free_list.h

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/*
 * free_list.h
 *
 * Copyright (C) 2010   Thomas A. Vaughan
 * All rights reserved.
 *
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the <organization> nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THOMAS A. VAUGHAN ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THOMAS A. VAUGHAN BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * Template for a free list of objects
 */

#ifndef WAVEPACKET_UTIL_FREE_LIST_H__
#define WAVEPACKET_UTIL_FREE_LIST_H__

// includes --------------------------------------------------------------------
#include "common/common.h"
#include "threadsafe/smart_ptr.h"


/// \ingroup util
///
/// Simple free list manager.  Your class T must have a public 'next' member.
/// The 'next' member MUST be a smart_ptr<T>.
template <class T>
class free_list_t {
public:
        // constructor ---------------------------------------------------------
        free_list_t(IN int maxSize) throw() {
                        ASSERT(maxSize > 0, "Bad maximum size: %d", maxSize);
                        m_max = maxSize;
                        m_size = 0;
                }

        ~free_list_t(void) throw() { this->clear(); }

        // free_list_t - public class methods ----------------------------------
        smart_ptr<T> getElement(void) {
                        smart_ptr<T> retval;
                        if (m_head) {
                                retval = m_head;
                                m_head = retval->next;
                                retval->next = NULL;
                                --m_size;
                        } else {
                                retval = new T;
                                ASSERT(retval,
                                    "Failed to allocate from free_list_t");
                                retval->next = NULL;
                        }
                        return retval;
                }

        void returnElement(IN smart_ptr<T>& p) throw() {
                        ASSERT(p, "returning null object to free_list_t");
                        ASSERT(!p->next, "canot return list to free_list_t");
                        if (m_size >= m_max) {
                                p = NULL;       // just delete outright
                        } else {
                                // add p to head of list
                                p->next = m_head;
                                m_head = p;
                                ++m_size;
                        }
                }

        void clear(void) throw() {
                        m_head = NULL;
                        m_size = 0;
                }

        int size(void) const throw() { return m_size; }

private:
        // private member data -------------------------------------------------
        smart_ptr<T>            m_head;
        int                     m_size;
        int                     m_max;
};



#endif  // WAVEPACKET_UTIL_FREE_LIST_H__