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a416341b30
When the null string is used as the terminator, it used to be the same as None, meaning "collect all the data". In the current code, however, it falls into an endless loop; this change reverts to the old behavior.
295 lines
10 KiB
Python
295 lines
10 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 socket
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import asyncore
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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 = 4096
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ac_out_buffer_size = 4096
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def __init__ (self, conn=None):
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self.ac_in_buffer = ''
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self.ac_out_buffer = ''
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self.producer_fifo = fifo()
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asyncore.dispatcher.__init__ (self, conn)
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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 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. Can be a fixed string of any length, an integer, or None"
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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 socket.error, why:
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self.handle_error()
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return
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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(1024).
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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 terminator is None or 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 = ''
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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 = ''
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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 (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 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 = ''
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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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self.producer_fifo.push (simple_producer (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.push (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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return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
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def writable (self):
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"predicate for inclusion in the writable for select()"
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# return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)
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# this is about twice as fast, though not as clear.
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return not (
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(self.ac_out_buffer == '') and
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self.producer_fifo.is_empty() and
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self.connected
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)
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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.push (None)
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# refill the outgoing buffer by calling the more() method
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# of the first producer in the queue
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def refill_buffer (self):
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while 1:
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if len(self.producer_fifo):
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p = self.producer_fifo.first()
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# a 'None' in the producer fifo is a sentinel,
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# telling us to close the channel.
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if p is None:
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if not self.ac_out_buffer:
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self.producer_fifo.pop()
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self.close()
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return
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elif isinstance(p, str):
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self.producer_fifo.pop()
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self.ac_out_buffer = self.ac_out_buffer + p
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return
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data = p.more()
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if data:
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self.ac_out_buffer = self.ac_out_buffer + data
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return
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else:
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self.producer_fifo.pop()
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else:
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return
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def initiate_send (self):
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obs = self.ac_out_buffer_size
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# try to refill the buffer
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if (len (self.ac_out_buffer) < obs):
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self.refill_buffer()
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if self.ac_out_buffer and self.connected:
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# try to send the buffer
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try:
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num_sent = self.send (self.ac_out_buffer[:obs])
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if num_sent:
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self.ac_out_buffer = self.ac_out_buffer[num_sent:]
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except socket.error, why:
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self.handle_error()
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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 = ''
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self.ac_out_buffer = ''
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while self.producer_fifo:
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self.producer_fifo.pop()
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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 = ''
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return result
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class fifo:
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def __init__ (self, list=None):
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if not list:
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self.list = []
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else:
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self.list = list
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def __len__ (self):
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return len(self.list)
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def is_empty (self):
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return self.list == []
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def first (self):
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return self.list[0]
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def push (self, data):
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self.list.append (data)
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def pop (self):
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if self.list:
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return (1, self.list.pop(0))
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else:
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return (0, None)
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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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