micropython: add micropython component

components/language/micropython/extmod/uasyncio/__init__.py

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+# MicroPython uasyncio module
+# MIT license; Copyright (c) 2019 Damien P. George
+
+from .core import *
+
+__version__ = (3, 0, 0)
+
+_attrs = {
+    "wait_for": "funcs",
+    "wait_for_ms": "funcs",
+    "gather": "funcs",
+    "Event": "event",
+    "ThreadSafeFlag": "event",
+    "Lock": "lock",
+    "open_connection": "stream",
+    "start_server": "stream",
+    "StreamReader": "stream",
+    "StreamWriter": "stream",
+}
+
+# Lazy loader, effectively does:
+#   global attr
+#   from .mod import attr
+def __getattr__(attr):
+    mod = _attrs.get(attr, None)
+    if mod is None:
+        raise AttributeError(attr)
+    value = getattr(__import__(mod, None, None, True, 1), attr)
+    globals()[attr] = value
+    return value

components/language/micropython/extmod/uasyncio/core.py

@@ -0,0 +1,300 @@
+# 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(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(sm[0])
+                sm[0] = None
+            if ev & ~select.POLLIN and sm[1] is not None:
+                # POLLOUT or error
+                _task_queue.push(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(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()
+        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:
+                # If the task is finished and on the run queue and gets here, then it
+                # had an exception and was not await'ed on.  Throwing into it now will
+                # raise StopIteration and the code below will catch this and run the
+                # call_exception_handler function.
+                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
+            if t.state:
+                # Task was running but is now finished.
+                waiting = False
+                if t.state is True:
+                    # "None" indicates that the task is complete and not await'ed on (yet).
+                    t.state = None
+                elif callable(t.state):
+                    # The task has a callback registered to be called on completion.
+                    t.state(t, er)
+                    t.state = False
+                    waiting = True
+                else:
+                    # Schedule any other tasks waiting on the completion of this task.
+                    while t.state.peek():
+                        _task_queue.push(t.state.pop())
+                        waiting = True
+                    # "False" indicates that the task is complete and has been await'ed on.
+                    t.state = False
+                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(t)
+                # Save return value of coro to pass up to caller.
+                t.data = er
+            elif t.state is None:
+                # Task is already finished and nothing await'ed on the task,
+                # so call the exception handler.
+                _exc_context["exception"] = exc
+                _exc_context["future"] = t
+                Loop.call_exception_handler(_exc_context)
+
+
+# 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(_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()

components/language/micropython/extmod/uasyncio/event.py

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+# 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(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.
+try:
+    import uio
+
+    class ThreadSafeFlag(uio.IOBase):
+        def __init__(self):
+            self._flag = 0
+
+        def ioctl(self, req, flags):
+            if req == 3:  # MP_STREAM_POLL
+                return self._flag * flags
+            return None
+
+        def set(self):
+            self._flag = 1
+
+        async def wait(self):
+            if not self._flag:
+                yield core._io_queue.queue_read(self)
+            self._flag = 0
+
+except ImportError:
+    pass

