| 1 | ///////////////////////////////////////////////////////////////////////////// |
| 2 | // Name: thread.h |
| 3 | // Purpose: interface of all thread-related wxWidgets classes |
| 4 | // Author: wxWidgets team |
| 5 | // RCS-ID: $Id$ |
| 6 | // Licence: wxWindows license |
| 7 | ///////////////////////////////////////////////////////////////////////////// |
| 8 | |
| 9 | |
| 10 | /** See wxCondition. */ |
| 11 | enum wxCondError |
| 12 | { |
| 13 | wxCOND_NO_ERROR = 0, |
| 14 | wxCOND_INVALID, |
| 15 | wxCOND_TIMEOUT, //!< WaitTimeout() has timed out |
| 16 | wxCOND_MISC_ERROR |
| 17 | }; |
| 18 | |
| 19 | |
| 20 | /** |
| 21 | @class wxCondition |
| 22 | |
| 23 | wxCondition variables correspond to pthread conditions or to Win32 event objects. |
| 24 | They may be used in a multithreaded application to wait until the given condition |
| 25 | becomes @true which happens when the condition becomes signaled. |
| 26 | |
| 27 | For example, if a worker thread is doing some long task and another thread has |
| 28 | to wait until it is finished, the latter thread will wait on the condition |
| 29 | object and the worker thread will signal it on exit (this example is not |
| 30 | perfect because in this particular case it would be much better to just |
| 31 | wxThread::Wait for the worker thread, but if there are several worker threads |
| 32 | it already makes much more sense). |
| 33 | |
| 34 | Note that a call to wxCondition::Signal may happen before the other thread calls |
| 35 | wxCondition::Wait and, just as with the pthread conditions, the signal is then |
| 36 | lost and so if you want to be sure that you don't miss it you must keep the |
| 37 | mutex associated with the condition initially locked and lock it again before calling |
| 38 | wxCondition::Signal. Of course, this means that this call is going to block |
| 39 | until wxCondition::Wait is called by another thread. |
| 40 | |
| 41 | @section condition_example Example |
| 42 | |
| 43 | This example shows how a main thread may launch a worker thread which starts |
| 44 | running and then waits until the main thread signals it to continue: |
| 45 | |
| 46 | @code |
| 47 | class MySignallingThread : public wxThread |
| 48 | { |
| 49 | public: |
| 50 | MySignallingThread(wxMutex *mutex, wxCondition *condition) |
| 51 | { |
| 52 | m_mutex = mutex; |
| 53 | m_condition = condition; |
| 54 | |
| 55 | Create(); |
| 56 | } |
| 57 | |
| 58 | virtual ExitCode Entry() |
| 59 | { |
| 60 | ... do our job ... |
| 61 | |
| 62 | // tell the other(s) thread(s) that we're about to terminate: we must |
| 63 | // lock the mutex first or we might signal the condition before the |
| 64 | // waiting threads start waiting on it! |
| 65 | wxMutexLocker lock(*m_mutex); |
| 66 | m_condition->Broadcast(); // same as Signal() here -- one waiter only |
| 67 | |
| 68 | return 0; |
| 69 | } |
| 70 | |
| 71 | private: |
| 72 | wxCondition *m_condition; |
| 73 | wxMutex *m_mutex; |
| 74 | }; |
| 75 | |
| 76 | int main() |
| 77 | { |
| 78 | wxMutex mutex; |
| 79 | wxCondition condition(mutex); |
| 80 | |
| 81 | // the mutex should be initially locked |
| 82 | mutex.Lock(); |
| 83 | |
| 84 | // create and run the thread but notice that it won't be able to |
| 85 | // exit (and signal its exit) before we unlock the mutex below |
| 86 | MySignallingThread *thread = new MySignallingThread(&mutex, &condition); |
| 87 | |
| 88 | thread->Run(); |
| 89 | |
| 90 | // wait for the thread termination: Wait() atomically unlocks the mutex |
| 91 | // which allows the thread to continue and starts waiting |
| 92 | condition.Wait(); |
| 93 | |
| 94 | // now we can exit |
| 95 | return 0; |
| 96 | } |
| 97 | @endcode |
| 98 | |
| 99 | Of course, here it would be much better to simply use a joinable thread and |
| 100 | call wxThread::Wait on it, but this example does illustrate the importance of |
| 101 | properly locking the mutex when using wxCondition. |
| 102 | |
| 103 | @library{wxbase} |
| 104 | @category{threading} |
| 105 | |
| 106 | @see wxThread, wxMutex |
| 107 | */ |
| 108 | class wxCondition |
| 109 | { |
| 110 | public: |
| 111 | /** |
| 112 | Default and only constructor. |
| 113 | The @a mutex must be locked by the caller before calling Wait() function. |
| 114 | Use IsOk() to check if the object was successfully initialized. |
| 115 | */ |
| 116 | wxCondition(wxMutex& mutex); |
| 117 | |
| 118 | /** |
| 119 | Destroys the wxCondition object. |
| 120 | |
| 121 | The destructor is not virtual so this class should not be used polymorphically. |
| 122 | */ |
| 123 | ~wxCondition(); |
| 124 | |
| 125 | /** |
| 126 | Broadcasts to all waiting threads, waking all of them up. |
| 127 | |
| 128 | Note that this method may be called whether the mutex associated with |
| 129 | this condition is locked or not. |
| 130 | |
| 131 | @see Signal() |
| 132 | */ |
| 133 | wxCondError Broadcast(); |
| 134 | |
| 135 | /** |
| 136 | Returns @true if the object had been initialized successfully, @false |
| 137 | if an error occurred. |
| 138 | */ |
| 139 | bool IsOk() const; |
| 140 | |
| 141 | /** |
| 142 | Signals the object waking up at most one thread. |
| 143 | |
| 144 | If several threads are waiting on the same condition, the exact thread |
| 145 | which is woken up is undefined. If no threads are waiting, the signal is |
| 146 | lost and the condition would have to be signalled again to wake up any |
| 147 | thread which may start waiting on it later. |
| 148 | |
| 149 | Note that this method may be called whether the mutex associated with this |
| 150 | condition is locked or not. |
| 151 | |
| 152 | @see Broadcast() |
| 153 | */ |
| 154 | wxCondError Signal(); |
| 155 | |
| 156 | /** |
| 157 | Waits until the condition is signalled. |
| 158 | |
| 159 | This method atomically releases the lock on the mutex associated with this |
| 160 | condition (this is why it must be locked prior to calling Wait()) and puts the |
| 161 | thread to sleep until Signal() or Broadcast() is called. |
| 162 | It then locks the mutex again and returns. |
| 163 | |
| 164 | Note that even if Signal() had been called before Wait() without waking |
| 165 | up any thread, the thread would still wait for another one and so it is |
| 166 | important to ensure that the condition will be signalled after |
| 167 | Wait() or the thread may sleep forever. |
| 168 | |
| 169 | @return Returns wxCOND_NO_ERROR on success, another value if an error occurred. |
| 170 | |
| 171 | @see WaitTimeout() |
| 172 | */ |
| 173 | wxCondError Wait(); |
| 174 | |
| 175 | /** |
| 176 | Waits until the condition is signalled or the timeout has elapsed. |
| 177 | |
| 178 | This method is identical to Wait() except that it returns, with the |
| 179 | return code of @c wxCOND_TIMEOUT as soon as the given timeout expires. |
| 180 | |
| 181 | @param milliseconds |
| 182 | Timeout in milliseconds |
| 183 | |
| 184 | @return Returns wxCOND_NO_ERROR if the condition was signalled, |
| 185 | wxCOND_TIMEOUT if the timeout elapsed before this happened or |
| 186 | another error code from wxCondError enum. |
| 187 | */ |
| 188 | wxCondError WaitTimeout(unsigned long milliseconds); |
| 189 | }; |
| 190 | |
| 191 | |
| 192 | /** |
| 193 | @class wxCriticalSectionLocker |
| 194 | |
| 195 | This is a small helper class to be used with wxCriticalSection objects. |
| 196 | |
| 197 | A wxCriticalSectionLocker enters the critical section in the constructor and |
| 198 | leaves it in the destructor making it much more difficult to forget to leave |
| 199 | a critical section (which, in general, will lead to serious and difficult |
| 200 | to debug problems). |
| 201 | |
| 202 | Example of using it: |
| 203 | |
| 204 | @code |
| 205 | void Set Foo() |
| 206 | { |
| 207 | // gs_critSect is some (global) critical section guarding access to the |
| 208 | // object "foo" |
| 209 | wxCriticalSectionLocker locker(gs_critSect); |
| 210 | |
| 211 | if ( ... ) |
| 212 | { |
| 213 | // do something |
| 214 | ... |
| 215 | |
| 216 | return; |
| 217 | } |
| 218 | |
| 219 | // do something else |
| 220 | ... |
| 221 | |
| 222 | return; |
| 223 | } |
| 224 | @endcode |
| 225 | |
| 226 | Without wxCriticalSectionLocker, you would need to remember to manually leave |
| 227 | the critical section before each @c return. |
| 228 | |
| 229 | @library{wxbase} |
| 230 | @category{threading} |
| 231 | |
