CThreadSafeVariable.h

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/* +---------------------------------------------------------------------------+
   |          The Mobile Robot Programming Toolkit (MRPT) C++ library          |
   |                                                                           |
   |                       http://www.mrpt.org/                                |
   |                                                                           |
   |   Copyright (C) 2005-2011  University of Malaga                           |
   |                                                                           |
   |    This software was written by the Machine Perception and Intelligent    |
   |      Robotics Lab, University of Malaga (Spain).                          |
   |    Contact: Jose-Luis Blanco  <jlblanco@ctima.uma.es>                     |
   |                                                                           |
   |  This file is part of the MRPT project.                                   |
   |                                                                           |
   |     MRPT 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.                                   |
   |                                                                           |
   |   MRPT 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 MRPT.  If not, see <http://www.gnu.org/licenses/>.         |
   |                                                                           |
   +---------------------------------------------------------------------------+ */
#ifndef  mrpt_synch_threadsafevar_H
#define  mrpt_synch_threadsafevar_H

#include <mrpt/synch/CCriticalSection.h>

namespace mrpt
{
namespace synch
{

        /** A template for created thread-safe variables with an internal critical section controlled each read or write.
          * Example:
          *  \code
          *    CThreadSafeVariable<double>   var1;
          *        ...
          *    var.set(2.3);    // Sets the value
          *    double x = var.get();  // Reads the variable
          *    ...
          *    double foo = var;  // Also reads the variable
          *    var = 2.3;       // ERROR: Not allowed, use ".set()" instead.
          *  \endcode
          *
          * \sa CCriticalSection
          * \ingroup synch_grp
          */
        template <typename T>
        class CThreadSafeVariable
        {
        private:
                CCriticalSection  m_cs;
                T       m_val;
        public:
                CThreadSafeVariable() : m_cs(), m_val()  {  }
                CThreadSafeVariable(const T& init_val) : m_cs(), m_val(init_val)  {  }

                virtual ~CThreadSafeVariable() { }

                /** Return a copy of the hold variable */
                T get() const
                {
                        T ret;
                        {
                                CCriticalSectionLocker l(&m_cs);
                                ret = m_val;
                        }
                        return ret;
                }

                /** Return a copy of the hold variable */
                void get(T &out_val) const
                {
                        CCriticalSectionLocker l(&m_cs);
                        out_val = m_val;
                }

                /** Return a copy of the hold variable */
                operator T(void) const
                {
                        CCriticalSectionLocker l(&m_cs);
                        return m_val;
                }

                /** Return a copy of the hold variable */
                void set(const T &new_val)
                {
                        CCriticalSectionLocker l(&m_cs);
                        m_val = new_val;
                }

                /** Swap the current value of the hold variable and the passed one, as one atomic operation. */
                void swap(T &in_out_var)
                {
                        CCriticalSectionLocker l(&m_cs);
                        std::swap(in_out_var,m_val);
                }
        };

} // End of namespace
} // End of namespace

#endif