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"""Stream-related things."""
__all__ = ['StreamReader', 'StreamReaderProtocol', 'open_connection']
import collections
from . import events
from . import futures
from . import protocols
from . import tasks
_DEFAULT_LIMIT = 2**16
@tasks.coroutine
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
Transport.
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()
reader = StreamReader(limit=limit, loop=loop)
protocol = StreamReaderProtocol(reader)
transport, _ = yield from loop.create_connection(
lambda: protocol, host, port, **kwds)
return reader, transport # (reader, writer)
class StreamReaderProtocol(protocols.Protocol):
"""Trivial 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.)
"""
def __init__(self, stream_reader):
self.stream_reader = stream_reader
def connection_made(self, transport):
self.stream_reader.set_transport(transport)
def connection_lost(self, exc):
if exc is None:
self.stream_reader.feed_eof()
else:
self.stream_reader.set_exception(exc)
def data_received(self, data):
self.stream_reader.feed_data(data)
def eof_received(self):
self.stream_reader.feed_eof()
class StreamReader:
def __init__(self, limit=_DEFAULT_LIMIT, loop=None):
# The line length limit is a security feature;
# it also doubles as half the buffer limit.
self.limit = limit
if loop is None:
loop = events.get_event_loop()
self.loop = loop
self.buffer = collections.deque() # Deque of bytes objects.
self.byte_count = 0 # Bytes in buffer.
self.eof = False # Whether we're done.
self.waiter = None # A future.
self._exception = None
self._transport = None
self._paused = False
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 set_transport(self, transport):
assert self._transport is None, 'Transport already set'
self._transport = transport
def _maybe_resume_transport(self):
if self._paused and self.byte_count <= self.limit:
self._paused = False
self._transport.resume()
def feed_eof(self):
self.eof = True
waiter = self.waiter
if waiter is not None:
self.waiter = None
if not waiter.cancelled():
waiter.set_result(True)
def feed_data(self, data):
if not data:
return
self.buffer.append(data)
self.byte_count += len(data)
waiter = self.waiter
if waiter is not None:
self.waiter = None
if not waiter.cancelled():
waiter.set_result(False)
if (self._transport is not None and
not self._paused and
self.byte_count > 2*self.limit):
try:
self._transport.pause()
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
@tasks.coroutine
def readline(self):
if self._exception is not None:
raise self._exception
parts = []
parts_size = 0
not_enough = True
while not_enough:
while self.buffer and not_enough:
data = self.buffer.popleft()
ichar = data.find(b'\n')
if ichar < 0:
parts.append(data)
parts_size += len(data)
else:
ichar += 1
head, tail = data[:ichar], data[ichar:]
if tail:
self.buffer.appendleft(tail)
not_enough = False
parts.append(head)
parts_size += len(head)
if parts_size > self.limit:
self.byte_count -= parts_size
self._maybe_resume_transport()
raise ValueError('Line is too long')
if self.eof:
break
if not_enough:
assert self.waiter is None
self.waiter = futures.Future(loop=self.loop)
try:
yield from self.waiter
finally:
self.waiter = None
line = b''.join(parts)
self.byte_count -= parts_size
self._maybe_resume_transport()
return line
@tasks.coroutine
def read(self, n=-1):
if self._exception is not None:
raise self._exception
if not n:
return b''
if n < 0:
while not self.eof:
assert not self.waiter
self.waiter = futures.Future(loop=self.loop)
try:
yield from self.waiter
finally:
self.waiter = None
else:
if not self.byte_count and not self.eof:
assert not self.waiter
self.waiter = futures.Future(loop=self.loop)
try:
yield from self.waiter
finally:
self.waiter = None
if n < 0 or self.byte_count <= n:
data = b''.join(self.buffer)
self.buffer.clear()
self.byte_count = 0
self._maybe_resume_transport()
return data
parts = []
parts_bytes = 0
while self.buffer and parts_bytes < n:
data = self.buffer.popleft()
data_bytes = len(data)
if n < parts_bytes + data_bytes:
data_bytes = n - parts_bytes
data, rest = data[:data_bytes], data[data_bytes:]
self.buffer.appendleft(rest)
parts.append(data)
parts_bytes += data_bytes
self.byte_count -= data_bytes
self._maybe_resume_transport()
return b''.join(parts)
@tasks.coroutine
def readexactly(self, n):
if self._exception is not None:
raise self._exception
if n <= 0:
return b''
while self.byte_count < n and not self.eof:
assert not self.waiter
self.waiter = futures.Future(loop=self.loop)
try:
yield from self.waiter
finally:
self.waiter = None
return (yield from self.read(n))
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