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      1 /*
      2  * Copyright 2012 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkCondVar_DEFINED
      9 #define SkCondVar_DEFINED
     10 
     11 /**
     12  * Import any thread model setting from configuration files.
     13  */
     14 #include "SkTypes.h"
     15 
     16 #ifdef SK_USE_POSIX_THREADS
     17 #include <pthread.h>
     18 #elif defined(SK_BUILD_FOR_WIN32)
     19 #include <windows.h>
     20 #else
     21 /**
     22  * Warn if the implementation of this class is empty, i.e. thread safety is not working.
     23  */
     24 #warning "Thread safety class SkCondVar has no implementation!"
     25 #endif
     26 
     27 /**
     28  * Condition variable for blocking access to shared data from other threads and
     29  * controlling which threads are awake.
     30  *
     31  * Currently only supported on platforms with posix threads and Windows Vista and
     32  * above.
     33  */
     34 class SkCondVar {
     35 public:
     36     SkCondVar();
     37     ~SkCondVar();
     38 
     39     /**
     40      * Lock a mutex. Must be done before calling the other functions on this object.
     41      */
     42     void lock();
     43 
     44     /**
     45      * Unlock the mutex.
     46      */
     47     void unlock();
     48 
     49     /**
     50      * Pause the calling thread. Will be awoken when signal() or broadcast() is called.
     51      * Must be called while lock() is held (but gives it up while waiting). Once awoken,
     52      * the calling thread will hold the lock once again.
     53      */
     54     void wait();
     55 
     56     /**
     57      * Wake one thread waiting on this condition. Must be called while lock()
     58      * is held.
     59      */
     60     void signal();
     61 
     62     /**
     63      * Wake all threads waiting on this condition. Must be called while lock()
     64      * is held.
     65      */
     66     void broadcast();
     67 
     68 private:
     69 #ifdef SK_USE_POSIX_THREADS
     70     pthread_mutex_t  fMutex;
     71     pthread_cond_t   fCond;
     72 #elif defined(SK_BUILD_FOR_WIN32)
     73     CRITICAL_SECTION   fCriticalSection;
     74     CONDITION_VARIABLE fCondition;
     75 #endif
     76 };
     77 
     78 #endif
     79