include/wx/thrimpl.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        include/wx/thrimpl.cpp
   3 // Purpose:     common part of wxThread Implementations
   4 // Author:      Vadim Zeitlin
   5 // Modified by:
   6 // Created:     04.06.02 (extracted from src/*/thread.cpp files)
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Vadim Zeitlin (2002)
   9 // Licence:     wxWindows licence
  10 /////////////////////////////////////////////////////////////////////////////
  11
  12 // this file is supposed to be included only by the various thread.cpp
  13
  14 // ----------------------------------------------------------------------------
  15 // wxMutex
  16 // ----------------------------------------------------------------------------
  17
  18 wxMutex::wxMutex(wxMutexType mutexType)
  19 {
  20     m_internal = new wxMutexInternal(mutexType);
  21
  22     if ( !m_internal->IsOk() )
  23     {
  24         delete m_internal;
  25         m_internal = NULL;
  26     }
  27 }
  28
  29 wxMutex::~wxMutex()
  30 {
  31     delete m_internal;
  32 }
  33
  34 bool wxMutex::IsOk() const
  35 {
  36     return m_internal != NULL;
  37 }
  38
  39 wxMutexError wxMutex::Lock()
  40 {
  41     wxCHECK_MSG( m_internal, wxMUTEX_INVALID,
  42                  wxT("wxMutex::Lock(): not initialized") );
  43
  44     return m_internal->Lock();
  45 }
  46
  47 wxMutexError wxMutex::LockTimeout(unsigned long ms)
  48 {
  49     wxCHECK_MSG( m_internal, wxMUTEX_INVALID,
  50                  wxT("wxMutex::Lock(): not initialized") );
  51
  52     return m_internal->Lock(ms);
  53 }
  54
  55 wxMutexError wxMutex::TryLock()
  56 {
  57     wxCHECK_MSG( m_internal, wxMUTEX_INVALID,
  58                  wxT("wxMutex::TryLock(): not initialized") );
  59
  60     return m_internal->TryLock();
  61 }
  62
  63 wxMutexError wxMutex::Unlock()
  64 {
  65     wxCHECK_MSG( m_internal, wxMUTEX_INVALID,
  66                  wxT("wxMutex::Unlock(): not initialized") );
  67
  68     return m_internal->Unlock();
  69 }
  70
  71 // --------------------------------------------------------------------------
  72 // wxConditionInternal
  73 // --------------------------------------------------------------------------
  74
  75 // Win32 and OS/2 don't have explicit support for the POSIX condition
  76 // variables and their events/event semaphores have quite different semantics,
  77 // so we reimplement the conditions from scratch using the mutexes and
  78 // semaphores
  79 #if defined(__WXMSW__) || defined(__OS2__) || defined(__EMX__)
  80
  81 class wxConditionInternal
  82 {
  83 public:
  84     wxConditionInternal(wxMutex& mutex);
  85
  86     bool IsOk() const { return m_mutex.IsOk() && m_semaphore.IsOk(); }
  87
  88     wxCondError Wait();
  89     wxCondError WaitTimeout(unsigned long milliseconds);
  90
  91     wxCondError Signal();
  92     wxCondError Broadcast();
  93
  94 private:
  95     // the number of threads currently waiting for this condition
  96     LONG m_numWaiters;
  97
  98     // the critical section protecting m_numWaiters
  99     wxCriticalSection m_csWaiters;
 100
 101     wxMutex& m_mutex;
 102     wxSemaphore m_semaphore;
 103
 104     wxDECLARE_NO_COPY_CLASS(wxConditionInternal);
 105 };
 106
 107 wxConditionInternal::wxConditionInternal(wxMutex& mutex)
 108                    : m_mutex(mutex)
 109 {
 110     // another thread can't access it until we return from ctor, so no need to
