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
  52 class async_chat (asyncore.dispatcher):
  53     """This is an abstract class.  You must derive from this class, and add
  54     the two methods collect_incoming_data() and found_terminator()"""
  55
  56     # these are overridable defaults
  57
  58     ac_in_buffer_size       = 4096
  59     ac_out_buffer_size      = 4096
  60
  61     def __init__ (self, conn=None):
  62         self.ac_in_buffer = ''
  63         self.ac_out_buffer = ''
  64         self.producer_fifo = fifo()
  65         asyncore.dispatcher.__init__ (self, conn)
  66
  67     def set_terminator (self, term):
  68         "Set the input delimiter.  Can be a fixed string of any length, an integer, or None"
  69         self.terminator = term
  70
  71     def get_terminator (self):
  72         return self.terminator
  73
  74     # grab some more data from the socket,
  75     # throw it to the collector method,
  76     # check for the terminator,
  77     # if found, transition to the next state.
  78
  79     def handle_read (self):
  80
  81         try:
  82             data = self.recv (self.ac_in_buffer_size)
  83         except socket.error, why:
  84             self.handle_error()
  85             return
  86
  87         self.ac_in_buffer = self.ac_in_buffer + data
  88
  89         # Continue to search for self.terminator in self.ac_in_buffer,
  90         # while calling self.collect_incoming_data.  The while loop
  91         # is necessary because we might read several data+terminator
  92         # combos with a single recv(1024).
  93
  94         while self.ac_in_buffer:
  95             lb = len(self.ac_in_buffer)
  96             terminator = self.get_terminator()
  97             if terminator is None:
  98                 # no terminator, collect it all
  99                 self.collect_incoming_data (self.ac_in_buffer)
 100                 self.ac_in_buffer = ''
 101             elif type(terminator) == type(0):
 102                 # numeric terminator
 103                 n = terminator
 104                 if lb < n:
 105                     self.collect_incoming_data (self.ac_in_buffer)
 106                     self.ac_in_buffer = ''
 107                     self.terminator = self.terminator - lb
 108                 else:
 109                     self.collect_incoming_data (self.ac_in_buffer[:n])
 110                     self.ac_in_buffer = self.ac_in_buffer[n:]
 111                     self.terminator = 0
 112                     self.found_terminator()
 113             else:
 114                 # 3 cases:
 115                 # 1) end of buffer matches terminator exactly:
 116                 #    collect data, transition
 117                 # 2) end of buffer matches some prefix:
 118                 #    collect data to the prefix
 119                 # 3) end of buffer does not match any prefix:
 120                 #    collect data
 121                 terminator_len = len(terminator)
 122                 index = self.ac_in_buffer.find(terminator)
 123                 if index != -1:
 124                     # we found the terminator
 125                     if index > 0:
 126                         # don't bother reporting the empty string (source of subtle bugs)
 127                         self.collect_incoming_data (self.ac_in_buffer[:index])
 128                     self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
 129                     # This does the Right Thing if the terminator is changed here.
 130                     self.found_terminator()
 131                 else:
 132                     # check for a prefix of the terminator
 133                     index = find_prefix_at_end (self.ac_in_buffer, terminator)
 134                     if index:
 135                         if index != lb:
 136                             # we found a prefix, collect up to the prefix
 137                             self.collect_incoming_data (self.ac_in_buffer[:-index])
 138                             self.ac_in_buffer = self.ac_in_buffer[-index:]
 139                         break
 140                     else:
 141                         # no prefix, collect it all
 142                         self.collect_incoming_data (self.ac_in_buffer)
 143                         self.ac_in_buffer = ''
 144
 145     def handle_write (self):
 146         self.initiate_send ()
 147
 148     def handle_close (self):
 149         self.close()
 150
 151     def push (self, data):
 152         self.producer_fifo.push (simple_producer (data))
 153         self.initiate_send()
 154
 155     def push_with_producer (self, producer):
 156         self.producer_fifo.push (producer)
 157         self.initiate_send()
 158
 159     def readable (self):
 160         "predicate for inclusion in the readable for select()"
 161         return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
 162
 163     def writable (self):
 164         "predicate for inclusion in the writable for select()"
 165         # return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)
 166         # this is about twice as fast, though not as clear.
