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// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_
#define BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_
#include <functional>
#include <map>
#include <string>
#include <utility>
#include "base/base_export.h"
#include "base/memory/singleton.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/field_trial_params.h"
#include "base/synchronization/lock.h"
#include "base/types/pass_key.h"
class AppShimController;
namespace base {
// Keeps track of the parameters of all field trials and ensures access to them
// is thread-safe.
class BASE_EXPORT FieldTrialParamAssociator {
public:
FieldTrialParamAssociator();
FieldTrialParamAssociator(const FieldTrialParamAssociator&) = delete;
FieldTrialParamAssociator& operator=(const FieldTrialParamAssociator&) =
delete;
~FieldTrialParamAssociator();
// Retrieve the singleton.
static FieldTrialParamAssociator* GetInstance();
// Sets parameters for the given field trial name and group.
bool AssociateFieldTrialParams(const std::string& trial_name,
const std::string& group_name,
const FieldTrialParams& params);
// Gets the parameters for a field trial and its chosen group. If not found in
// field_trial_params_, then tries to looks it up in shared memory. Returns
// false if no params are available or the passed |field_trial| is null.
bool GetFieldTrialParams(FieldTrial* field_trial, FieldTrialParams* params);
// Gets the parameters for a field trial and its chosen group. Does not
// fallback to looking it up in shared memory. This should only be used if you
// know for sure the params are in the mapping, like if you're in the browser
// process, and even then you should probably just use GetFieldTrialParams().
bool GetFieldTrialParamsWithoutFallback(const std::string& trial_name,
const std::string& group_name,
FieldTrialParams* params);
// Clears the internal field_trial_params_ mapping, plus removes all params in
// shared memory.
void ClearAllParamsForTesting();
// Clears a single field trial param.
// Note: this does NOT remove the param in shared memory.
void ClearParamsForTesting(const std::string& trial_name,
const std::string& group_name);
// Clears the internal field_trial_params_ mapping.
void ClearAllCachedParamsForTesting();
// Clears the internal field_trial_params_ mapping for use by
// AppShimController when switching over from initial "early access" field
// trial information to the real long-term field trial information.
void ClearAllCachedParams(PassKey<AppShimController>);
private:
friend struct DefaultSingletonTraits<FieldTrialParamAssociator>;
// (field_trial_name, field_trial_group)
using FieldTrialKey = std::pair<std::string, std::string>;
// The following type can be used for lookups without needing to copy strings.
using FieldTrialRefKey = std::pair<const std::string&, const std::string&>;
Lock lock_;
std::map<FieldTrialKey, FieldTrialParams, std::less<>> field_trial_params_;
};
} // namespace base
#endif // BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_
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