 111     // protect access to m_numWaiters here
 112     m_numWaiters = 0;
 113 }
 114
 115 wxCondError wxConditionInternal::Wait()
 116 {
 117     // increment the number of waiters
 118     {
 119         wxCriticalSectionLocker lock(m_csWaiters);
 120         m_numWaiters++;
 121     }
 122
 123     m_mutex.Unlock();
 124
 125     // after unlocking the mutex other threads may Signal() us, but it is ok
 126     // now as we had already incremented m_numWaiters so Signal() will post the
 127     // semaphore and decrement m_numWaiters back even if it is called before we
 128     // start to Wait()
 129     const wxSemaError err = m_semaphore.Wait();
 130
 131     m_mutex.Lock();
 132
 133     if ( err == wxSEMA_NO_ERROR )
 134     {
 135         // m_numWaiters was decremented by Signal()
 136         return wxCOND_NO_ERROR;
 137     }
 138
 139     // but in case of an error we need to do it manually
 140     {
 141         wxCriticalSectionLocker lock(m_csWaiters);
 142         m_numWaiters--;
 143     }
 144
 145     return err == wxSEMA_TIMEOUT ? wxCOND_TIMEOUT : wxCOND_MISC_ERROR;
 146 }
 147
 148 wxCondError wxConditionInternal::WaitTimeout(unsigned long milliseconds)
 149 {
 150     {
 151         wxCriticalSectionLocker lock(m_csWaiters);
 152         m_numWaiters++;
 153     }
 154
 155     m_mutex.Unlock();
 156
 157     wxSemaError err = m_semaphore.WaitTimeout(milliseconds);
 158
 159     m_mutex.Lock();
 160
 161     if ( err == wxSEMA_NO_ERROR )
 162         return wxCOND_NO_ERROR;
 163
 164     if ( err == wxSEMA_TIMEOUT )
 165     {
 166         // a potential race condition exists here: it happens when a waiting
 167         // thread times out but doesn't have time to decrement m_numWaiters yet
 168         // before Signal() is called in another thread
 169         //
 170         // to handle this particular case, check the semaphore again after
 171         // acquiring m_csWaiters lock -- this will catch the signals missed
 172         // during this window
 173         wxCriticalSectionLocker lock(m_csWaiters);
 174
 175         err = m_semaphore.WaitTimeout(0);
 176         if ( err == wxSEMA_NO_ERROR )
 177             return wxCOND_NO_ERROR;
 178
 179         // we need to decrement m_numWaiters ourselves as it wasn't done by
 180         // Signal()
 181         m_numWaiters--;
 182
 183         return err == wxSEMA_TIMEOUT ? wxCOND_TIMEOUT : wxCOND_MISC_ERROR;
 184     }
 185
 186     // undo m_numWaiters++ above in case of an error
 187     {
 188         wxCriticalSectionLocker lock(m_csWaiters);
 189         m_numWaiters--;
 190     }
 191
 192     return wxCOND_MISC_ERROR;
 193 }
 194
 195 wxCondError wxConditionInternal::Signal()
 196 {
 197     wxCriticalSectionLocker lock(m_csWaiters);
 198
 199     if ( m_numWaiters > 0 )
 200     {
 201         // increment the semaphore by 1
 202         if ( m_semaphore.Post() != wxSEMA_NO_ERROR )
 203             return wxCOND_MISC_ERROR;
 204
 205         m_numWaiters--;
 206     }
 207
 208     return wxCOND_NO_ERROR;
 209 }
 210
 211 wxCondError wxConditionInternal::Broadcast()
 212 {
 213     wxCriticalSectionLocker lock(m_csWaiters);
 214
 215     while ( m_numWaiters > 0 )
 216     {
 217         if ( m_semaphore.Post() != wxSEMA_NO_ERROR )
 218             return wxCOND_MISC_ERROR;
 219
 220         m_numWaiters--;
 221     }
 222
 223     return wxCOND_NO_ERROR;
 224 }
 225
 226 #endif // MSW or OS2
