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
28r"""A class supporting chat-style (command/response) protocols.
29
30This class adds support for 'chat' style protocols - where one side
31sends a 'command', and the other sends a response (examples would be
32the common internet protocols - smtp, nntp, ftp, etc..).
33
34The handle_read() method looks at the input stream for the current
35'terminator' (usually '\r\n' for single-line responses, '\r\n.\r\n'
36for multi-line output), calling self.found_terminator() on its
37receipt.
38
39for example:
40Say you build an async nntp client using this class.  At the start
41of the connection, you'll have self.terminator set to '\r\n', in
42order 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
44command will be accumulated (using your own 'collect_incoming_data'
45method) up to the terminator, and then control will be returned to
46you - by calling your self.found_terminator() method.
47"""
48import asyncore
49from collections import deque
50
51
52class 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 = 65536
59    ac_out_buffer_size = 65536
60
61    # we don't want to enable the use of encoding by default, because that is a
62    # sign of an application bug that we don't want to pass silently
63
64    use_encoding = 0
65    encoding = 'latin-1'
66
67    def __init__(self, sock=None, map=None):
68        # for string terminator matching
69        self.ac_in_buffer = b''
70
71        # we use a list here rather than io.BytesIO for a few reasons...
72        # del lst[:] is faster than bio.truncate(0)
73        # lst = [] is faster than bio.truncate(0)
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 = b''.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.
97
98        Can be a fixed string of any length, an integer, or None.
99        """
100        if isinstance(term, str) and self.use_encoding:
101            term = bytes(term, self.encoding)
102        elif isinstance(term, int) and term < 0:
103            raise ValueError('the number of received bytes must be positive')
104        self.terminator = term
105
106    def get_terminator(self):
107        return self.terminator
108
109    # grab some more data from the socket,
110    # throw it to the collector method,
111    # check for the terminator,
112    # if found, transition to the next state.
113
114    def handle_read(self):
115
116        try:
117            data = self.recv(self.ac_in_buffer_size)
118        except BlockingIOError:
119            return
120        except OSError as why:
121            self.handle_error()
122            return
123
124        if isinstance(data, str) and self.use_encoding:
125            data = bytes(str, self.encoding)
126        self.ac_in_buffer = self.ac_in_buffer + data
127
128        # Continue to search for self.terminator in self.ac_in_buffer,
129        # while calling self.collect_incoming_data.  The while loop
130        # is necessary because we might read several data+terminator
131        # combos with a single recv(4096).
132
133        while self.ac_in_buffer:
134            lb = len(self.ac_in_buffer)
135            terminator = self.get_terminator()
136            if not terminator:
137                # no terminator, collect it all
138                self.collect_incoming_data(self.ac_in_buffer)
139                self.ac_in_buffer = b''
140            elif isinstance(terminator, int):
141                # numeric terminator
142                n = terminator
143                if lb < n:
144                    self.collect_incoming_data(self.ac_in_buffer)
145                    self.ac_in_buffer = b''
146                    self.terminator = self.terminator - lb
147                else:
148                    self.collect_incoming_data(self.ac_in_buffer[:n])
149                    self.ac_in_buffer = self.ac_in_buffer[n:]
150                    self.terminator = 0
151                    self.found_terminator()
152            else:
153                # 3 cases:
154                # 1) end of buffer matches terminator exactly:
155                #    collect data, transition
156                # 2) end of buffer matches some prefix:
157                #    collect data to the prefix
158                # 3) end of buffer does not match any prefix:
159                #    collect data
160                terminator_len = len(terminator)
161                index = self.ac_in_buffer.find(terminator)
162                if index != -1:
163                    # we found the terminator
164                    if index > 0:
165                        # don't bother reporting the empty string
166                        # (source of subtle bugs)
167                        self.collect_incoming_data(self.ac_in_buffer[:index])
168                    self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
169                    # This does the Right Thing if the terminator
170                    # is changed here.
