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Edit File: asynchat.py
# -*- 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 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 = 65536 ac_out_buffer_size = 65536 # 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) elif isinstance(term, int) and term < 0: raise ValueError('the number of received bytes must be positive') 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 BlockingIOError: return except OSError: 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): if not isinstance(data, (bytes, bytearray, memoryview)): raise TypeError('data argument must be byte-ish (%r)', type(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) 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: self.handle_close() return # 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 OSError: 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 # 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