| 232 | @see wxCriticalSection, wxMutexLocker |
| 233 | */ |
| 234 | class wxCriticalSectionLocker |
| 235 | { |
| 236 | public: |
| 237 | /** |
| 238 | Constructs a wxCriticalSectionLocker object associated with given |
| 239 | @a criticalsection and enters it. |
| 240 | */ |
| 241 | wxCriticalSectionLocker(wxCriticalSection& criticalsection); |
| 242 | |
| 243 | /** |
| 244 | Destructor leaves the critical section. |
| 245 | */ |
| 246 | ~wxCriticalSectionLocker(); |
| 247 | }; |
| 248 | |
| 249 | |
| 250 | |
| 251 | /** |
| 252 | @class wxThreadHelper |
| 253 | |
| 254 | The wxThreadHelper class is a mix-in class that manages a single background |
| 255 | thread, either detached or joinable (see wxThread for the differences). |
| 256 | By deriving from wxThreadHelper, a class can implement the thread |
| 257 | code in its own wxThreadHelper::Entry() method and easily share data and |
| 258 | synchronization objects between the main thread and the worker thread. |
| 259 | |
| 260 | Doing this prevents the awkward passing of pointers that is needed when the |
| 261 | original object in the main thread needs to synchronize with its worker thread |
| 262 | in its own wxThread derived object. |
| 263 | |
| 264 | For example, wxFrame may need to make some calculations in a background thread |
| 265 | and then display the results of those calculations in the main window. |
| 266 | |
| 267 | Ordinarily, a wxThread derived object would be created with the calculation |
| 268 | code implemented in wxThread::Entry. To access the inputs to the calculation, |
| 269 | the frame object would often need to pass a pointer to itself to the thread object. |
| 270 | Similarly, the frame object would hold a pointer to the thread object. |
| 271 | |
| 272 | Shared data and synchronization objects could be stored in either object |
| 273 | though the object without the data would have to access the data through |
| 274 | a pointer. |
| 275 | However with wxThreadHelper the frame object and the thread object are |
| 276 | treated as the same object. Shared data and synchronization variables are |
| 277 | stored in the single object, eliminating a layer of indirection and the |
| 278 | associated pointers. |
| 279 | |
| 280 | Example: |
| 281 | @code |
| 282 | wxDECLARE_EVENT(wxEVT_COMMAND_MYTHREAD_UPDATE, wxThreadEvent); |
| 283 | |
| 284 | class MyFrame : public wxFrame, public wxThreadHelper |
| 285 | { |
| 286 | public: |
| 287 | MyFrame(...) { ... } |
| 288 | ~MyFrame() |
| 289 | { |
| 290 | // it's better to do any thread cleanup in the OnClose() |
| 291 | // event handler, rather than in the destructor. |
| 292 | // This is because the event loop for a top-level window is not |
| 293 | // active anymore when its destructor is called and if the thread |
| 294 | // sends events when ending, they won't be processed unless |
| 295 | // you ended the thread from OnClose. |
| 296 | // See @ref overview_windowdeletion for more info. |
| 297 | } |
| 298 | |
| 299 | ... |
| 300 | void DoStartALongTask(); |
| 301 | void OnThreadUpdate(wxThreadEvent& evt); |
| 302 | void OnClose(wxCloseEvent& evt); |
| 303 | ... |
| 304 | |
| 305 | protected: |
| 306 | virtual wxThread::ExitCode Entry(); |
| 307 | |
| 308 | // the output data of the Entry() routine: |
| 309 | char m_data[1024]; |
| 310 | wxCriticalSection m_dataCS; // protects field above |
| 311 | |
| 312 | DECLARE_EVENT_TABLE() |
| 313 | }; |
| 314 | |
| 315 | wxDEFINE_EVENT(wxEVT_COMMAND_MYTHREAD_UPDATE, wxThreadEvent) |
| 316 | BEGIN_EVENT_TABLE(MyFrame, wxFrame) |
| 317 | EVT_COMMAND(wxID_ANY, wxEVT_COMMAND_MYTHREAD_UPDATE, MyFrame::OnThreadUpdate) |
| 318 | EVT_CLOSE(MyFrame::OnClose) |
| 319 | END_EVENT_TABLE() |
| 320 | |
| 321 | void MyFrame::DoStartALongTask() |
| 322 | { |
| 323 | // we want to start a long task, but we don't want our GUI to block |
| 324 | // while it's executed, so we use a thread to do it. |
| 325 | if (CreateThread(wxTHREAD_JOINABLE) != wxTHREAD_NO_ERROR) |
| 326 | { |
| 327 | wxLogError("Could not create the worker thread!"); |
| 328 | return; |
| 329 | } |
| 330 | |
| 331 | // go! |
| 332 | if (GetThread()->Run() != wxTHREAD_NO_ERROR) |
| 333 | { |
| 334 | wxLogError("Could not run the worker thread!"); |
| 335 | return; |
| 336 | } |
| 337 | } |
| 338 | |
| 339 | wxThread::ExitCode MyFrame::Entry() |
| 340 | { |
| 341 | // IMPORTANT: |
| 342 | // this function gets executed in the secondary thread context! |
| 343 | |
| 344 | int offset = 0; |
| 345 | |
| 346 | // here we do our long task, periodically calling TestDestroy(): |
| 347 | while (!GetThread()->TestDestroy()) |
| 348 | { |
| 349 | // since this Entry() is implemented in MyFrame context we don't |
| 350 | // need any pointer to access the m_data, m_processedData, m_dataCS |
| 351 | // variables... very nice! |
| 352 | |
| 353 | // this is an example of the generic structure of a download thread: |
| 354 | char buffer[1024]; |
| 355 | download_chunk(buffer, 1024); // this takes time... |
| 356 | |
| 357 | { |
| 358 | // ensure noone reads m_data while we write it |
| 359 | wxCriticalSectionLocker lock(m_dataCS); |
| 360 | memcpy(m_data+offset, buffer, 1024); |
| 361 | offset += 1024; |
| 362 | } |
| 363 | |
| 364 | |
| 365 | // VERY IMPORTANT: do not call any GUI function inside this |
| 366 | // function; rather use wxQueueEvent(): |
| 367 | wxQueueEvent(this, new wxThreadEvent(wxEVT_COMMAND_MYTHREAD_UPDATE)); |
| 368 | // we used pointer 'this' assuming it's safe; see OnClose() |
| 369 | } |
| 370 | |
| 371 | // TestDestroy() returned true (which means the main thread asked us |
| 372 | // to terminate as soon as possible) or we ended the long task... |
| 373 | return (wxThread::ExitCode)0; |
| 374 | } |
| 375 | |
| 376 | void MyFrame::OnClose(wxCloseEvent&) |
| 377 | { |
| 378 | // important: before terminating, we _must_ wait for our joinable |
| 379 | // thread to end, if it's running; in fact it uses variables of this |
| 380 | // instance and posts events to *this event handler |
| 381 | |
| 382 | if (GetThread() && // DoStartALongTask() may have not been called |
| 383 | GetThread()->IsRunning()) |
| 384 | GetThread()->Wait(); |
| 385 | |
| 386 | Destroy(); |
| 387 | } |
| 388 | |
| 389 | void MyFrame::OnThreadUpdate(wxThreadEvent& evt) |
| 390 | { |
| 391 | // ...do something... e.g. m_pGauge->Pulse(); |
| 392 | |
| 393 | // read some parts of m_data just for fun: |
| 394 | wxCriticalSectionLocker lock(m_dataCS); |
| 395 | wxPrintf("%c", m_data[100]); |
| 396 | } |
| 397 | @endcode |
| 398 | |
| 399 | @library{wxbase} |
| 400 | @category{threading} |
| 401 | |
| 402 | @see wxThread, wxThreadEvent |
| 403 | */ |
| 404 | class wxThreadHelper |
| 405 | { |
| 406 | public: |
| 407 | /** |
| 408 | This constructor simply initializes internal member variables and tells |
| 409 | wxThreadHelper which type the thread internally managed should be. |
| 410 | */ |
| 411 | wxThreadHelper(wxThreadKind kind = wxTHREAD_JOINABLE); |
| 412 | |
| 413 | /** |
| 414 | The destructor frees the resources associated with the thread, forcing |
| 415 | it to terminate (it uses wxThread::Kill function). |
| 416 | |
| 417 | Because of the wxThread::Kill unsafety, you should always wait |
| 418 | (with wxThread::Wait) for joinable threads to end or call wxThread::Delete |
| 419 | on detached threads, instead of relying on this destructor for stopping |
| 420 | the thread. |
| 421 | */ |
| 422 | virtual ~wxThreadHelper(); |
| 423 | |
| 424 | /** |
| 425 | This is the entry point of the thread. |
| 426 | |
| 427 | This function is pure virtual and must be implemented by any derived class. |
| 428 | The thread execution will start here. |
| 429 | |
| 430 | You'll typically want your Entry() to look like: |
| 431 | @code |
| 432 | wxThread::ExitCode Entry() |
| 433 | { |
| 434 | while (!GetThread()->TestDestroy()) |
| 435 | { |
| 436 | // ... do some work ... |
| 437 | |
| 438 | if (IsWorkCompleted) |
| 439 | break; |
| 440 | |
| 441 | if (HappenedStoppingError) |
| 442 | return (wxThread::ExitCode)1; // failure |
| 443 | } |
| 444 | |
| 445 | return (wxThread::ExitCode)0; // success |
| 446 | } |
| 447 | @endcode |
| 448 | |
| 449 | The returned value is the thread exit code which is only useful for |
| 450 | joinable threads and is the value returned by @c "GetThread()->Wait()". |
| 451 | |
| 452 | This function is called by wxWidgets itself and should never be called |
