451 lines
15 KiB
Python
451 lines
15 KiB
Python
"""Stream-related things."""
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__all__ = ['StreamReader', 'StreamWriter', 'StreamReaderProtocol',
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'open_connection', 'start_server', 'IncompleteReadError',
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]
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import collections
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from . import events
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from . import futures
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from . import protocols
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from . import tasks
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_DEFAULT_LIMIT = 2**16
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class IncompleteReadError(EOFError):
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"""
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Incomplete read error. Attributes:
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- partial: read bytes string before the end of stream was reached
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- expected: total number of expected bytes
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"""
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def __init__(self, partial, expected):
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EOFError.__init__(self, "%s bytes read on a total of %s expected bytes"
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% (len(partial), expected))
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self.partial = partial
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self.expected = expected
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@tasks.coroutine
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def open_connection(host=None, port=None, *,
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loop=None, limit=_DEFAULT_LIMIT, **kwds):
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"""A wrapper for create_connection() returning a (reader, writer) pair.
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The reader returned is a StreamReader instance; the writer is a
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StreamWriter instance.
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The arguments are all the usual arguments to create_connection()
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except protocol_factory; most common are positional host and port,
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with various optional keyword arguments following.
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Additional optional keyword arguments are loop (to set the event loop
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instance to use) and limit (to set the buffer limit passed to the
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StreamReader).
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(If you want to customize the StreamReader and/or
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StreamReaderProtocol classes, just copy the code -- there's
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really nothing special here except some convenience.)
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"""
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if loop is None:
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loop = events.get_event_loop()
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reader = StreamReader(limit=limit, loop=loop)
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protocol = StreamReaderProtocol(reader, loop=loop)
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transport, _ = yield from loop.create_connection(
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lambda: protocol, host, port, **kwds)
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writer = StreamWriter(transport, protocol, reader, loop)
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return reader, writer
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@tasks.coroutine
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def start_server(client_connected_cb, host=None, port=None, *,
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loop=None, limit=_DEFAULT_LIMIT, **kwds):
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"""Start a socket server, call back for each client connected.
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The first parameter, `client_connected_cb`, takes two parameters:
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client_reader, client_writer. client_reader is a StreamReader
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object, while client_writer is a StreamWriter object. This
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parameter can either be a plain callback function or a coroutine;
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if it is a coroutine, it will be automatically converted into a
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Task.
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The rest of the arguments are all the usual arguments to
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loop.create_server() except protocol_factory; most common are
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positional host and port, with various optional keyword arguments
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following. The return value is the same as loop.create_server().
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Additional optional keyword arguments are loop (to set the event loop
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instance to use) and limit (to set the buffer limit passed to the
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StreamReader).
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The return value is the same as loop.create_server(), i.e. a
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Server object which can be used to stop the service.
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"""
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if loop is None:
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loop = events.get_event_loop()
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def factory():
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reader = StreamReader(limit=limit, loop=loop)
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protocol = StreamReaderProtocol(reader, client_connected_cb,
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loop=loop)
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return protocol
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return (yield from loop.create_server(factory, host, port, **kwds))
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class FlowControlMixin(protocols.Protocol):
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"""Reusable flow control logic for StreamWriter.drain().
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This implements the protocol methods pause_writing(),
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resume_reading() and connection_lost(). If the subclass overrides
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these it must call the super methods.
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StreamWriter.drain() must check for error conditions and then call
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_make_drain_waiter(), which will return either () or a Future
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depending on the paused state.
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"""
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def __init__(self, loop=None):
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self._loop = loop # May be None; we may never need it.
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self._paused = False
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self._drain_waiter = None
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def pause_writing(self):
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assert not self._paused
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self._paused = True
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def resume_writing(self):
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assert self._paused
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self._paused = False
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waiter = self._drain_waiter
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if waiter is not None:
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self._drain_waiter = None
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if not waiter.done():
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waiter.set_result(None)
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def connection_lost(self, exc):
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# Wake up the writer if currently paused.
