OLD | NEW |
(Empty) | |
| 1 # Protocol Buffers - Google's data interchange format |
| 2 # Copyright 2008 Google Inc. All rights reserved. |
| 3 # http://code.google.com/p/protobuf/ |
| 4 # |
| 5 # Redistribution and use in source and binary forms, with or without |
| 6 # modification, are permitted provided that the following conditions are |
| 7 # met: |
| 8 # |
| 9 # * Redistributions of source code must retain the above copyright |
| 10 # notice, this list of conditions and the following disclaimer. |
| 11 # * Redistributions in binary form must reproduce the above |
| 12 # copyright notice, this list of conditions and the following disclaimer |
| 13 # in the documentation and/or other materials provided with the |
| 14 # distribution. |
| 15 # * Neither the name of Google Inc. nor the names of its |
| 16 # contributors may be used to endorse or promote products derived from |
| 17 # this software without specific prior written permission. |
| 18 # |
| 19 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 20 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 21 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 22 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 23 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 24 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 25 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 26 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 27 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 28 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 29 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 30 |
| 31 """Defines a listener interface for observing certain |
| 32 state transitions on Message objects. |
| 33 |
| 34 Also defines a null implementation of this interface. |
| 35 """ |
| 36 |
| 37 __author__ = 'robinson@google.com (Will Robinson)' |
| 38 |
| 39 |
| 40 class MessageListener(object): |
| 41 |
| 42 """Listens for modifications made to a message. Meant to be registered via |
| 43 Message._SetListener(). |
| 44 |
| 45 Attributes: |
| 46 dirty: If True, then calling Modified() would be a no-op. This can be |
| 47 used to avoid these calls entirely in the common case. |
| 48 """ |
| 49 |
| 50 def Modified(self): |
| 51 """Called every time the message is modified in such a way that the parent |
| 52 message may need to be updated. This currently means either: |
| 53 (a) The message was modified for the first time, so the parent message |
| 54 should henceforth mark the message as present. |
| 55 (b) The message's cached byte size became dirty -- i.e. the message was |
| 56 modified for the first time after a previous call to ByteSize(). |
| 57 Therefore the parent should also mark its byte size as dirty. |
| 58 Note that (a) implies (b), since new objects start out with a client cached |
| 59 size (zero). However, we document (a) explicitly because it is important. |
| 60 |
| 61 Modified() will *only* be called in response to one of these two events -- |
| 62 not every time the sub-message is modified. |
| 63 |
| 64 Note that if the listener's |dirty| attribute is true, then calling |
| 65 Modified at the moment would be a no-op, so it can be skipped. Performance- |
| 66 sensitive callers should check this attribute directly before calling since |
| 67 it will be true most of the time. |
| 68 """ |
| 69 |
| 70 raise NotImplementedError |
| 71 |
| 72 |
| 73 class NullMessageListener(object): |
| 74 |
| 75 """No-op MessageListener implementation.""" |
| 76 |
| 77 def Modified(self): |
| 78 pass |
OLD | NEW |