| 453 | directly. |
| 454 | */ |
| 455 | virtual ExitCode Entry() = 0; |
| 456 | |
| 457 | /** |
| 458 | @deprecated |
| 459 | Use CreateThread() instead. |
| 460 | */ |
| 461 | wxThreadError Create(unsigned int stackSize = 0); |
| 462 | |
| 463 | /** |
| 464 | Creates a new thread of the given @a kind. |
| 465 | |
| 466 | The thread object is created in the suspended state, and you |
| 467 | should call @ref wxThread::Run "GetThread()->Run()" to start running it. |
| 468 | |
| 469 | You may optionally specify the stack size to be allocated to it (ignored |
| 470 | on platforms that don't support setting it explicitly, e.g. Unix). |
| 471 | |
| 472 | @return One of the ::wxThreadError enum values. |
| 473 | */ |
| 474 | wxThreadError CreateThread(wxThreadKind kind = wxTHREAD_JOINABLE, |
| 475 | unsigned int stackSize = 0); |
| 476 | |
| 477 | /** |
| 478 | This is a public function that returns the wxThread object associated with |
| 479 | the thread. |
| 480 | */ |
| 481 | wxThread* GetThread() const; |
| 482 | |
| 483 | /** |
| 484 | Returns the last type of thread given to the CreateThread() function |
| 485 | or to the constructor. |
| 486 | */ |
| 487 | wxThreadKind GetThreadKind() const; |
| 488 | }; |
| 489 | |
| 490 | /** |
| 491 | Possible critical section types |
| 492 | */ |
| 493 | |
| 494 | enum wxCriticalSectionType |
| 495 | { |
| 496 | wxCRITSEC_DEFAULT, |
| 497 | /** Recursive critical section under both Windows and Unix */ |
| 498 | |
| 499 | wxCRITSEC_NON_RECURSIVE |
| 500 | /** Non-recursive critical section under Unix, recursive under Windows */ |
| 501 | }; |
| 502 | |
| 503 | /** |
| 504 | @class wxCriticalSection |
| 505 | |
| 506 | A critical section object is used for exactly the same purpose as a wxMutex. |
| 507 | The only difference is that under Windows platform critical sections are only |
| 508 | visible inside one process, while mutexes may be shared among processes, |
| 509 | so using critical sections is slightly more efficient. |
| 510 | |
| 511 | The terminology is also slightly different: mutex may be locked (or acquired) |
| 512 | and unlocked (or released) while critical section is entered and left by the program. |
| 513 | |
| 514 | Finally, you should try to use wxCriticalSectionLocker class whenever |
| 515 | possible instead of directly using wxCriticalSection for the same reasons |
| 516 | wxMutexLocker is preferrable to wxMutex - please see wxMutex for an example. |
| 517 | |
| 518 | @library{wxbase} |
| 519 | @category{threading} |
| 520 | |
| 521 | @see wxThread, wxCondition, wxCriticalSectionLocker |
| 522 | */ |
| 523 | class wxCriticalSection |
| 524 | { |
| 525 | public: |
| 526 | /** |
| 527 | Default constructor initializes critical section object. |
| 528 | By default critical sections are recursive under Unix and Windows. |
| 529 | */ |
| 530 | wxCriticalSection( wxCriticalSectionType critSecType = wxCRITSEC_DEFAULT ); |
| 531 | |
| 532 | /** |
| 533 | Destructor frees the resources. |
| 534 | */ |
| 535 | ~wxCriticalSection(); |
| 536 | |
| 537 | /** |
| 538 | Enter the critical section (same as locking a mutex): if another thread |
| 539 | has already entered it, this call will block until the other thread |
| 540 | calls Leave(). |
| 541 | There is no error return for this function. |
| 542 | |
| 543 | After entering the critical section protecting a data variable, |
| 544 | the thread running inside the critical section may safely use/modify it. |
| 545 | |
| 546 | Note that entering the same critical section twice or more from the same |
| 547 | thread doesn't result in a deadlock; in this case in fact this function will |
| 548 | immediately return. |
| 549 | */ |
| 550 | void Enter(); |
| 551 | |
| 552 | /** |
| 553 | Leave the critical section allowing other threads use the global data |
| 554 | protected by it. There is no error return for this function. |
| 555 | */ |
| 556 | void Leave(); |
| 557 | }; |
| 558 | |
| 559 | /** |
| 560 | The possible thread kinds. |
| 561 | */ |
| 562 | enum wxThreadKind |
| 563 | { |
| 564 | /** Detached thread */ |
| 565 | wxTHREAD_DETACHED, |
| 566 | |
| 567 | /** Joinable thread */ |
| 568 | wxTHREAD_JOINABLE |
| 569 | }; |
| 570 | |
| 571 | /** |
| 572 | The possible thread errors. |
| 573 | */ |
| 574 | enum wxThreadError |
| 575 | { |
| 576 | /** No error */ |
| 577 | wxTHREAD_NO_ERROR = 0, |
| 578 | |
| 579 | /** No resource left to create a new thread. */ |
| 580 | wxTHREAD_NO_RESOURCE, |
| 581 | |
| 582 | /** The thread is already running. */ |
| 583 | wxTHREAD_RUNNING, |
| 584 | |
| 585 | /** The thread isn't running. */ |
| 586 | wxTHREAD_NOT_RUNNING, |
| 587 | |
| 588 | /** Thread we waited for had to be killed. */ |
| 589 | wxTHREAD_KILLED, |
| 590 | |
| 591 | /** Some other error */ |
| 592 | wxTHREAD_MISC_ERROR |
| 593 | }; |
| 594 | |
| 595 | /** |
| 596 | Defines the interval of priority |
| 597 | */ |
| 598 | enum |
| 599 | { |
| 600 | WXTHREAD_MIN_PRIORITY = 0u, |
| 601 | WXTHREAD_DEFAULT_PRIORITY = 50u, |
| 602 | WXTHREAD_MAX_PRIORITY = 100u |
| 603 | }; |
| 604 | |
| 605 | |
| 606 | /** |
| 607 | @class wxThread |
| 608 | |
| 609 | A thread is basically a path of execution through a program. |
| 610 | Threads are sometimes called @e light-weight processes, but the fundamental difference |
| 611 | between threads and processes is that memory spaces of different processes are |
| 612 | separated while all threads share the same address space. |
| 613 | |
| 614 | While it makes it much easier to share common data between several threads, it |
| 615 | also makes it much easier to shoot oneself in the foot, so careful use of |
| 616 | synchronization objects such as mutexes (see wxMutex) or critical sections |
| 617 | (see wxCriticalSection) is recommended. |
| 618 | In addition, don't create global thread objects because they allocate memory |
| 619 | in their constructor, which will cause problems for the memory checking system. |
| 620 | |
| 621 | |
| 622 | @section thread_types Types of wxThreads |
| 623 | |
| 624 | There are two types of threads in wxWidgets: @e detached and @e joinable, |
| 625 | modeled after the the POSIX thread API. This is different from the Win32 API |
| 626 | where all threads are joinable. |
| 627 | |
| 628 | By default wxThreads in wxWidgets use the @b detached behavior. |
| 629 | Detached threads delete themselves once they have completed, either by themselves |
| 630 | when they complete processing or through a call to Delete(), and thus |
| 631 | @b must be created on the heap (through the new operator, for example). |
| 632 | |
| 633 | Typically you'll want to store the instances of the detached wxThreads you |
| 634 | allocate, so that you can call functions on them. |
| 635 | Because of their nature however you'll need to always use a critical section |
| 636 | when accessing them: |
| 637 | |
| 638 | @code |
| 639 | // declare a new type of event, to be used by our MyThread class: |
| 640 | wxDECLARE_EVENT(wxEVT_COMMAND_MYTHREAD_COMPLETED, wxThreadEvent); |
| 641 | wxDECLARE_EVENT(wxEVT_COMMAND_MYTHREAD_UPDATE, wxThreadEvent); |
| 642 | class MyFrame; |
| 643 | |
| 644 | class MyThread : public wxThread |
| 645 | { |
| 646 | public: |
| 647 | MyThread(MyFrame *handler) |
| 648 | : wxThread(wxTHREAD_DETACHED) |
| 649 | { m_pHandler = handler } |
| 650 | ~MyThread(); |
| 651 | |
| 652 | protected: |
| 653 | virtual ExitCode Entry(); |
| 654 | MyFrame *m_pHandler; |
| 655 | }; |
| 656 | |
| 657 | class MyFrame : public wxFrame |
| 658 | { |
| 659 | public: |
| 660 | ... |
| 661 | ~MyFrame() |
| 662 | { |
| 663 | // it's better to do any thread cleanup in the OnClose() |
| 664 | // event handler, rather than in the destructor. |
| 665 | // This is because the event loop for a top-level window is not |
| 666 | // active anymore when its destructor is called and if the thread |
| 667 | // sends events when ending, they won't be processed unless |
| 668 | // you ended the thread from OnClose. |
| 669 | // See @ref overview_windowdeletion for more info. |
| 670 | } |
| 671 | ... |
| 672 | void DoStartThread(); |
| 673 | void DoPauseThread(); |
| 674 | |
| 675 | // a resume routine would be nearly identic to DoPauseThread() |
| 676 | void DoResumeThread() { ... } |
| 677 | |
| 678 | void OnThreadUpdate(wxThreadEvent&); |
| 679 | void OnThreadCompletion(wxThreadEvent&); |
