Source code for grpc.aio._metadata

# Copyright 2020 gRPC authors.
# 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
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.
"""Implementation of the metadata abstraction for gRPC Asyncio Python."""
from collections import OrderedDict
from collections import abc
from typing import Any, Iterator, List, Tuple, Union

MetadataKey = str
MetadataValue = Union[str, bytes]

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