cpp-descriptive-pointers/include/pointers/const_propogating_ptr.hpp

//
//  const_propogating_ptr.hpp
//  pointers
//
//  Created by Sam Jaffe on 12/3/16.
//

#pragma once
#include <memory>

#include "detail/compare.hpp"
#include "detail/get_ptr.hpp"
#include "pointer_fwd.hpp"

template <typename P>
class const_propogating_ptr
    : private detail::get_ptr<P>,
      public detail::pointer_compare<const_propogating_ptr<P>> {
public:
  using element_type = typename std::pointer_traits<P>::element_type;
  using pointer = element_type *;
  using reference = element_type &;
  using const_pointer = element_type const *;
  using const_reference = element_type const &;

  const_propogating_ptr() noexcept : _ptr() {}
  const_propogating_ptr(P const & p) noexcept(
      std::is_nothrow_copy_constructible<P>::value)
      : _ptr(p) {}
  const_propogating_ptr(P && p) noexcept(
      std::is_nothrow_move_constructible<P>::value)
      : _ptr(std::move(p)) {}
  template <typename Y, typename = typename std::enable_if<
                            std::is_constructible<P, Y>::value>::type>
  const_propogating_ptr(Y const & p) : _ptr(p) {}
  template <typename Y, typename = typename std::enable_if<
                            std::is_constructible<P, Y>::value>::type>
  const_propogating_ptr(Y && p) : _ptr(std::forward<Y>(p)) {}

  const_propogating_ptr(const_propogating_ptr &) noexcept(
      std::is_nothrow_copy_constructible<P>::value) = default;
  const_propogating_ptr(const_propogating_ptr &&) noexcept(
      std::is_nothrow_move_constructible<P>::value) = default;
  const_propogating_ptr(const_propogating_ptr const &) = delete;
  const_propogating_ptr & operator=(const_propogating_ptr &) noexcept(
      std::is_nothrow_copy_assignable<P>::value) = default;
  const_propogating_ptr & operator=(const_propogating_ptr &&) noexcept(
      std::is_nothrow_move_assignable<P>::value) = default;
  const_propogating_ptr & operator=(const_propogating_ptr const &) = delete;

  template <typename Y>
      explicit operator const_propogating_ptr<Y>() &
      noexcept(std::is_nothrow_constructible<P, Y>::value) {
    return _ptr;
  }

  template <typename Y>
  explicit operator const_ptr<Y>() const
      noexcept(std::is_nothrow_constructible<P, Y>::value) {
    return _ptr;
  }

  template <typename Y>
  explicit operator const_propogating_ptr<Y>() const & = delete;

  operator bool() const noexcept { return static_cast<bool>(_ptr); }

  reference operator*() noexcept(noexcept(*_ptr)) { return *_ptr; }
  pointer get() noexcept(noexcept(detail::get_ptr<P>::get(_ptr))) {
    return detail::get_ptr<P>::get(_ptr);
  }
  pointer operator->() noexcept(noexcept(get())) { return get(); }

  const_reference operator*() const noexcept(noexcept(*_ptr)) { return *_ptr; }
  const_pointer get() const noexcept(noexcept(detail::get_ptr<P>::get(_ptr))) {
    return detail::get_ptr<P>::get(_ptr);
  }
  const_pointer operator->() const noexcept(noexcept(get())) { return get(); }

private:
  P _ptr;
};