| 680 | void OnClose(wxCloseEvent&); |
| 681 | |
| 682 | protected: |
| 683 | MyThread *m_pThread; |
| 684 | wxCriticalSection m_pThreadCS; // protects the m_pThread pointer |
| 685 | |
| 686 | DECLARE_EVENT_TABLE() |
| 687 | }; |
| 688 | |
| 689 | BEGIN_EVENT_TABLE(MyFrame, wxFrame) |
| 690 | EVT_CLOSE(MyFrame::OnClose) |
| 691 | EVT_MENU(Minimal_Start, MyFrame::DoStartThread) |
| 692 | EVT_COMMAND(wxID_ANY, wxEVT_COMMAND_MYTHREAD_UPDATE, MyFrame::OnThreadUpdate) |
| 693 | EVT_COMMAND(wxID_ANY, wxEVT_COMMAND_MYTHREAD_COMPLETED, MyFrame::OnThreadCompletion) |
| 694 | END_EVENT_TABLE() |
| 695 | |
| 696 | wxDEFINE_EVENT(wxEVT_COMMAND_MYTHREAD_COMPLETED, wxThreadEvent) |
| 697 | wxDEFINE_EVENT(wxEVT_COMMAND_MYTHREAD_UPDATE, wxThreadEvent) |
| 698 | |
| 699 | void MyFrame::DoStartThread() |
| 700 | { |
| 701 | m_pThread = new MyThread(this); |
| 702 | |
| 703 | if ( m_pThread->Create() != wxTHREAD_NO_ERROR ) |
| 704 | { |
| 705 | wxLogError("Can't create the thread!"); |
| 706 | delete m_pThread; |
| 707 | m_pThread = NULL; |
| 708 | } |
| 709 | else |
| 710 | { |
| 711 | if (m_pThread->Run() != wxTHREAD_NO_ERROR ) |
| 712 | { |
| 713 | wxLogError("Can't create the thread!"); |
| 714 | delete m_pThread; |
| 715 | m_pThread = NULL; |
| 716 | } |
| 717 | |
| 718 | // after the call to wxThread::Run(), the m_pThread pointer is "unsafe": |
| 719 | // at any moment the thread may cease to exist (because it completes its work). |
| 720 | // To avoid dangling pointers OnThreadExit() will set m_pThread |
| 721 | // to NULL when the thread dies. |
| 722 | } |
| 723 | } |
| 724 | |
| 725 | wxThread::ExitCode MyThread::Entry() |
| 726 | { |
| 727 | while (!TestDestroy()) |
| 728 | { |
| 729 | // ... do a bit of work... |
| 730 | |
| 731 | wxQueueEvent(m_pHandler, new wxThreadEvent(wxEVT_COMMAND_MYTHREAD_UPDATE)); |
| 732 | } |
| 733 | |
| 734 | // signal the event handler that this thread is going to be destroyed |
| 735 | // NOTE: here we assume that using the m_pHandler pointer is safe, |
| 736 | // (in this case this is assured by the MyFrame destructor) |
| 737 | wxQueueEvent(m_pHandler, new wxThreadEvent(wxEVT_COMMAND_MYTHREAD_COMPLETED)); |
| 738 | |
| 739 | return (wxThread::ExitCode)0; // success |
| 740 | } |
| 741 | |
| 742 | MyThread::~MyThread() |
| 743 | { |
| 744 | wxCriticalSectionLocker enter(m_pHandler->m_pThreadCS); |
| 745 | |
| 746 | // the thread is being destroyed; make sure not to leave dangling pointers around |
| 747 | m_pHandler->m_pThread = NULL; |
| 748 | } |
| 749 | |
| 750 | void MyFrame::OnThreadCompletion(wxThreadEvent&) |
| 751 | { |
| 752 | wxMessageOutputDebug().Printf("MYFRAME: MyThread exited!\n"); |
| 753 | } |
| 754 | |
| 755 | void MyFrame::OnThreadUpdate(wxThreadEvent&) |
| 756 | { |
| 757 | wxMessageOutputDebug().Printf("MYFRAME: MyThread update...\n"); |
| 758 | } |
| 759 | |
| 760 | void MyFrame::DoPauseThread() |
| 761 | { |
| 762 | // anytime we access the m_pThread pointer we must ensure that it won't |
| 763 | // be modified in the meanwhile; since only a single thread may be |
| 764 | // inside a given critical section at a given time, the following code |
| 765 | // is safe: |
| 766 | wxCriticalSectionLocker enter(m_pThreadCS); |
| 767 | |
| 768 | if (m_pThread) // does the thread still exist? |
| 769 | { |
| 770 | // without a critical section, once reached this point it may happen |
| 771 | // that the OS scheduler gives control to the MyThread::Entry() function, |
| 772 | // which in turn may return (because it completes its work) making |
| 773 | // invalid the m_pThread pointer |
| 774 | |
| 775 | if (m_pThread->Pause() != wxTHREAD_NO_ERROR ) |
| 776 | wxLogError("Can't pause the thread!"); |
| 777 | } |
| 778 | } |
| 779 | |
| 780 | void MyFrame::OnClose(wxCloseEvent&) |
| 781 | { |
| 782 | { |
| 783 | wxCriticalSectionLocker enter(m_pThreadCS); |
| 784 | |
| 785 | if (m_pThread) // does the thread still exist? |
| 786 | { |
| 787 | m_out.Printf("MYFRAME: deleting thread"); |
| 788 | |
| 789 | if (m_pThread->Delete() != wxTHREAD_NO_ERROR ) |
| 790 | wxLogError("Can't delete the thread!"); |
| 791 | } |
| 792 | } // exit from the critical section to give the thread |
| 793 | // the possibility to enter its destructor |
| 794 | // (which is guarded with m_pThreadCS critical section!) |
| 795 | |
| 796 | while (1) |
| 797 | { |
| 798 | { // was the ~MyThread() function executed? |
| 799 | wxCriticalSectionLocker enter(m_pThreadCS); |
| 800 | if (!m_pThread) break; |
| 801 | } |
| 802 | |
| 803 | // wait for thread completion |
| 804 | wxThread::This()->Sleep(1); |
| 805 | } |
| 806 | |
| 807 | Destroy(); |
| 808 | } |
| 809 | @endcode |
| 810 | |
| 811 | For a more detailed and comprehensive example, see @sample{thread}. |
| 812 | For a simpler way to share data and synchronization objects between |
| 813 | the main and the secondary thread see wxThreadHelper. |
| 814 | |
| 815 | Conversely, @b joinable threads do not delete themselves when they are done |
| 816 | processing and as such are safe to create on the stack. Joinable threads |
| 817 | also provide the ability for one to get value it returned from Entry() |
| 818 | through Wait(). |
| 819 | You shouldn't hurry to create all the threads joinable, however, because this |
| 820 | has a disadvantage as well: you @b must Wait() for a joinable thread or the |
| 821 | system resources used by it will never be freed, and you also must delete the |
| 822 | corresponding wxThread object yourself if you did not create it on the stack. |
| 823 | In contrast, detached threads are of the "fire-and-forget" kind: you only have |
| 824 | to start a detached thread and it will terminate and destroy itself. |
| 825 | |
| 826 | |
| 827 | @section thread_deletion wxThread Deletion |
| 828 | |
| 829 | Regardless of whether it has terminated or not, you should call Wait() on a |
| 830 | @b joinable thread to release its memory, as outlined in @ref thread_types. |
| 831 | If you created a joinable thread on the heap, remember to delete it manually |
| 832 | with the @c delete operator or similar means as only detached threads handle |
| 833 | this type of memory management. |
| 834 | |
| 835 | Since @b detached threads delete themselves when they are finished processing, |
| 836 | you should take care when calling a routine on one. If you are certain the |
| 837 | thread is still running and would like to end it, you may call Delete() |
| 838 | to gracefully end it (which implies that the thread will be deleted after |
| 839 | that call to Delete()). It should be implied that you should @b never attempt |
| 840 | to delete a detached thread with the @c delete operator or similar means. |
| 841 | |
| 842 | As mentioned, Wait() or Delete() functions attempt to gracefully terminate a |
| 843 | joinable and a detached thread, respectively. They do this by waiting until |
| 844 | the thread in question calls TestDestroy() or ends processing (i.e. returns |
| 845 | from wxThread::Entry). |
| 846 | |
| 847 | Obviously, if the thread does call TestDestroy() and does not end, the |
| 848 | thread which called Wait() or Delete() will come to halt. |
| 849 | This is why it's important to call TestDestroy() in the Entry() routine of |
| 850 | your threads as often as possible and immediately exit when it returns @true. |
| 851 | |
| 852 | As a last resort you can end the thread immediately through Kill(). It is |
| 853 | strongly recommended that you do not do this, however, as it does not free |
| 854 | the resources associated with the object (although the wxThread object of |
| 855 | detached threads will still be deleted) and could leave the C runtime |
| 856 | library in an undefined state. |
| 857 | |
| 858 | |
| 859 | @section thread_secondary wxWidgets Calls in Secondary Threads |
| 860 | |
| 861 | All threads other than the "main application thread" (the one running |
| 862 | wxApp::OnInit() or the one your main function runs in, for example) are |
| 863 | considered "secondary threads". These include all threads created by Create() |
| 864 | or the corresponding constructors. |
| 865 | |
| 866 | GUI calls, such as those to a wxWindow or wxBitmap are explicitly not safe |
| 867 | at all in secondary threads and could end your application prematurely. |
| 868 | This is due to several reasons, including the underlying native API and |
