generic_copier_ptr.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */
#pragma once

#include <stdexcept>
#include <cstdlib>

namespace mrpt
{
namespace utils
{
/** \addtogroup stlext_grp
  * @{ */

namespace internal
{
template <typename T>
struct CopyStatic
{
        T* copy(const T* o)
        {
                if (!o) return nullptr;
                return new T(*o);
        }
};

template <typename T>
struct CopyCloner
{
        T* copy(const T* o)
        {
                if (!o) return nullptr;
                T* n = dynamic_cast<T*>(o->clone());
                if (!n)
                        throw std::runtime_error("error: clone() returned unexpected type");
                return n;
        }
};

template <typename T, typename Copier>
class generic_copier_ptr
{
   public:
        typedef T value_type;
        typedef Copier copier_t;
        /** Ctor from a pointer; takes ownership. */
        explicit generic_copier_ptr(T* ptr) : m_ptr(ptr) {}
        /** Default ctor; init to nullptr. */
        generic_copier_ptr() : m_ptr(nullptr) {}
        /** copy ctor: makes a copy of the object via `clone()` */
        generic_copier_ptr(const generic_copier_ptr<T, Copier>& o)
                : m_ptr(Copier().copy(o.m_ptr))
        {
        }
        ~generic_copier_ptr()
        {
                if (m_ptr) delete m_ptr;
        }

        void move_from(generic_copier_ptr& o)
        {
                m_ptr = o.m_ptr;
                o.m_ptr = nullptr;
        }
        /** move ctor */
        generic_copier_ptr(generic_copier_ptr<T, Copier>&& o)
        {
                m_ptr = o.m_ptr;
                o.m_ptr = nullptr;
        }
        /** move operator */
        generic_copier_ptr<T, Copier>& operator=(generic_copier_ptr<T, Copier>&& o)
        {
                if (this == &o) return *this;
                m_ptr = o.m_ptr;
                o.m_ptr = nullptr;
                return *this;
        }

        /** copy operator */
        generic_copier_ptr<T, Copier>& operator=(
                const generic_copier_ptr<T, Copier>& o)
        {
                if (this == &o) return *this;
                this->reset();
                m_ptr = Copier().copy(o.m_ptr);
                return *this;
        }

        T* operator->()
        {
                if (m_ptr)
                        return m_ptr;
                else
                        throw std::runtime_error("dereferencing nullptr poly_ptr");
        }
        const T* operator->() const
        {
                if (m_ptr)
                        return m_ptr;
                else
                        throw std::runtime_error("dereferencing nullptr poly_ptr");
        }

        T& operator*(void)
        {
                if (m_ptr)
                        return *m_ptr;
                else
                        throw std::runtime_error("dereferencing nullptr poly_ptr");
        }
        const T& operator*(void)const
        {
                if (m_ptr)
                        return *m_ptr;
                else
                        throw std::runtime_error("dereferencing nullptr poly_ptr");
        }

        T* get() { return m_ptr; }
        const T* get() const { return m_ptr; }
        operator bool() const { return m_ptr != nullptr; }
        bool operator!(void)const { return m_ptr == nullptr; }
        /** Releases the pointer (do not destroy the object) */
        T* release()
        {
                T* r = m_ptr;
                m_ptr = nullptr;
                return r;
        }

        void reset(T* ptr = nullptr)
        {
                if (ptr == m_ptr) return;
                if (m_ptr) delete m_ptr;
                m_ptr = ptr;
        }
        void resetDefaultCtor() { this->reset(new T()); }
   protected:
        T* m_ptr;
};

}  // end NS internal

/** Smart pointer for polymorphic classes with a `clone()` method.
  * No shared copies, that is, each `poly_ptr<T>` owns a unique instance of `T`.
  * Copying a `poly_ptr<T>` invokes the copy operator for `T`.
  * \sa copy_ptr<T>
  */
template <typename T>
using poly_ptr = internal::generic_copier_ptr<T, internal::CopyCloner<T>>;

/** Smart pointer for non-polymorphic classes.
* No shared copies, that is, each `copy_ptr<T>` owns a unique instance of `T`.
* Copying a `copy_ptr<T>` invokes the copy operator for `T`.
* \sa poly_ptr<T>
*/
template <typename T>
using copy_ptr = internal::generic_copier_ptr<T, internal::CopyStatic<T>>;

/** @} */  // end of grouping
}  // End of namespace
}  // End of namespace