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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_VARIATIONS_LIMITED_LAYER_ENTROPY_COST_TRACKER_H_
#define COMPONENTS_VARIATIONS_LIMITED_LAYER_ENTROPY_COST_TRACKER_H_
#include <cstdint>
#include <map>
#include <set>
#include "base/component_export.h"
#include "base/gtest_prod_util.h"
namespace variations {
class Study;
class VariationsLayers;
class VariationsSeed;
// Provides methods to calculate and monitor the total entropy used by studies
// assigned to a limited layer.
class COMPONENT_EXPORT(VARIATIONS) LimitedLayerEntropyCostTracker {
public:
LimitedLayerEntropyCostTracker(const VariationsLayers& layers,
const VariationsSeed& seed,
double entropy_limit_in_bits);
~LimitedLayerEntropyCostTracker();
LimitedLayerEntropyCostTracker(const LimitedLayerEntropyCostTracker&) =
delete;
LimitedLayerEntropyCostTracker& operator=(
const LimitedLayerEntropyCostTracker&) = delete;
// Calculates the entropy used by the study and adds it to the total entropy
// used by the layer. This method returns true if there is enough entropy
// remaining to handle the study assignment or if the study does not consume
// entropy on the limited layer.
bool TryAddEntropyUsedByStudy(const Study& study);
// Returns the total entropy used by studies currently assigned to the limited
// layer.
double GetTotalEntropyUsedForTesting();
// Returns true if the total entropy currently used by the limited layer is
// over the allowed entropy limit.
bool IsEntropyLimitReached() const { return entropy_limit_reached_; }
private:
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_WithNoLimitedLayer);
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_WithNonLimitedEntropyMode);
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_WithNoLayerMembers);
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_WithManyLimitedLayers);
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_WithMisconfiguredLimitedLayer);
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_WithLimitedLayer);
FRIEND_TEST_ALL_PREFIXES(LimitedLayerEntropyCostTrackerTest,
TestConstructor_LayerMembersUsingEntropyAboveLimit);
static constexpr uint64_t kInvalidLayerId = 0;
// Id of the active limited layer for this client. A layer is "active" for a
// client if the client's slot for that layer is associated with a layer
// member.
uint32_t active_limited_layer_id_ = kInvalidLayerId;
const double entropy_limit_in_bits_;
bool includes_entropy_used_by_studies_ = false;
bool entropy_limit_reached_ = false;
// Entropy used by each layer member keyed by its ID. Using uint32_t as the
// key type since the ID of a layer member proto is a uint32_t.
std::map<uint32_t, double> entropy_used_by_layer_members_;
// Contains the Ids of all limited layers in the seed. This field is used in
// `TryAddEntropyUsedByStudy` to check if a study references a limited layer
// because the Study class does not contain enough information to perform that
// check.
// TODO(siakabaro): If a study references a layer, cache the layer information
// in the ProcessedStudy class and update `TryAddEntropyUsedByStudy` to take a
// ProcessedStudy object as input instead of a Study object. Remove this field
// after the update.
std::set<uint32_t> limited_layers_ids_;
};
} // namespace variations
#endif // COMPONENTS_VARIATIONS_LIMITED_LAYER_ENTROPY_COST_TRACKER_H_
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