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 from sys import py3kwarning
  53 from warnings import filterwarnings, catch_warnings
  54
  55 class async_chat (asyncore.dispatcher):
  56     """This is an abstract class.  You must derive from this class, and add
  57     the two methods collect_incoming_data() and found_terminator()"""
  58
  59     # these are overridable defaults
  60
  61     ac_in_buffer_size       = 4096
  62     ac_out_buffer_size      = 4096
  63
  64     def __init__ (self, sock=None, map=None):
  65         # for string terminator matching
  66         self.ac_in_buffer = ''
  67
  68         # we use a list here rather than cStringIO for a few reasons...
  69         # del lst[:] is faster than sio.truncate(0)
  70         # lst = [] is faster than sio.truncate(0)
  71         # cStringIO will be gaining unicode support in py3k, which
  72         # will negatively affect the performance of bytes compared to
  73         # a ''.join() equivalent
  74         self.incoming = []
  75
  76         # we toss the use of the "simple producer" and replace it with
  77         # a pure deque, which the original fifo was a wrapping of
  78         self.producer_fifo = deque()
  79         asyncore.dispatcher.__init__ (self, sock, map)
  80
  81     def collect_incoming_data(self, data):
  82         raise NotImplementedError("must be implemented in subclass")
  83
  84     def _collect_incoming_data(self, data):
  85         self.incoming.append(data)
  86
  87     def _get_data(self):
  88         d = ''.join(self.incoming)
  89         del self.incoming[:]
  90         return d
  91
  92     def found_terminator(self):
  93         raise NotImplementedError("must be implemented in subclass")
  94
  95     def set_terminator (self, term):
  96         "Set the input delimiter.  Can be a fixed string of any length, an integer, or None"
  97         self.terminator = term
  98
  99     def get_terminator (self):
 100         return self.terminator
 101
 102     # grab some more data from the socket,
 103     # throw it to the collector method,
 104     # check for the terminator,
 105     # if found, transition to the next state.
 106
 107     def handle_read (self):
 108
 109         try:
 110             data = self.recv (self.ac_in_buffer_size)
 111         except socket.error, why:
 112             self.handle_error()
 113             return
 114
 115         self.ac_in_buffer = self.ac_in_buffer + data
 116
 117         # Continue to search for self.terminator in self.ac_in_buffer,
 118         # while calling self.collect_incoming_data.  The while loop
 119         # is necessary because we might read several data+terminator
 120         # combos with a single recv(4096).
 121
 122         while self.ac_in_buffer:
 123             lb = len(self.ac_in_buffer)
 124             terminator = self.get_terminator()
 125             if not terminator:
 126                 # no terminator, collect it all
 127                 self.collect_incoming_data (self.ac_in_buffer)
 128                 self.ac_in_buffer = ''
 129             elif isinstance(terminator, int) or isinstance(terminator, long):
 130                 # numeric terminator
 131                 n = terminator
 132                 if lb < n:
 133                     self.collect_incoming_data (self.ac_in_buffer)
 134                     self.ac_in_buffer = ''
 135                     self.terminator = self.terminator - lb
 136                 else:
 137                     self.collect_incoming_data (self.ac_in_buffer[:n])
 138                     self.ac_in_buffer = self.ac_in_buffer[n:]
 139                     self.terminator = 0
 140                     self.found_terminator()
 141             else:
 142                 # 3 cases:
 143                 # 1) end of buffer matches terminator exactly:
 144                 #    collect data, transition
 145                 # 2) end of buffer matches some prefix:
 146                 #    collect data to the prefix
 147                 # 3) end of buffer does not match any prefix:
 148                 #    collect data
 149                 terminator_len = len(terminator)
 150                 index = self.ac_in_buffer.find(terminator)
 151                 if index != -1:
 152                     # we found the terminator
 153                     if index > 0:
 154                         # don't bother reporting the empty string (source of subtle bugs)
 155                         self.collect_incoming_data (self.ac_in_buffer[:index])
 156                     self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
 157                     # This does the Right Thing if the terminator is changed here.
