semutils.h

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/*
 * Copyright (C) 2010-2013 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2013 John Emmas <john@creativepost.co.uk>
 * Copyright (C) 2015-2017 Robin Gareus <robin@gareus.org>
 *
 * This program 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
#pragma once
 
#if (defined PLATFORM_WINDOWS && !defined USE_PTW32_SEMAPHORE)
#define WINDOWS_SEMAPHORE 1
#endif
 
#ifdef WINDOWS_SEMAPHORE
# include <windows.h>
#elif defined USE_FUTEX_SEMAPHORE
# include <atomic>
#else
# include <pthread.h>
# include <semaphore.h>
#endif
 
#include "pbd/libpbd_visibility.h"
 
namespace PBD {
 
class LIBPBD_API Semaphore {
  private:
#ifdef WINDOWS_SEMAPHORE
        HANDLE _sem;
 
#elif __APPLE__
        sem_t* _sem;
        sem_t* ptr_to_sem() const { return _sem; }
#elif defined USE_FUTEX_SEMAPHORE
        int              _futex;
        std::atomic<int> _value;
#else
        mutable sem_t _sem;
        sem_t* ptr_to_sem() const { return &_sem; }
#endif
 
  public:
        Semaphore (const char* name, int val);
        ~Semaphore ();
 
#if defined WINDOWS_SEMAPHORE || defined USE_FUTEX_SEMAPHORE
 
        int signal ();
        int wait ();
        int reset ();
 
#else
        int signal () { return sem_post (ptr_to_sem()); }
        int wait () { return sem_wait (ptr_to_sem()); }
        int reset () { int rv = 0 ; while (sem_trywait (ptr_to_sem()) == 0) ++rv; return rv; }
#endif
};
 
}