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