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if not self._paused:
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return
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waiter = self._drain_waiter
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if waiter is None:
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return
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self._drain_waiter = None
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if waiter.done():
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return
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if exc is None:
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waiter.set_result(None)
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else:
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waiter.set_exception(exc)
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def _make_drain_waiter(self):
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if not self._paused:
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return ()
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waiter = self._drain_waiter
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assert waiter is None or waiter.cancelled()
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waiter = futures.Future(loop=self._loop)
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self._drain_waiter = waiter
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return waiter
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class StreamReaderProtocol(FlowControlMixin, protocols.Protocol):
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"""Helper class to adapt between Protocol and StreamReader.
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(This is a helper class instead of making StreamReader itself a
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Protocol subclass, because the StreamReader has other potential
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uses, and to prevent the user of the StreamReader to accidentally
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call inappropriate methods of the protocol.)
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"""
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def __init__(self, stream_reader, client_connected_cb=None, loop=None):
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super().__init__(loop=loop)
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self._stream_reader = stream_reader
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self._stream_writer = None
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self._client_connected_cb = client_connected_cb
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def connection_made(self, transport):
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self._stream_reader.set_transport(transport)
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if self._client_connected_cb is not None:
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self._stream_writer = StreamWriter(transport, self,
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self._stream_reader,
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self._loop)
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res = self._client_connected_cb(self._stream_reader,
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self._stream_writer)
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if tasks.iscoroutine(res):
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tasks.Task(res, loop=self._loop)
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def connection_lost(self, exc):
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if exc is None:
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self._stream_reader.feed_eof()
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else:
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self._stream_reader.set_exception(exc)
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super().connection_lost(exc)
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def data_received(self, data):
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self._stream_reader.feed_data(data)
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def eof_received(self):
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self._stream_reader.feed_eof()
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class StreamWriter:
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"""Wraps a Transport.
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This exposes write(), writelines(), [can_]write_eof(),
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get_extra_info() and close(). It adds drain() which returns an
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optional Future on which you can wait for flow control. It also
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adds a transport property which references the Transport
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directly.
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"""
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def __init__(self, transport, protocol, reader, loop):
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self._transport = transport
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self._protocol = protocol
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self._reader = reader
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self._loop = loop
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@property
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def transport(self):
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return self._transport
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def write(self, data):
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self._transport.write(data)
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def writelines(self, data):
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self._transport.writelines(data)
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def write_eof(self):
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return self._transport.write_eof()
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def can_write_eof(self):
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return self._transport.can_write_eof()
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def close(self):
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return self._transport.close()
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def get_extra_info(self, name, default=None):
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return self._transport.get_extra_info(name, default)
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def drain(self):
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"""This method has an unusual return value.
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The intended use is to write
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w.write(data)
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yield from w.drain()
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When there's nothing to wait for, drain() returns (), and the
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yield-from continues immediately. When the transport buffer
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is full (the protocol is paused), drain() creates and returns
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a Future and the yield-from will block until that Future is
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completed, which will happen when the buffer is (partially)
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drained and the protocol is resumed.
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"""
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if self._reader is not None and self._reader._exception is not None:
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raise self._reader._exception
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if self._transport._conn_lost: # Uses private variable.
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raise ConnectionResetError('Connection lost')
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return self._protocol._make_drain_waiter()
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class StreamReader:
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def __init__(self, limit=_DEFAULT_LIMIT, loop=None):
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# The line length limit is a security feature;
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# it also doubles as half the buffer limit.
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self._limit = limit
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if loop is None:
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loop = events.get_event_loop()
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self._loop = loop
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# TODO: Use a bytearray for a buffer, like the transport.
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self._buffer = collections.deque() # Deque of bytes objects.
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self._byte_count = 0 # Bytes in buffer.
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self._eof = False # Whether we're done.
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self._waiter = None # A future.