 167         return not (
 168                 (self.ac_out_buffer == '') and
 169                 self.producer_fifo.is_empty() and
 170                 self.connected
 171                 )
 172
 173     def close_when_done (self):
 174         "automatically close this channel once the outgoing queue is empty"
 175         self.producer_fifo.push (None)
 176
 177     # refill the outgoing buffer by calling the more() method
 178     # of the first producer in the queue
 179     def refill_buffer (self):
 180         _string_type = type('')
 181         while 1:
 182             if len(self.producer_fifo):
 183                 p = self.producer_fifo.first()
 184                 # a 'None' in the producer fifo is a sentinel,
 185                 # telling us to close the channel.
 186                 if p is None:
 187                     if not self.ac_out_buffer:
 188                         self.producer_fifo.pop()
 189                         self.close()
 190                     return
 191                 elif type(p) is _string_type:
 192                     self.producer_fifo.pop()
 193                     self.ac_out_buffer = self.ac_out_buffer + p
 194                     return
 195                 data = p.more()
 196                 if data:
 197                     self.ac_out_buffer = self.ac_out_buffer + data
 198                     return
 199                 else:
 200                     self.producer_fifo.pop()
 201             else:
 202                 return
 203
 204     def initiate_send (self):
 205         obs = self.ac_out_buffer_size
 206         # try to refill the buffer
 207         if (len (self.ac_out_buffer) < obs):
 208             self.refill_buffer()
 209
 210         if self.ac_out_buffer and self.connected:
 211             # try to send the buffer
 212             try:
 213                 num_sent = self.send (self.ac_out_buffer[:obs])
 214                 if num_sent:
 215                     self.ac_out_buffer = self.ac_out_buffer[num_sent:]
 216
 217             except socket.error, why:
 218                 self.handle_error()
 219                 return
 220
 221     def discard_buffers (self):
 222         # Emergencies only!
 223         self.ac_in_buffer = ''
 224         self.ac_out_buffer = ''
 225         while self.producer_fifo:
 226             self.producer_fifo.pop()
 227
 228
 229 class simple_producer:
 230
 231     def __init__ (self, data, buffer_size=512):
 232         self.data = data
 233         self.buffer_size = buffer_size
 234
 235     def more (self):
 236         if len (self.data) > self.buffer_size:
 237             result = self.data[:self.buffer_size]
 238             self.data = self.data[self.buffer_size:]
 239             return result
 240         else:
 241             result = self.data
 242             self.data = ''
 243             return result
 244
 245 class fifo:
 246     def __init__ (self, list=None):
 247         if not list:
 248             self.list = []
 249         else:
 250             self.list = list
 251
 252     def __len__ (self):
 253         return len(self.list)
 254
 255     def is_empty (self):
 256         return self.list == []
 257
 258     def first (self):
 259         return self.list[0]
 260
 261     def push (self, data):
 262         self.list.append (data)
 263
 264     def pop (self):
 265         if self.list:
 266             result = self.list[0]
 267             del self.list[0]
 268             return (1, result)
 269         else:
 270             return (0, None)
 271
 272 # Given 'haystack', see if any prefix of 'needle' is at its end.  This
 273 # assumes an exact match has already been checked.  Return the number of
 274 # characters matched.
 275 # for example:
 276 # f_p_a_e ("qwerty\r", "\r\n") => 1
 277 # f_p_a_e ("qwerty\r\n", "\r\n") => 2
 278 # f_p_a_e ("qwertydkjf", "\r\n") => 0
 279
 280 # this could maybe be made faster with a computed regex?
 281 # [answer: no; circa Python-2.0, Jan 2001]
 282 # python:    18307/s
 283 # re:        12820/s
 284 # regex:     14035/s
 285
 286 def find_prefix_at_end (haystack, needle):
 287     nl = len(needle)
 288     result = 0
 289     for i in range (1,nl):
 290         if haystack[-(nl-i):] == needle[:(nl-i)]:
 291             result = nl-i
 292             break
 293     return result