cpython/Lib/asyncio/streams.py at 3.15 · python/cpython · GitHub

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__all__ = (

'StreamReader', 'StreamWriter', 'StreamReaderProtocol',

'open_connection', 'start_server')

import collections

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, *,

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.)

"""

loop = events.get_running_loop()

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, *,

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 argument is 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.

"""

loop = events.get_running_loop()

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, *,

limit=_DEFAULT_LIMIT, **kwds):

"""Similar to `open_connection` but works with UNIX Domain Sockets."""

loop = events.get_running_loop()

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, *,

limit=_DEFAULT_LIMIT, **kwds):

"""Similar to `start_server` but works with UNIX Domain Sockets."""

loop = events.get_running_loop()

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_waiters = collections.deque()

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)

for waiter in self._drain_waiters:

if not waiter.done():

waiter.set_result(None)

def connection_lost(self, exc):

self._connection_lost = True

# Wake up the writer(s) if currently paused.

if not self._paused:

return

for waiter in self._drain_waiters:

if not waiter.done():

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._loop.create_future()

self._drain_waiters.append(waiter)

try:

await waiter

finally:

self._drain_waiters.remove(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._task = 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 _replace_transport(self, transport):

self._transport = transport

self._over_ssl = transport.get_extra_info('sslcontext') is not None

reader = self._stream_reader

if reader is not None:

reader._replace_transport(transport)

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:

writer = StreamWriter(transport, self, reader, self._loop)

try:

res = self._client_connected_cb(reader, writer)

except Exception as exc:

self._loop.call_exception_handler({

'message': 'Unhandled exception in client_connected_cb',

'exception': exc,

'transport': transport,

})

transport.close()

self._strong_reader = None

return

if coroutines.iscoroutine(res):

def callback(task):

if task.cancelled():

transport.close()

return

exc = task.exception()

if exc is not None:

self._loop.call_exception_handler({

'message': 'Unhandled exception in client_connected_cb',

'exception': exc,

'transport': transport,

})

transport.close()

self._task = self._loop.create_task(res)

self._task.add_done_callback(callback)

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._task = 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

try:

closed = self._closed

except AttributeError:

pass # failed constructor

else:

if closed.done() and not closed.cancelled():

closed.exception()

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

def write(self, data):

self._transport.write(data)

def writelines(self, data):

self._transport.writelines(data)

def write_eof(self):

return self._transport.write_eof()

def can_write_eof(self):

return self._transport.can_write_eof()

def close(self):

return self._transport.close()

def is_closing(self):

return self._transport.is_closing()

async def wait_closed(self):

await self._protocol._get_close_waiter(self)

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()

async def start_tls(self, sslcontext, *,

server_hostname=None,

ssl_handshake_timeout=None,

ssl_shutdown_timeout=None):

"""Upgrade an existing stream-based connection to TLS."""

server_side = self._protocol._client_connected_cb is not None

protocol = self._protocol

await self.drain()

new_transport = await self._loop.start_tls( # type: ignore

self._transport, protocol, sslcontext,

server_side=server_side, server_hostname=server_hostname,

ssl_handshake_timeout=ssl_handshake_timeout,

ssl_shutdown_timeout=ssl_shutdown_timeout)

self._transport = new_transport

protocol._replace_transport(new_transport)

def __del__(self, warnings=warnings):

if not self._transport.is_closing():

if self._loop.is_closed():

warnings.warn("loop is closed", ResourceWarning)

else:

self.close()

warnings.warn(f"unclosed {self!r}", ResourceWarning)

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 _replace_transport(self, transport):

assert self._transport is not None, 'Transport not 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()

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):

r"""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.

The ``separator`` may also be a tuple of separators. In this

case the return value will be the shortest possible that has any

separator as the suffix. For the purposes of LimitOverrunError,

the shortest possible separator is considered to be the one that

matched.

"""

if isinstance(separator, tuple):

# Makes sure shortest matches wins

separator = sorted(separator, key=len)

else:

separator = [separator]

if not separator:

raise ValueError('Separator should contain at least one element')

min_seplen = len(separator[0])

max_seplen = len(separator[-1])

if min_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 max_seplen. Let's check corner cases with

# separator[-1]='SEPARATOR':

# * we have received almost complete separator (without last

# byte). i.e buffer='some textSEPARATO'. In this case we

# can safely consume max_seplen - 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 any `separator`.

offset = 0

# Loop until we find a `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 shortest

# separator to fit.

if buflen - offset >= min_seplen:

match_start = None

match_end = None

for sep in separator:

isep = self._buffer.find(sep, offset)

if isep != -1:

# `separator` is in the buffer. `match_start` and

# `match_end` will be used later to retrieve the

# data.

end = isep + len(sep)

if match_end is None or end < match_end:

match_end = end

match_start = isep

if match_end is not None:

break

# see upper comment for explanation.

offset = max(0, buflen + 1 - max_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 *after* inspecting the buffer.

if self._eof:

chunk = self._buffer.take_bytes()

raise exceptions.IncompleteReadError(chunk, None)

# _wait_for_data() will resume reading if stream was paused.

await self._wait_for_data('readuntil')

if match_start > self._limit:

raise exceptions.LimitOverrunError(

'Separator is found, but chunk is longer than limit', match_start)

chunk = self._buffer.take_bytes(match_end)

self._maybe_resume_transport()

return 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, then return all read bytes.

If EOF was received and the internal buffer is empty,

return an empty bytes object.

If `n` is 0, return an empty bytes object immediately.

If `n` is positive, return at most `n` available bytes

as soon as at least 1 byte is available in the internal buffer.

If EOF is received before any byte is read, return an 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 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.

joined = bytearray()

while block := await self.read(self._limit):

joined += block

return joined.take_bytes()

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 = self._buffer.take_bytes(min(len(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 = self._buffer.take_bytes()

raise exceptions.IncompleteReadError(incomplete, n)

await self._wait_for_data('readexactly')

data = self._buffer.take_bytes(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

cpython/Lib/asyncio/streams.py at 3.15 · python/cpython · GitHub

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