guard_ptr.hpp

//
// Copyright (c) 2018-2020 Manuel Pöter.
// Licensed under the MIT License. See LICENSE file in the project root for full license information.
//
 
#ifndef XENIUM_DETAL_GUARD_PTR_HPP
#define XENIUM_DETAL_GUARD_PTR_HPP
 
#include <utility>
 
namespace xenium::reclamation::detail {
 
template <class T, class MarkedPtr, class Derived>
class guard_ptr {
public:
  ~guard_ptr() { self().reset(); }
 
  // Get underlying pointer
  [[nodiscard]] T* get() const noexcept { return ptr.get(); }
 
  // Get mark bits
  [[nodiscard]] uintptr_t mark() const noexcept { return ptr.mark(); }
 
  operator MarkedPtr() const noexcept { return ptr; } // NOLINT (explicit)
 
  // True if get() != nullptr || mark() != 0
  explicit operator bool() const noexcept { return static_cast<bool>(ptr); }
 
  // Get pointer with mark bits stripped off. Undefined if target has been reclaimed.
  T* operator->() const noexcept { return ptr.get(); }
 
  // Get reference to target of pointer. Undefined if target has been reclaimed.
  T& operator*() const noexcept { return *ptr; }
 
  // Swap two guards
  void swap(Derived& g) noexcept {
    std::swap(ptr, g.ptr);
    self().do_swap(g);
  }
 
protected:
  // NOLINTNEXTLINE (explicit-constructor)
  guard_ptr(const MarkedPtr& p = MarkedPtr{}) noexcept : ptr(p) {}
  MarkedPtr ptr;
 
  void do_swap(Derived&) noexcept {} // empty dummy
 
private:
  Derived& self() { return static_cast<Derived&>(*this); }
};
} // namespace xenium::reclamation::detail
 
#endif