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/*
Copyright (c) 2007-2011 iMatix Corporation
Copyright (c) 2007-2011 Other contributors as noted in the AUTHORS file
This file is part of 0MQ.
0MQ 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.
0MQ 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ZMQ_SEMAPHORE_HPP_INCLUDED__
#define __ZMQ_SEMAPHORE_HPP_INCLUDED__
#include "platform.hpp"
#include "err.hpp"
#if defined ZMQ_HAVE_WINDOWS
#include "windows.hpp"
#else
#include <semaphore.h>
#endif
namespace zmq
{
// Simple semaphore. Only single thread may be waiting at any given time.
// Also, the semaphore may not be posted before the previous post
// was matched by corresponding wait and the waiting thread was
// released.
#if defined ZMQ_HAVE_WINDOWS
// On Windows platform simple semaphore is implemeted using event object.
class semaphore_t
{
public:
// Initialise the semaphore.
inline semaphore_t ()
{
ev = CreateEvent (NULL, FALSE, FALSE, NULL);
win_assert (ev != NULL);
}
// Destroy the semaphore.
inline ~semaphore_t ()
{
int rc = CloseHandle (ev);
win_assert (rc != 0);
}
// Wait for the semaphore.
inline void wait ()
{
DWORD rc = WaitForSingleObject (ev, INFINITE);
win_assert (rc != WAIT_FAILED);
}
// Post the semaphore.
inline void post ()
{
int rc = SetEvent (ev);
win_assert (rc != 0);
}
private:
HANDLE ev;
semaphore_t (const semaphore_t&);
const semaphore_t &operator = (const semaphore_t&);
};
#elif defined ZMQ_HAVE_LINUX || defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS
// On platforms that allow for double locking of a mutex from the same
// thread, simple semaphore is implemented using mutex, as it is more
// efficient than full-blown semaphore.
// Note that OS-level semaphore is not implemented on OSX, so the below
// code is not only optimisation, it's necessary to make 0MQ work on OSX.
class semaphore_t
{
public:
// Initialise the semaphore.
inline semaphore_t ()
{
int rc = pthread_mutex_init (&mutex, NULL);
posix_assert (rc);
rc = pthread_mutex_lock (&mutex);
posix_assert (rc);
}
// Destroy the semaphore.
inline ~semaphore_t ()
{
int rc = pthread_mutex_unlock (&mutex);
posix_assert (rc);
rc = pthread_mutex_destroy (&mutex);
posix_assert (rc);
}
// Wait for the semaphore.
inline void wait ()
{
int rc = pthread_mutex_lock (&mutex);
posix_assert (rc);
}
// Post the semaphore.
inline void post ()
{
int rc = pthread_mutex_unlock (&mutex);
posix_assert (rc);
}
private:
pthread_mutex_t mutex;
semaphore_t (const semaphore_t&);
const semaphore_t &operator = (const semaphore_t&);
};
#else
// Default implementation maps simple semaphore to POSIX semaphore.
class semaphore_t
{
public:
// Initialise the semaphore.
inline semaphore_t ()
{
int rc = sem_init (&sem, 0, 0);
errno_assert (rc != -1);
}
// Destroy the semaphore.
inline ~semaphore_t ()
{
int rc = sem_destroy (&sem);
errno_assert (rc != -1);
}
// Wait for the semaphore.
inline void wait ()
{
int rc = sem_wait (&sem);
errno_assert (rc != -1);
}
// Post the semaphore.
inline void post ()
{
int rc = sem_post (&sem);
errno_assert (rc != -1);
}
private:
// Underlying system semaphore object.
sem_t sem;
semaphore_t (const semaphore_t&);
const semaphore_t &operator = (const semaphore_t&);
};
#endif
}
#endif
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