semaphore.hpp

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/*********************************************************************/
// libthreadar - is a library providing several C++ classes to work with threads
// Copyright (C) 2014-2025 Denis Corbin
//
// This file is part of libthreadar
//
//  libthreadar is free software: you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  libhtreadar 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 Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public License
//  along with libthreadar.  If not, see <http://www.gnu.org/licenses/>
//
//----
//  to contact the author: dar.linux@free.fr
/*********************************************************************/
 
#ifndef LIBTHREADAR_SEMAPHORE_HPP
#define LIBTHREADAR_SEMAPHORE_HPP
 
 
#include "config.h"
 
    // C system headers
extern "C"
{
 
}
    // C++ standard headers
#include <string>
 
 
    // libthreadar headers
#include "mutex.hpp"
 
namespace libthreadar
{
 
 
    class semaphore
    {
    public:
 
        semaphore(unsigned int max_value);
 
        semaphore(const semaphore & ref) = delete;
 
        semaphore(semaphore && ref) noexcept = default;
 
        semaphore & operator = (const semaphore & ref) = delete;
 
        semaphore & operator = (semaphore && ref) noexcept = default;
 
        ~semaphore();
 
        bool waiting_thread() const;
 
 
        bool working_thread() const;
 
 
        void lock();
 
 
        void unlock();
 
        void reset();
 
 
        int get_value() const { return value; };
 
    private:
        int value;            //< this is the semaphore value
        mutex val_mutex;      //< this controls modification to value
        mutex semaph;         //< this mutex is used to suspend thread semaphore value get negative
        int max_value;        //< maximum value the semaphore cannot exceed
    };
 
} // end of namespace
 
#endif