384 lines
9.5 KiB
Python
384 lines
9.5 KiB
Python
"""
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aiosched: Yet another Python async scheduler
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Copyright (C) 2022 nocturn9x
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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https:www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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from collections import deque
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from abc import ABC, abstractmethod
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from typing import Any
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from aiosched.errors import SchedulerError, ResourceClosed
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from aiosched.internals.syscalls import (
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suspend,
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schedule,
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current_task,
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wait_readable,
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)
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from aiosched.task import Task
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from aiosched.socket import wrap_socket
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from socket import socketpair
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class Event:
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"""
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An asynchronous, non thread-safe event
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"""
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def __init__(self):
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"""
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Object constructor
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"""
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self.set = False
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self.waiters = set()
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def reset(self):
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"""
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Resets the event's state
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"""
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self.__init__()
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async def trigger(self):
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"""
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Sets the event, waking up all tasks that called
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wait() on it
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"""
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if self.set:
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raise SchedulerError("The event has already been set")
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self.set = True
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for waiter in self.waiters:
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await schedule(waiter)
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async def wait(self) -> Any:
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"""
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Waits until the event is set
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"""
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self.waiters.add(await current_task())
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await suspend() # We get unsuspended by trigger()
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class Queue:
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"""
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An asynchronous FIFO queue. As it is based
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on events, it is not thread safe
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"""
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def __init__(self, maxsize: int | None = None):
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"""
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Object constructor
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"""
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self.maxsize = maxsize
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# Stores event objects for tasks wanting to
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# get items from the queue
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self.getters = deque()
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# Stores event objects for tasks wanting to
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# put items on the queue
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self.putters = deque()
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self.container = deque()
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def __len__(self):
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"""
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Returns the length of the queue
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"""
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return len(self.container)
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def __repr__(self) -> str:
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return f"{type(self).__name__}({f', '.join(map(str, self.container))})"
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async def __aiter__(self):
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"""
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Implements the asynchronous iterator protocol
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"""
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return self
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async def __anext__(self):
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"""
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Implements the asynchronous iterator protocol
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"""
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return await self.get()
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async def put(self, item: Any):
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"""
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Pushes an element onto the queue. If the
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queue is full, waits until there's
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enough space for the queue
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"""
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if not self.maxsize or len(self.container) < self.maxsize:
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self.container.append(item)
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if self.getters:
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await self.getters.popleft().trigger()
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else:
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ev = Event()
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self.putters.append(ev)
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await ev.wait()
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self.container.append(item)
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async def get(self) -> Any:
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"""
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Pops an element off the queue. Blocks until
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an element is put onto it again if the queue
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is empty
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"""
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if self.container:
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if self.putters:
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await self.putters.popleft().trigger()
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else:
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ev = Event()
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self.getters.append(ev)
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await ev.wait()
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return self.container.popleft()
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async def clear(self):
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"""
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Clears the queue
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"""
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self.container.clear()
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async def reset(self):
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"""
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Resets the queue
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"""
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await self.clear()
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self.getters.clear()
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self.putters.clear()
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class Channel(ABC):
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"""
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A generic, two-way, full-duplex communication channel
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between tasks. This is just an abstract base class and
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should not be instantiated directly. Please also note
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that the read() and write() methods are not implemented
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here because their signatures vary across subclasses
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depending on the underlying communication mechanism
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that is used. Implementors must provide those two methods
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when subclassing Channel
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"""
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def __init__(self, maxsize: int | None = None):
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"""
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Public object constructor
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"""
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self.maxsize = maxsize
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self.closed = False
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@abstractmethod
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async def close(self):
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"""
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Closes the memory channel. Any underlying
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data is left for other tasks to read
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"""
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return NotImplemented
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@abstractmethod
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async def pending(self):
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"""
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Returns if there's pending
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data to be read
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"""
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return NotImplemented
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class MemoryChannel(Channel):
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"""
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A two-way communication channel between tasks.
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Operations on this object are based on the Queue
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class and do not involve any I/O, making this
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an extremely efficient way to pass data around
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to tasks. Since this channel is based on queues,
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it is not thread safe
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"""
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def __init__(self, maxsize: int | None = None):
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"""
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Public object constructor
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"""
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super().__init__(maxsize)
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# We use a queue as our buffer
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self.buffer = Queue(maxsize=maxsize)
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async def write(self, data: str):
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"""
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Writes data to the channel. Blocks if the internal
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queue is full until a spot is available. Does nothing
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if the channel has been closed
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"""
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if self.closed:
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return
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await self.buffer.put(data)
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async def read(self):
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"""
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Reads data from the channel. Blocks until
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a message arrives or returns immediately if
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one is already waiting
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"""
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return await self.buffer.get()
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async def close(self):
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"""
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Closes the memory channel. Any underlying
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data is left for other tasks to read
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"""
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self.closed = True
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async def pending(self):
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"""
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Returns if there's pending
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data to be read
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"""
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return bool(len(self.buffer))
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class NetworkChannel(Channel):
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"""
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A two-way communication channel between tasks
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that uses an underlying socket pair to communicate
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instead of in-memory queues. Not thread safe
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"""
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def __init__(self):
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"""
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Public object constructor
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"""
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super().__init__(None)
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# We use a socket as our buffer instead of a queue
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sockets = socketpair()
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self.reader = wrap_socket(sockets[0])
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self.writer = wrap_socket(sockets[1])
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self.reader.needs_closing = True
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self.writer.needs_closing = True
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async def write(self, data: bytes):
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"""
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Writes data to the channel. Blocks if the internal
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socket is not currently available. Does nothing
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if the channel has been closed
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"""
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if self.closed:
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raise ValueError("I/O operation on closed channel")
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await self.writer.send_all(data)
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async def read(self, size: int):
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"""
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Reads exactly size bytes from the channel. Blocks until
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enough data arrives. Extra data is cached and used on the
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next read
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"""
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if self.closed:
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raise ValueError("I/O operation on closed channel")
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return await self.reader.receive_exactly(size)
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async def close(self):
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"""
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Closes the memory channel. Any underlying
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data is flushed out of the internal socket
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and is lost
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"""
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self.closed = True
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await self.reader.close()
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await self.writer.close()
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async def pending(self):
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"""
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Returns if there's pending
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data to be read
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"""
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if self.closed:
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return False
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elif self.reader.fileno == -1:
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return False
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else:
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try:
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await wait_readable(self.reader.stream)
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except ResourceClosed:
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return False
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return True
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class Lock:
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"""
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A simple asynchronous single-owner lock.
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Not thread safe
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"""
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def __init__(self):
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"""
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Public constructor
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"""
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self.owner: Task | None = None
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self.tasks: deque[Event] = deque()
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async def acquire(self):
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"""
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Acquires the lock
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"""
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task = await current_task()
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if self.owner is None:
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self.owner = task
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elif task is self.owner:
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raise RuntimeError("lock is already acquired by current task")
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elif self.owner is not task:
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self.tasks.append(Event())
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await self.tasks[-1].wait()
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self.owner = task
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async def release(self):
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"""
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Releases the lock
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"""
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task = await current_task()
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if self.owner is None:
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raise RuntimeError("lock is not acquired")
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elif self.owner is not task:
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raise RuntimeError("lock can only released by its owner")
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elif self.tasks:
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await self.tasks.popleft().trigger()
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else:
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self.owner = None
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async def __aenter__(self):
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await self.acquire()
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return self
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async def __aexit__(self, *args):
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await self.release()
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