A gift from Sam Rushing - modules asyncore and asynchat for the
standard Python library. (Async socket support.)
diff --git a/Lib/asynchat.py b/Lib/asynchat.py
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+# -*- Mode: Python; tab-width: 4 -*-
+# $Id$
+# Author: Sam Rushing <rushing@nightmare.com>
+
+# ======================================================================
+# Copyright 1996 by Sam Rushing
+#
+# All Rights Reserved
+#
+# Permission to use, copy, modify, and distribute this software and
+# its documentation for any purpose and without fee is hereby
+# granted, provided that the above copyright notice appear in all
+# copies and that both that copyright notice and this permission
+# notice appear in supporting documentation, and that the name of Sam
+# Rushing not be used in advertising or publicity pertaining to
+# distribution of the software without specific, written prior
+# permission.
+#
+# SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
+# NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+# ======================================================================
+
+import socket
+import asyncore
+import string
+
+# This class adds support for 'chat' style protocols - where one side
+# sends a 'command', and the other sends a response (examples would be
+# the common internet protocols - smtp, nntp, ftp, etc..).
+
+# The handle_read() method looks at the input stream for the current
+# 'terminator' (usually '\r\n' for single-line responses, '\r\n.\r\n'
+# for multi-line output), calling self.found_terminator() on its
+# receipt.
+
+# for example:
+# Say you build an async nntp client using this class. At the start
+# of the connection, you'll have self.terminator set to '\r\n', in
+# order to process the single-line greeting. Just before issuing a
+# 'LIST' command you'll set it to '\r\n.\r\n'. The output of the LIST
+# command will be accumulated (using your own 'collect_incoming_data'
+# method) up to the terminator, and then control will be returned to
+# you - by calling your self.found_terminator() method
+
+class async_chat (asyncore.dispatcher):
+ """This is an abstract class. You must derive from this class, and add
+ the two methods collect_incoming_data() and found_terminator()"""
+
+ # these are overridable defaults
+
+ ac_in_buffer_size = 4096
+ ac_out_buffer_size = 4096
+
+ def __init__ (self, conn=None):
+ self.ac_in_buffer = ''
+ self.ac_out_buffer = ''
+ self.producer_fifo = fifo()
+ asyncore.dispatcher.__init__ (self, conn)
+
+ def set_terminator (self, term):
+ "Set the input delimiter. Can be a fixed string of any length, or None"
+ if term is None:
+ self.terminator = ''
+ else:
+ self.terminator = term
+
+ def get_terminator (self):
+ return self.terminator
+
+ # grab some more data from the socket,
+ # throw it to the collector method,
+ # check for the terminator,
+ # if found, transition to the next state.
+
+ def handle_read (self):
+
+ try:
+ data = self.recv (self.ac_in_buffer_size)
+ except socket.error, why:
+ import sys
+ self.handle_error (sys.exc_type, sys.exc_value, sys.exc_traceback)
+ return
+
+ self.ac_in_buffer = self.ac_in_buffer + data
+
+ # Continue to search for self.terminator in self.ac_in_buffer,
+ # while calling self.collect_incoming_data. The while loop
+ # is necessary because we might read several data+terminator
+ # combos with a single recv(1024).
+
+ while self.ac_in_buffer:
+ terminator = self.get_terminator()
+ terminator_len = len(terminator)
+ # 4 cases:
+ # 1) end of buffer matches terminator exactly:
+ # collect data, transition
+ # 2) end of buffer matches some prefix:
+ # collect data to the prefix
+ # 3) end of buffer does not match any prefix:
+ # collect data
+ # 4) no terminator, just collect the data
+ if terminator:
+ index = string.find (self.ac_in_buffer, terminator)
+ if index != -1:
+ # we found the terminator
+ self.collect_incoming_data (self.ac_in_buffer[:index])
+ self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
+ # This does the Right Thing if the terminator is changed here.