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self._exception = None
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self._transport = None
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self._paused = False
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def exception(self):
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return self._exception
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def set_exception(self, exc):
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self._exception = exc
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waiter = self._waiter
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if waiter is not None:
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self._waiter = None
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if not waiter.cancelled():
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waiter.set_exception(exc)
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def set_transport(self, transport):
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assert self._transport is None, 'Transport already set'
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self._transport = transport
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def _maybe_resume_transport(self):
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if self._paused and self._byte_count <= self._limit:
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self._paused = False
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self._transport.resume_reading()
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def feed_eof(self):
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self._eof = True
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waiter = self._waiter
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if waiter is not None:
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self._waiter = None
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if not waiter.cancelled():
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waiter.set_result(True)
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def feed_data(self, data):
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if not data:
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return
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self._buffer.append(data)
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self._byte_count += len(data)
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waiter = self._waiter
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if waiter is not None:
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self._waiter = None
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if not waiter.cancelled():
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waiter.set_result(False)
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if (self._transport is not None and
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not self._paused and
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self._byte_count > 2*self._limit):
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try:
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self._transport.pause_reading()
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except NotImplementedError:
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# The transport can't be paused.
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# We'll just have to buffer all data.
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# Forget the transport so we don't keep trying.
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self._transport = None
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else:
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self._paused = True
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def _create_waiter(self, func_name):
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# StreamReader uses a future to link the protocol feed_data() method
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# to a read coroutine. Running two read coroutines at the same time
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# would have an unexpected behaviour. It would not possible to know
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# which coroutine would get the next data.
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if self._waiter is not None:
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raise RuntimeError('%s() called while another coroutine is '
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'already waiting for incoming data' % func_name)
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return futures.Future(loop=self._loop)
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@tasks.coroutine
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def readline(self):
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if self._exception is not None:
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raise self._exception
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parts = []
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parts_size = 0
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not_enough = True
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while not_enough:
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while self._buffer and not_enough:
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data = self._buffer.popleft()
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ichar = data.find(b'\n')
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if ichar < 0:
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parts.append(data)
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parts_size += len(data)
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else:
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ichar += 1
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head, tail = data[:ichar], data[ichar:]
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if tail:
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self._buffer.appendleft(tail)
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not_enough = False
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parts.append(head)
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parts_size += len(head)
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if parts_size > self._limit:
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self._byte_count -= parts_size
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self._maybe_resume_transport()
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raise ValueError('Line is too long')
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if self._eof:
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break
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if not_enough:
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self._waiter = self._create_waiter('readline')
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try:
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yield from self._waiter
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finally:
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self._waiter = None
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line = b''.join(parts)
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self._byte_count -= parts_size
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self._maybe_resume_transport()
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return line
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@tasks.coroutine
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def read(self, n=-1):
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if self._exception is not None:
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raise self._exception
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if not n:
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return b''
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if n < 0:
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while not self._eof:
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self._waiter = self._create_waiter('read')
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try:
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yield from self._waiter
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finally:
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self._waiter = None
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else:
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if not self._byte_count and not self._eof:
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self._waiter = self._create_waiter('read')
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try:
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yield from self._waiter
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finally:
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self._waiter = None
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if n < 0 or self._byte_count <= n:
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data = b''.join(self._buffer)
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self._buffer.clear()
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self._byte_count = 0
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self._maybe_resume_transport()
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return data
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parts = []
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parts_bytes = 0
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while self._buffer and parts_bytes < n:
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data = self._buffer.popleft()
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data_bytes = len(data)
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if n < parts_bytes + data_bytes:
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data_bytes = n - parts_bytes
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data, rest = data[:data_bytes], data[data_bytes:]
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self._buffer.appendleft(rest)
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parts.append(data)
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parts_bytes += data_bytes
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self._byte_count -= data_bytes
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self._maybe_resume_transport()
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return b''.join(parts)
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@tasks.coroutine
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def readexactly(self, n):
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if self._exception is not None:
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raise self._exception
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# There used to be "optimized" code here. It created its own
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# Future and waited until self._buffer had at least the n
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# bytes, then called read(n). Unfortunately, this could pause
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# the transport if the argument was larger than the pause
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# limit (which is twice self._limit). So now we just read()
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# into a local buffer.
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blocks = []
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while n > 0:
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block = yield from self.read(n)
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if not block:
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partial = b''.join(blocks)
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raise IncompleteReadError(partial, len(partial) + n)
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blocks.append(block)
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n -= len(block)
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return b''.join(blocks)
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