summaryrefslogtreecommitdiffstats
path: root/Lib/asynchat.py
blob: 6f99ba1063c85e48dae1c7f9a15965edcec4db61 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
# -*- 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

    def __init__ (self, conn=None):
        self.ac_in_buffer = ''
        self.ac_out_buffer = ''
        self.producer_fifo = fifo()
        asyncore.dispatcher.__init__ (self, conn)

    def collect_incoming_data(self, data):
        raise NotImplementedError, "must be implemented in subclass"

    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"
        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, why:
            self.handle_error()
            return

        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(1024).

        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 = ''
            elif isinstance(terminator, int) or isinstance(terminator, long):
                # numeric terminator
                n = terminator
                if lb < n:
                    self.collect_incoming_data (self.ac_in_buffer)
                    self.ac_in_buffer = ''
                    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 = ''

    def handle_write (self):
        self.initiate_send ()

    def handle_close (self):
        self.close()

    def push (self, data):
        self.producer_fifo.push (simple_producer (data))
        self.initiate_send()

    def push_with_producer (self, producer):
        self.producer_fifo.push (producer)
        self.initiate_send()

    def readable (self):
        "predicate for inclusion in the readable for select()"
        return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)

    def writable (self):
        "predicate for inclusion in the writable for select()"
        # return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)
        # this is about twice as fast, though not as clear.
        return not (
                (self.ac_out_buffer == '') and
                self.producer_fifo.is_empty() and
                self.connected
                )

    def close_when_done (self):
        "automatically close this channel once the outgoing queue is empty"
        self.producer_fifo.push (None)

    # refill the outgoing buffer by calling the more() method
    # of the first producer in the queue
    def refill_buffer (self):
        while 1:
            if len(self.producer_fifo):
                p = self.producer_fifo.first()
                # a 'None' in the producer fifo is a sentinel,
                # telling us to close the channel.
                if p is None:
                    if not self.ac_out_buffer:
                        self.producer_fifo.pop()
                        self.close()
                    return
                elif isinstance(p, str):
                    self.producer_fifo.pop()
                    self.ac_out_buffer = self.ac_out_buffer + p
                    return
                data = p.more()
                if data:
                    self.ac_out_buffer = self.ac_out_buffer + data
                    return
                else:
                    self.producer_fifo.pop()
            else:
                return

    def initiate_send (self):
        obs = self.ac_out_buffer_size
        # try to refill the buffer
        if (len (self.ac_out_buffer) < obs):
            self.refill_buffer()

        if self.ac_out_buffer and self.connected:
            # try to send the buffer
            try:
                num_sent = self.send (self.ac_out_buffer[:obs])
                if num_sent:
                    self.ac_out_buffer = self.ac_out_buffer[num_sent:]

            except socket.error, why:
                self.handle_error()
                return

    def discard_buffers (self):
        # Emergencies only!
        self.ac_in_buffer = ''
        self.ac_out_buffer = ''
        while self.producer_fifo:
            self.producer_fifo.pop()


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 = ''
            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