handle.hpp

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#pragma once
 
#include "core/forward.hpp"

 
#include <cstddef>
#include <cstdint>
#include <functional>
 
namespace pgl {
 
namespace detail {

template <class Tag>
class Handle {
public:
    using IndexType = std::uint32_t;

    constexpr Handle() = default;

    constexpr explicit Handle(IndexType index) : index_(index) {}

    [[nodiscard]] constexpr IndexType index() const {
        return index_;
    }

    [[nodiscard]] constexpr bool valid() const {
        return index_ != invalidIndex;
    }

    constexpr explicit operator bool() const {
        return valid();
    }

    constexpr bool operator==(const Handle&) const = default;

    constexpr auto operator<=>(const Handle&) const = default;
 
private:
    static constexpr IndexType invalidIndex = ~IndexType{};
    IndexType index_ = invalidIndex;
};
 
}  // namespace detail
 
}  // namespace pgl
 
namespace std {

template <class Tag>
struct hash<pgl::detail::Handle<Tag>> {
    std::size_t operator()(const pgl::detail::Handle<Tag>& handle) const noexcept {
        return std::hash<std::uint32_t>{}(handle.index());
    }
};
 
}  // namespace std