PoolPointer.h

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/******************************************************************************
 * Project:  libspatialindex - A C++ library for spatial indexing
 * Author:   Marios Hadjieleftheriou, mhadji@gmail.com
 ******************************************************************************
 * Copyright (c) 2004, Marios Hadjieleftheriou
 *
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
******************************************************************************/

#pragma once

#include "PointerPool.h"

namespace Tools
{
    template <class X> class PointerPool;

    template <class X> class PoolPointer
    {
    public:
        explicit PoolPointer(X* p = nullptr) : m_pointer(p), m_pPool(nullptr) { m_prev = m_next = this; }
        explicit PoolPointer(X* p, PointerPool<X>* pPool) noexcept : m_pointer(p), m_pPool(pPool) { m_prev = m_next = this; }
        ~PoolPointer() { release(); }
        PoolPointer(const PoolPointer& p) noexcept { acquire(p); }
        PoolPointer& operator=(const PoolPointer& p)
        {
            if (this != &p)
            {
                release();
                acquire(p);
            }
            return *this;
        }

        X& operator*() const noexcept { return *m_pointer; }
        X* operator->() const noexcept { return m_pointer; }
        X* get() const noexcept { return m_pointer; }
        bool unique() const noexcept { return m_prev ? m_prev == this : true; }
        void relinquish() noexcept
        {
            m_pPool = nullptr;
            m_pointer = nullptr;
            release();
        }

    private:
        X* m_pointer;
        mutable const PoolPointer* m_prev;
        mutable const PoolPointer* m_next;
        PointerPool<X>* m_pPool;

        void acquire(const PoolPointer& p) noexcept
        {
            m_pPool = p.m_pPool;
            m_pointer = p.m_pointer;
            m_next = p.m_next;
            m_next->m_prev = this;
            m_prev = &p;
            #ifndef mutable
            p.m_next = this;
            #else
            (const_cast<linked_ptr<X>*>(&p))->m_next = this;
            #endif
        }

        void release()
        {
            if (unique())
            {
                if (m_pPool != nullptr) m_pPool->release(m_pointer);
                else delete m_pointer;
            }
            else
            {
                m_prev->m_next = m_next;
                m_next->m_prev = m_prev;
                m_prev = m_next = nullptr;
            }
            m_pointer = nullptr;
            m_pPool = nullptr;
        }
    };
}