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https://github.com/kidfromjupiter/nearby.git
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93 lines
2.9 KiB
C++
93 lines
2.9 KiB
C++
// Copyright 2020 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef CORE_INTERNAL_MEDIUMS_LOST_ENTITY_TRACKER_H_
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#define CORE_INTERNAL_MEDIUMS_LOST_ENTITY_TRACKER_H_
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#include "absl/container/flat_hash_set.h"
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#include "internal/platform/mutex.h"
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#include "internal/platform/mutex_lock.h"
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namespace nearby {
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namespace connections {
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namespace mediums {
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// Tracks "lost" entities based on a manual update/compute model. Used by
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// mediums that only report found devices. Lost entities are computed based off
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// of whether a specific entity was rediscovered since the last call to
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// ComputeLostEntities.
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//
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// Note: Entity must overload the < and == operators.
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template <typename Entity>
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class LostEntityTracker {
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public:
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using EntitySet = absl::flat_hash_set<Entity>;
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LostEntityTracker();
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~LostEntityTracker();
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// Records the given entity as being recently found, whether or not this is
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// our first time discovering the entity.
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void RecordFoundEntity(const Entity& entity) ABSL_LOCKS_EXCLUDED(mutex_);
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// Computes and returns the set of entities considered lost since the last
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// time this method was called.
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EntitySet ComputeLostEntities() ABSL_LOCKS_EXCLUDED(mutex_);
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private:
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Mutex mutex_;
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EntitySet current_entities_ ABSL_GUARDED_BY(mutex_);
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EntitySet previously_found_entities_ ABSL_GUARDED_BY(mutex_);
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};
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template <typename Entity>
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LostEntityTracker<Entity>::LostEntityTracker()
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: current_entities_{}, previously_found_entities_{} {}
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template <typename Entity>
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LostEntityTracker<Entity>::~LostEntityTracker() {
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previously_found_entities_.clear();
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current_entities_.clear();
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}
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template <typename Entity>
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void LostEntityTracker<Entity>::RecordFoundEntity(const Entity& entity) {
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MutexLock lock(&mutex_);
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current_entities_.insert(entity);
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}
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template <typename Entity>
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typename LostEntityTracker<Entity>::EntitySet
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LostEntityTracker<Entity>::ComputeLostEntities() {
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MutexLock lock(&mutex_);
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// The set of lost entities is the previously found set MINUS the currently
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// found set.
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for (const auto& item : current_entities_) {
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previously_found_entities_.erase(item);
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}
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auto lost_entities = std::move(previously_found_entities_);
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previously_found_entities_ = std::move(current_entities_);
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current_entities_ = {};
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return lost_entities;
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}
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} // namespace mediums
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} // namespace connections
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} // namespace nearby
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#endif // CORE_INTERNAL_MEDIUMS_LOST_ENTITY_TRACKER_H_
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