android condition

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

// ---------------------------------------------------------------------------

// DO NOT USE: please use std::condition_variable instead.

/*
 * Condition variable class.  The implementation is system-dependent.
 *
 * Condition variables are paired up with mutexes.  Lock the mutex,
 * call wait(), then either re-wait() if things aren't quite what you want,
 * or unlock the mutex and continue.  All threads calling wait() must
 * use the same mutex for a given Condition.
 *
 * On Android and Apple platforms, these are implemented as a simple wrapper
 * around pthread condition variables.  Care must be taken to abide by
 * the pthreads semantics, in particular, a boolean predicate must
 * be re-evaluated after a wake-up, as spurious wake-ups may happen.
 */
class Condition {
public:
    enum {
        PRIVATE = 0,
        SHARED = 1
    };

    enum WakeUpType {
        WAKE_UP_ONE = 0,
        WAKE_UP_ALL = 1
    };

    Condition();
    explicit Condition(int type);
    ~Condition();
    // Wait on the condition variable.  Lock the mutex before calling.
    // Note that spurious wake-ups may happen.
    status_t wait(Mutex& mutex);
    // same with relative timeout
    status_t waitRelative(Mutex& mutex, nsecs_t reltime);
    // Signal the condition variable, allowing one thread to continue.
    void signal();
    // Signal the condition variable, allowing one or all threads to continue.
    void signal(WakeUpType type) {
        if (type == WAKE_UP_ONE) {
            signal();
        } else {
            broadcast();
        }
    }
    // Signal the condition variable, allowing all threads to continue.
    void broadcast();

private:
#if !defined(_WIN32)
    pthread_cond_t mCond;
#else
    void*   mState;
#endif
};