83 lines
2.9 KiB
Python
83 lines
2.9 KiB
Python
# Copyright 2018 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import collections
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from proto.utils import cached_property
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from google.protobuf.message import Message
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class MapComposite(collections.abc.MutableMapping):
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"""A view around a mutable sequence in protocol buffers.
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This implements the full Python MutableMapping interface, but all methods
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modify the underlying field container directly.
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"""
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@cached_property
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def _pb_type(self):
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"""Return the protocol buffer type for this sequence."""
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# Huzzah, another hack. Still less bad than RepeatedComposite.
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return type(self.pb.GetEntryClass()().value)
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def __init__(self, sequence, *, marshal):
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"""Initialize a wrapper around a protobuf map.
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Args:
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sequence: A protocol buffers map.
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marshal (~.MarshalRegistry): An instantiated marshal, used to
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convert values going to and from this map.
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"""
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self._pb = sequence
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self._marshal = marshal
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def __contains__(self, key):
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# Protocol buffers is so permissive that querying for the existence
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# of a key will in of itself create it.
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#
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# By taking a tuple of the keys and querying that, we avoid sending
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# the lookup to protocol buffers and therefore avoid creating the key.
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return key in tuple(self.keys())
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def __getitem__(self, key):
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# We handle raising KeyError ourselves, because otherwise protocol
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# buffers will create the key if it does not exist.
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if key not in self:
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raise KeyError(key)
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return self._marshal.to_python(self._pb_type, self.pb[key])
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def __setitem__(self, key, value):
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pb_value = self._marshal.to_proto(self._pb_type, value, strict=True)
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# Directly setting a key is not allowed; however, protocol buffers
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# is so permissive that querying for the existence of a key will in
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# of itself create it.
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#
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# Therefore, we create a key that way (clearing any fields that may
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# be set) and then merge in our values.
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self.pb[key].Clear()
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self.pb[key].MergeFrom(pb_value)
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def __delitem__(self, key):
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self.pb.pop(key)
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def __len__(self):
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return len(self.pb)
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def __iter__(self):
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return iter(self.pb)
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@property
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def pb(self):
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return self._pb
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