| 869 | the fact that wxThread does not run a GUI event loop similar to other APIs |
| 870 | as MFC. |
| 871 | |
| 872 | A workaround for some wxWidgets ports is calling wxMutexGUIEnter() |
| 873 | before any GUI calls and then calling wxMutexGUILeave() afterwords. |
| 874 | However, the recommended way is to simply process the GUI calls in the main |
| 875 | thread through an event that is posted by wxQueueEvent(). |
| 876 | This does not imply that calls to these classes are thread-safe, however, |
| 877 | as most wxWidgets classes are not thread-safe, including wxString. |
| 878 | |
| 879 | |
| 880 | @section thread_poll Don't Poll a wxThread |
| 881 | |
| 882 | A common problem users experience with wxThread is that in their main thread |
| 883 | they will check the thread every now and then to see if it has ended through |
| 884 | IsRunning(), only to find that their application has run into problems |
| 885 | because the thread is using the default behavior (i.e. it's @b detached) and |
| 886 | has already deleted itself. |
| 887 | Naturally, they instead attempt to use joinable threads in place of the previous |
| 888 | behavior. However, polling a wxThread for when it has ended is in general a |
| 889 | bad idea - in fact calling a routine on any running wxThread should be avoided |
| 890 | if possible. Instead, find a way to notify yourself when the thread has ended. |
| 891 | |
| 892 | Usually you only need to notify the main thread, in which case you can |
| 893 | post an event to it via wxQueueEvent(). |
| 894 | In the case of secondary threads you can call a routine of another class |
| 895 | when the thread is about to complete processing and/or set the value of |
| 896 | a variable, possibly using mutexes (see wxMutex) and/or other synchronization |
| 897 | means if necessary. |
| 898 | |
| 899 | @library{wxbase} |
| 900 | @category{threading} |
| 901 | |
| 902 | @see wxThreadHelper, wxMutex, wxCondition, wxCriticalSection, |
| 903 | @ref overview_thread |
| 904 | */ |
| 905 | class wxThread |
| 906 | { |
| 907 | public: |
| 908 | /** |
| 909 | The return type for the thread functions. |
| 910 | */ |
| 911 | typedef void* ExitCode; |
| 912 | |
| 913 | /** |
| 914 | This constructor creates a new detached (default) or joinable C++ |
| 915 | thread object. It does not create or start execution of the real thread - |
| 916 | for this you should use the Create() and Run() methods. |
| 917 | |
| 918 | The possible values for @a kind parameters are: |
| 919 | - @b wxTHREAD_DETACHED - Creates a detached thread. |
| 920 | - @b wxTHREAD_JOINABLE - Creates a joinable thread. |
| 921 | */ |
| 922 | wxThread(wxThreadKind kind = wxTHREAD_DETACHED); |
| 923 | |
| 924 | /** |
| 925 | The destructor frees the resources associated with the thread. |
| 926 | Notice that you should never delete a detached thread -- you may only call |
| 927 | Delete() on it or wait until it terminates (and auto destructs) itself. |
| 928 | |
| 929 | Because the detached threads delete themselves, they can only be allocated on the heap. |
| 930 | Joinable threads should be deleted explicitly. The Delete() and Kill() functions |
| 931 | will not delete the C++ thread object. It is also safe to allocate them on stack. |
| 932 | */ |
| 933 | virtual ~wxThread(); |
| 934 | |
| 935 | /** |
| 936 | Creates a new thread. |
| 937 | |
| 938 | The thread object is created in the suspended state, and you should call Run() |
| 939 | to start running it. You may optionally specify the stack size to be allocated |
| 940 | to it (Ignored on platforms that don't support setting it explicitly, |
| 941 | eg. Unix system without @c pthread_attr_setstacksize). |
| 942 | |
| 943 | If you do not specify the stack size,the system's default value is used. |
| 944 | |
| 945 | @warning |
| 946 | It is a good idea to explicitly specify a value as systems' |
| 947 | default values vary from just a couple of KB on some systems (BSD and |
| 948 | OS/2 systems) to one or several MB (Windows, Solaris, Linux). |
| 949 | So, if you have a thread that requires more than just a few KB of memory, you |
| 950 | will have mysterious problems on some platforms but not on the common ones. |
| 951 | On the other hand, just indicating a large stack size by default will give you |
| 952 | performance issues on those systems with small default stack since those |
| 953 | typically use fully committed memory for the stack. |
| 954 | On the contrary, if you use a lot of threads (say several hundred), |
| 955 | virtual adress space can get tight unless you explicitly specify a |
| 956 | smaller amount of thread stack space for each thread. |
| 957 | |
| 958 | @return One of: |
| 959 | - @b wxTHREAD_NO_ERROR - No error. |
| 960 | - @b wxTHREAD_NO_RESOURCE - There were insufficient resources to create the thread. |
| 961 | - @b wxTHREAD_NO_RUNNING - The thread is already running |
| 962 | */ |
| 963 | wxThreadError Create(unsigned int stackSize = 0); |
| 964 | |
| 965 | /** |
| 966 | Calling Delete() gracefully terminates a @b detached thread, either when |
| 967 | the thread calls TestDestroy() or when it finishes processing. |
| 968 | |
| 969 | @note |
| 970 | This function works on a joinable thread but in that case makes |
| 971 | the TestDestroy() function of the thread return @true and then |
| 972 | waits for its completion (i.e. it differs from Wait() because |
| 973 | it asks the thread to terminate before waiting). |
| 974 | |
| 975 | See @ref thread_deletion for a broader explanation of this routine. |
| 976 | */ |
| 977 | wxThreadError Delete(void** rc = NULL); |
| 978 | |
| 979 | /** |
| 980 | Returns the number of system CPUs or -1 if the value is unknown. |
| 981 | |
| 982 | For multi-core systems the returned value is typically the total number |
| 983 | of @e cores, since the OS usually abstract a single N-core CPU |
| 984 | as N different cores. |
| 985 | |
| 986 | @see SetConcurrency() |
| 987 | */ |
| 988 | static int GetCPUCount(); |
| 989 | |
| 990 | /** |
| 991 | Returns the platform specific thread ID of the current thread as a long. |
| 992 | This can be used to uniquely identify threads, even if they are not wxThreads. |
| 993 | */ |
| 994 | static wxThreadIdType GetCurrentId(); |
| 995 | |
| 996 | /** |
| 997 | Gets the thread identifier: this is a platform dependent number that uniquely |
| 998 | identifies the thread throughout the system during its existence |
| 999 | (i.e. the thread identifiers may be reused). |
| 1000 | */ |
| 1001 | wxThreadIdType GetId() const; |
| 1002 | |
| 1003 | /** |
| 1004 | Returns the thread kind as it was given in the ctor. |
| 1005 | |
| 1006 | @since 2.9.0 |
| 1007 | */ |
| 1008 | wxThreadKind GetKind() const; |
| 1009 | |
| 1010 | /** |
| 1011 | Gets the priority of the thread, between zero and 100. |
| 1012 | |
| 1013 | The following priorities are defined: |
| 1014 | - @b WXTHREAD_MIN_PRIORITY: 0 |
| 1015 | - @b WXTHREAD_DEFAULT_PRIORITY: 50 |
| 1016 | - @b WXTHREAD_MAX_PRIORITY: 100 |
| 1017 | */ |
| 1018 | unsigned int GetPriority() const; |
| 1019 | |
| 1020 | /** |
| 1021 | Returns @true if the thread is alive (i.e. started and not terminating). |
| 1022 | |
| 1023 | Note that this function can only safely be used with joinable threads, not |
| 1024 | detached ones as the latter delete themselves and so when the real thread is |
| 1025 | no longer alive, it is not possible to call this function because |
| 1026 | the wxThread object no longer exists. |
| 1027 | */ |
| 1028 | bool IsAlive() const; |
| 1029 | |
| 1030 | /** |
| 1031 | Returns @true if the thread is of the detached kind, @false if it is a |
| 1032 | joinable one. |
| 1033 | */ |
| 1034 | bool IsDetached() const; |
| 1035 | |
| 1036 | /** |
| 1037 | Returns @true if the calling thread is the main application thread. |
| 1038 | */ |
| 1039 | static bool IsMain(); |
| 1040 | |
| 1041 | /** |
| 1042 | Returns @true if the thread is paused. |
| 1043 | */ |
| 1044 | bool IsPaused() const; |
| 1045 | |
| 1046 | /** |
| 1047 | Returns @true if the thread is running. |
| 1048 | |
| 1049 | This method may only be safely used for joinable threads, see the remark in |
| 1050 | IsAlive(). |
| 1051 | */ |
| 1052 | bool IsRunning() const; |
| 1053 | |
| 1054 | /** |
| 1055 | Immediately terminates the target thread. |
| 1056 | |
| 1057 | @b "This function is dangerous and should be used with extreme care" |
