Lib/asynchat.py

   1 # -*- Mode: Python; tab-width: 4 -*-
   2 #       Id: asynchat.py,v 2.26 2000/09/07 22:29:26 rushing Exp
   3 #       Author: Sam Rushing <rushing@nightmare.com>
   4
   5 # ======================================================================
   6 # Copyright 1996 by Sam Rushing
   7 #
   8 #                         All Rights Reserved
   9 #
  10 # Permission to use, copy, modify, and distribute this software and
  11 # its documentation for any purpose and without fee is hereby
  12 # granted, provided that the above copyright notice appear in all
  13 # copies and that both that copyright notice and this permission
  14 # notice appear in supporting documentation, and that the name of Sam
  15 # Rushing not be used in advertising or publicity pertaining to
  16 # distribution of the software without specific, written prior
  17 # permission.
  18 #
  19 # SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  20 # INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
  21 # NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  22 # CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
  23 # OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
  24 # NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  25 # CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  26 # ======================================================================
  27
  28 r"""A class supporting chat-style (command/response) protocols.
  29
  30 This class adds support for 'chat' style protocols - where one side
  31 sends a 'command', and the other sends a response (examples would be
  32 the common internet protocols - smtp, nntp, ftp, etc..).
  33
  34 The handle_read() method looks at the input stream for the current
  35 'terminator' (usually '\r\n' for single-line responses, '\r\n.\r\n'
  36 for multi-line output), calling self.found_terminator() on its
  37 receipt.
  38
  39 for example:
  40 Say you build an async nntp client using this class.  At the start
  41 of the connection, you'll have self.terminator set to '\r\n', in
  42 order to process the single-line greeting.  Just before issuing a
  43 'LIST' command you'll set it to '\r\n.\r\n'.  The output of the LIST
  44 command will be accumulated (using your own 'collect_incoming_data'
  45 method) up to the terminator, and then control will be returned to
  46 you - by calling your self.found_terminator() method.
  47 """
  48
  49 import socket
  50 import asyncore
  51 from collections import deque
  52
  53 class async_chat (asyncore.dispatcher):
  54     """This is an abstract class.  You must derive from this class, and add
  55     the two methods collect_incoming_data() and found_terminator()"""
  56
  57     # these are overridable defaults
  58
  59     ac_in_buffer_size       = 4096
  60     ac_out_buffer_size      = 4096
  61
  62     def __init__ (self, conn=None):
  63         self.ac_in_buffer = ''
  64         self.ac_out_buffer = ''
  65         self.producer_fifo = fifo()
  66         asyncore.dispatcher.__init__ (self, conn)
  67
  68     def collect_incoming_data(self, data):
  69         raise NotImplementedError, "must be implemented in subclass"
  70
  71     def found_terminator(self):
  72         raise NotImplementedError, "must be implemented in subclass"
  73
  74     def set_terminator (self, term):
  75         "Set the input delimiter.  Can be a fixed string of any length, an integer, or None"
  76         self.terminator = term
  77
  78     def get_terminator (self):
  79         return self.terminator
  80
  81     # grab some more data from the socket,
  82     # throw it to the collector method,
  83     # check for the terminator,
  84     # if found, transition to the next state.
  85
  86     def handle_read (self):
  87
  88         try:
  89             data = self.recv (self.ac_in_buffer_size)
  90         except socket.error, why:
  91             self.handle_error()
  92             return
  93
  94         self.ac_in_buffer = self.ac_in_buffer + data
  95
  96         # Continue to search for self.terminator in self.ac_in_buffer,
  97         # while calling self.collect_incoming_data.  The while loop
  98         # is necessary because we might read several data+terminator
  99         # combos with a single recv(1024).
 100
 101         while self.ac_in_buffer:
 102             lb = len(self.ac_in_buffer)
 103             terminator = self.get_terminator()
 104             if not terminator:
 105                 # no terminator, collect it all
 106                 self.collect_incoming_data (self.ac_in_buffer)
 107                 self.ac_in_buffer = ''
 108             elif isinstance(terminator, int) or isinstance(terminator, long):
 109                 # numeric terminator
 110                 n = terminator
 111                 if lb < n:
 112                     self.collect_incoming_data (self.ac_in_buffer)
 113                     self.ac_in_buffer = ''
 114                     self.terminator = self.terminator - lb
 115                 else:
 116                     self.collect_incoming_data (self.ac_in_buffer[:n])
 117                     self.ac_in_buffer = self.ac_in_buffer[n:]
 118                     self.terminator = 0
 119                     self.found_terminator()
 120             else:
 121                 # 3 cases:
 122                 # 1) end of buffer matches terminator exactly:
 123                 #    collect data, transition
 124                 # 2) end of buffer matches some prefix:
 125                 #    collect data to the prefix
 126                 # 3) end of buffer does not match any prefix:
 127                 #    collect data
 128                 terminator_len = len(terminator)
 129                 index = self.ac_in_buffer.find(terminator)
 130                 if index != -1:
 131                     # we found the terminator
 132                     if index > 0:
 133                         # don't bother reporting the empty string (source of subtle bugs)
 134                         self.collect_incoming_data (self.ac_in_buffer[:index])
 135                     self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
 136                     # This does the Right Thing if the terminator is changed here.
