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106 lines
3.0 KiB
106 lines
3.0 KiB
#ifndef ENTT_RESOURCE_HANDLE_HPP
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#define ENTT_RESOURCE_HANDLE_HPP
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#include <memory>
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#include <utility>
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#include "../config/config.h"
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#include "fwd.hpp"
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namespace entt {
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/**
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* @brief Shared resource handle.
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*
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* A shared resource handle is a small class that wraps a resource and keeps it
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* alive even if it's deleted from the cache. It can be either copied or
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* moved. A handle shares a reference to the same resource with all the other
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* handles constructed for the same identifier.<br/>
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* As a rule of thumb, resources should never be copied nor moved. Handles are
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* the way to go to keep references to them.
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*
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* @tparam Resource Type of resource managed by a handle.
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*/
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template<typename Resource>
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class resource_handle {
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/*! @brief Resource handles are friends of their caches. */
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friend class resource_cache<Resource>;
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resource_handle(std::shared_ptr<Resource> res) ENTT_NOEXCEPT
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: resource{std::move(res)}
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{}
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public:
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/*! @brief Default constructor. */
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resource_handle() ENTT_NOEXCEPT = default;
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/**
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* @brief Gets a reference to the managed resource.
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*
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* @warning
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* The behavior is undefined if the handle doesn't contain a resource.<br/>
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* An assertion will abort the execution at runtime in debug mode if the
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* handle is empty.
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*
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* @return A reference to the managed resource.
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*/
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const Resource & get() const ENTT_NOEXCEPT {
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ENTT_ASSERT(static_cast<bool>(resource));
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return *resource;
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}
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/*! @copydoc get */
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Resource & get() ENTT_NOEXCEPT {
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return const_cast<Resource &>(std::as_const(*this).get());
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}
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/*! @copydoc get */
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inline operator const Resource & () const ENTT_NOEXCEPT { return get(); }
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/*! @copydoc get */
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inline operator Resource & () ENTT_NOEXCEPT { return get(); }
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/*! @copydoc get */
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inline const Resource & operator *() const ENTT_NOEXCEPT { return get(); }
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/*! @copydoc get */
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inline Resource & operator *() ENTT_NOEXCEPT { return get(); }
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/**
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* @brief Gets a pointer to the managed resource.
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*
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* @warning
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* The behavior is undefined if the handle doesn't contain a resource.<br/>
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* An assertion will abort the execution at runtime in debug mode if the
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* handle is empty.
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*
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* @return A pointer to the managed resource or `nullptr` if the handle
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* contains no resource at all.
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*/
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inline const Resource * operator->() const ENTT_NOEXCEPT {
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ENTT_ASSERT(static_cast<bool>(resource));
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return resource.get();
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}
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/*! @copydoc operator-> */
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inline Resource * operator->() ENTT_NOEXCEPT {
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return const_cast<Resource *>(std::as_const(*this).operator->());
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}
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/**
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* @brief Returns true if a handle contains a resource, false otherwise.
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* @return True if the handle contains a resource, false otherwise.
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*/
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explicit operator bool() const { return static_cast<bool>(resource); }
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private:
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std::shared_ptr<Resource> resource;
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};
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}
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#endif // ENTT_RESOURCE_HANDLE_HPP
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