| 1058 | (and not used at all whenever possible)! The resources allocated to the |
| 1059 | thread will not be freed and the state of the C runtime library may become |
| 1060 | inconsistent. Use Delete() for detached threads or Wait() for joinable |
| 1061 | threads instead. |
| 1062 | |
| 1063 | For detached threads Kill() will also delete the associated C++ object. |
| 1064 | However this will not happen for joinable threads and this means that you will |
| 1065 | still have to delete the wxThread object yourself to avoid memory leaks. |
| 1066 | |
| 1067 | In neither case OnExit() of the dying thread will be called, so no |
| 1068 | thread-specific cleanup will be performed. |
| 1069 | This function can only be called from another thread context, i.e. a thread |
| 1070 | cannot kill itself. |
| 1071 | |
| 1072 | It is also an error to call this function for a thread which is not running or |
| 1073 | paused (in the latter case, the thread will be resumed first) -- if you do it, |
| 1074 | a @b wxTHREAD_NOT_RUNNING error will be returned. |
| 1075 | */ |
| 1076 | wxThreadError Kill(); |
| 1077 | |
| 1078 | /** |
| 1079 | Suspends the thread. |
| 1080 | |
| 1081 | Under some implementations (Win32), the thread is suspended immediately, |
| 1082 | under others it will only be suspended when it calls TestDestroy() for |
| 1083 | the next time (hence, if the thread doesn't call it at all, it won't be |
| 1084 | suspended). |
| 1085 | |
| 1086 | This function can only be called from another thread context. |
| 1087 | */ |
| 1088 | wxThreadError Pause(); |
| 1089 | |
| 1090 | /** |
| 1091 | Resumes a thread suspended by the call to Pause(). |
| 1092 | |
| 1093 | This function can only be called from another thread context. |
| 1094 | */ |
| 1095 | wxThreadError Resume(); |
| 1096 | |
| 1097 | /** |
| 1098 | Starts the thread execution. Should be called after Create(). |
| 1099 | |
| 1100 | Note that once you Run() a @b detached thread, @e any function call you do |
| 1101 | on the thread pointer (you must allocate it on the heap) is @e "unsafe"; |
| 1102 | i.e. the thread may have terminated at any moment after Run() and your pointer |
| 1103 | may be dangling. See @ref thread_types for an example of safe manipulation |
| 1104 | of detached threads. |
| 1105 | |
| 1106 | This function can only be called from another thread context. |
| 1107 | */ |
| 1108 | wxThreadError Run(); |
| 1109 | |
| 1110 | /** |
| 1111 | Sets the thread concurrency level for this process. |
| 1112 | |
| 1113 | This is, roughly, the number of threads that the system tries to schedule |
| 1114 | to run in parallel. |
| 1115 | The value of 0 for @a level may be used to set the default one. |
| 1116 | |
| 1117 | @return @true on success or @false otherwise (for example, if this function is |
| 1118 | not implemented for this platform -- currently everything except Solaris). |
| 1119 | */ |
| 1120 | static bool SetConcurrency(size_t level); |
| 1121 | |
| 1122 | /** |
| 1123 | Sets the priority of the thread, between 0 and 100. |
| 1124 | It can only be set after calling Create() but before calling Run(). |
| 1125 | |
| 1126 | The following priorities are defined: |
| 1127 | - @b WXTHREAD_MIN_PRIORITY: 0 |
| 1128 | - @b WXTHREAD_DEFAULT_PRIORITY: 50 |
| 1129 | - @b WXTHREAD_MAX_PRIORITY: 100 |
| 1130 | */ |
| 1131 | void SetPriority(unsigned int priority); |
| 1132 | |
| 1133 | /** |
| 1134 | Pauses the thread execution for the given amount of time. |
| 1135 | |
| 1136 | This is the same as wxMilliSleep(). |
| 1137 | */ |
| 1138 | static void Sleep(unsigned long milliseconds); |
| 1139 | |
| 1140 | /** |
| 1141 | This function should be called periodically by the thread to ensure that |
| 1142 | calls to Pause() and Delete() will work. |
| 1143 | |
| 1144 | If it returns @true, the thread should exit as soon as possible. |
| 1145 | Notice that under some platforms (POSIX), implementation of Pause() also |
| 1146 | relies on this function being called, so not calling it would prevent |
| 1147 | both stopping and suspending thread from working. |
| 1148 | */ |
| 1149 | virtual bool TestDestroy(); |
| 1150 | |
| 1151 | /** |
| 1152 | Return the thread object for the calling thread. |
| 1153 | |
| 1154 | @NULL is returned if the calling thread is the main (GUI) thread, but |
| 1155 | IsMain() should be used to test whether the thread is really the main one |
| 1156 | because @NULL may also be returned for the thread not created with wxThread |
| 1157 | class. Generally speaking, the return value for such a thread is undefined. |
| 1158 | */ |
| 1159 | static wxThread* This(); |
| 1160 | |
| 1161 | /** |
| 1162 | Waits for a @b joinable thread to terminate and returns the value the thread |
| 1163 | returned from Entry() or @c "(ExitCode)-1" on error. Notice that, unlike |
| 1164 | Delete(), this function doesn't cancel the thread in any way so the caller |
| 1165 | waits for as long as it takes to the thread to exit. |
| 1166 | |
| 1167 | You can only Wait() for @b joinable (not detached) threads. |
| 1168 | |
| 1169 | This function can only be called from another thread context. |
| 1170 | |
| 1171 | See @ref thread_deletion for a broader explanation of this routine. |
| 1172 | */ |
| 1173 | ExitCode Wait(); |
| 1174 | |
| 1175 | /** |
| 1176 | Give the rest of the thread's time-slice to the system allowing the other |
| 1177 | threads to run. |
| 1178 | |
| 1179 | Note that using this function is @b strongly discouraged, since in |
| 1180 | many cases it indicates a design weakness of your threading model |
| 1181 | (as does using Sleep() functions). |
| 1182 | |
| 1183 | Threads should use the CPU in an efficient manner, i.e. they should |
| 1184 | do their current work efficiently, then as soon as the work is done block |
| 1185 | on a wakeup event (wxCondition, wxMutex, select(), poll(), ...) which will |
| 1186 | get signalled e.g. by other threads or a user device once further thread |
| 1187 | work is available. |
| 1188 | Using Yield() or Sleep() indicates polling-type behaviour, since we're |
| 1189 | fuzzily giving up our timeslice and wait until sometime later we'll get |
| 1190 | reactivated, at which time we realize that there isn't really much to do |
| 1191 | and Yield() again... |
| 1192 | |
| 1193 | The most critical characteristic of Yield() is that it's operating system |
| 1194 | specific: there may be scheduler changes which cause your thread to not |
| 1195 | wake up relatively soon again, but instead many seconds later, |
| 1196 | causing huge performance issues for your application. |
| 1197 | |
| 1198 | <strong> |
| 1199 | With a well-behaving, CPU-efficient thread the operating system is likely |
| 1200 | to properly care for its reactivation the moment it needs it, whereas with |
| 1201 | non-deterministic, Yield-using threads all bets are off and the system |
| 1202 | scheduler is free to penalize them drastically</strong>, and this effect |
| 1203 | gets worse with increasing system load due to less free CPU resources available. |
| 1204 | You may refer to various Linux kernel @c sched_yield discussions for more |
| 1205 | information. |
| 1206 | |
| 1207 | See also Sleep(). |
| 1208 | */ |
| 1209 | static void Yield(); |
| 1210 | |
| 1211 | protected: |
| 1212 | |
| 1213 | /** |
| 1214 | This is the entry point of the thread. |
| 1215 | |
| 1216 | This function is pure virtual and must be implemented by any derived class. |
| 1217 | The thread execution will start here. |
| 1218 | |
| 1219 | The returned value is the thread exit code which is only useful for |
| 1220 | joinable threads and is the value returned by Wait(). |
| 1221 | This function is called by wxWidgets itself and should never be called |
| 1222 | directly. |
| 1223 | */ |
| 1224 | virtual ExitCode Entry() = 0; |
| 1225 | |
| 1226 | /** |
| 1227 | This is a protected function of the wxThread class and thus can only be called |
| 1228 | from a derived class. It also can only be called in the context of this |
| 1229 | thread, i.e. a thread can only exit from itself, not from another thread. |
| 1230 | |
| 1231 | This function will terminate the OS thread (i.e. stop the associated path of |
| 1232 | execution) and also delete the associated C++ object for detached threads. |
| 1233 | OnExit() will be called just before exiting. |
| 1234 | */ |
| 1235 | void Exit(ExitCode exitcode = 0); |
