Source code for asyncio.streams
From Get docs
Python/docs/3.7/ modules/asyncio/streams
Source code for asyncio.streams
__all__ = (
'StreamReader', 'StreamWriter', 'StreamReaderProtocol',
'open_connection', 'start_server')
import socket
import sys
import warnings
import weakref
if hasattr(socket, 'AF_UNIX'):
__all__ += ('open_unix_connection', 'start_unix_server')
from . import coroutines
from . import events
from . import exceptions
from . import format_helpers
from . import protocols
from .log import logger
from .tasks import sleep
_DEFAULT_LIMIT = 2 ** 16 # 64 KiB
async def open_connection(host=None, port=None, *,
loop=None, limit=_DEFAULT_LIMIT, **kwds):
"""A wrapper for create_connection() returning a (reader, writer) pair.
The reader returned is a StreamReader instance; the writer is a
StreamWriter instance.
The arguments are all the usual arguments to 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
StreamReader).
(If you want to customize the StreamReader and/or
StreamReaderProtocol classes, just copy the code -- there's
really nothing special here except some convenience.)
"""
if loop is None:
loop = events.get_event_loop()
else:
warnings.warn("The loop argument is deprecated since Python 3.8, "
"and scheduled for removal in Python 3.10.",
DeprecationWarning, stacklevel=2)
reader = StreamReader(limit=limit, loop=loop)
protocol = StreamReaderProtocol(reader, loop=loop)
transport, _ = await loop.create_connection(
lambda: protocol, host, port, **kwds)
writer = StreamWriter(transport, protocol, reader, loop)
return reader, writer
async def start_server(client_connected_cb, host=None, port=None, *,
loop=None, limit=_DEFAULT_LIMIT, **kwds):
"""Start a socket server, call back for each client connected.
The first parameter, `client_connected_cb`, takes two parameters:
client_reader, client_writer. client_reader is a StreamReader
object, while client_writer is a StreamWriter object. This
parameter can either be a plain callback function or a coroutine;
if it is a coroutine, it will be automatically converted into a
Task.
The rest of the arguments are all the usual arguments to
loop.create_server() except protocol_factory; most common are
positional host and port, with various optional keyword arguments
following. The return value is the same as loop.create_server().
Additional optional keyword arguments are loop (to set the event loop
instance to use) and limit (to set the buffer limit passed to the
StreamReader).
The return value is the same as loop.create_server(), i.e. a
Server object which can be used to stop the service.
"""
if loop is None:
loop = events.get_event_loop()
else:
warnings.warn("The loop argument is deprecated since Python 3.8, "
"and scheduled for removal in Python 3.10.",
DeprecationWarning, stacklevel=2)
def factory():
reader = StreamReader(limit=limit, loop=loop)
protocol = StreamReaderProtocol(reader, client_connected_cb,
loop=loop)
return protocol
return await loop.create_server(factory, host, port, **kwds)
if hasattr(socket, 'AF_UNIX'):
# UNIX Domain Sockets are supported on this platform
async def open_unix_connection(path=None, *,
loop=None, limit=_DEFAULT_LIMIT, **kwds):
"""Similar to `open_connection` but works with UNIX Domain Sockets."""
if loop is None:
loop = events.get_event_loop()
else:
warnings.warn("The loop argument is deprecated since Python 3.8, "
"and scheduled for removal in Python 3.10.",
DeprecationWarning, stacklevel=2)
reader = StreamReader(limit=limit, loop=loop)
protocol = StreamReaderProtocol(reader, loop=loop)
transport, _ = await loop.create_unix_connection(
lambda: protocol, path, **kwds)
writer = StreamWriter(transport, protocol, reader, loop)
return reader, writer
async def start_unix_server(client_connected_cb, path=None, *,
loop=None, limit=_DEFAULT_LIMIT, **kwds):
"""Similar to `start_server` but works with UNIX Domain Sockets."""
if loop is None:
loop = events.get_event_loop()
else:
warnings.warn("The loop argument is deprecated since Python 3.8, "
"and scheduled for removal in Python 3.10.",
DeprecationWarning, stacklevel=2)
def factory():
reader = StreamReader(limit=limit, loop=loop)
protocol = StreamReaderProtocol(reader, client_connected_cb,
loop=loop)
return protocol
return await loop.create_unix_server(factory, path, **kwds)
class FlowControlMixin(protocols.Protocol):
"""Reusable flow control logic for StreamWriter.drain().
