CSemaphore.h

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/* +---------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)               |
   |                          http://www.mrpt.org/                             |
   |                                                                           |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file        |
   | See: http://www.mrpt.org/Authors - All rights reserved.                   |
   | Released under BSD License. See details in http://www.mrpt.org/License    |
   +---------------------------------------------------------------------------+ */
#ifndef  mrpt_synch_semaphore_H
#define  mrpt_synch_semaphore_H

#include <string>
#include <mutex>
#include <condition_variable>
#include <exception>
#include <mrpt/base/link_pragmas.h>

namespace mrpt
{
        namespace synch
        {
                /** A semaphore for inter-thread synchronization.
                  * The state of a semaphore object is signaled when its count is greater than zero,
                  *  and nonsignaled when its count is equal to zero. The initialCount parameter specifies
                  *  the initial count. Each time a waiting thread is released because of the semaphore's
                  *  signaled state, the count of the semaphore is decreased by one. Use the release function
                  *  to increment a semaphore's count by a specified amount. The count can never be less
                  *   than zero or greater than the value specified in the maxCount parameter.
                  * \ingroup synch_grp
                  */
                class BASE_IMPEXP CSemaphore
                {
                protected:
                        std::mutex m_mutex;
                        std::condition_variable m_condition;
                        unsigned long m_count{ 0 };

                public:
                        /** Creates a semaphore.*/
                        CSemaphore(unsigned int    initialCount, unsigned int    maxCount);

                        // throw instead of deleting the copy operator to allow mrpt-1.5 legacy code to build.
                        CSemaphore(const CSemaphore&o) { throw std::runtime_error("CSemaphore cannot be copied"); }

                        /** Blocks until the count of the semaphore to be non-zero.
                                * \param timeout_ms The timeout in milliseconds, or set to zero to wait indefinidely.
                                * \return true if the semaphore has been signaled, false on timeout or any other error.
                                */
                        bool waitForSignal( unsigned int timeout_ms = 0 );

                        /** Increments the count of the semaphore by a given amount */
                        void release(unsigned int increaseCount = 1);
                };

        } // End of namespace
} // End of namespace
#endif