/system/core/libutils/include/utils/Condition.h

 

 1 // ---------------------------------------------------------------------------
 2 
 3 // DO NOT USE: please use std::condition_variable instead.
 4 
 5 /*
 6  * Condition variable class.  The implementation is system-dependent.
 7  *
 8  * Condition variables are paired up with mutexes.  Lock the mutex,
 9  * call wait(), then either re-wait() if things aren't quite what you want,
10  * or unlock the mutex and continue.  All threads calling wait() must
11  * use the same mutex for a given Condition.
12  *
13  * On Android and Apple platforms, these are implemented as a simple wrapper
14  * around pthread condition variables.  Care must be taken to abide by
15  * the pthreads semantics, in particular, a boolean predicate must
16  * be re-evaluated after a wake-up, as spurious wake-ups may happen.
17  */
18 class Condition {
19 public:
20     enum {
21         PRIVATE = 0,
22         SHARED = 1
23     };
24 
25     enum WakeUpType {
26         WAKE_UP_ONE = 0,
27         WAKE_UP_ALL = 1
28     };
29 
30     Condition();
31     explicit Condition(int type);
32     ~Condition();
33     // Wait on the condition variable.  Lock the mutex before calling.
34     // Note that spurious wake-ups may happen.
35     status_t wait(Mutex& mutex);
36     // same with relative timeout
37     status_t waitRelative(Mutex& mutex, nsecs_t reltime);
38     // Signal the condition variable, allowing one thread to continue.
39     void signal();
40     // Signal the condition variable, allowing one or all threads to continue.
41     void signal(WakeUpType type) {
42         if (type == WAKE_UP_ONE) {
43             signal();
44         } else {
45             broadcast();
46         }
47     }
48     // Signal the condition variable, allowing all threads to continue.
49     void broadcast();
50 
51 private:
52 #if !defined(_WIN32)
53     pthread_cond_t mCond;
54 #else
55     void*   mState;
56 #endif
57 };