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
51from warnings import warn
52warn(
53    'The asynchat module is deprecated. '
54    'The recommended replacement is asyncio',
55    DeprecationWarning,
56    stacklevel=2)
57
58
59
60class async_chat(asyncore.dispatcher):
61    """This is an abstract class.  You must derive from this class, and add
62    the two methods collect_incoming_data() and found_terminator()"""
63
64    # these are overridable defaults
65
66    ac_in_buffer_size = 65536
67    ac_out_buffer_size = 65536
68
69    # we don't want to enable the use of encoding by default, because that is a
70    # sign of an application bug that we don't want to pass silently
71
72    use_encoding = 0
73    encoding = 'latin-1'
74
75    def __init__(self, sock=None, map=None):
76        # for string terminator matching
77        self.ac_in_buffer = b''
78
79        # we use a list here rather than io.BytesIO for a few reasons...
80        # del lst[:] is faster than bio.truncate(0)
81        # lst = [] is faster than bio.truncate(0)
82        self.incoming = []
83
84        # we toss the use of the "simple producer" and replace it with
85        # a pure deque, which the original fifo was a wrapping of
86        self.producer_fifo = deque()
87        asyncore.dispatcher.__init__(self, sock, map)
88
89    def collect_incoming_data(self, data):
90        raise NotImplementedError("must be implemented in subclass")
91
92    def _collect_incoming_data(self, data):
93        self.incoming.append(data)
94
95    def _get_data(self):
96        d = b''.join(self.incoming)
97        del self.incoming[:]
98        return d
99
100    def found_terminator(self):
101        raise NotImplementedError("must be implemented in subclass")
102
103    def set_terminator(self, term):
104        """Set the input delimiter.
105
106        Can be a fixed string of any length, an integer, or None.
107        """
108        if isinstance(term, str) and self.use_encoding:
109            term = bytes(term, self.encoding)
110        elif isinstance(term, int) and term < 0:
111            raise ValueError('the number of received bytes must be positive')
112        self.terminator = term
113
114    def get_terminator(self):
115        return self.terminator
116
117    # grab some more data from the socket,
118    # throw it to the collector method,
119    # check for the terminator,
120    # if found, transition to the next state.
121
122    def handle_read(self):
123
124        try:
125            data = self.recv(self.ac_in_buffer_size)
126        except BlockingIOError:
127            return
128        except OSError:
129            self.handle_error()
130            return
131
132        if isinstance(data, str) and self.use_encoding:
133            data = bytes(str, self.encoding)
134        self.ac_in_buffer = self.ac_in_buffer + data
135
136        # Continue to search for self.terminator in self.ac_in_buffer,
137        # while calling self.collect_incoming_data.  The while loop
138        # is necessary because we might read several data+terminator
139        # combos with a single recv(4096).
140
141        while self.ac_in_buffer:
142            lb = len(self.ac_in_buffer)
143            terminator = self.get_terminator()
144            if not terminator:
145                # no terminator, collect it all
146                self.collect_incoming_data(self.ac_in_buffer)
147                self.ac_in_buffer = b''
148            elif isinstance(terminator, int):
149                # numeric terminator
150                n = terminator
151                if lb < n:
152                    self.collect_incoming_data(self.ac_in_buffer)
153                    self.ac_in_buffer = b''
154                    self.terminator = self.terminator - lb
155                else:
156                    self.collect_incoming_data(self.ac_in_buffer[:n])
157                    self.ac_in_buffer = self.ac_in_buffer[n:]
158                    self.terminator = 0
159                    self.found_terminator()
160            else:
161                # 3 cases:
162                # 1) end of buffer matches terminator exactly:
163                #    collect data, transition
164                # 2) end of buffer matches some prefix:
165                #    collect data to the prefix
166                # 3) end of buffer does not match any prefix:
167                #    collect data
168                terminator_len = len(terminator)
169                index = self.ac_in_buffer.find(terminator)
170                if index != -1:
171                    # we found the terminator
172                    if index > 0:
173                        # don't bother reporting the empty string
174                        # (source of subtle bugs)
175                        self.collect_incoming_data(self.ac_in_buffer[:index])
176                    self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]
177                    # This does the Right Thing if the terminator
178                    # is changed here.
