mirror of https://github.com/python/cpython
681 lines
23 KiB
Python
681 lines
23 KiB
Python
"""Stream-related things."""
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__all__ = ['StreamReader', 'StreamWriter', 'StreamReaderProtocol',
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'open_connection', 'start_server',
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'IncompleteReadError',
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'LimitOverrunError',
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]
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import socket
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if hasattr(socket, 'AF_UNIX'):
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__all__.extend(['open_unix_connection', 'start_unix_server'])
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from . import coroutines
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from . import compat
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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 .coroutines import coroutine
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from .log import logger
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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 (or None if unknown)
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"""
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def __init__(self, partial, expected):
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super().__init__("%d bytes read on a total of %r 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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class LimitOverrunError(Exception):
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"""Reached buffer limit while looking for the separator.
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Attributes:
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- message: error message
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- consumed: total number of bytes that should be consumed
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"""
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def __init__(self, message, consumed):
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super().__init__(message)
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self.message = message
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self.consumed = consumed
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@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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@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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if hasattr(socket, 'AF_UNIX'):
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# UNIX Domain Sockets are supported on this platform
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@coroutine
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def open_unix_connection(path=None, *,
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loop=None, limit=_DEFAULT_LIMIT, **kwds):
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"""Similar to `open_connection` but works with UNIX Domain Sockets."""
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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_unix_connection(
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lambda: protocol, path, **kwds)
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writer = StreamWriter(transport, protocol, reader, loop)
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return reader, writer
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@coroutine
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def start_unix_server(client_connected_cb, path=None, *,
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loop=None, limit=_DEFAULT_LIMIT, **kwds):
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"""Similar to `start_server` but works with UNIX Domain Sockets."""
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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_unix_server(factory, path, **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 wait for _drain_helper() coroutine.
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"""
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def __init__(self, loop=None):
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if loop is None:
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self._loop = events.get_event_loop()
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else:
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self._loop = loop
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self._paused = False
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self._drain_waiter = None
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self._connection_lost = False
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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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if self._loop.get_debug():
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logger.debug("%r pauses writing", self)
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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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if self._loop.get_debug():
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logger.debug("%r resumes writing", self)
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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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self._connection_lost = True
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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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@coroutine
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def _drain_helper(self):
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if self._connection_lost:
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raise ConnectionResetError('Connection lost')
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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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yield from 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 coroutines.iscoroutine(res):
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self._loop.create_task(res)
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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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return True
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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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# drain() expects that the reader has an exception() method
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assert reader is None or isinstance(reader, StreamReader)
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self._reader = reader
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self._loop = loop
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def __repr__(self):
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info = [self.__class__.__name__, 'transport=%r' % self._transport]
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if self._reader is not None:
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info.append('reader=%r' % self._reader)
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return '<%s>' % ' '.join(info)
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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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@coroutine
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def drain(self):
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"""Flush the write buffer.
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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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"""
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if self._reader is not None:
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exc = self._reader.exception()
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if exc is not None:
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raise exc
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if self._transport is not None:
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if self._transport.is_closing():
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# Yield to the event loop so connection_lost() may be
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# called. Without this, _drain_helper() would return
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# immediately, and code that calls
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# write(...); yield from drain()
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# in a loop would never call connection_lost(), so it
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# would not see an error when the socket is closed.
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yield
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yield from self._protocol._drain_helper()
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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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if limit <= 0:
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raise ValueError('Limit cannot be <= 0')
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self._limit = limit
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if loop is None:
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self._loop = events.get_event_loop()
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else:
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self._loop = loop
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self._buffer = bytearray()
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self._eof = False # Whether we're done.
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self._waiter = None # A future used by _wait_for_data()
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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 __repr__(self):
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info = ['StreamReader']
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if self._buffer:
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info.append('%d bytes' % len(self._buffer))
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if self._eof:
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info.append('eof')
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if self._limit != _DEFAULT_LIMIT:
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info.append('l=%d' % self._limit)
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if self._waiter:
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info.append('w=%r' % self._waiter)
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if self._exception:
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info.append('e=%r' % self._exception)
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if self._transport:
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info.append('t=%r' % self._transport)
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if self._paused:
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info.append('paused')
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return '<%s>' % ' '.join(info)
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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 _wakeup_waiter(self):
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"""Wakeup read*() functions waiting for data or EOF."""
