internal.h

/*
    SPDX-FileCopyrightText: 2020 Volker Krause <vkrause@kde.org>
 
    SPDX-License-Identifier: LGPL-2.0-or-later
*/
 
#ifndef OSM_INTERNAL_H
#define OSM_INTERNAL_H
 
#include <cstdint>
 
namespace OSM {
 
namespace Internal {
/** Pointer with the lower bits used for compact flag storage. */
template <typename T> class TaggedPointer
{
public:
    explicit inline constexpr TaggedPointer() = default;
    explicit inline constexpr TaggedPointer(T *ptr, uint8_t tag)
        : m_data(reinterpret_cast<std::uintptr_t>(ptr) | (tag & TagMask))
    {}
 
    [[nodiscard]] constexpr inline T* get() const { return reinterpret_cast<T*>(m_data & ~TagMask); }
    constexpr inline void set(T *data) { m_data = (m_data & TagMask) | (reinterpret_cast<std::uintptr_t>(data) & ~TagMask); }
    [[nodiscard]] constexpr inline uint8_t tag() const { return m_data & TagMask; }
    constexpr inline void setTag(uint8_t tag) { m_data = (tag & TagMask) | (m_data & ~TagMask); }
    [[nodiscard]] constexpr inline operator bool() const { return (m_data & ~TagMask); }
    [[nodiscard]] constexpr inline bool operator==(TaggedPointer<T> other) const { return m_data == other.m_data; }
    [[nodiscard]] constexpr inline bool operator!=(TaggedPointer<T> other) const { return m_data != other.m_data; }
    [[nodiscard]] constexpr inline bool operator<(TaggedPointer<T> other) const { return m_data < other.m_data; }
 
private:
    enum { TagMask = 0x3 };
    std::uintptr_t m_data = 0;
};
 
}
}
 
#endif