This implements the protocol methods pause_writing(),
resume_writing() and connection_lost(). If the subclass overrides
these it must call the super methods.
StreamWriter.drain() must wait for _drain_helper() coroutine.
"""
def __init__(self, loop=None):
if loop is None:
self._loop = events.get_event_loop()
else:
self._loop = loop
self._paused = False
self._drain_waiter = None
self._connection_lost = False
def pause_writing(self):
assert not self._paused
self._paused = True
if self._loop.get_debug():
logger.debug("%r pauses writing", self)
def resume_writing(self):
assert self._paused
self._paused = False
if self._loop.get_debug():
logger.debug("%r resumes writing", self)
waiter = self._drain_waiter
if waiter is not None:
self._drain_waiter = None
if not waiter.done():
waiter.set_result(None)
def connection_lost(self, exc):
self._connection_lost = True
# Wake up the writer if currently paused.
if not self._paused:
return
waiter = self._drain_waiter
if waiter is None:
return
self._drain_waiter = None
if waiter.done():
return
if exc is None:
waiter.set_result(None)
else:
waiter.set_exception(exc)
async def _drain_helper(self):
if self._connection_lost:
raise ConnectionResetError('Connection lost')
if not self._paused:
return
waiter = self._drain_waiter
assert waiter is None or waiter.cancelled()
waiter = self._loop.create_future()
self._drain_waiter = waiter
await waiter
def _get_close_waiter(self, stream):
raise NotImplementedError
class StreamReaderProtocol(FlowControlMixin, protocols.Protocol):
"""Helper class to adapt between Protocol and StreamReader.
(This is a helper class instead of making StreamReader itself a
Protocol subclass, because the StreamReader has other potential
uses, and to prevent the user of the StreamReader to accidentally
call inappropriate methods of the protocol.)
"""
_source_traceback = None
def __init__(self, stream_reader, client_connected_cb=None, loop=None):
super().__init__(loop=loop)
if stream_reader is not None:
self._stream_reader_wr = weakref.ref(stream_reader)
self._source_traceback = stream_reader._source_traceback
else:
self._stream_reader_wr = None
if client_connected_cb is not None:
# This is a stream created by the `create_server()` function.
# Keep a strong reference to the reader until a connection
# is established.
self._strong_reader = stream_reader
self._reject_connection = False
self._stream_writer = None
self._transport = None
self._client_connected_cb = client_connected_cb
self._over_ssl = False
self._closed = self._loop.create_future()
@property
def _stream_reader(self):
if self._stream_reader_wr is None:
return None
return self._stream_reader_wr()
def connection_made(self, transport):
if self._reject_connection:
context = {
'message': ('An open stream was garbage collected prior to '
'establishing network connection; '
'call "stream.close()" explicitly.')
}
if self._source_traceback:
context['source_traceback'] = self._source_traceback
self._loop.call_exception_handler(context)
transport.abort()
return
self._transport = transport
reader = self._stream_reader
if reader is not None:
reader.set_transport(transport)
self._over_ssl = transport.get_extra_info('sslcontext') is not None
if self._client_connected_cb is not None:
self._stream_writer = StreamWriter(transport, self,
reader,
self._loop)
res = self._client_connected_cb(reader,
self._stream_writer)
if coroutines.iscoroutine(res):
self._loop.create_task(res)
self._strong_reader = None
def connection_lost(self, exc):
reader = self._stream_reader
if reader is not None:
if exc is None:
reader.feed_eof()
else:
reader.set_exception(exc)
if not self._closed.done():
if exc is None:
self._closed.set_result(None)
else:
self._closed.set_exception(exc)
super().connection_lost(exc)
self._stream_reader_wr = None
self._stream_writer = None
self._transport = None
def data_received(self, data):
reader = self._stream_reader
if reader is not None:
reader.feed_data(data)
def eof_received(self):
reader = self._stream_reader
if reader is not None:
reader.feed_eof()
if self._over_ssl:
# Prevent a warning in SSLProtocol.eof_received:
# "returning true from eof_received()
# has no effect when using ssl"
return False
return True
def _get_close_waiter(self, stream):
return self._closed
def __del__(self):
# Prevent reports about unhandled exceptions.
# Better than self._closed._log_traceback = False hack
closed = self._closed
if closed.done() and not closed.cancelled():
closed.exception()
[docs]class StreamWriter:
"""Wraps a Transport.
This exposes write(), writelines(), [can_]write_eof(),
get_extra_info() and close(). It adds drain() which returns an
optional Future on which you can wait for flow control. It also
adds a transport property which references the Transport
directly.