179                    self.found_terminator()
180                else:
181                    # check for a prefix of the terminator
182                    index = find_prefix_at_end(self.ac_in_buffer, terminator)
183                    if index:
184                        if index != lb:
185                            # we found a prefix, collect up to the prefix
186                            self.collect_incoming_data(self.ac_in_buffer[:-index])
187                            self.ac_in_buffer = self.ac_in_buffer[-index:]
188                        break
189                    else:
190                        # no prefix, collect it all
191                        self.collect_incoming_data(self.ac_in_buffer)
192                        self.ac_in_buffer = b''
193
194    def handle_write(self):
195        self.initiate_send()
196
197    def handle_close(self):
198        self.close()
199
200    def push(self, data):
201        if not isinstance(data, (bytes, bytearray, memoryview)):
202            raise TypeError('data argument must be byte-ish (%r)',
203                            type(data))
204        sabs = self.ac_out_buffer_size
205        if len(data) > sabs:
206            for i in range(0, len(data), sabs):
207                self.producer_fifo.append(data[i:i+sabs])
208        else:
209            self.producer_fifo.append(data)
210        self.initiate_send()
211
212    def push_with_producer(self, producer):
213        self.producer_fifo.append(producer)
214        self.initiate_send()
215
216    def readable(self):
217        "predicate for inclusion in the readable for select()"
218        # cannot use the old predicate, it violates the claim of the
219        # set_terminator method.
220
221        # return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
222        return 1
223
224    def writable(self):
225        "predicate for inclusion in the writable for select()"
226        return self.producer_fifo or (not self.connected)
227
228    def close_when_done(self):
229        "automatically close this channel once the outgoing queue is empty"
230        self.producer_fifo.append(None)
231
232    def initiate_send(self):
233        while self.producer_fifo and self.connected:
234            first = self.producer_fifo[0]
235            # handle empty string/buffer or None entry
236            if not first:
237                del self.producer_fifo[0]
238                if first is None:
239                    self.handle_close()
240                    return
241
242            # handle classic producer behavior
243            obs = self.ac_out_buffer_size
244            try:
245                data = first[:obs]
246            except TypeError:
247                data = first.more()
248                if data:
249                    self.producer_fifo.appendleft(data)
250                else:
251                    del self.producer_fifo[0]
252                continue
253
254            if isinstance(data, str) and self.use_encoding:
255                data = bytes(data, self.encoding)
256
257            # send the data
258            try:
259                num_sent = self.send(data)
260            except OSError:
261                self.handle_error()
262                return
263
264            if num_sent:
265                if num_sent < len(data) or obs < len(first):
266                    self.producer_fifo[0] = first[num_sent:]
267                else:
268                    del self.producer_fifo[0]
269            # we tried to send some actual data
270            return
271
272    def discard_buffers(self):
273        # Emergencies only!
274        self.ac_in_buffer = b''
275        del self.incoming[:]
276        self.producer_fifo.clear()
277
278
279class simple_producer:
280
281    def __init__(self, data, buffer_size=512):
282        self.data = data
283        self.buffer_size = buffer_size
284
285    def more(self):
286        if len(self.data) > self.buffer_size:
287            result = self.data[:self.buffer_size]
288            self.data = self.data[self.buffer_size:]
289            return result
290        else:
291            result = self.data
292            self.data = b''
293            return result
294
295
296# Given 'haystack', see if any prefix of 'needle' is at its end.  This
297# assumes an exact match has already been checked.  Return the number of
298# characters matched.
299# for example:
300# f_p_a_e("qwerty\r", "\r\n") => 1
301# f_p_a_e("qwertydkjf", "\r\n") => 0
302# f_p_a_e("qwerty\r\n", "\r\n") => <undefined>
303
304# this could maybe be made faster with a computed regex?
305# [answer: no; circa Python-2.0, Jan 2001]
306# new python:   28961/s
307# old python:   18307/s
308# re:        12820/s
309# regex:     14035/s
310
311def find_prefix_at_end(haystack, needle):
312    l = len(needle) - 1
313    while l and not haystack.endswith(needle[:l]):
314        l -= 1
315    return l
316