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
|
# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc. All rights reserved.
# http://code.google.com/p/protobuf/
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""Defines a listener interface for observing certain
state transitions on Message objects.
Also defines a null implementation of this interface.
"""
__author__ = 'robinson@google.com (Will Robinson)'
class MessageListener(object):
"""Listens for modifications made to a message. Meant to be registered via
Message._SetListener().
Attributes:
dirty: If True, then calling Modified() would be a no-op. This can be
used to avoid these calls entirely in the common case.
"""
def Modified(self):
"""Called every time the message is modified in such a way that the parent
message may need to be updated. This currently means either:
(a) The message was modified for the first time, so the parent message
should henceforth mark the message as present.
(b) The message's cached byte size became dirty -- i.e. the message was
modified for the first time after a previous call to ByteSize().
Therefore the parent should also mark its byte size as dirty.
Note that (a) implies (b), since new objects start out with a client cached
size (zero). However, we document (a) explicitly because it is important.
Modified() will *only* be called in response to one of these two events --
not every time the sub-message is modified.
Note that if the listener's |dirty| attribute is true, then calling
Modified at the moment would be a no-op, so it can be skipped. Performance-
sensitive callers should check this attribute directly before calling since
it will be true most of the time.
"""
raise NotImplementedError
class NullMessageListener(object):
"""No-op MessageListener implementation."""
def Modified(self):
pass
|
