1 files changed, 66 insertions, 0 deletions
diff --git a/extmod/asyncio/event.py b/extmod/asyncio/event.py
new file mode 100644
index 000000000..e0b41f732
--- /dev/null
+++ b/extmod/asyncio/event.py
@@ -0,0 +1,66 @@
+# MicroPython asyncio 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(self.waiting.pop())
+        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(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
+
+
+# MicroPython-extension: This can be set from outside the asyncio event loop,
+# such as other threads, IRQs or scheduler context. Implementation is a stream
+# that asyncio will poll until a flag is set.
+# Note: Unlike Event, this is self-clearing after a wait().
+try:
+    import io
+
+    class ThreadSafeFlag(io.IOBase):
+        def __init__(self):
+            self.state = 0
+
+        def ioctl(self, req, flags):
+            if req == 3:  # MP_STREAM_POLL
+                return self.state * flags
+            return None
+
+        def set(self):
+            self.state = 1
+
+        def clear(self):
+            self.state = 0
+
+        async def wait(self):
+            if not self.state:
+                yield core._io_queue.queue_read(self)
+            self.state = 0
+
+except ImportError:
+    pass