#!/usr/bin/env python # # Copyright 2007 Google Inc. # # 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. # """Contains an abstract base class for protocol messages.""" class Error(Exception): pass class DecodeError(Error): pass class EncodeError(Error): pass class Message(object): """Abstract base class for protocol messages. Protocol message classes are almost always generated by the protocol compiler. These generated types subclass Message and implement the methods shown below. TODO: Link to an HTML document here. TODO: Document that instances of this class will also have an Extensions attribute with __getitem__ and __setitem__. Again, not sure how to best convey this. TODO: Document that the class must also have a static RegisterExtension(extension_field) method. Not sure how to best express at this point. """ __slots__ = [] DESCRIPTOR = None def __deepcopy__(self, memo=None): clone = type(self)() clone.MergeFrom(self) return clone def __eq__(self, other_msg): """Recursively compares two messages by value and structure.""" raise NotImplementedError def __ne__(self, other_msg): return not self == other_msg def __hash__(self): raise TypeError('unhashable object') def __str__(self): """Outputs a human-readable representation of the message.""" raise NotImplementedError def __unicode__(self): """Outputs a human-readable representation of the message.""" raise NotImplementedError def MergeFrom(self, other_msg): """Merges the contents of the specified message into current message. This method merges the contents of the specified message into the current message. Singular fields that are set in the specified message overwrite the corresponding fields in the current message. Repeated fields are appended. Singular sub-messages and groups are recursively merged. Args: other_msg: Message to merge into the current message. """ raise NotImplementedError def CopyFrom(self, other_msg): """Copies the content of the specified message into the current message. The method clears the current message and then merges the specified message using MergeFrom. Args: other_msg: Message to copy into the current one. """ if self is other_msg: return self.Clear() self.MergeFrom(other_msg) def Clear(self): """Clears all data that was set in the message.""" raise NotImplementedError def SetInParent(self): """Mark this as present in the parent. This normally happens automatically when you assign a field of a sub-message, but sometimes you want to make the sub-message present while keeping it empty. If you find yourself using this, you may want to reconsider your design.""" raise NotImplementedError def IsInitialized(self): """Checks if the message is initialized. Returns: The method returns True if the message is initialized (i.e. all of its required fields are set). """ raise NotImplementedError def MergeFromString(self, serialized): """Merges serialized protocol buffer data into this message. When we find a field in |serialized| that is already present in this message: - If it's a "repeated" field, we append to the end of our list. - Else, if it's a scalar, we overwrite our field. - Else, (it's a nonrepeated composite), we recursively merge into the existing composite. TODO: Document handling of unknown fields. Args: serialized: Any object that allows us to call buffer(serialized) to access a string of bytes using the buffer interface. TODO: When we switch to a helper, this will return None. Returns: The number of bytes read from |serialized|. For non-group messages, this will always be len(serialized), but for messages which are actually groups, this will generally be less than len(serialized), since we must stop when we reach an END_GROUP tag. Note that if we *do* stop because of an END_GROUP tag, the number of bytes returned does not include the bytes for the END_GROUP tag information. """ raise NotImplementedError def ParseFromString(self, serialized): """Parse serialized protocol buffer data into this message. Like MergeFromString(), except we clear the object first and do not return the value that MergeFromString returns. """ self.Clear() self.MergeFromString(serialized) def SerializeToString(self): """Serializes the protocol message to a binary string. Returns: A binary string representation of the message if all of the required fields in the message are set (i.e. the message is initialized). Raises: message.EncodeError if the message isn't initialized. """ raise NotImplementedError def SerializePartialToString(self): """Serializes the protocol message to a binary string. This method is similar to SerializeToString but doesn't check if the message is initialized. Returns: A string representation of the partial message. """ raise NotImplementedError def ListFields(self): """Returns a list of (FieldDescriptor, value) tuples for all fields in the message which are not empty. A singular field is non-empty if HasField() would return true, and a repeated field is non-empty if it contains at least one element. The fields are ordered by field number""" raise NotImplementedError def HasField(self, field_name): """Checks if a certain field is set for the message, or if any field inside a oneof group is set. Note that if the field_name is not defined in the message descriptor, ValueError will be raised.""" raise NotImplementedError def ClearField(self, field_name): """Clears the contents of a given field, or the field set inside a oneof group. If the name neither refers to a defined field or oneof group, ValueError is raised.""" raise NotImplementedError def WhichOneof(self, oneof_group): """Returns the name of the field that is set inside a oneof group, or None if no field is set. If no group with the given name exists, ValueError will be raised.""" raise NotImplementedError def HasExtension(self, extension_handle): raise NotImplementedError def ClearExtension(self, extension_handle): raise NotImplementedError def ByteSize(self): """Returns the serialized size of this message. Recursively calls ByteSize() on all contained messages. """ raise NotImplementedError def _SetListener(self, message_listener): """Internal method used by the protocol message implementation. Clients should not call this directly. Sets a listener that this message will call on certain state transitions. The purpose of this method is to register back-edges from children to parents at runtime, for the purpose of setting "has" bits and byte-size-dirty bits in the parent and ancestor objects whenever a child or descendant object is modified. If the client wants to disconnect this Message from the object tree, she explicitly sets callback to None. If message_listener is None, unregisters any existing listener. Otherwise, message_listener must implement the MessageListener interface in internal/message_listener.py, and we discard any listener registered via a previous _SetListener() call. """ raise NotImplementedError def __getstate__(self): """Support the pickle protocol.""" return dict(serialized=self.SerializePartialToString()) def __setstate__(self, state): """Support the pickle protocol.""" self.__init__() self.ParseFromString(state['serialized'])