171                    self.found_terminator()
172                else:
173                    # check for a prefix of the terminator
174                    index = find_prefix_at_end(self.ac_in_buffer, terminator)
175                    if index:
176                        if index != lb:
177                            # we found a prefix, collect up to the prefix
178                            self.collect_incoming_data(self.ac_in_buffer[:-index])
179                            self.ac_in_buffer = self.ac_in_buffer[-index:]
180                        break
181                    else:
182                        # no prefix, collect it all
183                        self.collect_incoming_data(self.ac_in_buffer)
184                        self.ac_in_buffer = b''
185
186    def handle_write(self):
187        self.initiate_send()
188
189    def handle_close(self):
190        self.close()
191
192    def push(self, data):
193        if not isinstance(data, (bytes, bytearray, memoryview)):
194            raise TypeError('data argument must be byte-ish (%r)',
195                            type(data))
196        sabs = self.ac_out_buffer_size
197        if len(data) > sabs:
198            for i in range(0, len(data), sabs):
199                self.producer_fifo.append(data[i:i+sabs])
200        else:
201            self.producer_fifo.append(data)
202        self.initiate_send()
203
204    def push_with_producer(self, producer):
205        self.producer_fifo.append(producer)
206        self.initiate_send()
207
208    def readable(self):
209        "predicate for inclusion in the readable for select()"
210        # cannot use the old predicate, it violates the claim of the
211        # set_terminator method.
212
213        # return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
214        return 1
215
216    def writable(self):
217        "predicate for inclusion in the writable for select()"
218        return self.producer_fifo or (not self.connected)
219
220    def close_when_done(self):
221        "automatically close this channel once the outgoing queue is empty"
222        self.producer_fifo.append(None)
223
224    def initiate_send(self):
225        while self.producer_fifo and self.connected:
226            first = self.producer_fifo[0]
227            # handle empty string/buffer or None entry
228            if not first:
229                del self.producer_fifo[0]
230                if first is None:
231                    self.handle_close()
232                    return
233
234            # handle classic producer behavior
235            obs = self.ac_out_buffer_size
236            try:
237                data = first[:obs]
238            except TypeError:
239                data = first.more()
240                if data:
241                    self.producer_fifo.appendleft(data)
242                else:
243                    del self.producer_fifo[0]
244                continue
245
246            if isinstance(data, str) and self.use_encoding:
247                data = bytes(data, self.encoding)
248
249            # send the data
250            try:
251                num_sent = self.send(data)
252            except OSError:
253                self.handle_error()
254                return
255
256            if num_sent:
257                if num_sent < len(data) or obs < len(first):
258                    self.producer_fifo[0] = first[num_sent:]
259                else:
260                    del self.producer_fifo[0]
261            # we tried to send some actual data
262            return
263
264    def discard_buffers(self):
265        # Emergencies only!
266        self.ac_in_buffer = b''
267        del self.incoming[:]
268        self.producer_fifo.clear()
269
270
271class simple_producer:
272
273    def __init__(self, data, buffer_size=512):
274        self.data = data
275        self.buffer_size = buffer_size
276
277    def more(self):
278        if len(self.data) > self.buffer_size:
279            result = self.data[:self.buffer_size]
280            self.data = self.data[self.buffer_size:]
281            return result
282        else:
283            result = self.data
284            self.data = b''
285            return result
286
287
288# Given 'haystack', see if any prefix of 'needle' is at its end.  This
289# assumes an exact match has already been checked.  Return the number of
290# characters matched.
291# for example:
292# f_p_a_e("qwerty\r", "\r\n") => 1
293# f_p_a_e("qwertydkjf", "\r\n") => 0
294# f_p_a_e("qwerty\r\n", "\r\n") => <undefined>
295
296# this could maybe be made faster with a computed regex?
297# [answer: no; circa Python-2.0, Jan 2001]
298# new python:   28961/s
299# old python:   18307/s
300# re:        12820/s
301# regex:     14035/s
302
303def find_prefix_at_end(haystack, needle):
304    l = len(needle) - 1
305    while l and not haystack.endswith(needle[:l]):
306        l -= 1
307    return l
308