1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_ 6 #define BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_ 7 8 #include <map> 9 #include <string> 10 #include <utility> 11 12 #include "base/base_export.h" 13 #include "base/memory/singleton.h" 14 #include "base/metrics/field_trial.h" 15 #include "base/synchronization/lock.h" 16 17 namespace base { 18 19 // Keeps track of the parameters of all field trials and ensures access to them 20 // is thread-safe. 21 class BASE_EXPORT FieldTrialParamAssociator { 22 public: 23 FieldTrialParamAssociator(); 24 ~FieldTrialParamAssociator(); 25 26 // Key-value mapping type for field trial parameters. 27 typedef std::map<std::string, std::string> FieldTrialParams; 28 29 // Retrieve the singleton. 30 static FieldTrialParamAssociator* GetInstance(); 31 32 // Sets parameters for the given field trial name and group. 33 bool AssociateFieldTrialParams(const std::string& trial_name, 34 const std::string& group_name, 35 const FieldTrialParams& params); 36 37 // Gets the parameters for a field trial and its chosen group. If not found in 38 // field_trial_params_, then tries to looks it up in shared memory. 39 bool GetFieldTrialParams(const std::string& trial_name, 40 FieldTrialParams* params); 41 42 // Gets the parameters for a field trial and its chosen group. Does not 43 // fallback to looking it up in shared memory. This should only be used if you 44 // know for sure the params are in the mapping, like if you're in the browser 45 // process, and even then you should probably just use GetFieldTrialParams(). 46 bool GetFieldTrialParamsWithoutFallback(const std::string& trial_name, 47 const std::string& group_name, 48 FieldTrialParams* params); 49 50 // Clears the internal field_trial_params_ mapping, plus removes all params in 51 // shared memory. 52 void ClearAllParamsForTesting(); 53 54 // Clears a single field trial param. 55 // Note: this does NOT remove the param in shared memory. 56 void ClearParamsForTesting(const std::string& trial_name, 57 const std::string& group_name); 58 59 // Clears the internal field_trial_params_ mapping. 60 void ClearAllCachedParamsForTesting(); 61 62 private: 63 friend struct DefaultSingletonTraits<FieldTrialParamAssociator>; 64 65 // (field_trial_name, field_trial_group) 66 typedef std::pair<std::string, std::string> FieldTrialKey; 67 68 Lock lock_; 69 std::map<FieldTrialKey, FieldTrialParams> field_trial_params_; 70 71 DISALLOW_COPY_AND_ASSIGN(FieldTrialParamAssociator); 72 }; 73 74 } // namespace base 75 76 #endif // BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_ 77