1 // SGThread - Simple pthread class wrappers.
3 // Written by Bernie Bright, started April 2001.
5 // Copyright (C) 2001 Bernard Bright - bbright@bigpond.net.au
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 #ifndef SGTHREAD_HXX_INCLUDED
24 #define SGTHREAD_HXX_INCLUDED 1
26 #include <simgear/compiler.h>
29 #if defined ( SG_HAVE_STD_INCLUDES )
34 # include <sys/errno.h>
40 void* start_handler( void* );
44 * Encapsulate generic threading methods.
45 * Users derive a class from SGThread and implement the run() member function.
51 * SGThread cancelation modes.
62 * Create a new thread object.
63 * When a SGThread object is created it does not begin execution
64 * immediately. It is started by calling the start() member function.
69 * Start the underlying thread of execution.
70 * @return Pthread error code if execution fails, otherwise returns 0.
75 * Sends a cancellation request to the underlying thread. The target
76 * thread will either ignore the request, honor it immediately or defer
77 * it until it reaches a cancellation point.
82 * Suspends the exection of the calling thread until this thread
89 * Destroy a thread object.
90 * This is protected so that its illegal to simply delete a thread
91 * - it must return from its run() function.
96 * Set the threads cancellation mode.
97 * @param mode The required cancellation mode.
99 void set_cancel( cancel_t mode );
102 * All threads execute by deriving the run() method of SGThread.
103 * If this function terminates then the thread also terminates.
105 virtual void run() = 0;
110 * Pthread thread identifier.
114 friend void* start_handler( void* );
118 SGThread( const SGThread& );
119 SGThread& operator=( const SGThread& );
128 SGThread::~SGThread()
135 int status = pthread_create( &tid, 0, start_handler, this );
136 assert( status == 0 );
143 int status = pthread_join( tid, 0 );
144 assert( status == 0 );
150 int status = pthread_cancel( tid );
151 assert( status == 0 );
155 * A mutex is used to protect a section of code such that at any time
156 * only a single thread can execute the code.
160 friend class SGCondition;
165 * Create a new mutex.
166 * Under Linux this is a 'fast' mutex.
171 * Destroy a mutex object.
172 * Note: it is the responsibility of the caller to ensure the mutex is
173 * unlocked before destruction occurs.
179 * If the mutex is currently unlocked, it becomes locked and owned by
180 * the calling thread. If the mutex is already locked by another thread,
181 * the calling thread is suspended until the mutex is unlocked. If the
182 * mutex is already locked and owned by the calling thread, the calling
183 * thread is suspended until the mutex is unlocked, effectively causing
184 * the calling thread to deadlock.
186 * @see SGMutex::trylock
191 * Try to lock the mutex for the current thread. Behaves like lock except
192 * that it doesn't block the calling thread.
193 * @return true if mutex was successfully locked, otherwise false.
200 * It is assumed that the mutex is locked and owned by the calling thread.
209 pthread_mutex_t mutex;
212 inline SGMutex::SGMutex()
214 int status = pthread_mutex_init( &mutex, 0 );
215 assert( status == 0 );
218 inline SGMutex::~SGMutex()
220 int status = pthread_mutex_destroy( &mutex );
221 assert( status == 0 );
224 inline void SGMutex::lock()
226 int status = pthread_mutex_lock( &mutex );
227 assert( status == 0 );
230 inline void SGMutex::unlock()
232 int status = pthread_mutex_unlock( &mutex );
233 assert( status == 0 );
237 * A condition variable is a synchronization device that allows threads to
238 * suspend execution until some predicate on shared data is satisfied.
239 * A condition variable is always associated with a mutex to avoid race
246 * Create a new condition variable.
251 * Destroy the condition object.
256 * Wait for this condition variable to be signaled.
258 * @param SGMutex& reference to a locked mutex.
260 void wait( SGMutex& );
263 * Wait for this condition variable to be signaled for at most
266 * @param mutex reference to a locked mutex.
267 * @param ms milliseconds to wait for a signal.
271 bool wait( SGMutex& mutex, unsigned long ms );
274 * Wake one thread waiting on this condition variable.
275 * Nothing happens if no threads are waiting.
276 * If several threads are waiting exactly one thread is restarted. It
277 * is not specified which.
282 * Wake all threads waiting on this condition variable.
283 * Nothing happens if no threads are waiting.
289 SGCondition(const SGCondition& );
290 SGCondition& operator=(const SGCondition& );
295 * The Pthread conditon variable.
300 inline SGCondition::SGCondition()
302 int status = pthread_cond_init( &cond, 0 );
303 assert( status == 0 );
306 inline SGCondition::~SGCondition()
308 int status = pthread_cond_destroy( &cond );
309 assert( status == 0 );
312 inline void SGCondition::signal()
314 int status = pthread_cond_signal( &cond );
315 assert( status == 0 );
318 inline void SGCondition::broadcast()
320 int status = pthread_cond_broadcast( &cond );
321 assert( status == 0 );
324 inline void SGCondition::wait( SGMutex& mutex )
326 int status = pthread_cond_wait( &cond, &mutex.mutex );
327 assert( status == 0 );
330 #endif /* SGTHREAD_HXX_INCLUDED */