/*
 * This file is part of libgim.
 *
 * libgim is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Copyright 2011 Danny Robson <danny@blubinc.net>
 */

#ifndef __UTIL_POOL_HPP
#define __UTIL_POOL_HPP

#include "nocopy.hpp"

namespace util {
template <typename T>
    class pool : public nocopy {
        protected:
            union node {
                char  _data[sizeof (T)];
                node *_chain;
            };

            node         *m_head;
            node         *m_next;
            unsigned int  m_capacity;

        public:
            pool (unsigned int _capacity):
                m_capacity (_capacity)
            {
                static_assert (sizeof (T) >= sizeof (uintptr_t),
                               "pool<T>'s chained block system requires that T be at least pointer sized");

                m_head = (node *)operator new (sizeof (T) * m_capacity);
                m_next = m_head;

                for (unsigned int i = 0; i < m_capacity - 1; ++i)
                    m_next[i]._chain = &m_next[i + 1];
                m_next[m_capacity - 1]._chain = NULL;
            }


            ~pool () {
                check (m_next != NULL);

                unsigned int doomed_count = 0;
                for (node *cursor = m_next; cursor != NULL; cursor = cursor->_chain)
                    ++doomed_count;

                check_eq (doomed_count, m_capacity);
                operator delete (m_head);
            }
            

            unsigned int capacity (void) const
                { return m_capacity; }


            template <typename ...Args>
            T*   acquire (Args&... args) {
                if (!m_next)
                    throw std::bad_alloc ();

                node *newnext = m_next->_chain;
                T *data = (T*)&m_next->_data;
                
                try {
                    new (data) T (args...);
                } catch (...) {
                    m_next->_chain = newnext;
                    throw;
                }

                m_next  = newnext;
                return data;
            }


            void release (T *data) {
                data->~T();
                node *newnode = (node *)data;

                newnode->_chain = m_next;
                m_next = newnode;
            }
    };
}

#endif // __UTIL_POOL_HPP