1 files changed, 33 insertions, 0 deletions
diff --git a/circuitpython/extmod/uasyncio/event.py b/circuitpython/extmod/uasyncio/event.py
new file mode 100644
index 0000000..a5b3bf9
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+++ b/circuitpython/extmod/uasyncio/event.py
@@ -0,0 +1,33 @@
+# MicroPython uasyncio module
+# MIT license; Copyright (c) 2019-2020 Damien P. George
+
+from . import core
+
+# Event class for primitive events that can be waited on, set, and cleared
+class Event:
+    def __init__(self):
+        self.state = False  # False=unset; True=set
+        self.waiting = core.TaskQueue()  # Queue of Tasks waiting on completion of this event
+
+    def is_set(self):
+        return self.state
+
+    def set(self):
+        # Event becomes set, schedule any tasks waiting on it
+        # Note: This must not be called from anything except the thread running
+        # the asyncio loop (i.e. neither hard or soft IRQ, or a different thread).
+        while self.waiting.peek():
+            core._task_queue.push_head(self.waiting.pop_head())
+        self.state = True
+
+    def clear(self):
+        self.state = False
+
+    async def wait(self):
+        if not self.state:
+            # Event not set, put the calling task on the event's waiting queue
+            self.waiting.push_head(core.cur_task)
+            # Set calling task's data to the event's queue so it can be removed if needed
+            core.cur_task.data = self.waiting
+            yield
+        return True