components/language/micropython/extmod/uasyncio/funcs.py

@@ -0,0 +1,126 @@
+# MicroPython uasyncio module
+# MIT license; Copyright (c) 2019-2022 Damien P. George
+
+from . import core
+
+
+def _run(waiter, aw):
+    try:
+        result = await aw
+        status = True
+    except BaseException as er:
+        result = None
+        status = er
+    if waiter.data is None:
+        # The waiter is still waiting, cancel it.
+        if waiter.cancel():
+            # Waiter was cancelled by us, change its CancelledError to an instance of
+            # CancelledError that contains the status and result of waiting on aw.
+            # If the wait_for task subsequently gets cancelled externally then this
+            # instance will be reset to a CancelledError instance without arguments.
+            waiter.data = core.CancelledError(status, result)
+
+
+async def wait_for(aw, timeout, sleep=core.sleep):
+    aw = core._promote_to_task(aw)
+    if timeout is None:
+        return await aw
+
+    # Run aw in a separate runner task that manages its exceptions.
+    runner_task = core.create_task(_run(core.cur_task, aw))
+
+    try:
+        # Wait for the timeout to elapse.
+        await sleep(timeout)
+    except core.CancelledError as er:
+        status = er.value
+        if status is None:
+            # This wait_for was cancelled externally, so cancel aw and re-raise.
+            runner_task.cancel()
+            raise er
+        elif status is True:
+            # aw completed successfully and cancelled the sleep, so return aw's result.
+            return er.args[1]
+        else:
+            # aw raised an exception, propagate it out to the caller.
+            raise status
+
+    # The sleep finished before aw, so cancel aw and raise TimeoutError.
+    runner_task.cancel()
+    await runner_task
+    raise core.TimeoutError
+
+
+def wait_for_ms(aw, timeout):
+    return wait_for(aw, timeout, core.sleep_ms)
+
+
+class _Remove:
+    @staticmethod
+    def remove(t):
+        pass
+
+
+async def gather(*aws, return_exceptions=False):
+    def done(t, er):
+        # Sub-task "t" has finished, with exception "er".
+        nonlocal state
+        if gather_task.data is not _Remove:
+            # The main gather task has already been scheduled, so do nothing.
+            # This happens if another sub-task already raised an exception and
+            # woke the main gather task (via this done function), or if the main
+            # gather task was cancelled externally.
+            return
+        elif not return_exceptions and not isinstance(er, StopIteration):
+            # A sub-task raised an exception, indicate that to the gather task.
+            state = er
+        else:
+            state -= 1
+            if state:
+                # Still some sub-tasks running.
+                return
+        # Gather waiting is done, schedule the main gather task.
+        core._task_queue.push(gather_task)
+
+    ts = [core._promote_to_task(aw) for aw in aws]
+    for i in range(len(ts)):
+        if ts[i].state is not True:
+            # Task is not running, gather not currently supported for this case.
+            raise RuntimeError("can't gather")
+        # Register the callback to call when the task is done.
+        ts[i].state = done
+
+    # Set the state for execution of the gather.
+    gather_task = core.cur_task
+    state = len(ts)
+    cancel_all = False
+
+    # Wait for the a sub-task to need attention.
+    gather_task.data = _Remove
+    try:
+        yield
+    except core.CancelledError as er:
+        cancel_all = True
+        state = er
+
+    # Clean up tasks.
+    for i in range(len(ts)):
+        if ts[i].state is done:
+            # Sub-task is still running, deregister the callback and cancel if needed.
+            ts[i].state = True
+            if cancel_all:
+                ts[i].cancel()
+        elif isinstance(ts[i].data, StopIteration):
+            # Sub-task ran to completion, get its return value.
+            ts[i] = ts[i].data.value
+        else:
+            # Sub-task had an exception with return_exceptions==True, so get its exception.
+            ts[i] = ts[i].data
+
+    # Either this gather was cancelled, or one of the sub-tasks raised an exception with
+    # return_exceptions==False, so reraise the exception here.
+    if state is not 0:
+        raise state
+
+    # Return the list of return values of each sub-task.
+    return ts