+ self.found_terminator()
+ else:
+ # check for a prefix of the terminator
+ index = find_prefix_at_end (self.ac_in_buffer, terminator)
+ if index:
+ # we found a prefix, collect up to the prefix
+ self.collect_incoming_data (self.ac_in_buffer[:-index])
+ self.ac_in_buffer = self.ac_in_buffer[-index:]
+ break
+ else:
+ # no prefix, collect it all
+ self.collect_incoming_data (self.ac_in_buffer)
+ self.ac_in_buffer = ''
+ else:
+ # no terminator, collect it all
+ self.collect_incoming_data (self.ac_in_buffer)
+ self.ac_in_buffer = ''
+
+ def handle_write (self):
+ self.initiate_send ()
+
+ def handle_close (self):
+ self.close()
+
+ def push (self, data):
+ self.producer_fifo.push (simple_producer (data))
+ self.initiate_send()
+
+ def push_with_producer (self, producer):
+ self.producer_fifo.push (producer)
+ self.initiate_send()
+
+ def readable (self):
+ return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
+
+ def writable (self):
+ return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)
+
+ def close_when_done (self):
+ self.producer_fifo.push (None)
+
+ # refill the outgoing buffer by calling the more() method
+ # of the first producer in the queue
+ def refill_buffer (self):
+ while 1:
+ if len(self.producer_fifo):
+ p = self.producer_fifo.first()
+ # a 'None' in the producer fifo is a sentinel,
+ # telling us to close the channel.
+ if p is None:
+ if not self.ac_out_buffer:
+ self.producer_fifo.pop()
+ self.close()
+ return
+ data = p.more()
+ if data:
+ self.ac_out_buffer = self.ac_out_buffer + data
+ return
+ else:
+ self.producer_fifo.pop()
+ else:
+ return
+
+ def initiate_send (self):
+ obs = self.ac_out_buffer_size
+ # try to refill the buffer
+ if (not self._push_mode) and (len (self.ac_out_buffer) < obs):
+ self.refill_buffer()
+
+ if self.ac_out_buffer and self.connected:
+ # try to send the buffer
+ num_sent = self.send (self.ac_out_buffer[:obs])
+ if num_sent:
+ self.ac_out_buffer = self.ac_out_buffer[num_sent:]
+
+ def discard_buffers (self):
+ # Emergencies only!
+ self.ac_in_buffer = ''
+ self.ac_out_buffer == ''
+ while self.producer_fifo:
+ self.producer_fifo.pop()
+
+ # ==================================================
+ # support for push mode.
+ # ==================================================
+ _push_mode = 0
+ def push_mode (self, boolean):
+ self._push_mode = boolean
+
+ def writable_push (self):
+ return self.connected and len(self.ac_out_buffer)
+
+class simple_producer:
+ def __init__ (self, data, buffer_size=512):
+ self.data = data
+ self.buffer_size = buffer_size
+
+ def more (self):
+ if len (self.data) > self.buffer_size:
+ result = self.data[:self.buffer_size]
+ self.data = self.data[self.buffer_size:]
+ return result
+ else:
+ result = self.data
+ self.data = ''
+ return result
+
+class fifo:
+ def __init__ (self, list=None):
+ if not list:
+ self.list = []
+ else:
+ self.list = list
+
+ def __len__ (self):
+ return len(self.list)
+
+ def first (self):
+ return self.list[0]
+
+ def push (self, data):
+ self.list.append (data)
+
+ def pop (self):
+ if self.list:
+ result = self.list[0]
+ del self.list[0]
+ return (1, result)
+ else:
+ return (0, None)
+
+# Given 'haystack', see if any prefix of 'needle' is at its end. This
+# assumes an exact match has already been checked. Return the number of
+# characters matched.
+# for example:
+# f_p_a_e ("qwerty\r", "\r\n") => 1
+# f_p_a_e ("qwerty\r\n", "\r\n") => 2
+# f_p_a_e ("qwertydkjf", "\r\n") => 0
+
+# this could maybe be made faster with a computed regex?
+
+##def find_prefix_at_end (haystack, needle):
+## nl = len(needle)
+## result = 0
+## for i in range (1,nl):
+## if haystack[-(nl-i):] == needle[:(nl-i)]:
+## result = nl-i
+## break
+## return result
+
+# yes, this is about twice as fast, but still seems
+# to be neglible CPU. The previous could do about 290
+# searches/sec. the new one about 555/sec.
+
+import regex
+
+prefix_cache = {}
+
+def prefix_regex (needle):
+ if prefix_cache.has_key (needle):
+ return prefix_cache[needle]
+ else:
+ reg = needle[-1]
+ for i in range(1,len(needle)):
+ reg = '%c\(%s\)?' % (needle[-(i+1)], reg)
+ reg = regex.compile (reg+'$')
+ prefix_cache[needle] = reg, len(needle)
+ return reg, len(needle)
+
+def find_prefix_at_end (haystack, needle):
+ reg, length = prefix_regex (needle)
+ lh = len(haystack)
+ result = reg.search (haystack, max(0,lh-length))
+ if result >= 0:
+ return (lh - result)
+ else:
+ return 0