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293dd23477
Capturing exceptions into names can lead to reference cycles though the __traceback__ attribute of the exceptions in some obscure cases that have been reported previously and fixed individually. As these variables are not used anyway, we can remove the binding to reduce the chances of creating reference cycles. See for example GH-13135
308 lines
11 KiB
Python
308 lines
11 KiB
Python
# -*- Mode: Python; tab-width: 4 -*-
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# Id: asynchat.py,v 2.26 2000/09/07 22:29:26 rushing Exp
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# Author: Sam Rushing <rushing@nightmare.com>
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# ======================================================================
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# Copyright 1996 by Sam Rushing
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#
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# All Rights Reserved
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#
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# Permission to use, copy, modify, and distribute this software and
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# its documentation for any purpose and without fee is hereby
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# granted, provided that the above copyright notice appear in all
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# copies and that both that copyright notice and this permission
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# notice appear in supporting documentation, and that the name of Sam
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# Rushing not be used in advertising or publicity pertaining to
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# distribution of the software without specific, written prior
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# permission.
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#
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# SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
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# NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
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# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
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# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
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# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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# ======================================================================
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r"""A class supporting chat-style (command/response) protocols.
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This class adds support for 'chat' style protocols - where one side
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sends a 'command', and the other sends a response (examples would be
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the common internet protocols - smtp, nntp, ftp, etc..).
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The handle_read() method looks at the input stream for the current
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'terminator' (usually '\r\n' for single-line responses, '\r\n.\r\n'
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for multi-line output), calling self.found_terminator() on its
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receipt.
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for example:
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Say you build an async nntp client using this class. At the start
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of the connection, you'll have self.terminator set to '\r\n', in
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order to process the single-line greeting. Just before issuing a
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'LIST' command you'll set it to '\r\n.\r\n'. The output of the LIST
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command will be accumulated (using your own 'collect_incoming_data'
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method) up to the terminator, and then control will be returned to
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you - by calling your self.found_terminator() method.
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"""
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import asyncore
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from collections import deque
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class async_chat(asyncore.dispatcher):
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"""This is an abstract class. You must derive from this class, and add
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the two methods collect_incoming_data() and found_terminator()"""
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# these are overridable defaults
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ac_in_buffer_size = 65536
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ac_out_buffer_size = 65536
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# we don't want to enable the use of encoding by default, because that is a
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# sign of an application bug that we don't want to pass silently
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use_encoding = 0
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encoding = 'latin-1'
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def __init__(self, sock=None, map=None):
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# for string terminator matching
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self.ac_in_buffer = b''
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# we use a list here rather than io.BytesIO for a few reasons...
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# del lst[:] is faster than bio.truncate(0)
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# lst = [] is faster than bio.truncate(0)
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self.incoming = []
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# we toss the use of the "simple producer" and replace it with
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# a pure deque, which the original fifo was a wrapping of
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self.producer_fifo = deque()
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asyncore.dispatcher.__init__(self, sock, map)
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def collect_incoming_data(self, data):
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raise NotImplementedError("must be implemented in subclass")
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def _collect_incoming_data(self, data):
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self.incoming.append(data)
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def _get_data(self):
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d = b''.join(self.incoming)
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del self.incoming[:]
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return d
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def found_terminator(self):
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raise NotImplementedError("must be implemented in subclass")
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def set_terminator(self, term):
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"""Set the input delimiter.
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Can be a fixed string of any length, an integer, or None.
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"""
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if isinstance(term, str) and self.use_encoding:
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term = bytes(term, self.encoding)
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elif isinstance(term, int) and term < 0:
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raise ValueError('the number of received bytes must be positive')
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self.terminator = term
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def get_terminator(self):
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return self.terminator
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# grab some more data from the socket,
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# throw it to the collector method,
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# check for the terminator,
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# if found, transition to the next state.
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def handle_read(self):
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try:
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data = self.recv(self.ac_in_buffer_size)
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except BlockingIOError:
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return
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except OSError:
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self.handle_error()
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return
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if isinstance(data, str) and self.use_encoding:
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data = bytes(str, self.encoding)
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self.ac_in_buffer = self.ac_in_buffer + data
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# Continue to search for self.terminator in self.ac_in_buffer,
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# while calling self.collect_incoming_data. The while loop
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# is necessary because we might read several data+terminator
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# combos with a single recv(4096).
