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+/*
+ Copyright (c) 2007-2010 iMatix Corporation
+
+ 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&);
+ void 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&);
+ void 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&);
+ void operator = (const semaphore_t&);
+ };
+
+#endif
+
+}
+
+#endif
+