ref_or_owned.h

/**************************************************************************/
/*                                                                        */
/*  DF-0: Data processing Framework with Zero-overhead                    */
/*                                                                        */
/*  Copyright (c) DF-0 Team               https://github.com/df0-io/df0   */
/*  SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-DF0-Commercial   */
/*                                                                        */
/**************************************************************************/
 
#ifndef DF0_REF_OR_OWNED_H
#define DF0_REF_OR_OWNED_H
 
#include <memory>
#include <type_traits>
 
namespace df0
{
 
template<typename U, typename T>
concept ref_or_owned_compatible = std::is_convertible_v<std::shared_ptr<std::remove_reference_t<U>>, std::shared_ptr<T>>;

template <typename T>
class ref_or_owned
{
  static_assert(!std::is_reference<T>::value, "ref_or_owned<T> cannot be instantiated with a reference type");
  static_assert(!std::is_void<T>::value, "ref_or_owned<T> cannot be instantiated with void type");
 
public:
  ref_or_owned(ref_or_owned<T>&& other) noexcept
    : v{other.to_shared_ptr()}
  {}
 
  ref_or_owned(const ref_or_owned<T>& other)
    : v{other.to_shared_ptr()}
  {}

  ref_or_owned& operator=(const ref_or_owned<T>& other) {
    v = other.v;
    return *this;
  }

  ref_or_owned& operator=(ref_or_owned<T>&& other) noexcept {
    v = std::move(other.v);
    return *this;
  }

  template<ref_or_owned_compatible<T> U>
  ref_or_owned(U& value)
    : v{std::shared_ptr<T>{&value, [](auto*) {}}}
  {}

  template<ref_or_owned_compatible<T> U>
  ref_or_owned(U&& value)
    : v{std::make_shared<std::remove_reference_t<U>>(std::forward<U>(value))}
  {}
 
  template<ref_or_owned_compatible<T> U>
  ref_or_owned(std::shared_ptr<U> ptr)
    : v{ptr}
  {}

  const T& get() const {
    return *v;
  }

  T& get() {
    return *v;
  }
 
  std::shared_ptr<T> to_shared_ptr() const
  {
    return v;
  }
 
private:
  std::shared_ptr<T> v;
};
 
} // namespace df0
 
#endif //DF0_REF_OR_OWNED_H