components/language/micropython/extmod/uasyncio/lock.py

@@ -0,0 +1,53 @@
+# MicroPython uasyncio module
+# MIT license; Copyright (c) 2019-2020 Damien P. George
+
+from . import core
+
+# Lock class for primitive mutex capability
+class Lock:
+    def __init__(self):
+        # The state can take the following values:
+        # - 0: unlocked
+        # - 1: locked
+        # - <Task>: unlocked but this task has been scheduled to acquire the lock next
+        self.state = 0
+        # Queue of Tasks waiting to acquire this Lock
+        self.waiting = core.TaskQueue()
+
+    def locked(self):
+        return self.state == 1
+
+    def release(self):
+        if self.state != 1:
+            raise RuntimeError("Lock not acquired")
+        if self.waiting.peek():
+            # Task(s) waiting on lock, schedule next Task
+            self.state = self.waiting.pop()
+            core._task_queue.push(self.state)
+        else:
+            # No Task waiting so unlock
+            self.state = 0
+
+    async def acquire(self):
+        if self.state != 0:
+            # Lock unavailable, put the calling Task on the waiting queue
+            self.waiting.push(core.cur_task)
+            # Set calling task's data to the lock's queue so it can be removed if needed
+            core.cur_task.data = self.waiting
+            try:
+                yield
+            except core.CancelledError as er:
+                if self.state == core.cur_task:
+                    # Cancelled while pending on resume, schedule next waiting Task
+                    self.state = 1
+                    self.release()
+                raise er
+        # Lock available, set it as locked
+        self.state = 1
+        return True
+
+    async def __aenter__(self):
+        return await self.acquire()
+
+    async def __aexit__(self, exc_type, exc, tb):
+        return self.release()

components/language/micropython/extmod/uasyncio/manifest.py

@@ -0,0 +1,13 @@
+# This list of frozen files doesn't include task.py because that's provided by the C module.
+freeze(
+    "..",
+    (
+        "uasyncio/__init__.py",
+        "uasyncio/core.py",
+        "uasyncio/event.py",
+        "uasyncio/funcs.py",
+        "uasyncio/lock.py",
+        "uasyncio/stream.py",
+    ),
+    opt=3,
+)

components/language/micropython/extmod/uasyncio/stream.py

@@ -0,0 +1,164 @@
+# MicroPython uasyncio module
+# MIT license; Copyright (c) 2019-2020 Damien P. George
+
+from . import core
+
+
+class Stream:
+    def __init__(self, s, e={}):
+        self.s = s
+        self.e = e
+        self.out_buf = b""
+
+    def get_extra_info(self, v):
+        return self.e[v]
+
+    async def __aenter__(self):
+        return self
+
+    async def __aexit__(self, exc_type, exc, tb):
+        await self.close()
+
+    def close(self):
+        pass
+
+    async def wait_closed(self):
+        # TODO yield?
+        self.s.close()
+
+    async def read(self, n):
+        yield core._io_queue.queue_read(self.s)
+        return self.s.read(n)
+
+    async def readinto(self, buf):
+        yield core._io_queue.queue_read(self.s)
+        return self.s.readinto(buf)
+
+    async def readexactly(self, n):
+        r = b""
+        while n:
+            yield core._io_queue.queue_read(self.s)
+            r2 = self.s.read(n)
+            if r2 is not None:
+                if not len(r2):
+                    raise EOFError
+                r += r2
