Source: encoding.go in package google.golang.org/grpc/encoding

* * Copyright 2017 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. *

Package encoding defines the interface for the compressor and codec, and functions to register and retrieve compressors and codecs. This package is EXPERIMENTAL.

package encoding

import (
	"io"
	"strings"
)

Identity specifies the optional encoding for uncompressed streams. It is intended for grpc internal use only.

const Identity = "identity"

Compressor is used for compressing and decompressing when sending or receiving messages.

Compress writes the data written to wc to w after compressing it. If an error occurs while initializing the compressor, that error is returned instead.

Decompress reads data from r, decompresses it, and provides the uncompressed data via the returned io.Reader. If an error occurs while initializing the decompressor, that error is returned instead.

Name is the name of the compression codec and is used to set the content coding header. The result must be static; the result cannot change between calls.

EXPERIMENTAL: if a Compressor implements DecompressedSize(compressedBytes []byte) int, gRPC will call it to determine the size of the buffer allocated for the result of decompression. Return -1 to indicate unknown size.

}

var registeredCompressor = make(map[string]Compressor)

RegisterCompressor registers the compressor with gRPC by its name. It can be activated when sending an RPC via grpc.UseCompressor(). It will be automatically accessed when receiving a message based on the content coding header. Servers also use it to send a response with the same encoding as the request. NOTE: this function must only be called during initialization time (i.e. in an init() function), and is not thread-safe. If multiple Compressors are registered with the same name, the one registered last will take effect.

func RegisterCompressor(c Compressor) {
	registeredCompressor[c.Name()] = c
}

GetCompressor returns Compressor for the given compressor name.

func GetCompressor(name string) Compressor {
	return registeredCompressor[name]
}

Codec defines the interface gRPC uses to encode and decode messages. Note that implementations of this interface must be thread safe; a Codec's methods can be called from concurrent goroutines.

Marshal returns the wire format of v.

Unmarshal parses the wire format into v.

Name returns the name of the Codec implementation. The returned string will be used as part of content type in transmission. The result must be static; the result cannot change between calls.

	Name() string
}

var registeredCodecs = make(map[string]Codec)

RegisterCodec registers the provided Codec for use with all gRPC clients and servers. The Codec will be stored and looked up by result of its Name() method, which should match the content-subtype of the encoding handled by the Codec. This is case-insensitive, and is stored and looked up as lowercase. If the result of calling Name() is an empty string, RegisterCodec will panic. See Content-Type on https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for more details. NOTE: this function must only be called during initialization time (i.e. in an init() function), and is not thread-safe. If multiple Compressors are registered with the same name, the one registered last will take effect.

func RegisterCodec(codec Codec) {
	if codec == nil {
		panic("cannot register a nil Codec")
	}
	if codec.Name() == "" {
		panic("cannot register Codec with empty string result for Name()")
	}
	contentSubtype := strings.ToLower(codec.Name())
	registeredCodecs[contentSubtype] = codec
}

GetCodec gets a registered Codec by content-subtype, or nil if no Codec is registered for the content-subtype. The content-subtype is expected to be lowercase.

func GetCodec(contentSubtype string) Codec {
	return registeredCodecs[contentSubtype]