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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(None)
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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 len(self._buffer) <= 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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self._wakeup_waiter()
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def at_eof(self):
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"""Return True if the buffer is empty and 'feed_eof' was called."""
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return self._eof and not self._buffer
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def feed_data(self, data):
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assert not self._eof, 'feed_data after feed_eof'
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if not data:
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return
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self._buffer.extend(data)
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self._wakeup_waiter()
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if (self._transport is not None and
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not self._paused and
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len(self._buffer) > 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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@coroutine
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def _wait_for_data(self, func_name):
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"""Wait until feed_data() or feed_eof() is called.
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If stream was paused, automatically resume it.
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"""
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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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assert not self._eof, '_wait_for_data after EOF'
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# Waiting for data while paused will make deadlock, so prevent it.
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if self._paused:
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self._paused = False
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self._transport.resume_reading()
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self._waiter = futures.Future(loop=self._loop)
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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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@coroutine
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def readline(self):
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"""Read chunk of data from the stream until newline (b'\n') is found.
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On success, return chunk that ends with newline. If only partial
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line can be read due to EOF, return incomplete line without
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terminating newline. When EOF was reached while no bytes read, empty
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bytes object is returned.
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If limit is reached, ValueError will be raised. In that case, if
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newline was found, complete line including newline will be removed
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from internal buffer. Else, internal buffer will be cleared. Limit is
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compared against part of the line without newline.
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If stream was paused, this function will automatically resume it if
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needed.
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"""
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sep = b'\n'
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seplen = len(sep)
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try:
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line = yield from self.readuntil(sep)
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except IncompleteReadError as e:
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return e.partial
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except LimitOverrunError as e:
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if self._buffer.startswith(sep, e.consumed):
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del self._buffer[:e.consumed + seplen]
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else:
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self._buffer.clear()
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self._maybe_resume_transport()
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raise ValueError(e.args[0])
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return line
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@coroutine
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def readuntil(self, separator=b'\n'):
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"""Read chunk of data from the stream until `separator` is found.
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On success, chunk and its separator will be removed from internal buffer
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(i.e. consumed). Returned chunk will include separator at the end.
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Configured stream limit is used to check result. Limit means maximal
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length of chunk that can be returned, not counting the separator.
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If EOF occurs and complete separator still not found,
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IncompleteReadError(<partial data>, None) will be raised and internal
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buffer becomes empty. This partial data may contain a partial separator.
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If chunk cannot be read due to overlimit, LimitOverrunError will be raised
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and data will be left in internal buffer, so it can be read again, in
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some different way.
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If stream was paused, this function will automatically resume it if
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needed.
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"""
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seplen = len(separator)
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if seplen == 0:
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raise ValueError('Separator should be at least one-byte string')
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if self._exception is not None:
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raise self._exception
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# Consume whole buffer except last bytes, which length is
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# one less than seplen. Let's check corner cases with
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# separator='SEPARATOR':
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# * we have received almost complete separator (without last
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# byte). i.e buffer='some textSEPARATO'. In this case we
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# can safely consume len(separator) - 1 bytes.
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# * last byte of buffer is first byte of separator, i.e.
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# buffer='abcdefghijklmnopqrS'. We may safely consume
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# everything except that last byte, but this require to
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# analyze bytes of buffer that match partial separator.
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# This is slow and/or require FSM. For this case our
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# implementation is not optimal, since require rescanning
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# of data that is known to not belong to separator. In
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# real world, separator will not be so long to notice
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# performance problems. Even when reading MIME-encoded
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# messages :)
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# `offset` is the number of bytes from the beginning of the buffer where
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# is no occurrence of `separator`.
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offset = 0
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# Loop until we find `separator` in the buffer, exceed the buffer size,
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# or an EOF has happened.
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while True:
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buflen = len(self._buffer)
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# Check if we now have enough data in the buffer for `separator` to
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# fit.