"""
def __init__(self, transport, protocol, reader, loop):
self._transport = transport
self._protocol = protocol
# drain() expects that the reader has an exception() method
assert reader is None or isinstance(reader, StreamReader)
self._reader = reader
self._loop = loop
self._complete_fut = self._loop.create_future()
self._complete_fut.set_result(None)
def __repr__(self):
info = [self.__class__.__name__, f'transport={self._transport!r}']
if self._reader is not None:
info.append(f'reader={self._reader!r}')
return '<{}>'.format(' '.join(info))
@property
def transport(self):
return self._transport
[docs] def write(self, data):
self._transport.write(data)
[docs] def writelines(self, data):
self._transport.writelines(data)
[docs] def write_eof(self):
return self._transport.write_eof()
[docs] def can_write_eof(self):
return self._transport.can_write_eof()
[docs] def close(self):
return self._transport.close()
[docs] def is_closing(self):
return self._transport.is_closing()
async def wait_closed(self):
await self._protocol._get_close_waiter(self)
[docs] def get_extra_info(self, name, default=None):
return self._transport.get_extra_info(name, default)
async def drain(self):
"""Flush the write buffer.
The intended use is to write
w.write(data)
await w.drain()
"""
if self._reader is not None:
exc = self._reader.exception()
if exc is not None:
raise exc
if self._transport.is_closing():
# Wait for protocol.connection_lost() call
# Raise connection closing error if any,
# ConnectionResetError otherwise
# Yield to the event loop so connection_lost() may be
# called. Without this, _drain_helper() would return
# immediately, and code that calls
# write(...); await drain()
# in a loop would never call connection_lost(), so it
# would not see an error when the socket is closed.
await sleep(0)
await self._protocol._drain_helper()
[docs]class StreamReader:
_source_traceback = None
def __init__(self, limit=_DEFAULT_LIMIT, loop=None):
# The line length limit is a security feature;
# it also doubles as half the buffer limit.
if limit <= 0:
raise ValueError('Limit cannot be <= 0')
self._limit = limit
if loop is None:
self._loop = events.get_event_loop()
else:
self._loop = loop
self._buffer = bytearray()
self._eof = False # Whether we're done.
self._waiter = None # A future used by _wait_for_data()
self._exception = None
self._transport = None
self._paused = False
if self._loop.get_debug():
self._source_traceback = format_helpers.extract_stack(
sys._getframe(1))
def __repr__(self):
info = ['StreamReader']
if self._buffer:
info.append(f'{len(self._buffer)} bytes')
if self._eof:
info.append('eof')
if self._limit != _DEFAULT_LIMIT:
info.append(f'limit={self._limit}')
if self._waiter:
info.append(f'waiter={self._waiter!r}')
if self._exception:
info.append(f'exception={self._exception!r}')
if self._transport:
info.append(f'transport={self._transport!r}')
if self._paused:
info.append('paused')
return '<{}>'.format(' '.join(info))
def exception(self):
return self._exception
def set_exception(self, exc):
self._exception = exc
waiter = self._waiter
if waiter is not None:
self._waiter = None
if not waiter.cancelled():
waiter.set_exception(exc)
def _wakeup_waiter(self):
"""Wakeup read*() functions waiting for data or EOF."""
waiter = self._waiter
if waiter is not None:
self._waiter = None
if not waiter.cancelled():
waiter.set_result(None)
def set_transport(self, transport):
assert self._transport is None, 'Transport already set'
self._transport = transport
def _maybe_resume_transport(self):
if self._paused and len(self._buffer) <= self._limit:
self._paused = False
self._transport.resume_reading()
def feed_eof(self):
self._eof = True
self._wakeup_waiter()
[docs] def at_eof(self):
"""Return True if the buffer is empty and 'feed_eof' was called."""
return self._eof and not self._buffer
def feed_data(self, data):
assert not self._eof, 'feed_data after feed_eof'
if not data:
return
self._buffer.extend(data)
self._wakeup_waiter()
if (self._transport is not None and
not self._paused and
len(self._buffer) > 2 * self._limit):
try:
self._transport.pause_reading()
except NotImplementedError:
# The transport can't be paused.
# We'll just have to buffer all data.
# Forget the transport so we don't keep trying.
self._transport = None
else:
self._paused = True
async def _wait_for_data(self, func_name):
"""Wait until feed_data() or feed_eof() is called.
If stream was paused, automatically resume it.
