Semaphore.hpp

/* This file is part of Raul.
 * Copyright (C) 2007-2009 David Robillard <http://drobilla.net>
 *
 * Raul 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.
 *
 * Raul 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 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 St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef RAUL_SEMAPHORE_HPP
#define RAUL_SEMAPHORE_HPP

#ifdef __APPLE__
#include <limits.h>
#include <CoreServices/CoreServices.h>
#else
#include <semaphore.h>
#endif

#include <boost/utility.hpp>

namespace Raul {


class Semaphore : boost::noncopyable {
public:
    inline Semaphore(unsigned int initial) {
        #ifdef __APPLE__
        MPCreateSemaphore(UINT_MAX, initial, &_sem);
        #else
        sem_init(&_sem, 0, initial);
        #endif
    }

    inline ~Semaphore() {
        #ifdef __APPLE__
        MPDeleteSemaphore(_sem);
        #else
        sem_destroy(&_sem);
        #endif
    }

    inline void reset(unsigned int initial) {
        #ifdef __APPLE__
        MPDeleteSemaphore(_sem);
        MPCreateSemaphore(UINT_MAX, initial, &_sem);
        #else
        sem_destroy(&_sem);
        sem_init(&_sem, 0, initial);
        #endif
    }

    inline void post() {
        #ifdef __APPLE__
        MPSignalSemaphore(_sem);
        #else
        sem_post(&_sem);
        #endif
    }

    inline void wait() {
        #ifdef __APPLE__
        MPWaitOnSemaphore(_sem, kDurationForever);
        #else
        /* Note that sem_wait always returns 0 in practice, except in
           gdb (at least), where it returns nonzero, so the while is
           necessary (and is the correct/safe solution in any case).
        */
        while (sem_wait(&_sem) != 0) {}
        #endif
    }

    inline bool try_wait() {
        #ifdef __APPLE__
        return MPWaitOnSemaphore(_sem, kDurationImmediate) == noErr;
        #else
        return (sem_trywait(&_sem) == 0);
        #endif
    }

private:
    #ifdef __APPLE__
    MPSemaphoreID _sem;
    #else
    sem_t _sem;
    #endif
};


} // namespace Raul

#endif // RAUL_SEMAPHORE_HPP