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6fd7120616
http://groups.yahoo.com/group/medusa/message/333 It's clear that Medusa should not be checking for an empty buffer via "buf is ''". The patch merely changes "is" to "==". However, there's a mystery here all the same: Python attempts to store null strings uniquely, so it's unclear why "buf is ''" ever returned false when buf actually was empty. *Some* string operations produce non-unique null strings, e.g. >>> "abc"*0 is "abc"*0 0 >>> but they're rare, and I don't see any such operations in asynchat.
294 lines
10 KiB
Python
294 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 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:
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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 type(terminator) == type(0):
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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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_string_type = type('')
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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 type(p) is _string_type:
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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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result = self.list[0]
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del self.list[0]
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return (1, result)
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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 ("qwerty\r\n", "\r\n") => 2
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# f_p_a_e ("qwertydkjf", "\r\n") => 0
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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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# 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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nl = len(needle)
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result = 0
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for i in range (1,nl):
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if haystack[-(nl-i):] == needle[:(nl-i)]:
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result = nl-i
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break
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return result
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