| 1236 | |
| 1237 | private: |
| 1238 | |
| 1239 | /** |
| 1240 | Called when the thread exits. |
| 1241 | |
| 1242 | This function is called in the context of the thread associated with the |
| 1243 | wxThread object, not in the context of the main thread. |
| 1244 | This function will not be called if the thread was @ref Kill() killed. |
| 1245 | |
| 1246 | This function should never be called directly. |
| 1247 | */ |
| 1248 | virtual void OnExit(); |
| 1249 | }; |
| 1250 | |
| 1251 | |
| 1252 | /** See wxSemaphore. */ |
| 1253 | enum wxSemaError |
| 1254 | { |
| 1255 | wxSEMA_NO_ERROR = 0, |
| 1256 | wxSEMA_INVALID, //!< semaphore hasn't been initialized successfully |
| 1257 | wxSEMA_BUSY, //!< returned by TryWait() if Wait() would block |
| 1258 | wxSEMA_TIMEOUT, //!< returned by WaitTimeout() |
| 1259 | wxSEMA_OVERFLOW, //!< Post() would increase counter past the max |
| 1260 | wxSEMA_MISC_ERROR |
| 1261 | }; |
| 1262 | |
| 1263 | /** |
| 1264 | @class wxSemaphore |
| 1265 | |
| 1266 | wxSemaphore is a counter limiting the number of threads concurrently accessing |
| 1267 | a shared resource. This counter is always between 0 and the maximum value |
| 1268 | specified during the semaphore creation. When the counter is strictly greater |
| 1269 | than 0, a call to wxSemaphore::Wait() returns immediately and decrements the |
| 1270 | counter. As soon as it reaches 0, any subsequent calls to wxSemaphore::Wait |
| 1271 | block and only return when the semaphore counter becomes strictly positive |
| 1272 | again as the result of calling wxSemaphore::Post which increments the counter. |
| 1273 | |
| 1274 | In general, semaphores are useful to restrict access to a shared resource |
| 1275 | which can only be accessed by some fixed number of clients at the same time. |
| 1276 | For example, when modeling a hotel reservation system a semaphore with the counter |
| 1277 | equal to the total number of available rooms could be created. Each time a room |
| 1278 | is reserved, the semaphore should be acquired by calling wxSemaphore::Wait |
| 1279 | and each time a room is freed it should be released by calling wxSemaphore::Post. |
| 1280 | |
| 1281 | @library{wxbase} |
| 1282 | @category{threading} |
| 1283 | */ |
| 1284 | class wxSemaphore |
| 1285 | { |
| 1286 | public: |
| 1287 | /** |
| 1288 | Specifying a @a maxcount of 0 actually makes wxSemaphore behave as if |
| 1289 | there is no upper limit. If @a maxcount is 1, the semaphore behaves almost as a |
| 1290 | mutex (but unlike a mutex it can be released by a thread different from the one |
| 1291 | which acquired it). |
| 1292 | |
| 1293 | @a initialcount is the initial value of the semaphore which must be between |
| 1294 | 0 and @a maxcount (if it is not set to 0). |
| 1295 | */ |
| 1296 | wxSemaphore(int initialcount = 0, int maxcount = 0); |
| 1297 | |
| 1298 | /** |
| 1299 | Destructor is not virtual, don't use this class polymorphically. |
| 1300 | */ |
| 1301 | ~wxSemaphore(); |
| 1302 | |
| 1303 | /** |
| 1304 | Increments the semaphore count and signals one of the waiting |
| 1305 | threads in an atomic way. Returns @e wxSEMA_OVERFLOW if the count |
| 1306 | would increase the counter past the maximum. |
| 1307 | |
| 1308 | @return One of: |
| 1309 | - wxSEMA_NO_ERROR: There was no error. |
| 1310 | - wxSEMA_INVALID : Semaphore hasn't been initialized successfully. |
| 1311 | - wxSEMA_OVERFLOW: Post() would increase counter past the max. |
| 1312 | - wxSEMA_MISC_ERROR: Miscellaneous error. |
| 1313 | */ |
| 1314 | wxSemaError Post(); |
| 1315 | |
| 1316 | /** |
| 1317 | Same as Wait(), but returns immediately. |
| 1318 | |
| 1319 | @return One of: |
| 1320 | - wxSEMA_NO_ERROR: There was no error. |
| 1321 | - wxSEMA_INVALID: Semaphore hasn't been initialized successfully. |
| 1322 | - wxSEMA_BUSY: Returned by TryWait() if Wait() would block, i.e. the count is zero. |
| 1323 | - wxSEMA_MISC_ERROR: Miscellaneous error. |
| 1324 | */ |
| 1325 | wxSemaError TryWait(); |
| 1326 | |
| 1327 | /** |
| 1328 | Wait indefinitely until the semaphore count becomes strictly positive |
| 1329 | and then decrement it and return. |
| 1330 | |
| 1331 | @return One of: |
| 1332 | - wxSEMA_NO_ERROR: There was no error. |
| 1333 | - wxSEMA_INVALID: Semaphore hasn't been initialized successfully. |
| 1334 | - wxSEMA_MISC_ERROR: Miscellaneous error. |
| 1335 | */ |
| 1336 | wxSemaError Wait(); |
| 1337 | |
| 1338 | /** |
| 1339 | Same as Wait(), but with a timeout limit. |
| 1340 | |
| 1341 | @return One of: |
| 1342 | - wxSEMA_NO_ERROR: There was no error. |
| 1343 | - wxSEMA_INVALID: Semaphore hasn't been initialized successfully. |
| 1344 | - wxSEMA_TIMEOUT: Timeout occurred without receiving semaphore. |
| 1345 | - wxSEMA_MISC_ERROR: Miscellaneous error. |
| 1346 | */ |
| 1347 | wxSemaError WaitTimeout(unsigned long timeout_millis); |
| 1348 | }; |
| 1349 | |
| 1350 | |
| 1351 | |
| 1352 | /** |
| 1353 | @class wxMutexLocker |
| 1354 | |
| 1355 | This is a small helper class to be used with wxMutex objects. |
| 1356 | |
| 1357 | A wxMutexLocker acquires a mutex lock in the constructor and releases |
| 1358 | (or unlocks) the mutex in the destructor making it much more difficult to |
| 1359 | forget to release a mutex (which, in general, will promptly lead to serious |
| 1360 | problems). See wxMutex for an example of wxMutexLocker usage. |
| 1361 | |
| 1362 | @library{wxbase} |
| 1363 | @category{threading} |
| 1364 | |
| 1365 | @see wxMutex, wxCriticalSectionLocker |
| 1366 | */ |
| 1367 | class wxMutexLocker |
| 1368 | { |
| 1369 | public: |
| 1370 | /** |
| 1371 | Constructs a wxMutexLocker object associated with mutex and locks it. |
| 1372 | Call IsOk() to check if the mutex was successfully locked. |
| 1373 | */ |
| 1374 | wxMutexLocker(wxMutex& mutex); |
| 1375 | |
| 1376 | /** |
| 1377 | Destructor releases the mutex if it was successfully acquired in the ctor. |
| 1378 | */ |
| 1379 | ~wxMutexLocker(); |
| 1380 | |
| 1381 | /** |
| 1382 | Returns @true if mutex was acquired in the constructor, @false otherwise. |
| 1383 | */ |
| 1384 | bool IsOk() const; |
| 1385 | }; |
| 1386 | |
| 1387 | |
| 1388 | /** |
| 1389 | The possible wxMutex kinds. |
| 1390 | */ |
| 1391 | enum wxMutexType |
| 1392 | { |
| 1393 | /** Normal non-recursive mutex: try to always use this one. */ |
| 1394 | wxMUTEX_DEFAULT, |
| 1395 | |
| 1396 | /** Recursive mutex: don't use these ones with wxCondition. */ |
| 1397 | wxMUTEX_RECURSIVE |
| 1398 | }; |
| 1399 | |
| 1400 | |
| 1401 | /** |
| 1402 | The possible wxMutex errors. |
| 1403 | */ |
| 1404 | enum wxMutexError |
| 1405 | { |
| 1406 | /** The operation completed successfully. */ |
| 1407 | wxMUTEX_NO_ERROR = 0, |
| 1408 | |
| 1409 | /** The mutex hasn't been initialized. */ |
| 1410 | wxMUTEX_INVALID, |
| 1411 | |
| 1412 | /** The mutex is already locked by the calling thread. */ |
| 1413 | wxMUTEX_DEAD_LOCK, |
| 1414 | |
| 1415 | /** The mutex is already locked by another thread. */ |
| 1416 | wxMUTEX_BUSY, |
| 1417 | |
| 1418 | /** An attempt to unlock a mutex which is not locked. */ |
| 1419 | wxMUTEX_UNLOCKED, |
| 1420 | |
| 1421 | /** wxMutex::LockTimeout() has timed out. */ |
| 1422 | wxMUTEX_TIMEOUT, |
| 1423 | |
| 1424 | /** Any other error */ |
| 1425 | wxMUTEX_MISC_ERROR |
| 1426 | }; |
| 1427 | |
| 1428 | |
| 1429 | /** |
| 1430 | @class wxMutex |
| 1431 | |
| 1432 | A mutex object is a synchronization object whose state is set to signaled when |
| 1433 | it is not owned by any thread, and nonsignaled when it is owned. Its name comes |
| 1434 | from its usefulness in coordinating mutually-exclusive access to a shared |
| 1435 | resource as only one thread at a time can own a mutex object. |
| 1436 | |
| 1437 | Mutexes may be recursive in the sense that a thread can lock a mutex which it |
| 1438 | had already locked before (instead of dead locking the entire process in this |
| 1439 | situation by starting to wait on a mutex which will never be released while the |
| 1440 | thread is waiting) but using them is not recommended under Unix and they are |
| 1441 | @b not recursive by default. The reason for this is that recursive |
| 1442 | mutexes are not supported by all Unix flavours and, worse, they cannot be used |
| 1443 | with wxCondition. |
| 1444 | |
| 1445 | For example, when several threads use the data stored in the linked list, |
