circuitpython/extmod/uasyncio/core.py

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# MicroPython uasyncio module
# MIT license; Copyright (c) 2019 Damien P. George
from time import ticks_ms as ticks, ticks_diff, ticks_add
import sys, select
# Import TaskQueue and Task, preferring built-in C code over Python code
try:
from _uasyncio import TaskQueue, Task
except:
from .task import TaskQueue, Task
################################################################################
# Exceptions
class CancelledError(BaseException):
pass
class TimeoutError(Exception):
pass
# Used when calling Loop.call_exception_handler
_exc_context = {"message": "Task exception wasn't retrieved", "exception": None, "future": None}
################################################################################
# Sleep functions
# "Yield" once, then raise StopIteration
class SingletonGenerator:
def __init__(self):
self.state = None
self.exc = StopIteration()
def __iter__(self):
return self
def __next__(self):
if self.state is not None:
_task_queue.push_sorted(cur_task, self.state)
self.state = None
return None
else:
self.exc.__traceback__ = None
raise self.exc
# Pause task execution for the given time (integer in milliseconds, uPy extension)
# Use a SingletonGenerator to do it without allocating on the heap
def sleep_ms(t, sgen=SingletonGenerator()):
assert sgen.state is None
sgen.state = ticks_add(ticks(), max(0, t))
return sgen
# Pause task execution for the given time (in seconds)
def sleep(t):
return sleep_ms(int(t * 1000))
################################################################################
# Queue and poller for stream IO
class IOQueue:
def __init__(self):
self.poller = select.poll()
self.map = {} # maps id(stream) to [task_waiting_read, task_waiting_write, stream]
def _enqueue(self, s, idx):
if id(s) not in self.map:
entry = [None, None, s]
entry[idx] = cur_task
self.map[id(s)] = entry
self.poller.register(s, select.POLLIN if idx == 0 else select.POLLOUT)
else:
sm = self.map[id(s)]
assert sm[idx] is None
assert sm[1 - idx] is not None
sm[idx] = cur_task
self.poller.modify(s, select.POLLIN | select.POLLOUT)
# Link task to this IOQueue so it can be removed if needed
cur_task.data = self
def _dequeue(self, s):
del self.map[id(s)]
self.poller.unregister(s)
def queue_read(self, s):
self._enqueue(s, 0)
def queue_write(self, s):
self._enqueue(s, 1)
def remove(self, task):
while True:
del_s = None
for k in self.map: # Iterate without allocating on the heap
q0, q1, s = self.map[k]
if q0 is task or q1 is task:
del_s = s
break
if del_s is not None:
self._dequeue(s)
else:
break
def wait_io_event(self, dt):
for s, ev in self.poller.ipoll(dt):
sm = self.map[id(s)]
# print('poll', s, sm, ev)
if ev & ~select.POLLOUT and sm[0] is not None:
# POLLIN or error
_task_queue.push_head(sm[0])
sm[0] = None
if ev & ~select.POLLIN and sm[1] is not None:
# POLLOUT or error
_task_queue.push_head(sm[1])
sm[1] = None
if sm[0] is None and sm[1] is None:
self._dequeue(s)
elif sm[0] is None:
self.poller.modify(s, select.POLLOUT)
else:
self.poller.modify(s, select.POLLIN)
################################################################################
# Main run loop
# Ensure the awaitable is a task
def _promote_to_task(aw):
return aw if isinstance(aw, Task) else create_task(aw)
# Create and schedule a new task from a coroutine
def create_task(coro):
if not hasattr(coro, "send"):
raise TypeError("coroutine expected")
t = Task(coro, globals())
_task_queue.push_head(t)
return t
# Keep scheduling tasks until there are none left to schedule
def run_until_complete(main_task=None):
global cur_task
excs_all = (CancelledError, Exception) # To prevent heap allocation in loop
excs_stop = (CancelledError, StopIteration) # To prevent heap allocation in loop
while True:
# Wait until the head of _task_queue is ready to run
dt = 1
while dt > 0:
dt = -1
t = _task_queue.peek()
if t:
# A task waiting on _task_queue; "ph_key" is time to schedule task at
dt = max(0, ticks_diff(t.ph_key, ticks()))
elif not _io_queue.map:
# No tasks can be woken so finished running
return
# print('(poll {})'.format(dt), len(_io_queue.map))
_io_queue.wait_io_event(dt)
# Get next task to run and continue it
t = _task_queue.pop_head()
cur_task = t
try:
# Continue running the coroutine, it's responsible for rescheduling itself
exc = t.data
if not exc:
t.coro.send(None)
else:
t.data = None
t.coro.throw(exc)
except excs_all as er:
# Check the task is not on any event queue
assert t.data is None
# This task is done, check if it's the main task and then loop should stop
if t is main_task:
if isinstance(er, StopIteration):
return er.value
raise er
# Schedule any other tasks waiting on the completion of this task
waiting = False
if hasattr(t, "waiting"):
while t.waiting.peek():
_task_queue.push_head(t.waiting.pop_head())
waiting = True
t.waiting = None # Free waiting queue head
if not waiting and not isinstance(er, excs_stop):
# An exception ended this detached task, so queue it for later
# execution to handle the uncaught exception if no other task retrieves
# the exception in the meantime (this is handled by Task.throw).
_task_queue.push_head(t)
# Indicate task is done by setting coro to the task object itself
t.coro = t
# Save return value of coro to pass up to caller
t.data = er
# Create a new task from a coroutine and run it until it finishes
def run(coro):
return run_until_complete(create_task(coro))
################################################################################
# Event loop wrapper
async def _stopper():
pass
_stop_task = None
class Loop:
_exc_handler = None
def create_task(coro):
return create_task(coro)
def run_forever():
global _stop_task
_stop_task = Task(_stopper(), globals())
run_until_complete(_stop_task)
# TODO should keep running until .stop() is called, even if there're no tasks left
def run_until_complete(aw):
return run_until_complete(_promote_to_task(aw))
def stop():
global _stop_task
if _stop_task is not None:
_task_queue.push_head(_stop_task)
# If stop() is called again, do nothing
_stop_task = None
def close():
pass
def set_exception_handler(handler):
Loop._exc_handler = handler
def get_exception_handler():
return Loop._exc_handler
def default_exception_handler(loop, context):
print(context["message"])
print("future:", context["future"], "coro=", context["future"].coro)
sys.print_exception(context["exception"])
def call_exception_handler(context):
(Loop._exc_handler or Loop.default_exception_handler)(Loop, context)
# The runq_len and waitq_len arguments are for legacy uasyncio compatibility
def get_event_loop(runq_len=0, waitq_len=0):
return Loop
def current_task():
return cur_task
def new_event_loop():
global _task_queue, _io_queue
# TaskQueue of Task instances
_task_queue = TaskQueue()
# Task queue and poller for stream IO
_io_queue = IOQueue()
return Loop
# Initialise default event loop
new_event_loop()