MakeUniqueHelper.h

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/*******************************************************************************
 * Copyright (c) The JETSCAPE Collaboration, 2018
 *
 * Modular, task-based framework for simulating all aspects of heavy-ion collisions
 * 
 * For the list of contributors see AUTHORS.
 *
 * Report issues at https://github.com/JETSCAPE/JETSCAPE/issues
 *
 * or via email to bugs.jetscape@gmail.com
 *
 * Distributed under the GNU General Public License 3.0 (GPLv3 or later).
 * See COPYING for details.
 ******************************************************************************/

/*******************************************************************************
 * Allow C++14 style make_unique for C++11
 * Taken from STL's solution,
 * https://isocpp.org/files/papers/N3656.txt
 ******************************************************************************/

#ifndef MAKEUNIQUEHELPER_H
#define MAKEUNIQUEHELPER_H

#include <cstddef>
#include <memory>
#include <type_traits>
#include <utility>

namespace Jetscape {
template <class T> struct _Unique_if {
  typedef std::unique_ptr<T> _Single_object;
};

template <class T> struct _Unique_if<T[]> {
  typedef std::unique_ptr<T[]> _Unknown_bound;
};

template <class T, size_t N> struct _Unique_if<T[N]> {
  typedef void _Known_bound;
};

template <class T, class... Args>
typename _Unique_if<T>::_Single_object make_unique(Args &&... args) {
  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
}

template <class T>
typename _Unique_if<T>::_Unknown_bound make_unique(size_t n) {
  typedef typename std::remove_extent<T>::type U;
  return std::unique_ptr<T>(new U[n]());
}

template <class T, class... Args>
typename _Unique_if<T>::_Known_bound make_unique(Args &&...) = delete;

// check whether a weak pointer is initialized or not
template <typename T>
bool weak_ptr_is_uninitialized(std::weak_ptr<T> const &weak) {
  using wt = std::weak_ptr<T>;
  return !weak.owner_before(wt{}) && !wt{}.owner_before(weak);
}

} // namespace Jetscape

#endif // MAKEUNIQUEHELPER_H