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| # 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 | |
| # | |
| # 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. | |
| """Implementation of the metadata abstraction for gRPC Asyncio Python.""" | |
| from collections import OrderedDict | |
| from collections import abc | |
| from typing import Any, Iterator, List, Optional, Tuple, Union | |
| MetadataKey = str | |
| MetadataValue = Union[str, bytes] | |
| class Metadata(abc.Collection): | |
| """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) | |
| 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) | |
| 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())) | |
| 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 | |
| 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:]] | |
| 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:] | |
| 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) | |
| def keys(self) -> abc.KeysView: | |
| return abc.KeysView(self) | |
| def values(self) -> abc.ValuesView: | |
| return abc.ValuesView(self) | |
| def items(self) -> abc.ItemsView: | |
| return abc.ItemsView(self) | |
| def get( | |
| self, key: MetadataKey, default: MetadataValue = None | |
| ) -> Optional[MetadataValue]: | |
| try: | |
| return self[key] | |
| except KeyError: | |
| return default | |
| 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) | |