Added tools to retrieve CQ builders from a CQ config

third_party/google/protobuf/internal/message_listener.py

+# 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