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 #include "SkTypes.h"
12 
13 #ifdef SK_BUILD_FOR_WIN32
14     #include <windows.h>
15 #else
16     #include <pthread.h>
17 #endif
18 
19 /**
20  * Condition variable for blocking access to shared data from other threads and
21  * controlling which threads are awake.
22  *
23  * Currently only supported on platforms with posix threads and Windows Vista and above.
24  */
25 class SkCondVar {
26 public:
27     /** Returns true if it makes sense to create and use SkCondVars.
28      *  You _MUST_ call this method and it must return true before creating any SkCondVars.
29      */
30     static bool Supported();
31 
32     SkCondVar();
33     ~SkCondVar();
34 
35     /**
36      * Lock a mutex. Must be done before calling the other functions on this object.
37      */
38     void lock();
39 
40     /**
41      * Unlock the mutex.
42      */
43     void unlock();
44 
45     /**
46      * Pause the calling thread. Will be awoken when signal() or broadcast() is called.
47      * Must be called while lock() is held (but gives it up while waiting). Once awoken,
48      * the calling thread will hold the lock once again.
49      */
50     void wait();
51 
52     /**
53      * Wake one thread waiting on this condition. Must be called while lock()
54      * is held.
55      */
56     void signal();
57 
58     /**
59      * Wake all threads waiting on this condition. Must be called while lock()
60      * is held.
61      */
62     void broadcast();
63 
64 private:
65 #ifdef SK_BUILD_FOR_WIN32
66     CRITICAL_SECTION   fCriticalSection;
67     CONDITION_VARIABLE fCondition;
68 #else
69     pthread_mutex_t  fMutex;
70     pthread_cond_t   fCond;
71 #endif
72 };
73 
74 #endif
75