Ref.h

/*
 * Gamedev Framework (gf)
 * Copyright (C) 2016-2022 Julien Bernard
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */
#ifndef GF_REF_H
#define GF_REF_H
 
#include <memory>
#include <type_traits>
 
namespace gf {
#ifndef DOXYGEN_SHOULD_SKIP_THIS
inline namespace v1 {
#endif
 
  template<typename T>
  class Ref {
  public:
    Ref(T& ref) noexcept
    : m_ptr(std::addressof(ref))
    {
 
    }
 
    Ref(T&&) = delete;
 
    Ref(const Ref& other) noexcept = default;
 
    template<typename U, typename = std::enable_if_t<std::is_base_of<T, U>::value>>
    Ref(const Ref<U>& other) noexcept
    : m_ptr(std::addressof(other.get()))
    {
    }
 
    Ref& operator=(const Ref& other) noexcept = default;
 
    template<typename U, typename = std::enable_if_t<std::is_base_of<T, U>::value>>
    Ref& operator=(const Ref<U>& other) noexcept {
      m_ptr = std::addressof(other.get());
    }
 
    T& get() const noexcept {
      return *m_ptr;
    }
 
    operator T& () const noexcept {
      return *m_ptr;
    }
 
  private:
    T *m_ptr;
  };
 
  template<typename T>
  constexpr bool operator==(Ref<T> lhs, Ref<T> rhs) noexcept {
    return std::addressof(lhs.get()) == std::addressof(rhs.get());
  }
 
  template<typename T>
  constexpr bool operator==(Ref<T> lhs, const T& rhs) noexcept {
    return std::addressof(lhs.get()) == std::addressof(rhs);
  }
 
  template<typename T>
  constexpr bool operator==(const T& lhs, Ref<T> rhs) noexcept {
    return std::addressof(lhs) == std::addressof(rhs.get());
  }
 
  template<typename T>
  Ref<T> ref(T& object) {
    return Ref<T>(object);
  }
 
#ifndef DOXYGEN_SHOULD_SKIP_THIS
  template<typename T>
  Ref<T> ref(const T&&) = delete;
#endif
 
#ifndef DOXYGEN_SHOULD_SKIP_THIS
}
#endif
}
 
#endif // GF_REF_H