| 1446 | modifications to the list should only be allowed to one thread at a time |
| 1447 | because during a new node addition the list integrity is temporarily broken |
| 1448 | (this is also called @e program @e invariant). |
| 1449 | |
| 1450 | @code |
| 1451 | // this variable has an "s_" prefix because it is static: seeing an "s_" in |
| 1452 | // a multithreaded program is in general a good sign that you should use a |
| 1453 | // mutex (or a critical section) |
| 1454 | static wxMutex *s_mutexProtectingTheGlobalData; |
| 1455 | |
| 1456 | // we store some numbers in this global array which is presumably used by |
| 1457 | // several threads simultaneously |
| 1458 | wxArrayInt s_data; |
| 1459 | |
| 1460 | void MyThread::AddNewNode(int num) |
| 1461 | { |
| 1462 | // ensure that no other thread accesses the list |
| 1463 | s_mutexProtectingTheGlobalList->Lock(); |
| 1464 | |
| 1465 | s_data.Add(num); |
| 1466 | |
| 1467 | s_mutexProtectingTheGlobalList->Unlock(); |
| 1468 | } |
| 1469 | |
| 1470 | // return true if the given number is greater than all array elements |
| 1471 | bool MyThread::IsGreater(int num) |
| 1472 | { |
| 1473 | // before using the list we must acquire the mutex |
| 1474 | wxMutexLocker lock(s_mutexProtectingTheGlobalData); |
| 1475 | |
| 1476 | size_t count = s_data.Count(); |
| 1477 | for ( size_t n = 0; n < count; n++ ) |
| 1478 | { |
| 1479 | if ( s_data[n] > num ) |
| 1480 | return false; |
| 1481 | } |
| 1482 | |
| 1483 | return true; |
| 1484 | } |
| 1485 | @endcode |
| 1486 | |
| 1487 | Notice how wxMutexLocker was used in the second function to ensure that the |
| 1488 | mutex is unlocked in any case: whether the function returns true or false |
| 1489 | (because the destructor of the local object @e lock is always called). |
| 1490 | Using this class instead of directly using wxMutex is, in general, safer |
| 1491 | and is even more so if your program uses C++ exceptions. |
| 1492 | |
| 1493 | @library{wxbase} |
| 1494 | @category{threading} |
| 1495 | |
| 1496 | @see wxThread, wxCondition, wxMutexLocker, wxCriticalSection |
| 1497 | */ |
| 1498 | class wxMutex |
| 1499 | { |
| 1500 | public: |
| 1501 | /** |
| 1502 | Default constructor. |
| 1503 | */ |
| 1504 | wxMutex(wxMutexType type = wxMUTEX_DEFAULT); |
| 1505 | |
| 1506 | /** |
| 1507 | Destroys the wxMutex object. |
| 1508 | */ |
| 1509 | ~wxMutex(); |
| 1510 | |
| 1511 | /** |
| 1512 | Locks the mutex object. |
| 1513 | This is equivalent to LockTimeout() with infinite timeout. |
| 1514 | |
| 1515 | Note that if this mutex is already locked by the caller thread, |
| 1516 | this function doesn't block but rather immediately returns. |
| 1517 | |
| 1518 | @return One of: @c wxMUTEX_NO_ERROR, @c wxMUTEX_DEAD_LOCK. |
| 1519 | */ |
| 1520 | wxMutexError Lock(); |
| 1521 | |
| 1522 | /** |
| 1523 | Try to lock the mutex object during the specified time interval. |
| 1524 | |
| 1525 | @return One of: @c wxMUTEX_NO_ERROR, @c wxMUTEX_DEAD_LOCK, @c wxMUTEX_TIMEOUT. |
| 1526 | */ |
| 1527 | wxMutexError LockTimeout(unsigned long msec); |
| 1528 | |
| 1529 | /** |
| 1530 | Tries to lock the mutex object. If it can't, returns immediately with an error. |
| 1531 | |
| 1532 | @return One of: @c wxMUTEX_NO_ERROR, @c wxMUTEX_BUSY. |
| 1533 | */ |
| 1534 | wxMutexError TryLock(); |
| 1535 | |
| 1536 | /** |
| 1537 | Unlocks the mutex object. |
| 1538 | |
| 1539 | @return One of: @c wxMUTEX_NO_ERROR, @c wxMUTEX_UNLOCKED. |
| 1540 | */ |
| 1541 | wxMutexError Unlock(); |
| 1542 | }; |
| 1543 | |
| 1544 | |
| 1545 | |
| 1546 | // ============================================================================ |
| 1547 | // Global functions/macros |
| 1548 | // ============================================================================ |
| 1549 | |
| 1550 | /** @addtogroup group_funcmacro_thread */ |
| 1551 | //@{ |
| 1552 | |
| 1553 | /** |
| 1554 | This macro declares a (static) critical section object named @a cs if |
| 1555 | @c wxUSE_THREADS is 1 and does nothing if it is 0. |
| 1556 | |
| 1557 | @header{wx/thread.h} |
| 1558 | */ |
| 1559 | #define wxCRIT_SECT_DECLARE(cs) |
| 1560 | |
| 1561 | /** |
| 1562 | This macro declares a critical section object named @a cs if |
| 1563 | @c wxUSE_THREADS is 1 and does nothing if it is 0. As it doesn't include |
| 1564 | the @c static keyword (unlike wxCRIT_SECT_DECLARE()), it can be used to |
| 1565 | declare a class or struct member which explains its name. |
| 1566 | |
| 1567 | @header{wx/thread.h} |
| 1568 | */ |
| 1569 | #define wxCRIT_SECT_DECLARE_MEMBER(cs) |
| 1570 | |
| 1571 | /** |
| 1572 | This macro creates a wxCriticalSectionLocker named @a name and associated |
| 1573 | with the critical section @a cs if @c wxUSE_THREADS is 1 and does nothing |
| 1574 | if it is 0. |
| 1575 | |
| 1576 | @header{wx/thread.h} |
| 1577 | */ |
| 1578 | #define wxCRIT_SECT_LOCKER(name, cs) |
| 1579 | |
| 1580 | /** |
| 1581 | This macro combines wxCRIT_SECT_DECLARE() and wxCRIT_SECT_LOCKER(): it |
| 1582 | creates a static critical section object and also the lock object |
| 1583 | associated with it. Because of this, it can be only used inside a function, |
| 1584 | not at global scope. For example: |
| 1585 | |
| 1586 | @code |
| 1587 | int IncCount() |
| 1588 | { |
| 1589 | static int s_counter = 0; |
| 1590 | |
| 1591 | wxCRITICAL_SECTION(counter); |
| 1592 | |
| 1593 | return ++s_counter; |
| 1594 | } |
| 1595 | @endcode |
| 1596 | |
| 1597 | Note that this example assumes that the function is called the first time |
| 1598 | from the main thread so that the critical section object is initialized |
| 1599 | correctly by the time other threads start calling it, if this is not the |
| 1600 | case this approach can @b not be used and the critical section must be made |
| 1601 | a global instead. |
| 1602 | |
| 1603 | @header{wx/thread.h} |
| 1604 | */ |
| 1605 | #define wxCRITICAL_SECTION(name) |
| 1606 | |
| 1607 | /** |
| 1608 | This macro is equivalent to |
| 1609 | @ref wxCriticalSection::Leave "critical_section.Leave()" if |
| 1610 | @c wxUSE_THREADS is 1 and does nothing if it is 0. |
| 1611 | |
| 1612 | @header{wx/thread.h} |
| 1613 | */ |
| 1614 | #define wxLEAVE_CRIT_SECT(critical_section) |
| 1615 | |
| 1616 | /** |
| 1617 | This macro is equivalent to |
| 1618 | @ref wxCriticalSection::Enter "critical_section.Enter()" if |
| 1619 | @c wxUSE_THREADS is 1 and does nothing if it is 0. |
| 1620 | |
| 1621 | @header{wx/thread.h} |
| 1622 | */ |
| 1623 | #define wxENTER_CRIT_SECT(critical_section) |
| 1624 | |
| 1625 | /** |
| 1626 | Returns @true if this thread is the main one. Always returns @true if |
| 1627 | @c wxUSE_THREADS is 0. |
| 1628 | |
| 1629 | @header{wx/thread.h} |
| 1630 | */ |
| 1631 | bool wxIsMainThread(); |
| 1632 | |
| 1633 | |
| 1634 | |
| 1635 | /** |
| 1636 | This function must be called when any thread other than the main GUI thread |
| 1637 | wants to get access to the GUI library. This function will block the |
| 1638 | execution of the calling thread until the main thread (or any other thread |
| 1639 | holding the main GUI lock) leaves the GUI library and no other thread will |
| 1640 | enter the GUI library until the calling thread calls wxMutexGuiLeave(). |
| 1641 | |
| 1642 | Typically, these functions are used like this: |
| 1643 | |
| 1644 | @code |
| 1645 | void MyThread::Foo(void) |
| 1646 | { |
| 1647 | // before doing any GUI calls we must ensure that |
| 1648 | // this thread is the only one doing it! |
| 1649 | |
| 1650 | wxMutexGuiEnter(); |
| 1651 | |
| 1652 | // Call GUI here: |
| 1653 | my_window->DrawSomething(); |
| 1654 | |
| 1655 | wxMutexGuiLeave(); |
| 1656 | } |
| 1657 | @endcode |
| 1658 | |
| 1659 | This function is only defined on platforms which support preemptive |
| 1660 | threads and only works under some ports (wxMSW currently). |
| 1661 | |
| 1662 | @note Under GTK, no creation of top-level windows is allowed in any thread |
| 1663 | but the main one. |
| 1664 | |
| 1665 | @header{wx/thread.h} |
| 1666 | */ |
| 1667 | void wxMutexGuiEnter(); |
| 1668 | |
| 1669 | /** |
| 1670 | This function is only defined on platforms which support preemptive |
| 1671 | threads. |
| 1672 | |
| 1673 | @see wxMutexGuiEnter() |
| 1674 | |
| 1675 | @header{wx/thread.h} |
| 1676 | */ |
| 1677 | void wxMutexGuiLeave(); |
| 1678 | |
| 1679 | //@} |
| 1680 | |