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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) | |