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if buflen - offset >= seplen:
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isep = self._buffer.find(separator, offset)
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|
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if isep != -1:
|
|
# `separator` is in the buffer. `isep` will be used later to
|
|
# retrieve the data.
|
|
break
|
|
|
|
# see upper comment for explanation.
|
|
offset = buflen + 1 - seplen
|
|
if offset > self._limit:
|
|
raise LimitOverrunError('Separator is not found, and chunk exceed the limit', offset)
|
|
|
|
# Complete message (with full separator) may be present in buffer
|
|
# even when EOF flag is set. This may happen when the last chunk
|
|
# adds data which makes separator be found. That's why we check for
|
|
# EOF *ater* inspecting the buffer.
|
|
if self._eof:
|
|
chunk = bytes(self._buffer)
|
|
self._buffer.clear()
|
|
raise IncompleteReadError(chunk, None)
|
|
|
|
# _wait_for_data() will resume reading if stream was paused.
|
|
yield from self._wait_for_data('readuntil')
|
|
|
|
if isep > self._limit:
|
|
raise LimitOverrunError('Separator is found, but chunk is longer than limit', isep)
|
|
|
|
chunk = self._buffer[:isep + seplen]
|
|
del self._buffer[:isep + seplen]
|
|
self._maybe_resume_transport()
|
|
return bytes(chunk)
|
|
|
|
@coroutine
|
|
def read(self, n=-1):
|
|
"""Read up to `n` bytes from the stream.
|
|
|
|
If n is not provided, or set to -1, read until EOF and return all read
|
|
bytes. If the EOF was received and the internal buffer is empty, return
|
|
an empty bytes object.
|
|
|
|
If n is zero, return empty bytes object immediatelly.
|
|
|
|
If n is positive, this function try to read `n` bytes, and may return
|
|
less or equal bytes than requested, but at least one byte. If EOF was
|
|
received before any byte is read, this function returns empty byte
|
|
object.
|
|
|
|
Returned value is not limited with limit, configured at stream creation.
|
|
|
|
If stream was paused, this function will automatically resume it if
|
|
needed.
|
|
"""
|
|
|
|
if self._exception is not None:
|
|
raise self._exception
|
|
|
|
if n == 0:
|
|
return b''
|
|
|
|
if n < 0:
|
|
# This used to just loop creating a new waiter hoping to
|
|
# collect everything in self._buffer, but that would
|
|
# deadlock if the subprocess sends more than self.limit
|
|
# bytes. So just call self.read(self._limit) until EOF.
|
|
blocks = []
|
|
while True:
|
|
block = yield from self.read(self._limit)
|
|
if not block:
|
|
break
|
|
blocks.append(block)
|
|
return b''.join(blocks)
|
|
|
|
if not self._buffer and not self._eof:
|
|
yield from self._wait_for_data('read')
|
|
|
|
# This will work right even if buffer is less than n bytes
|
|
data = bytes(self._buffer[:n])
|
|
del self._buffer[:n]
|
|
|
|
self._maybe_resume_transport()
|
|
return data
|
|
|
|
@coroutine
|
|
def readexactly(self, n):
|
|
"""Read exactly `n` bytes.
|
|
|
|
Raise an `IncompleteReadError` if EOF is reached before `n` bytes can be
|
|
read. The `IncompleteReadError.partial` attribute of the exception will
|
|
contain the partial read bytes.
|
|
|
|
if n is zero, return empty bytes object.
|
|
|
|
Returned value is not limited with limit, configured at stream creation.
|
|
|
|
If stream was paused, this function will automatically resume it if
|
|
needed.
|
|
"""
|
|
if n < 0:
|
|
raise ValueError('readexactly size can not be less than zero')
|
|
|
|
if self._exception is not None:
|
|
raise self._exception
|
|
|
|
if n == 0:
|
|
return b''
|
|
|
|
# There used to be "optimized" code here. It created its own
|
|
# Future and waited until self._buffer had at least the n
|
|
# bytes, then called read(n). Unfortunately, this could pause
|
|
# the transport if the argument was larger than the pause
|
|
# limit (which is twice self._limit). So now we just read()
|
|
# into a local buffer.
|
|
|
|
blocks = []
|
|
while n > 0:
|
|
block = yield from self.read(n)
|
|
if not block:
|
|
partial = b''.join(blocks)
|
|
raise IncompleteReadError(partial, len(partial) + n)
|
|
blocks.append(block)
|
|
n -= len(block)
|
|
|
|
assert n == 0
|
|
|
|
return b''.join(blocks)
|
|
|
|
if compat.PY35:
|
|
@coroutine
|
|
def __aiter__(self):
|
|
return self
|
|
|
|
@coroutine
|
|
def __anext__(self):
|
|
val = yield from self.readline()
|
|
if val == b'':
|
|
raise StopAsyncIteration
|
|
return val
|