Removed Common
Change-Id: I01ea8f07220375c2ad9bc0092281d4f27c642303
diff --git a/aos/event.h b/aos/event.h
new file mode 100644
index 0000000..c2ad1bc
--- /dev/null
+++ b/aos/event.h
@@ -0,0 +1,60 @@
+#ifndef AOS_EVENT_H_
+#define AOS_EVENT_H_
+
+#include "aos/time/time.h"
+
+#include "aos/linux_code/ipc_lib/aos_sync.h"
+
+namespace aos {
+
+// An abstraction of an event which is easy to implement for Linux and in other
+// environments.
+// On Linux at least, this is definitely safe for passing through C code with
+// memcpy etc.
+//
+// An event is either "set" or "unset". Any thread can transition it between
+// these two states and other threads can wait for an unset->set transition.
+// This is not a particularly powerful synchronization primitive, but it can be
+// much easier to use than more complicated ones in some situations. The name is
+// taken from Python's implementation of the same thing.
+//
+// An event is equivalent to a semaphore which is either set to 0 or infinity.
+// It is also equivalent to a condition variable with the monitored condition
+// being "is it set or not".
+//
+// IMPORTANT: You can NOT use this to successfully replace a standard condition
+// variable in most cases. When the condition being monitored changes separately
+// from the actual state of the condition variable/event, there WILL be race
+// conditions if you try to use this class.
+//
+// It is undefined behavior to destroy an Event while there are current
+// Wait()ers.
+class Event {
+ public:
+ // Creates an unset event.
+ Event();
+ // There must be no waiters when an Event is destroyed.
+ ~Event() = default;
+
+ // Waits for the event to be set. Returns immediately if it is already set.
+ void Wait();
+
+ // Waits for the event to be set or until timeout has elapsed. Returns
+ // immediately if it is already set.
+ // Returns true if the event was Set or false if the timeout expired.
+ bool WaitTimeout(monotonic_clock::duration timeout);
+
+ // Wakes up all Wait()ers and sets the event (atomically).
+ void Set();
+ // Unsets the event so future Wait() callers will block instead of returning
+ // immediately.
+ // Returns true if the event was previously set.
+ bool Clear();
+
+ private:
+ aos_futex impl_;
+};
+
+} // namespace aos
+
+#endif // AOS_EVENT_H_