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while self.ac_in_buffer:
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lb = len(self.ac_in_buffer)
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terminator = self.get_terminator()
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if not terminator:
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# no terminator, collect it all
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self.collect_incoming_data(self.ac_in_buffer)
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self.ac_in_buffer = b''
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elif isinstance(terminator, int):
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# numeric terminator
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n = terminator
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if lb < n:
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self.collect_incoming_data(self.ac_in_buffer)
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self.ac_in_buffer = b''
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self.terminator = self.terminator - lb
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else:
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self.collect_incoming_data(self.ac_in_buffer[:n])
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self.ac_in_buffer = self.ac_in_buffer[n:]
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self.terminator = 0
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self.found_terminator()
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else:
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# 3 cases:
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# 1) end of buffer matches terminator exactly:
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# collect data, transition
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# 2) end of buffer matches some prefix:
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# collect data to the prefix
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# 3) end of buffer does not match any prefix:
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# collect data
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terminator_len = len(terminator)
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index = self.ac_in_buffer.find(terminator)
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if index != -1:
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# we found the terminator
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if index > 0:
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# don't bother reporting the empty string
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# (source of subtle bugs)
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self.collect_incoming_data(self.ac_in_buffer[:index])
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self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
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# This does the Right Thing if the terminator
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# is changed here.
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self.found_terminator()
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else:
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# check for a prefix of the terminator
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index = find_prefix_at_end(self.ac_in_buffer, terminator)
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if index:
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if index != lb:
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# we found a prefix, collect up to the prefix
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self.collect_incoming_data(self.ac_in_buffer[:-index])
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self.ac_in_buffer = self.ac_in_buffer[-index:]
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break
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else:
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# no prefix, collect it all
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self.collect_incoming_data(self.ac_in_buffer)
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self.ac_in_buffer = b''
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def handle_write(self):
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self.initiate_send()
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def handle_close(self):
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self.close()
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def push(self, data):
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if not isinstance(data, (bytes, bytearray, memoryview)):
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raise TypeError('data argument must be byte-ish (%r)',
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type(data))
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sabs = self.ac_out_buffer_size
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if len(data) > sabs:
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for i in range(0, len(data), sabs):
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self.producer_fifo.append(data[i:i+sabs])
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else:
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self.producer_fifo.append(data)
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self.initiate_send()
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def push_with_producer(self, producer):
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self.producer_fifo.append(producer)
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self.initiate_send()
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def readable(self):
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"predicate for inclusion in the readable for select()"
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# cannot use the old predicate, it violates the claim of the
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# set_terminator method.
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# return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
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return 1
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def writable(self):
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"predicate for inclusion in the writable for select()"
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return self.producer_fifo or (not self.connected)
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def close_when_done(self):
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"automatically close this channel once the outgoing queue is empty"
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self.producer_fifo.append(None)
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def initiate_send(self):
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while self.producer_fifo and self.connected:
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first = self.producer_fifo[0]
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# handle empty string/buffer or None entry
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if not first:
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del self.producer_fifo[0]
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if first is None:
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self.handle_close()
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return
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# handle classic producer behavior
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obs = self.ac_out_buffer_size
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try:
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data = first[:obs]
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except TypeError:
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data = first.more()
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if data:
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self.producer_fifo.appendleft(data)
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else:
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del self.producer_fifo[0]
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continue
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if isinstance(data, str) and self.use_encoding:
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data = bytes(data, self.encoding)
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# send the data
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try:
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num_sent = self.send(data)
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except OSError:
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self.handle_error()
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return
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if num_sent:
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if num_sent < len(data) or obs < len(first):
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self.producer_fifo[0] = first[num_sent:]
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else:
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del self.producer_fifo[0]
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# we tried to send some actual data
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return
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def discard_buffers(self):
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# Emergencies only!
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self.ac_in_buffer = b''
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del self.incoming[:]
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self.producer_fifo.clear()
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class simple_producer:
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def __init__(self, data, buffer_size=512):
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self.data = data
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self.buffer_size = buffer_size
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def more(self):
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if len(self.data) > self.buffer_size:
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result = self.data[:self.buffer_size]
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self.data = self.data[self.buffer_size:]
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return result
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else:
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result = self.data
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self.data = b''
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return result
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# Given 'haystack', see if any prefix of 'needle' is at its end. This
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# assumes an exact match has already been checked. Return the number of
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# characters matched.
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# for example:
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# f_p_a_e("qwerty\r", "\r\n") => 1
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# f_p_a_e("qwertydkjf", "\r\n") => 0
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# f_p_a_e("qwerty\r\n", "\r\n") => <undefined>
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# this could maybe be made faster with a computed regex?
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# [answer: no; circa Python-2.0, Jan 2001]
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# new python: 28961/s
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# old python: 18307/s
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# re: 12820/s
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# regex: 14035/s
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def find_prefix_at_end(haystack, needle):
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l = len(needle) - 1
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while l and not haystack.endswith(needle[:l]):
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l -= 1
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return l
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