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264 lines
7.4 KiB
ReStructuredText
264 lines
7.4 KiB
ReStructuredText
.. currentmodule:: asyncio
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.. _asyncio-streams:
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++++++++++++++++++++++++
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Streams (high-level API)
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++++++++++++++++++++++++
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Stream functions
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================
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.. function:: open_connection(host=None, port=None, \*, loop=None, limit=None, **kwds)
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A wrapper for :meth:`~BaseEventLoop.create_connection()` returning a (reader,
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writer) pair.
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The reader returned is a :class:`StreamReader` instance; the writer is
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a :class:`StreamWriter` instance.
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The arguments are all the usual arguments to
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:meth:`BaseEventLoop.create_connection` except *protocol_factory*; most
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common are positional host and port, with various optional keyword arguments
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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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:class:`StreamReader`).
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(If you want to customize the :class:`StreamReader` and/or
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:class:`StreamReaderProtocol` classes, just copy the code -- there's really
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nothing special here except some convenience.)
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This function returns a :ref:`coroutine object <coroutine>`.
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.. function:: start_server(client_connected_cb, host=None, port=None, \*, loop=None, limit=None, **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
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:class:`StreamReader` object, while *client_writer* is a
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:class:`StreamWriter` object. This parameter can either be a plain callback
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function or a :ref:`coroutine function <coroutine>`; if it is a coroutine
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function, it will be automatically converted into a :class:`Task`.
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The rest of the arguments are all the usual arguments to
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:meth:`~BaseEventLoop.create_server()` except *protocol_factory*; most
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common are positional host and port, with various optional keyword arguments
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following. The return value is the same as
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:meth:`~BaseEventLoop.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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:class:`StreamReader`).
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The return value is the same as :meth:`~BaseEventLoop.create_server()`, i.e.
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a :class:`AbstractServer` object which can be used to stop the service.
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This function returns a :ref:`coroutine object <coroutine>`.
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StreamReader
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============
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.. class:: StreamReader(limit=None, loop=None)
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.. method:: exception()
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Get the exception.
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.. method:: feed_eof()
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XXX
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.. method:: feed_data(data)
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XXX
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.. method:: set_exception(exc)
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Set the exception.
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.. method:: set_transport(transport)
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Set the transport.
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.. method:: read(n=-1)
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XXX
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This method returns a :ref:`coroutine object <coroutine>`.
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.. method:: readline()
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XXX
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This method returns a :ref:`coroutine object <coroutine>`.
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.. method:: readexactly(n)
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Read exactly *n* bytes. Raise an :exc:`IncompleteReadError` if the end of
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the stream is reached before *n* can be read, the
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:attr:`IncompleteReadError.partial` attribute of the exception contains
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the partial read bytes.
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This method returns a :ref:`coroutine object <coroutine>`.
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StreamWriter
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============
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.. class:: StreamWriter(transport, protocol, reader, loop)
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Wraps a Transport.
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This exposes :meth:`write`, :meth:`writelines`, :meth:`can_write_eof()`,
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:meth:`write_eof`, :meth:`get_extra_info` and :meth:`close`. It adds
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:meth:`drain` which returns an optional :class:`Future` on which you can
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wait for flow control. It also adds a transport attribute which references
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the :class:`Transport` directly.
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.. attribute:: transport
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Transport.
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.. method:: can_write_eof()
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Return :const:`True` if the transport supports :meth:`write_eof`,
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:const:`False` if not. See :meth:`WriteTransport.can_write_eof`.
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.. method:: close()
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Close the transport: see :meth:`BaseTransport.close`.
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.. method:: drain()
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Wait until the write buffer of the underlying transport is flushed.
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This method has an unusual return value. 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, :meth:`drain()` returns ``()``, and the
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yield-from continues immediately. When the transport buffer is full (the
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protocol is paused), :meth:`drain` creates and returns a
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:class:`Future` and the yield-from will block until
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that Future is completed, which will happen when the buffer is
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(partially) drained and the protocol is resumed.
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.. method:: get_extra_info(name, default=None)
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Return optional transport information: see
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:meth:`BaseTransport.get_extra_info`.
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.. method:: write(data)
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Write some *data* bytes to the transport: see
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:meth:`WriteTransport.write`.
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.. method:: writelines(data)
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Write a list (or any iterable) of data bytes to the transport:
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see :meth:`WriteTransport.writelines`.
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.. method:: write_eof()
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Close the write end of the transport after flushing buffered data:
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see :meth:`WriteTransport.write_eof`.
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StreamReaderProtocol
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====================
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.. class:: StreamReaderProtocol(stream_reader, client_connected_cb=None, loop=None)
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Trivial helper class to adapt between :class:`Protocol` and
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:class:`StreamReader`. Sublclass of :class:`Protocol`.
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*stream_reader* is a :class:`StreamReader` instance, *client_connected_cb*
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is an optional function called with (stream_reader, stream_writer) when a
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connection is made, *loop* is the event loop instance to use.
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(This is a helper class instead of making :class:`StreamReader` itself a
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:class:`Protocol` subclass, because the :class:`StreamReader` has other
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potential uses, and to prevent the user of the :class:`StreamReader` to
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accidentally call inappropriate methods of the protocol.)
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.. method:: connection_made(transport)
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XXX
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.. method:: connection_lost(exc)
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XXX
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.. method:: data_received(data)
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XXX
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.. method:: eof_received()
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XXX
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.. method:: pause_writing()
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XXX
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.. method:: resume_writing()
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XXX
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IncompleteReadError
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===================
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.. exception:: IncompleteReadError
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Incomplete read error, subclass of :exc:`EOFError`.
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.. attribute:: expected
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Total number of expected bytes (:class:`int`).
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.. attribute:: partial
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Read bytes string before the end of stream was reached (:class:`bytes`).
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Example
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=======
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Simple example querying HTTP headers of the URL passed on the command line::
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import asyncio
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import urllib.parse
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import sys
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@asyncio.coroutine
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def print_http_headers(url):
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url = urllib.parse.urlsplit(url)
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reader, writer = yield from asyncio.open_connection(url.hostname, 80)
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query = ('HEAD {url.path} HTTP/1.0\r\n'
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'Host: {url.hostname}\r\n'
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'\r\n').format(url=url)
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writer.write(query.encode('latin-1'))
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while True:
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line = yield from reader.readline()
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if not line:
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break
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line = line.decode('latin1').rstrip()
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if line:
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print('HTTP header> %s' % line)
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url = sys.argv[1]
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loop = asyncio.get_event_loop()
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task = asyncio.async(print_http_headers(url))
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loop.run_until_complete(task)
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loop.close()
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Usage::
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python example.py http://example.com/path/page.html
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