97 lines
2.7 KiB
C
97 lines
2.7 KiB
C
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/*
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* Copyright (C) 2017 The Android Open Source Project
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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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* http://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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*/
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#ifndef TNT_UTILS_ENTITY_H
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#define TNT_UTILS_ENTITY_H
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// FIXME: could we get rid of <functional>
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#include <functional> // for std::hash
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#include <stdint.h>
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#include <stddef.h>
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namespace utils {
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class Entity {
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public:
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// this can be used to create an array of to-be-filled entities (see create())
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Entity() noexcept = default;
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// Entities can be copied
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Entity(const Entity& e) noexcept = default;
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Entity(Entity&& e) noexcept = default;
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Entity& operator=(const Entity& e) noexcept = default;
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Entity& operator=(Entity&& e) noexcept = default;
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// Entities can be compared
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bool operator==(Entity e) const { return e.mIdentity == mIdentity; }
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bool operator!=(Entity e) const { return e.mIdentity != mIdentity; }
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// Entities can be sorted
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bool operator<(Entity e) const { return e.mIdentity < mIdentity; }
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bool isNull() const noexcept {
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return mIdentity == 0;
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}
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// an id that can be used for debugging/printing
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uint32_t getId() const noexcept {
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return mIdentity;
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}
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explicit operator bool() const noexcept { return !isNull(); }
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void clear() noexcept { mIdentity = 0; }
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// Exports an entity to an int32_t which can be used "as is" in the Java programing language.
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static int32_t smuggle(Entity entity) noexcept {
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return int32_t(entity.getId());
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}
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// Imports an entity from an int32_t generated by smuggle() above.
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static Entity import(int32_t identity) noexcept {
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return Entity{ Type(identity) };
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}
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private:
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friend class EntityManager;
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friend class EntityManagerImpl;
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friend struct std::hash<Entity>;
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using Type = uint32_t;
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explicit Entity(Type identity) noexcept : mIdentity(identity) { }
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Type mIdentity = 0;
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};
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} // namespace utils
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namespace std {
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template<>
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struct hash<utils::Entity> {
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typedef utils::Entity argument_type;
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typedef size_t result_type;
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result_type operator()(argument_type const& e) const {
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return e.getId();
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}
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};
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} // namespace std
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#endif // TNT_UTILS_ENTITY_H
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