diff options
Diffstat (limited to 'generator/google/protobuf/internal/message_listener.py')
-rw-r--r-- | generator/google/protobuf/internal/message_listener.py | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/generator/google/protobuf/internal/message_listener.py b/generator/google/protobuf/internal/message_listener.py new file mode 100644 index 0000000..1080234 --- /dev/null +++ b/generator/google/protobuf/internal/message_listener.py @@ -0,0 +1,78 @@ +# 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 |