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

* * Copyright 2018 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 proto defines the protobuf codec. Importing this package will register the codec.

package proto

import (
	"math"
	"sync"

	"github.com/golang/protobuf/proto"
	"google.golang.org/grpc/encoding"
)

Name is the name registered for the proto compressor.

const Name = "proto"

func init() {
	encoding.RegisterCodec(codec{})
}

codec is a Codec implementation with protobuf. It is the default codec for gRPC.

type codec struct{}

type cachedProtoBuffer struct {
	lastMarshaledSize uint32
	proto.Buffer
}

func capToMaxInt32(val int) uint32 {
	if val > math.MaxInt32 {
		return uint32(math.MaxInt32)
	}
	return uint32(val)
}

func marshal(v interface{}, cb *cachedProtoBuffer) ([]byte, error) {
	protoMsg := v.(proto.Message)
	newSlice := make([]byte, 0, cb.lastMarshaledSize)

	cb.SetBuf(newSlice)
	cb.Reset()
	if err := cb.Marshal(protoMsg); err != nil {
		return nil, err
	}
	out := cb.Bytes()
	cb.lastMarshaledSize = capToMaxInt32(len(out))
	return out, nil
}

func (codec) Marshal(v interface{}) ([]byte, error) {

object can marshal itself, no need for buffer

		return pm.Marshal()
	}

	cb := protoBufferPool.Get().(*cachedProtoBuffer)
	out, err := marshal(v, cb)

put back buffer and lose the ref to the slice

	cb.SetBuf(nil)
	protoBufferPool.Put(cb)
	return out, err
}

func (codec) Unmarshal(data []byte, v interface{}) error {
	protoMsg := v.(proto.Message)
	protoMsg.Reset()

object can unmarshal itself, no need for buffer

		return pu.Unmarshal(data)
	}

	cb := protoBufferPool.Get().(*cachedProtoBuffer)
	cb.SetBuf(data)
	err := cb.Unmarshal(protoMsg)
	cb.SetBuf(nil)
	protoBufferPool.Put(cb)
	return err
}

func (codec) Name() string {
	return Name
}

var protoBufferPool = &sync.Pool{
	New: func() interface{} {
		return &cachedProtoBuffer{
			Buffer:            proto.Buffer{},
			lastMarshaledSize: 16,
		}
	},