1 files changed, 259 insertions, 0 deletions
diff --git a/deps/include/entt/resource/resource.hpp b/deps/include/entt/resource/resource.hpp
new file mode 100644
index 0000000..8d73ace
--- /dev/null
+++ b/deps/include/entt/resource/resource.hpp
@@ -0,0 +1,259 @@
+#ifndef ENTT_RESOURCE_RESOURCE_HPP
+#define ENTT_RESOURCE_RESOURCE_HPP
+
+#include <memory>
+#include <type_traits>
+#include <utility>
+#include "fwd.hpp"
+
+namespace entt {
+
+/**
+ * @brief Basic resource handle.
+ *
+ * A handle wraps a resource and extends its lifetime. It also shares the same
+ * resource with all other handles constructed from the same element.<br/>
+ * As a rule of thumb, resources should never be copied nor moved. Handles are
+ * the way to go to push references around.
+ *
+ * @tparam Type Type of resource managed by a handle.
+ */
+template<typename Type>
+class resource {
+    template<typename>
+    friend class resource;
+
+    template<typename Other>
+    static constexpr bool is_acceptable_v = !std::is_same_v<Type, Other> && std::is_constructible_v<Type &, Other &>;
+
+public:
+    /*! @brief Resource type. */
+    using element_type = Type;
+    /*! @brief Handle type. */
+    using handle_type = std::shared_ptr<element_type>;
+
+    /*! @brief Default constructor. */
+    resource() noexcept
+        : value{} {}
+
+    /**
+     * @brief Creates a new resource handle.
+     * @param res A handle to a resource.
+     */
+    explicit resource(handle_type res) noexcept
+        : value{std::move(res)} {}
+
+    /*! @brief Default copy constructor. */
+    resource(const resource &) noexcept = default;
+
+    /*! @brief Default move constructor. */
+    resource(resource &&) noexcept = default;
+
+    /**
+     * @brief Aliasing constructor.
+     * @tparam Other Type of resource managed by the received handle.
+     * @param other The handle with which to share ownership information.
+     * @param res Unrelated and unmanaged resources.
+     */
+    template<typename Other>
+    resource(const resource<Other> &other, element_type &res) noexcept
+        : value{other.value, std::addressof(res)} {}
+
+    /**
+     * @brief Copy constructs a handle which shares ownership of the resource.
+     * @tparam Other Type of resource managed by the received handle.
+     * @param other The handle to copy from.
+     */
+    template<typename Other, typename = std::enable_if_t<is_acceptable_v<Other>>>
+    resource(const resource<Other> &other) noexcept
+        : value{other.value} {}
+
+    /**
+     * @brief Move constructs a handle which takes ownership of the resource.
+     * @tparam Other Type of resource managed by the received handle.
+     * @param other The handle to move from.
+     */
+    template<typename Other, typename = std::enable_if_t<is_acceptable_v<Other>>>
+    resource(resource<Other> &&other) noexcept
+        : value{std::move(other.value)} {}
+
+    /*! @brief Default destructor. */
+    ~resource() noexcept = default;
+
+    /**
+     * @brief Default copy assignment operator.
+     * @return This resource handle.
+     */
+    resource &operator=(const resource &) noexcept = default;
+
+    /**
+     * @brief Default move assignment operator.
+     * @return This resource handle.
+     */
+    resource &operator=(resource &&) noexcept = default;
+
+    /**
+     * @brief Copy assignment operator from foreign handle.
+     * @tparam Other Type of resource managed by the received handle.
+     * @param other The handle to copy from.
+     * @return This resource handle.
+     */
+    template<typename Other, typename = std::enable_if_t<is_acceptable_v<Other>>>
+    resource &operator=(const resource<Other> &other) noexcept {
+        value = other.value;
+        return *this;
+    }
+
+    /**
+     * @brief Move assignment operator from foreign handle.
+     * @tparam Other Type of resource managed by the received handle.
+     * @param other The handle to move from.
+     * @return This resource handle.
+     */
+    template<typename Other, typename = std::enable_if_t<is_acceptable_v<Other>>>
+    resource &operator=(resource<Other> &&other) noexcept {
+        value = std::move(other.value);
+        return *this;
+    }
+
+    /**
+     * @brief Returns a reference to the managed resource.
+     *
+     * @warning
+     * The behavior is undefined if the handle doesn't contain a resource.
+     *
+     * @return A reference to the managed resource.