 227
 228 // ----------------------------------------------------------------------------
 229 // wxCondition
 230 // ----------------------------------------------------------------------------
 231
 232 wxCondition::wxCondition(wxMutex& mutex)
 233 {
 234     m_internal = new wxConditionInternal(mutex);
 235
 236     if ( !m_internal->IsOk() )
 237     {
 238         delete m_internal;
 239         m_internal = NULL;
 240     }
 241 }
 242
 243 wxCondition::~wxCondition()
 244 {
 245     delete m_internal;
 246 }
 247
 248 bool wxCondition::IsOk() const
 249 {
 250     return m_internal != NULL;
 251 }
 252
 253 wxCondError wxCondition::Wait()
 254 {
 255     wxCHECK_MSG( m_internal, wxCOND_INVALID,
 256                  wxT("wxCondition::Wait(): not initialized") );
 257
 258     return m_internal->Wait();
 259 }
 260
 261 wxCondError wxCondition::WaitTimeout(unsigned long milliseconds)
 262 {
 263     wxCHECK_MSG( m_internal, wxCOND_INVALID,
 264                  wxT("wxCondition::Wait(): not initialized") );
 265
 266     return m_internal->WaitTimeout(milliseconds);
 267 }
 268
 269 wxCondError wxCondition::Signal()
 270 {
 271     wxCHECK_MSG( m_internal, wxCOND_INVALID,
 272                  wxT("wxCondition::Signal(): not initialized") );
 273
 274     return m_internal->Signal();
 275 }
 276
 277 wxCondError wxCondition::Broadcast()
 278 {
 279     wxCHECK_MSG( m_internal, wxCOND_INVALID,
 280                  wxT("wxCondition::Broadcast(): not initialized") );
 281
 282     return m_internal->Broadcast();
 283 }
 284
 285 // --------------------------------------------------------------------------
 286 // wxSemaphore
 287 // --------------------------------------------------------------------------
 288
 289 wxSemaphore::wxSemaphore(int initialcount, int maxcount)
 290 {
 291     m_internal = new wxSemaphoreInternal( initialcount, maxcount );
 292     if ( !m_internal->IsOk() )
 293     {
 294         delete m_internal;
 295         m_internal = NULL;
 296     }
 297 }
 298
 299 wxSemaphore::~wxSemaphore()
 300 {
 301     delete m_internal;
 302 }
 303
 304 bool wxSemaphore::IsOk() const
 305 {
 306     return m_internal != NULL;
 307 }
 308
 309 wxSemaError wxSemaphore::Wait()
 310 {
 311     wxCHECK_MSG( m_internal, wxSEMA_INVALID,
 312                  wxT("wxSemaphore::Wait(): not initialized") );
 313
 314     return m_internal->Wait();
 315 }
 316
 317 wxSemaError wxSemaphore::TryWait()
 318 {
 319     wxCHECK_MSG( m_internal, wxSEMA_INVALID,
 320                  wxT("wxSemaphore::TryWait(): not initialized") );
 321
 322     return m_internal->TryWait();
 323 }
 324
 325 wxSemaError wxSemaphore::WaitTimeout(unsigned long milliseconds)
 326 {
 327     wxCHECK_MSG( m_internal, wxSEMA_INVALID,
 328                  wxT("wxSemaphore::WaitTimeout(): not initialized") );
 329
 330     return m_internal->WaitTimeout(milliseconds);
 331 }
 332
 333 wxSemaError wxSemaphore::Post()
 334 {
 335     wxCHECK_MSG( m_internal, wxSEMA_INVALID,
 336                  wxT("wxSemaphore::Post(): not initialized") );
 337
 338     return m_internal->Post();
 339 }
 340
 341 // ----------------------------------------------------------------------------
 342 // wxThread
 343 // ----------------------------------------------------------------------------
 344
 345 #include "wx/utils.h"
 346
 347 void wxThread::Sleep(unsigned long milliseconds)
 348 {
 349     wxMilliSleep(milliseconds);
 350 }