| # 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 |
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| |
| """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 |