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

* * Copyright 2019 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 grpc

import (
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

PreparedMsg is responsible for creating a Marshalled and Compressed object. This API is EXPERIMENTAL.

Struct for preparing msg before sending them

	encodedData []byte
	hdr         []byte
	payload     []byte
}

Encode marshalls and compresses the message using the codec and compressor for the stream.

func (p *PreparedMsg) Encode(s Stream, msg interface{}) error {
	ctx := s.Context()
	rpcInfo, ok := rpcInfoFromContext(ctx)
	if !ok {
		return status.Errorf(codes.Internal, "grpc: unable to get rpcInfo")
	}

check if the context has the relevant information to prepareMsg

	if rpcInfo.preloaderInfo == nil {
		return status.Errorf(codes.Internal, "grpc: rpcInfo.preloaderInfo is nil")
	}
	if rpcInfo.preloaderInfo.codec == nil {
		return status.Errorf(codes.Internal, "grpc: rpcInfo.preloaderInfo.codec is nil")
	}

prepare the msg

	data, err := encode(rpcInfo.preloaderInfo.codec, msg)
	if err != nil {
		return err
	}
	p.encodedData = data
	compData, err := compress(data, rpcInfo.preloaderInfo.cp, rpcInfo.preloaderInfo.comp)
	if err != nil {
		return err
	}
	p.hdr, p.payload = msgHeader(data, compData)
	return nil