src/python/grpcio/grpc/_compression.py

# Copyright 2019 The 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.

from __future__ import annotations

from typing import Optional

import grpc
from grpc._cython import cygrpc
from grpc._typing import MetadataType

NoCompression = cygrpc.CompressionAlgorithm.none
Deflate = cygrpc.CompressionAlgorithm.deflate
Gzip = cygrpc.CompressionAlgorithm.gzip

_METADATA_STRING_MAPPING = {
    NoCompression: "identity",
    Deflate: "deflate",
    Gzip: "gzip",
}


def _compression_algorithm_to_metadata_value(
    compression: grpc.Compression,
) -> str:
    return _METADATA_STRING_MAPPING[compression]


def compression_algorithm_to_metadata(compression: grpc.Compression):
    return (
        cygrpc.GRPC_COMPRESSION_REQUEST_ALGORITHM_MD_KEY,
        _compression_algorithm_to_metadata_value(compression),
    )


def create_channel_option(compression: Optional[grpc.Compression]):
    return (
        ((cygrpc.GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM, int(compression)),)
        if compression
        else ()
    )


def augment_metadata(
    metadata: Optional[MetadataType], compression: Optional[grpc.Compression]
):
    if not metadata and not compression:
        return None
    base_metadata = tuple(metadata) if metadata else ()
    compression_metadata = (
        (compression_algorithm_to_metadata(compression),) if compression else ()
    )
    return base_metadata + compression_metadata


__all__ = (
    "NoCompression",
    "Deflate",
    "Gzip",
)