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 * @param cpu An optional parameter to specify on which CPU to run this
71 * thread (only supported on IRIX at this time).
72 * @return Pthread error code if execution fails, otherwise returns 0.
74 int start( unsigned cpu = 0 );
77 * Sends a cancellation request to the underlying thread. The target
78 * thread will either ignore the request, honor it immediately or defer
79 * it until it reaches a cancellation point.
84 * Suspends the exection of the calling thread until this thread
91 * Destroy a thread object.
92 * This is protected so that its illegal to simply delete a thread
93 * - it must return from its run() function.
98 * Set the threads cancellation mode.
99 * @param mode The required cancellation mode.
101 void set_cancel( cancel_t mode );
104 * All threads execute by deriving the run() method of SGThread.
105 * If this function terminates then the thread also terminates.
107 virtual void run() = 0;
112 * Pthread thread identifier.
116 friend void* start_handler( void* );
120 SGThread( const SGThread& );
121 SGThread& operator=( const SGThread& );
130 SGThread::~SGThread()
135 SGThread::start( unsigned cpu )
137 int status = pthread_create( &tid, 0, start_handler, this );
138 assert( status == 0 );
140 if ( !status && !cpu )
141 pthread_setrunon_np( cpu );
149 int status = pthread_join( tid, 0 );
150 assert( status == 0 );
156 int status = pthread_cancel( tid );
157 assert( status == 0 );
161 * A mutex is used to protect a section of code such that at any time
162 * only a single thread can execute the code.
166 friend class SGPthreadCond;
171 * Create a new mutex.
172 * Under Linux this is a 'fast' mutex.
177 * Destroy a mutex object.
178 * Note: it is the responsibility of the caller to ensure the mutex is
179 * unlocked before destruction occurs.
185 * If the mutex is currently unlocked, it becomes locked and owned by
186 * the calling thread. If the mutex is already locked by another thread,
187 * the calling thread is suspended until the mutex is unlocked. If the
188 * mutex is already locked and owned by the calling thread, the calling
189 * thread is suspended until the mutex is unlocked, effectively causing
190 * the calling thread to deadlock.
192 * @see SGMutex::trylock
197 * Try to lock the mutex for the current thread. Behaves like lock except
198 * that it doesn't block the calling thread.
199 * @return true if mutex was successfully locked, otherwise false.
206 * It is assumed that the mutex is locked and owned by the calling thread.
215 pthread_mutex_t mutex;
218 inline SGMutex::SGMutex()
220 int status = pthread_mutex_init( &mutex, 0 );
221 assert( status == 0 );
224 inline SGMutex::~SGMutex()
226 int status = pthread_mutex_destroy( &mutex );
227 assert( status == 0 );
230 inline void SGMutex::lock()
232 int status = pthread_mutex_lock( &mutex );
233 assert( status == 0 );
236 inline void SGMutex::unlock()
238 int status = pthread_mutex_unlock( &mutex );
239 assert( status == 0 );
243 * A condition variable is a synchronization device that allows threads to
244 * suspend execution until some predicate on shared data is satisfied.
245 * A condition variable is always associated with a mutex to avoid race
252 * Create a new condition variable.
257 * Destroy the condition object.
262 * Wait for this condition variable to be signaled.
264 * @param SGMutex& reference to a locked mutex.
266 void wait( SGMutex& );
269 * Wait for this condition variable to be signaled for at most
272 * @param mutex reference to a locked mutex.
273 * @param ms milliseconds to wait for a signal.
277 bool wait( SGMutex& mutex, unsigned long ms );
280 * Wake one thread waiting on this condition variable.
281 * Nothing happens if no threads are waiting.
282 * If several threads are waiting exactly one thread is restarted. It
283 * is not specified which.
288 * Wake all threads waiting on this condition variable.
289 * Nothing happens if no threads are waiting.
295 SGPthreadCond(const SGPthreadCond& );
296 SGPthreadCond& operator=(const SGPthreadCond& );
301 * The Pthread conditon variable.
306 inline SGPthreadCond::SGPthreadCond()
308 int status = pthread_cond_init( &cond, 0 );
309 assert( status == 0 );
312 inline SGPthreadCond::~SGPthreadCond()
314 int status = pthread_cond_destroy( &cond );
315 assert( status == 0 );
318 inline void SGPthreadCond::signal()
320 int status = pthread_cond_signal( &cond );
321 assert( status == 0 );
324 inline void SGPthreadCond::broadcast()
326 int status = pthread_cond_broadcast( &cond );
327 assert( status == 0 );
330 inline void SGPthreadCond::wait( SGMutex& mutex )
332 int status = pthread_cond_wait( &cond, &mutex.mutex );
333 assert( status == 0 );
336 #endif /* SGTHREAD_HXX_INCLUDED */