+                n -= len(r2)
+        return r
+
+    async def readline(self):
+        l = b""
+        while True:
+            yield core._io_queue.queue_read(self.s)
+            l2 = self.s.readline()  # may do multiple reads but won't block
+            l += l2
+            if not l2 or l[-1] == 10:  # \n (check l in case l2 is str)
+                return l
+
+    def write(self, buf):
+        self.out_buf += buf
+
+    async def drain(self):
+        mv = memoryview(self.out_buf)
+        off = 0
+        while off < len(mv):
+            yield core._io_queue.queue_write(self.s)
+            ret = self.s.write(mv[off:])
+            if ret is not None:
+                off += ret
+        self.out_buf = b""
+
+
+# Stream can be used for both reading and writing to save code size
+StreamReader = Stream
+StreamWriter = Stream
+
+
+# Create a TCP stream connection to a remote host
+async def open_connection(host, port):
+    from uerrno import EINPROGRESS
+    import usocket as socket
+
+    ai = socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM)[0]  # TODO this is blocking!
+    s = socket.socket(ai[0], ai[1], ai[2])
+    s.setblocking(False)
+    ss = Stream(s)
+    try:
+        s.connect(ai[-1])
+    except OSError as er:
+        if er.errno != EINPROGRESS:
+            raise er
+    yield core._io_queue.queue_write(s)
+    return ss, ss
+
+
+# Class representing a TCP stream server, can be closed and used in "async with"
+class Server:
+    async def __aenter__(self):
+        return self
+
+    async def __aexit__(self, exc_type, exc, tb):
+        self.close()
+        await self.wait_closed()
+
+    def close(self):
+        self.task.cancel()
+
+    async def wait_closed(self):
+        await self.task
+
+    async def _serve(self, s, cb):
+        # Accept incoming connections
+        while True:
+            try:
+                yield core._io_queue.queue_read(s)
+            except core.CancelledError:
+                # Shutdown server
+                s.close()
+                return
+            try:
+                s2, addr = s.accept()
+            except:
+                # Ignore a failed accept
+                continue
+            s2.setblocking(False)
+            s2s = Stream(s2, {"peername": addr})
+            core.create_task(cb(s2s, s2s))
+
+
+# Helper function to start a TCP stream server, running as a new task
+# TODO could use an accept-callback on socket read activity instead of creating a task
+async def start_server(cb, host, port, backlog=5):
+    import usocket as socket
+
+    # Create and bind server socket.
+    host = socket.getaddrinfo(host, port)[0]  # TODO this is blocking!
+    s = socket.socket()
+    s.setblocking(False)
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    s.bind(host[-1])
+    s.listen(backlog)
+
+    # Create and return server object and task.
+    srv = Server()
+    srv.task = core.create_task(srv._serve(s, cb))
+    return srv
+
+
+################################################################################
+# Legacy uasyncio compatibility
+
+
+async def stream_awrite(self, buf, off=0, sz=-1):
+    if off != 0 or sz != -1:
+        buf = memoryview(buf)
+        if sz == -1:
+            sz = len(buf)
+        buf = buf[off : off + sz]
+    self.write(buf)
+    await self.drain()
+
+
+Stream.aclose = Stream.wait_closed
+Stream.awrite = stream_awrite
+Stream.awritestr = stream_awrite  # TODO explicitly convert to bytes?

