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# Copyright 2018 Google LLC
#
# 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
#
# https://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.
import collections
from proto.utils import cached_property
from google.protobuf.message import Message
class MapComposite(collections.abc.MutableMapping):
"""A view around a mutable sequence in protocol buffers.
This implements the full Python MutableMapping interface, but all methods
modify the underlying field container directly.
"""
@cached_property
def _pb_type(self):
"""Return the protocol buffer type for this sequence."""
# Huzzah, another hack. Still less bad than RepeatedComposite.
return type(self.pb.GetEntryClass()().value)
def __init__(self, sequence, *, marshal):
"""Initialize a wrapper around a protobuf map.
Args:
sequence: A protocol buffers map.
marshal (~.MarshalRegistry): An instantiated marshal, used to
convert values going to and from this map.
"""
self._pb = sequence
self._marshal = marshal
def __contains__(self, key):
# Protocol buffers is so permissive that querying for the existence
# of a key will in of itself create it.
#
# By taking a tuple of the keys and querying that, we avoid sending
# the lookup to protocol buffers and therefore avoid creating the key.
return key in tuple(self.keys())
def __getitem__(self, key):
# We handle raising KeyError ourselves, because otherwise protocol
# buffers will create the key if it does not exist.
if key not in self:
raise KeyError(key)
return self._marshal.to_python(self._pb_type, self.pb[key])
def __setitem__(self, key, value):
pb_value = self._marshal.to_proto(self._pb_type, value, strict=True)
# Directly setting a key is not allowed; however, protocol buffers
# is so permissive that querying for the existence of a key will in
# of itself create it.
#
# Therefore, we create a key that way (clearing any fields that may
# be set) and then merge in our values.
self.pb[key].Clear()
self.pb[key].MergeFrom(pb_value)
def __delitem__(self, key):
self.pb.pop(key)
def __len__(self):
return len(self.pb)
def __iter__(self):
return iter(self.pb)
@property
def pb(self):
return self._pb
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