA1EntropyProvider with the high | 73 // An TrialEntropyGenerator that uses the SHA1EntropyProvider with the high |
| 74 // entropy source (random GUID with 128 bits of entropy + 13 additional bits of | 74 // entropy source (random GUID with 128 bits of entropy + 13 additional bits of |
| 75 // entropy corresponding to a low entropy source). | 75 // entropy corresponding to a low entropy source). |
| 76 class SHA1EntropyGenerator : public TrialEntropyGenerator { | 76 class SHA1EntropyGenerator : public TrialEntropyGenerator { |
| 77 public: | 77 public: |
| 78 explicit SHA1EntropyGenerator(const std::string& trial_name) | 78 explicit SHA1EntropyGenerator(const std::string& trial_name) |
| 79 : trial_name_(trial_name) { | 79 : trial_name_(trial_name) { |
| 80 } | 80 } |
| 81 | 81 |
| 82 ~SHA1EntropyGenerator() { | 82 virtual ~SHA1EntropyGenerator() { |
| 83 } | 83 } |
| 84 | 84 |
| 85 virtual double GenerateEntropyValue() const OVERRIDE { | 85 virtual double GenerateEntropyValue() const OVERRIDE { |
| 86 // Use a random GUID + 13 additional bits of entropy to match how the | 86 // Use a random GUID + 13 additional bits of entropy to match how the |
| 87 // SHA1EntropyProvider is used in metrics_service.cc. | 87 // SHA1EntropyProvider is used in metrics_service.cc. |
| 88 const int low_entropy_source = | 88 const int low_entropy_source = |
| 89 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); | 89 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); |
| 90 const std::string high_entropy_source = | 90 const std::string high_entropy_source = |
| 91 base::GenerateGUID() + base::IntToString(low_entropy_source); | 91 base::GenerateGUID() + base::IntToString(low_entropy_source); |
| 92 return GenerateSHA1Entropy(high_entropy_source, trial_name_); | 92 return GenerateSHA1Entropy(high_entropy_source, trial_name_); |
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| 103 class PermutedEntropyGenerator : public TrialEntropyGenerator { | 103 class PermutedEntropyGenerator : public TrialEntropyGenerator { |
| 104 public: | 104 public: |
| 105 explicit PermutedEntropyGenerator(const std::string& trial_name) | 105 explicit PermutedEntropyGenerator(const std::string& trial_name) |
| 106 : mapping_(kMaxLowEntropySize) { | 106 : mapping_(kMaxLowEntropySize) { |
| 107 // Note: Given a trial name, the computed mapping will be the same. | 107 // Note: Given a trial name, the computed mapping will be the same. |
| 108 // As a performance optimization, pre-compute the mapping once per trial | 108 // As a performance optimization, pre-compute the mapping once per trial |
| 109 // name and index into it for each entropy value. | 109 // name and index into it for each entropy value. |
| 110 internal::PermuteMappingUsingTrialName(trial_name, &mapping_); | 110 internal::PermuteMappingUsingTrialName(trial_name, &mapping_); |
| 111 } | 111 } |
| 112 | 112 |
| 113 ~PermutedEntropyGenerator() { | 113 virtual ~PermutedEntropyGenerator() { |
| 114 } | 114 } |
| 115 | 115 |
| 116 virtual double GenerateEntropyValue() const OVERRIDE { | 116 virtual double GenerateEntropyValue() const OVERRIDE { |
| 117 const int low_entropy_source = | 117 const int low_entropy_source = |
| 118 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); | 118 static_cast<uint16>(base::RandInt(0, kMaxLowEntropySize - 1)); |
| 119 return mapping_[low_entropy_source] / | 119 return mapping_[low_entropy_source] / |
| 120 static_cast<double>(kMaxLowEntropySize); | 120 static_cast<double>(kMaxLowEntropySize); |
| 121 } | 121 } |
| 122 | 122 |
| 123 private: | 123 private: |
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| 329 ++count; | 329 ++count; |
| 330 } | 330 } |
| 331 | 331 |
| 332 ASSERT_LT(count, kMaxAttempts) << "Expected average was " << | 332 ASSERT_LT(count, kMaxAttempts) << "Expected average was " << |
| 333 kExpectedAverage << ", average ended at " << cumulative_average << | 333 kExpectedAverage << ", average ended at " << cumulative_average << |
| 334 ", for trial " << kTestTrialNames[i]; | 334 ", for trial " << kTestTrialNames[i]; |
| 335 } | 335 } |
| 336 } | 336 } |
| 337 | 337 |
| 338 } // namespace metrics | 338 } // namespace metrics |
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