components/language/micropython/extmod/uasyncio/task.py

@@ -0,0 +1,177 @@
+# MicroPython uasyncio module
+# MIT license; Copyright (c) 2019-2020 Damien P. George
+
+# This file contains the core TaskQueue based on a pairing heap, and the core Task class.
+# They can optionally be replaced by C implementations.
+
+from . import core
+
+
+# pairing-heap meld of 2 heaps; O(1)
+def ph_meld(h1, h2):
+    if h1 is None:
+        return h2
+    if h2 is None:
+        return h1
+    lt = core.ticks_diff(h1.ph_key, h2.ph_key) < 0
+    if lt:
+        if h1.ph_child is None:
+            h1.ph_child = h2
+        else:
+            h1.ph_child_last.ph_next = h2
+        h1.ph_child_last = h2
+        h2.ph_next = None
+        h2.ph_rightmost_parent = h1
+        return h1
+    else:
+        h1.ph_next = h2.ph_child
+        h2.ph_child = h1
+        if h1.ph_next is None:
+            h2.ph_child_last = h1
+            h1.ph_rightmost_parent = h2
+        return h2
+
+
+# pairing-heap pairing operation; amortised O(log N)
+def ph_pairing(child):
+    heap = None
+    while child is not None:
+        n1 = child
+        child = child.ph_next
+        n1.ph_next = None
+        if child is not None:
+            n2 = child
+            child = child.ph_next
+            n2.ph_next = None
+            n1 = ph_meld(n1, n2)
+        heap = ph_meld(heap, n1)
+    return heap
+
+
+# pairing-heap delete of a node; stable, amortised O(log N)
+def ph_delete(heap, node):
+    if node is heap:
+        child = heap.ph_child
+        node.ph_child = None
+        return ph_pairing(child)
+    # Find parent of node
+    parent = node
+    while parent.ph_next is not None:
+        parent = parent.ph_next
+    parent = parent.ph_rightmost_parent
+    # Replace node with pairing of its children
+    if node is parent.ph_child and node.ph_child is None:
+        parent.ph_child = node.ph_next
+        node.ph_next = None
+        return heap
+    elif node is parent.ph_child:
+        child = node.ph_child
+        next = node.ph_next
+        node.ph_child = None
+        node.ph_next = None
+        node = ph_pairing(child)
+        parent.ph_child = node
+    else:
+        n = parent.ph_child
+        while node is not n.ph_next:
+            n = n.ph_next
+        child = node.ph_child
+        next = node.ph_next
+        node.ph_child = None
+        node.ph_next = None
+        node = ph_pairing(child)
+        if node is None:
+            node = n
+        else:
+            n.ph_next = node
+    node.ph_next = next
+    if next is None:
+        node.ph_rightmost_parent = parent
+        parent.ph_child_last = node
+    return heap
+
+
+# TaskQueue class based on the above pairing-heap functions.
+class TaskQueue:
+    def __init__(self):
+        self.heap = None
+
+    def peek(self):
+        return self.heap
+
+    def push(self, v, key=None):
+        assert v.ph_child is None
+        assert v.ph_next is None
+        v.data = None
+        v.ph_key = key if key is not None else core.ticks()
+        self.heap = ph_meld(v, self.heap)
+
+    def pop(self):
+        v = self.heap
+        assert v.ph_next is None
+        self.heap = ph_pairing(v.ph_child)
+        v.ph_child = None
+        return v
+
+    def remove(self, v):
+        self.heap = ph_delete(self.heap, v)
+
+
+# Task class representing a coroutine, can be waited on and cancelled.
+class Task:
+    def __init__(self, coro, globals=None):
+        self.coro = coro  # Coroutine of this Task
+        self.data = None  # General data for queue it is waiting on
+        self.state = True  # None, False, True, a callable, or a TaskQueue instance
+        self.ph_key = 0  # Pairing heap
+        self.ph_child = None  # Paring heap
+        self.ph_child_last = None  # Paring heap
+        self.ph_next = None  # Paring heap
+        self.ph_rightmost_parent = None  # Paring heap
+
+    def __iter__(self):
+        if not self.state:
+            # Task finished, signal that is has been await'ed on.
+            self.state = False
+        elif self.state is True:
+            # Allocated head of linked list of Tasks waiting on completion of this task.
+            self.state = TaskQueue()
+        elif type(self.state) is not TaskQueue:
+            # Task has state used for another purpose, so can't also wait on it.
+            raise RuntimeError("can't wait")
+        return self
+
+    def __next__(self):
+        if not self.state:
+            # Task finished, raise return value to caller so it can continue.
+            raise self.data
+        else:
+            # Put calling task on waiting queue.
+            self.state.push(core.cur_task)
+            # Set calling task's data to this task that it waits on, to double-link it.
+            core.cur_task.data = self
+
+    def done(self):
+        return not self.state
+
+    def cancel(self):
+        # Check if task is already finished.
+        if not self.state:
+            return False
+        # Can't cancel self (not supported yet).
+        if self is core.cur_task:
+            raise RuntimeError("can't cancel self")
+        # If Task waits on another task then forward the cancel to the one it's waiting on.
+        while isinstance(self.data, Task):
+            self = self.data
+        # Reschedule Task as a cancelled task.
+        if hasattr(self.data, "remove"):
+            # Not on the main running queue, remove the task from the queue it's on.
+            self.data.remove(self)
+            core._task_queue.push(self)
+        elif core.ticks_diff(self.ph_key, core.ticks()) > 0:
+            # On the main running queue but scheduled in the future, so bring it forward to now.
+            core._task_queue.remove(self)
+            core._task_queue.push(self)
+        self.data = core.CancelledError
+        return True