SingleItemBuffer.h

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/* ============================================================
 *
 * This file is a part of CCA project
 *
 * Copyright (C) 2011 by Arne Nordmann <anordman at cor-lab dot uni-bielefeld dot de>
 *
 * This file may be licensed under the terms of the
 * GNU Lesser General Public License Version 3 (the ``LGPL''),
 * or (at your option) any later version.
 *
 * Software distributed under the License is distributed
 * on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
 * express or implied. See the LGPL for the specific language
 * governing rights and limitations.
 *
 * You should have received a copy of the LGPL along with this
 * program. If not, go to http://www.gnu.org/licenses/lgpl.html
 * or write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The development of this software was supported by:
 *   CoR-Lab, Research Institute for Cognition and Robotics
 *     Bielefeld University
 *
 * ============================================================ */

#pragma once

#include <string>
#include <sstream>
#include <iostream>
#include <exception>

#include <boost/thread/recursive_mutex.hpp>

#include "cca/buffer/Buffer.h"

namespace cca {

template<class DATATYPE>
class SingleItemBuffer: public Buffer<DATATYPE> {
public:

    typedef ::boost::shared_ptr<SingleItemBuffer<DATATYPE> > Ptr;

    typedef ::boost::shared_ptr<DATATYPE> DataPtr;

    SingleItemBuffer(bool alwaysKeepLatest = true) :
            Buffer<DATATYPE>(alwaysKeepLatest), _buffer(), bufferMutex() {
    }

    virtual ~SingleItemBuffer() {
    }

    std::string print() const {
        std::ostringstream outstream(std::ostringstream::out);
        outstream.precision(3); // Precision when printing double values
        outstream << "SingleItemBuffer";
        if (this->keepLatest) {
            outstream << ", keep latest";
            if (this->warm) {
                outstream << " (warm)";
            } else {
                outstream << " (cold)";
            }
        }
        if (this->newItem()) {
            outstream << ", 1 new item";
        }
        return outstream.str();
    }

    virtual DataPtr get() throw () {
        boost::recursive_mutex::scoped_lock scoped_lock(bufferMutex);
        if (this->keepLatest && this->warm) {
            this->numItems = 0;
            this->newitem = false;
            return _buffer;
        }

        if (this->empty()) {
            throw std::runtime_error("Single Item Buffer is empty.");
        }

        DataPtr item = this->_buffer;
        this->_buffer = DataPtr();
        this->numItems = 0;
        this->newitem = false;
        return item;
    }

    virtual void add(DataPtr item) {
        boost::recursive_mutex::scoped_lock scoped_lock(bufferMutex);
        this->_buffer = item;
        this->numItems = 1;
        this->newitem = true;
        this->warm = true;
    }

    virtual void purge() {
        boost::recursive_mutex::scoped_lock scoped_lock(bufferMutex);
        this->_buffer = DataPtr();
        this->numItems = 0;
        this->newitem = false;
        this->warm = false;
    }

private:
    SingleItemBuffer(SingleItemBuffer &buffer);

    void operator=(const SingleItemBuffer &buffer);

    DataPtr _buffer;
    mutable boost::recursive_mutex bufferMutex;
};

}