 137                     self.found_terminator()
 138                 else:
 139                     # check for a prefix of the terminator
 140                     index = find_prefix_at_end (self.ac_in_buffer, terminator)
 141                     if index:
 142                         if index != lb:
 143                             # we found a prefix, collect up to the prefix
 144                             self.collect_incoming_data (self.ac_in_buffer[:-index])
 145                             self.ac_in_buffer = self.ac_in_buffer[-index:]
 146                         break
 147                     else:
 148                         # no prefix, collect it all
 149                         self.collect_incoming_data (self.ac_in_buffer)
 150                         self.ac_in_buffer = ''
 151
 152     def handle_write (self):
 153         self.initiate_send ()
 154
 155     def handle_close (self):
 156         self.close()
 157
 158     def push (self, data):
 159         self.producer_fifo.push (simple_producer (data))
 160         self.initiate_send()
 161
 162     def push_with_producer (self, producer):
 163         self.producer_fifo.push (producer)
 164         self.initiate_send()
 165
 166     def readable (self):
 167         "predicate for inclusion in the readable for select()"
 168         return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
 169
 170     def writable (self):
 171         "predicate for inclusion in the writable for select()"
 172         # return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)
 173         # this is about twice as fast, though not as clear.
 174         return not (
 175                 (self.ac_out_buffer == '') and
 176                 self.producer_fifo.is_empty() and
 177                 self.connected
 178                 )
 179
 180     def close_when_done (self):
 181         "automatically close this channel once the outgoing queue is empty"
 182         self.producer_fifo.push (None)
 183
 184     # refill the outgoing buffer by calling the more() method
 185     # of the first producer in the queue
 186     def refill_buffer (self):
 187         while 1:
 188             if len(self.producer_fifo):
 189                 p = self.producer_fifo.first()
 190                 # a 'None' in the producer fifo is a sentinel,
 191                 # telling us to close the channel.
 192                 if p is None:
 193                     if not self.ac_out_buffer:
 194                         self.producer_fifo.pop()
 195                         self.close()
 196                     return
 197                 elif isinstance(p, str):
 198                     self.producer_fifo.pop()
 199                     self.ac_out_buffer = self.ac_out_buffer + p
 200                     return
 201                 data = p.more()
 202                 if data:
 203                     self.ac_out_buffer = self.ac_out_buffer + data
 204                     return
 205                 else:
 206                     self.producer_fifo.pop()
 207             else:
 208                 return
 209
 210     def initiate_send (self):
 211         obs = self.ac_out_buffer_size
 212         # try to refill the buffer
 213         if (len (self.ac_out_buffer) < obs):
 214             self.refill_buffer()
 215
 216         if self.ac_out_buffer and self.connected:
 217             # try to send the buffer
 218             try:
 219                 num_sent = self.send (self.ac_out_buffer[:obs])
 220                 if num_sent:
 221                     self.ac_out_buffer = self.ac_out_buffer[num_sent:]
 222
 223             except socket.error, why:
 224                 self.handle_error()
 225                 return
 226
 227     def discard_buffers (self):
 228         # Emergencies only!
 229         self.ac_in_buffer = ''
 230         self.ac_out_buffer = ''
 231         while self.producer_fifo:
 232             self.producer_fifo.pop()
 233
 234
 235 class simple_producer:
 236
 237     def __init__ (self, data, buffer_size=512):
 238         self.data = data
 239         self.buffer_size = buffer_size
 240
 241     def more (self):
 242         if len (self.data) > self.buffer_size:
 243             result = self.data[:self.buffer_size]
 244             self.data = self.data[self.buffer_size:]
 245             return result
 246         else:
 247             result = self.data
 248             self.data = ''
 249             return result
 250
 251 class fifo:
 252     def __init__ (self, list=None):
 253         if not list:
 254             self.list = deque()
 255         else:
 256             self.list = deque(list)
 257
 258     def __len__ (self):
 259         return len(self.list)
 260
 261     def is_empty (self):
 262         return not self.list
 263
 264     def first (self):
 265         return self.list[0]
 266
 267     def push (self, data):
 268         self.list.append(data)
 269
 270     def pop (self):
 271         if self.list:
 272             return (1, self.list.popleft())
 273         else:
 274             return (0, None)
 275
 276 # Given 'haystack', see if any prefix of 'needle' is at its end.  This
 277 # assumes an exact match has already been checked.  Return the number of
 278 # characters matched.
 279 # for example:
 280 # f_p_a_e ("qwerty\r", "\r\n") => 1
 281 # f_p_a_e ("qwertydkjf", "\r\n") => 0
 282 # f_p_a_e ("qwerty\r\n", "\r\n") => <undefined>
 283
 284 # this could maybe be made faster with a computed regex?
 285 # [answer: no; circa Python-2.0, Jan 2001]
 286 # new python:   28961/s
 287 # old python:   18307/s
 288 # re:        12820/s
 289 # regex:     14035/s
 290
 291 def find_prefix_at_end (haystack, needle):
 292     l = len(needle) - 1
 293     while l and not haystack.endswith(needle[:l]):
 294         l -= 1
 295     return l