 158                     self.found_terminator()
 159                 else:
 160                     # check for a prefix of the terminator
 161                     index = find_prefix_at_end (self.ac_in_buffer, terminator)
 162                     if index:
 163                         if index != lb:
 164                             # we found a prefix, collect up to the prefix
 165                             self.collect_incoming_data (self.ac_in_buffer[:-index])
 166                             self.ac_in_buffer = self.ac_in_buffer[-index:]
 167                         break
 168                     else:
 169                         # no prefix, collect it all
 170                         self.collect_incoming_data (self.ac_in_buffer)
 171                         self.ac_in_buffer = ''
 172
 173     def handle_write (self):
 174         self.initiate_send()
 175
 176     def handle_close (self):
 177         self.close()
 178
 179     def push (self, data):
 180         sabs = self.ac_out_buffer_size
 181         if len(data) > sabs:
 182             for i in xrange(0, len(data), sabs):
 183                 self.producer_fifo.append(data[i:i+sabs])
 184         else:
 185             self.producer_fifo.append(data)
 186         self.initiate_send()
 187
 188     def push_with_producer (self, producer):
 189         self.producer_fifo.append(producer)
 190         self.initiate_send()
 191
 192     def readable (self):
 193         "predicate for inclusion in the readable for select()"
 194         # cannot use the old predicate, it violates the claim of the
 195         # set_terminator method.
 196
 197         # return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
 198         return 1
 199
 200     def writable (self):
 201         "predicate for inclusion in the writable for select()"
 202         return self.producer_fifo or (not self.connected)
 203
 204     def close_when_done (self):
 205         "automatically close this channel once the outgoing queue is empty"
 206         self.producer_fifo.append(None)
 207
 208     def initiate_send(self):
 209         while self.producer_fifo and self.connected:
 210             first = self.producer_fifo[0]
 211             # handle empty string/buffer or None entry
 212             if not first:
 213                 del self.producer_fifo[0]
 214                 if first is None:
 215                     self.handle_close()
 216                     return
 217
 218             # handle classic producer behavior
 219             obs = self.ac_out_buffer_size
 220             try:
 221                 with catch_warnings():
 222                     if py3kwarning:
 223                         filterwarnings("ignore", ".*buffer", DeprecationWarning)
 224                     data = buffer(first, 0, obs)
 225             except TypeError:
 226                 data = first.more()
 227                 if data:
 228                     self.producer_fifo.appendleft(data)
 229                 else:
 230                     del self.producer_fifo[0]
 231                 continue
 232
 233             # send the data
 234             try:
 235                 num_sent = self.send(data)
 236             except socket.error:
 237                 self.handle_error()
 238                 return
 239
 240             if num_sent:
 241                 if num_sent < len(data) or obs < len(first):
 242                     self.producer_fifo[0] = first[num_sent:]
 243                 else:
 244                     del self.producer_fifo[0]
 245             # we tried to send some actual data
 246             return
 247
 248     def discard_buffers (self):
 249         # Emergencies only!
 250         self.ac_in_buffer = ''
 251         del self.incoming[:]
 252         self.producer_fifo.clear()
 253
 254 class simple_producer:
 255
 256     def __init__ (self, data, buffer_size=512):
 257         self.data = data
 258         self.buffer_size = buffer_size
 259
 260     def more (self):
 261         if len (self.data) > self.buffer_size:
 262             result = self.data[:self.buffer_size]
 263             self.data = self.data[self.buffer_size:]
 264             return result
 265         else:
 266             result = self.data
 267             self.data = ''
 268             return result
 269
 270 class fifo:
 271     def __init__ (self, list=None):
 272         if not list:
 273             self.list = deque()
 274         else:
 275             self.list = deque(list)
 276
 277     def __len__ (self):
 278         return len(self.list)
 279
 280     def is_empty (self):
 281         return not self.list
 282
 283     def first (self):
 284         return self.list[0]
 285
 286     def push (self, data):
 287         self.list.append(data)
 288
 289     def pop (self):
 290         if self.list:
 291             return (1, self.list.popleft())
 292         else:
 293             return (0, None)
 294
 295 # Given 'haystack', see if any prefix of 'needle' is at its end.  This
 296 # assumes an exact match has already been checked.  Return the number of
 297 # characters matched.
 298 # for example:
 299 # f_p_a_e ("qwerty\r", "\r\n") => 1
 300 # f_p_a_e ("qwertydkjf", "\r\n") => 0
 301 # f_p_a_e ("qwerty\r\n", "\r\n") => <undefined>
 302
 303 # this could maybe be made faster with a computed regex?
 304 # [answer: no; circa Python-2.0, Jan 2001]
 305 # new python:   28961/s
 306 # old python:   18307/s
 307 # re:        12820/s
 308 # regex:     14035/s
 309
 310 def find_prefix_at_end (haystack, needle):
 311     l = len(needle) - 1
 312     while l and not haystack.endswith(needle[:l]):
 313         l -= 1
 314     return l