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asynchat.py
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# -*- Mode: Python; tab-width: 4 -*-
# Id: asynchat.py,v 2.26 2000/09/07 22:29:26 rushing Exp
# 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.
# ======================================================================
r"""A class supporting chat-style (command/response) protocols.
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.
"""
import socket
import asyncore
from collections import deque
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
# we don't want to enable the use of encoding by default, because that is a
# sign of an application bug that we don't want to pass silently
use_encoding = 0
encoding = 'latin-1'
def __init__ (self, sock=None, map=None):
# for string terminator matching
self.ac_in_buffer = b''
# we use a list here rather than io.BytesIO for a few reasons...
# del lst[:] is faster than bio.truncate(0)
# lst = [] is faster than bio.truncate(0)
self.incoming = []
# we toss the use of the "simple producer" and replace it with
# a pure deque, which the original fifo was a wrapping of
self.producer_fifo = deque()
asyncore.dispatcher.__init__ (self, sock, map)
def collect_incoming_data(self, data):
raise NotImplementedError("must be implemented in subclass")
def _collect_incoming_data(self, data):
self.incoming.append(data)
def _get_data(self):
d = b''.join(self.incoming)
del self.incoming[:]
return d
def found_terminator(self):
raise NotImplementedError("must be implemented in subclass")
def set_terminator (self, term):
"Set the input delimiter. Can be a fixed string of any length, an integer, or None"
if isinstance(term, str) and self.use_encoding:
term = bytes(term, self.encoding)
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 as why:
self.handle_error()
return
if isinstance(data, str) and self.use_encoding:
data = bytes(str, self.encoding)
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(4096).
while self.ac_in_buffer:
lb = len(self.ac_in_buffer)
terminator = self.get_terminator()
if not terminator:
# no terminator, collect it all
self.collect_incoming_data (self.ac_in_buffer)
self.ac_in_buffer = b''
elif isinstance(terminator, int):
# numeric terminator
n = terminator
if lb < n:
self.collect_incoming_data (self.ac_in_buffer)
self.ac_in_buffer = b''
self.terminator = self.terminator - lb
else:
self.collect_incoming_data (self.ac_in_buffer[:n])
self.ac_in_buffer = self.ac_in_buffer[n:]
self.terminator = 0
self.found_terminator()
else:
# 3 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
terminator_len = len(terminator)
index = self.ac_in_buffer.find(terminator)
if index != -1:
# we found the terminator
if index > 0:
# don't bother reporting the empty string (source of subtle bugs)
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:
if index != lb:
# 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 = b''
def handle_write (self):
self.initiate_send()
def handle_close (self):
self.close()
def push (self, data):
sabs = self.ac_out_buffer_size
if len(data) > sabs:
for i in range(0, len(data), sabs):
self.producer_fifo.append(data[i:i+sabs])
else:
self.producer_fifo.append(data)
self.initiate_send()
def push_with_producer (self, producer):
self.producer_fifo.append(producer)
self.initiate_send()
def readable (self):
"predicate for inclusion in the readable for select()"
# cannot use the old predicate, it violates the claim of the
# set_terminator method.
# return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
A23F
return 1
def writable (self):
"predicate for inclusion in the writable for select()"
return self.producer_fifo or (not self.connected)
def close_when_done (self):
"automatically close this channel once the outgoing queue is empty"
self.producer_fifo.append(None)
def initiate_send(self):
while self.producer_fifo and self.connected:
first = self.producer_fifo[0]
# handle empty string/buffer or None entry
if not first:
del self.producer_fifo[0]
if first is None:
## print("first is None")
self.handle_close()
return
## print("first is not None")
# handle classic producer behavior
obs = self.ac_out_buffer_size
try:
data = first[:obs]
except TypeError:
data = first.more()
if data:
self.producer_fifo.appendleft(data)
else:
del self.producer_fifo[0]
continue
if isinstance(data, str) and self.use_encoding:
data = bytes(data, self.encoding)
# send the data
try:
num_sent = self.send(data)
except socket.error:
self.handle_error()
return
if num_sent:
if num_sent < len(data) or obs < len(first):
self.producer_fifo[0] = first[num_sent:]
else:
del self.producer_fifo[0]
# we tried to send some actual data
return
def discard_buffers (self):
# Emergencies only!
self.ac_in_buffer = b''
del self.incoming[:]
self.producer_fifo.clear()
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 = b''
return result
class fifo:
def __init__ (self, list=None):
if not list:
self.list = deque()
else:
self.list = deque(list)
def __len__ (self):
return len(self.list)
def is_empty (self):
return not self.list
def first (self):
return self.list[0]
def push (self, data):
self.list.append(data)
def pop (self):
if self.list:
return (1, self.list.popleft())
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 ("qwertydkjf", "\r\n") => 0
# f_p_a_e ("qwerty\r\n", "\r\n") => <undefined>
# this could maybe be made faster with a computed regex?
# [answer: no; circa Python-2.0, Jan 2001]
# new python: 28961/s
# old python: 18307/s
# re: 12820/s
# regex: 14035/s
def find_prefix_at_end (haystack, needle):
l = len(needle) - 1
while l and not haystack.endswith(needle[:l]):
l -= 1
return l