+     */
+    [[nodiscard]] element_type &operator*() const noexcept {
+        return *value;
+    }
+
+    /*! @copydoc operator* */
+    [[nodiscard]] operator element_type &() const noexcept {
+        return *value;
+    }
+
+    /**
+     * @brief Returns a pointer to the managed resource.
+     * @return A pointer to the managed resource.
+     */
+    [[nodiscard]] element_type *operator->() const noexcept {
+        return value.get();
+    }
+
+    /**
+     * @brief Returns true if a handle contains a resource, false otherwise.
+     * @return True if the handle contains a resource, false otherwise.
+     */
+    [[nodiscard]] explicit operator bool() const noexcept {
+        return static_cast<bool>(value);
+    }
+
+    /*! @brief Releases the ownership of the managed resource. */
+    void reset() {
+        value.reset();
+    }
+
+    /**
+     * @brief Replaces the managed resource.
+     * @param other A handle to a resource.
+     */
+    void reset(handle_type other) {
+        value = std::move(other);
+    }
+
+    /**
+     * @brief Returns the underlying resource handle.
+     * @return The underlying resource handle.
+     */
+    [[nodiscard]] const handle_type &handle() const noexcept {
+        return value;
+    }
+
+private:
+    handle_type value;
+};
+
+/**
+ * @brief Compares two handles.
+ * @tparam Lhs Type of resource managed by the first handle.
+ * @tparam Rhs Type of resource managed by the second handle.
+ * @param lhs A valid handle.
+ * @param rhs A valid handle.
+ * @return True if both handles refer to the same resource, false otherwise.
+ */
+template<typename Lhs, typename Rhs>
+[[nodiscard]] bool operator==(const resource<Lhs> &lhs, const resource<Rhs> &rhs) noexcept {
+    return (std::addressof(*lhs) == std::addressof(*rhs));
+}
+
+/**
+ * @brief Compares two handles.
+ * @tparam Lhs Type of resource managed by the first handle.
+ * @tparam Rhs Type of resource managed by the second handle.
+ * @param lhs A valid handle.
+ * @param rhs A valid handle.
+ * @return False if both handles refer to the same resource, true otherwise.
+ */
+template<typename Lhs, typename Rhs>
+[[nodiscard]] bool operator!=(const resource<Lhs> &lhs, const resource<Rhs> &rhs) noexcept {
+    return !(lhs == rhs);
+}
+
+/**
+ * @brief Compares two handles.
+ * @tparam Lhs Type of resource managed by the first handle.
+ * @tparam Rhs Type of resource managed by the second handle.
+ * @param lhs A valid handle.
+ * @param rhs A valid handle.
+ * @return True if the first handle is less than the second, false otherwise.
+ */
+template<typename Lhs, typename Rhs>
+[[nodiscard]] bool operator<(const resource<Lhs> &lhs, const resource<Rhs> &rhs) noexcept {
+    return (std::addressof(*lhs) < std::addressof(*rhs));
+}
+
+/**
+ * @brief Compares two handles.
+ * @tparam Lhs Type of resource managed by the first handle.
+ * @tparam Rhs Type of resource managed by the second handle.
+ * @param lhs A valid handle.
+ * @param rhs A valid handle.
+ * @return True if the first handle is greater than the second, false otherwise.
+ */
+template<typename Lhs, typename Rhs>
+[[nodiscard]] bool operator>(const resource<Lhs> &lhs, const resource<Rhs> &rhs) noexcept {
+    return rhs < lhs;
+}
+
+/**
+ * @brief Compares two handles.
+ * @tparam Lhs Type of resource managed by the first handle.
+ * @tparam Rhs Type of resource managed by the second handle.
+ * @param lhs A valid handle.
+ * @param rhs A valid handle.
+ * @return True if the first handle is less than or equal to the second, false
+ * otherwise.
+ */
+template<typename Lhs, typename Rhs>
+[[nodiscard]] bool operator<=(const resource<Lhs> &lhs, const resource<Rhs> &rhs) noexcept {
+    return !(lhs > rhs);
+}
+
+/**
+ * @brief Compares two handles.
+ * @tparam Lhs Type of resource managed by the first handle.
+ * @tparam Rhs Type of resource managed by the second handle.
+ * @param lhs A valid handle.
+ * @param rhs A valid handle.
+ * @return True if the first handle is greater than or equal to the second,
+ * false otherwise.
+ */
+template<typename Lhs, typename Rhs>
+[[nodiscard]] bool operator>=(const resource<Lhs> &lhs, const resource<Rhs> &rhs) noexcept {
+    return !(lhs < rhs);
+}
+
+} // namespace entt
+
+#endif