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// Copyright 2020 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_VARIATIONS_LAYERS_H_
#define COMPONENTS_VARIATIONS_VARIATIONS_LAYERS_H_
#include <map>
#include "base/component_export.h"
#include "base/metrics/field_trial.h"
#include "components/variations/entropy_provider.h"
#include "components/variations/proto/variations_seed.pb.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
namespace variations {
// A view over the layers defined within a variations seed.
//
// A layer defines a collection of mutually exclusive members. For each client,
// at most one member will be assigned as its active member. Studies may be
// conditioned on a particular member being active, in order to avoid overlap
// with studies that require a different member to be active.
class COMPONENT_EXPORT(VARIATIONS) VariationsLayers {
public:
VariationsLayers(const VariationsSeed& seed,
const EntropyProviders& entropy_providers);
VariationsLayers();
~VariationsLayers();
VariationsLayers(const VariationsLayers&) = delete;
VariationsLayers& operator=(const VariationsLayers&) = delete;
// Returns whether the given layer has the given member active.
bool IsLayerMemberActive(uint32_t layer_id, uint32_t member_id) const;
// Returns true if the layer has an active member and is configured to use
// DEFAULT entropy, which means that any study conditioned on it would leak
// information about the client's high entropy source (including whether or
// not the client _has_ a high entropy source).
bool ActiveLayerMemberDependsOnHighEntropy(uint32_t layer_id) const;
private:
void ConstructLayer(const EntropyProviders& entropy_providers,
const Layer& layer_proto);
struct LayerInfo {
// Which layer member is active in the layer.
uint32_t active_member_id;
// The type of entropy the layer was configured to use.
Layer::EntropyMode entropy_mode;
};
std::map<uint32_t, LayerInfo> active_member_for_layer_;
};
} // namespace variations
#endif // COMPONENTS_VARIATIONS_VARIATIONS_LAYERS_H_
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