"""
# StreamReader uses a future to link the protocol feed_data() method
# to a read coroutine. Running two read coroutines at the same time
# would have an unexpected behaviour. It would not possible to know
# which coroutine would get the next data.
if self._waiter is not None:
raise RuntimeError(
f'{func_name}() called while another coroutine is '
f'already waiting for incoming data')
assert not self._eof, '_wait_for_data after EOF'
# Waiting for data while paused will make deadlock, so prevent it.
# This is essential for readexactly(n) for case when n > self._limit.
if self._paused:
self._paused = False
self._transport.resume_reading()
self._waiter = self._loop.create_future()
try:
await self._waiter
finally:
self._waiter = None
async def readline(self):
"""Read chunk of data from the stream until newline (b'\n') is found.
On success, return chunk that ends with newline. If only partial
line can be read due to EOF, return incomplete line without
terminating newline. When EOF was reached while no bytes read, empty
bytes object is returned.
If limit is reached, ValueError will be raised. In that case, if
newline was found, complete line including newline will be removed
from internal buffer. Else, internal buffer will be cleared. Limit is
compared against part of the line without newline.
If stream was paused, this function will automatically resume it if
needed.
"""
sep = b'\n'
seplen = len(sep)
try:
line = await self.readuntil(sep)
except exceptions.IncompleteReadError as e:
return e.partial
except exceptions.LimitOverrunError as e:
if self._buffer.startswith(sep, e.consumed):
del self._buffer[:e.consumed + seplen]
else:
self._buffer.clear()
self._maybe_resume_transport()
raise ValueError(e.args[0])
return line
async def readuntil(self, separator=b'\n'):
"""Read data from the stream until ``separator`` is found.
On success, the data and separator will be removed from the
internal buffer (consumed). Returned data will include the
separator at the end.
Configured stream limit is used to check result. Limit sets the
maximal length of data that can be returned, not counting the
separator.
If an EOF occurs and the complete separator is still not found,
an IncompleteReadError exception will be raised, and the internal
buffer will be reset. The IncompleteReadError.partial attribute
may contain the separator partially.
If the data cannot be read because of over limit, a
LimitOverrunError exception will be raised, and the data
will be left in the internal buffer, so it can be read again.
"""
seplen = len(separator)
if seplen == 0:
raise ValueError('Separator should be at least one-byte string')
if self._exception is not None:
raise self._exception
# Consume whole buffer except last bytes, which length is
# one less than seplen. Let's check corner cases with
# separator='SEPARATOR':
# * we have received almost complete separator (without last
# byte). i.e buffer='some textSEPARATO'. In this case we
# can safely consume len(separator) - 1 bytes.
# * last byte of buffer is first byte of separator, i.e.
# buffer='abcdefghijklmnopqrS'. We may safely consume
# everything except that last byte, but this require to
# analyze bytes of buffer that match partial separator.
# This is slow and/or require FSM. For this case our
# implementation is not optimal, since require rescanning
# of data that is known to not belong to separator. In
# real world, separator will not be so long to notice
# performance problems. Even when reading MIME-encoded
# messages :)
# `offset` is the number of bytes from the beginning of the buffer
# where there is no occurrence of `separator`.
offset = 0
# Loop until we find `separator` in the buffer, exceed the buffer size,
# or an EOF has happened.
while True:
buflen = len(self._buffer)
# Check if we now have enough data in the buffer for `separator` to
# fit.
if buflen - offset >= seplen:
isep = self._buffer.find(separator, offset)
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 exceptions.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 exceptions.IncompleteReadError(chunk, None)
# _wait_for_data() will resume reading if stream was paused.
await self._wait_for_data('readuntil')
if isep > self._limit:
raise exceptions.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)
async 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 immediately.
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 = await self.read(self._limit)
if not block:
break
blocks.append(block)
return b''.join(blocks)
if not self._buffer and not self._eof:
await 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
async 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''
while len(self._buffer) < n:
if self._eof:
incomplete = bytes(self._buffer)
self._buffer.clear()
raise exceptions.IncompleteReadError(incomplete, n)
await self._wait_for_data('readexactly')
if len(self._buffer) == n:
data = bytes(self._buffer)
self._buffer.clear()
else:
data = bytes(self._buffer[:n])
del self._buffer[:n]
self._maybe_resume_transport()
return data
def __aiter__(self):
return self
async def __anext__(self):
val = await self.readline()
if val == b'':
raise StopAsyncIteration
return val
