120 lines
4.4 KiB
Python
120 lines
4.4 KiB
Python
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# Copyright 2020 gRPC authors.
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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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# http://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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"""Implementation of the metadata abstraction for gRPC Asyncio Python."""
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from typing import List, Tuple, Iterator, Any, Union
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from collections import abc, OrderedDict
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MetadataKey = str
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MetadataValue = Union[str, bytes]
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class Metadata(abc.Mapping):
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"""Metadata abstraction for the asynchronous calls and interceptors.
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The metadata is a mapping from str -> List[str]
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Traits
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* Multiple entries are allowed for the same key
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* The order of the values by key is preserved
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* Getting by an element by key, retrieves the first mapped value
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* Supports an immutable view of the data
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* Allows partial mutation on the data without recreating the new object from scratch.
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"""
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def __init__(self, *args: Tuple[MetadataKey, MetadataValue]) -> None:
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self._metadata = OrderedDict()
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for md_key, md_value in args:
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self.add(md_key, md_value)
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@classmethod
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def from_tuple(cls, raw_metadata: tuple):
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if raw_metadata:
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return cls(*raw_metadata)
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return cls()
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def add(self, key: MetadataKey, value: MetadataValue) -> None:
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self._metadata.setdefault(key, [])
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self._metadata[key].append(value)
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def __len__(self) -> int:
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"""Return the total number of elements that there are in the metadata,
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including multiple values for the same key.
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"""
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return sum(map(len, self._metadata.values()))
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def __getitem__(self, key: MetadataKey) -> MetadataValue:
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"""When calling <metadata>[<key>], the first element of all those
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mapped for <key> is returned.
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"""
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try:
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return self._metadata[key][0]
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except (ValueError, IndexError) as e:
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raise KeyError("{0!r}".format(key)) from e
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def __setitem__(self, key: MetadataKey, value: MetadataValue) -> None:
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"""Calling metadata[<key>] = <value>
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Maps <value> to the first instance of <key>.
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"""
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if key not in self:
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self._metadata[key] = [value]
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else:
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current_values = self.get_all(key)
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self._metadata[key] = [value, *current_values[1:]]
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def __delitem__(self, key: MetadataKey) -> None:
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"""``del metadata[<key>]`` deletes the first mapping for <key>."""
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current_values = self.get_all(key)
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if not current_values:
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raise KeyError(repr(key))
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self._metadata[key] = current_values[1:]
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def delete_all(self, key: MetadataKey) -> None:
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"""Delete all mappings for <key>."""
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del self._metadata[key]
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def __iter__(self) -> Iterator[Tuple[MetadataKey, MetadataValue]]:
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for key, values in self._metadata.items():
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for value in values:
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yield (key, value)
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def get_all(self, key: MetadataKey) -> List[MetadataValue]:
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"""For compatibility with other Metadata abstraction objects (like in Java),
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this would return all items under the desired <key>.
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"""
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return self._metadata.get(key, [])
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def set_all(self, key: MetadataKey, values: List[MetadataValue]) -> None:
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self._metadata[key] = values
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def __contains__(self, key: MetadataKey) -> bool:
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return key in self._metadata
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def __eq__(self, other: Any) -> bool:
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if isinstance(other, self.__class__):
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return self._metadata == other._metadata
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if isinstance(other, tuple):
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return tuple(self) == other
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return NotImplemented # pytype: disable=bad-return-type
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def __add__(self, other: Any) -> 'Metadata':
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if isinstance(other, self.__class__):
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return Metadata(*(tuple(self) + tuple(other)))
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if isinstance(other, tuple):
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return Metadata(*(tuple(self) + other))
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return NotImplemented # pytype: disable=bad-return-type
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def __repr__(self) -> str:
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view = tuple(self)
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return "{0}({1!r})".format(self.__class__.__name__, view)
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