| # Protocol Buffers - Google's data interchange format |
| # Copyright 2008 Google Inc. |
| # http://code.google.com/p/protobuf/ |
| # |
| # Licensed under the Apache License, Version 2.0 (the "License"); |
| # you may not use this file except in compliance with the License. |
| # You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| # See the License for the specific language governing permissions and |
| # limitations under the License. |
| |
| """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 transitions to nonempty and for invalidations of cached |
| byte sizes. Meant to be registered via Message._SetListener(). |
| """ |
| |
| def TransitionToNonempty(self): |
| """Called the *first* time that this message becomes nonempty. |
| Implementations are free (but not required) to call this method multiple |
| times after the message has become nonempty. |
| """ |
| raise NotImplementedError |
| |
| def ByteSizeDirty(self): |
| """Called *every* time the cached byte size value |
| for this object is invalidated (transitions from being |
| "clean" to "dirty"). |
| """ |
| raise NotImplementedError |
| |
| |
| class NullMessageListener(object): |
| |
| """No-op MessageListener implementation.""" |
| |
| def TransitionToNonempty(self): |
| pass |
| |
| def ByteSizeDirty(self): |
| pass |