79 lines
3.3 KiB
Python
79 lines
3.3 KiB
Python
# Protocol Buffers - Google's data interchange format
|
|
# Copyright 2008 Google Inc. All rights reserved.
|
|
# https://developers.google.com/protocol-buffers/
|
|
#
|
|
# 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
|