Go是如何实现protobuf的编解码的(1): 原理

➜  protoc-3.9.0-osx-x86_64 tree .
.
├── bin
│   └── protoc
├── include
│   └── google
│       └── protobuf
│           ├── any.proto
│           ├── api.proto
│           ├── compiler
│           │   └── plugin.proto
│           ├── descriptor.proto
│           ├── duration.proto
│           ├── empty.proto
│           ├── field_mask.proto
│           ├── source_context.proto
│           ├── struct.proto
│           ├── timestamp.proto
│           ├── type.proto
│           └── wrappers.proto
└── readme.txt

5 directories, 14 files

go get –u github.com/golang/protobuf/protoc-gen-go

➜  fabric git:(release-1.4) which protoc
/usr/local/bin/protoc
➜  fabric git:(release-1.4) which protoc-gen-go
/Users/shitaibin/go/bin/protoc-gen-go

➜  protobuf git:(master) tree helloworld1
helloworld1
├── main.go
├── request.proto
└── types
    └── request.pb.go

// file: request.proto
syntax = "proto3";
package helloworld;
option go_package="./types";

message Request {
    string data = 1;
}

$ protoc --go_out=. ./request.proto

// file: ./types/request.pb.go
// Code generated by protoc-gen-go. DO NOT EDIT.
// source: request.proto

package types

import (
    fmt "fmt"
    math "math"

    proto "github.com/golang/protobuf/proto"
)

// Reference imports to suppress errors if they are not otherwise used.
var _ = proto.Marshal
var _ = fmt.Errorf
var _ = math.Inf

// This is a compile-time assertion to ensure that this generated file
// is compatible with the proto package it is being compiled against.
// A compilation error at this line likely means your copy of the
// proto package needs to be updated.
const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package

type Request struct {
    Data                 string   `protobuf:"bytes,1,opt,name=data,proto3" json:"data,omitempty"`
    // 以下是protobuf自动填充的字段，protobuf需要使用
    XXX_NoUnkeyedLiteral struct{} `json:"-"`
    XXX_unrecognized     []byte   `json:"-"`
    XXX_sizecache        int32    `json:"-"`
}

func (m *Request) Reset()         { *m = Request{} }
func (m *Request) String() string { return proto.CompactTextString(m) }
func (*Request) ProtoMessage()    {}
func (*Request) Descriptor() ([]byte, []int) {
    return fileDescriptor_7f73548e33e655fe, []int{0}
}

// 反序列化函数
func (m *Request) XXX_Unmarshal(b []byte) error {
    return xxx_messageInfo_Request.Unmarshal(m, b)
}
// 序列化函数
func (m *Request) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
    return xxx_messageInfo_Request.Marshal(b, m, deterministic)
}
func (m *Request) XXX_Merge(src proto.Message) {
    xxx_messageInfo_Request.Merge(m, src)
}
func (m *Request) XXX_Size() int {
    return xxx_messageInfo_Request.Size(m)
}
func (m *Request) XXX_DiscardUnknown() {
    xxx_messageInfo_Request.DiscardUnknown(m)
}

var xxx_messageInfo_Request proto.InternalMessageInfo

// 获取字段
func (m *Request) GetData() string {
    if m != nil {
        return m.Data
    }
    return ""
}

func init() {
    proto.RegisterType((*Request)(nil), "helloworld.Request")
}

func init() { proto.RegisterFile("request.proto", fileDescriptor_7f73548e33e655fe) }

var fileDescriptor_7f73548e33e655fe = []byte{
    // 91 bytes of a gzipped FileDescriptorProto
    0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0xe2, 0x2d, 0x4a, 0x2d, 0x2c,
    0x4d, 0x2d, 0x2e, 0xd1, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0xe2, 0xca, 0x48, 0xcd, 0xc9, 0xc9,
    0x2f, 0xcf, 0x2f, 0xca, 0x49, 0x51, 0x92, 0xe5, 0x62, 0x0f, 0x82, 0x48, 0x0a, 0x09, 0x71, 0xb1,
    0xa4, 0x24, 0x96, 0x24, 0x4a, 0x30, 0x2a, 0x30, 0x6a, 0x70, 0x06, 0x81, 0xd9, 0x4e, 0x9c, 0x51,
    0xec, 0x7a, 0xfa, 0x25, 0x95, 0x05, 0xa9, 0xc5, 0x49, 0x6c, 0x60, 0xcd, 0xc6, 0x80, 0x00, 0x00,
    0x00, 0xff, 0xff, 0x2e, 0x52, 0x69, 0xb5, 0x4d, 0x00, 0x00, 0x00,
}

// file: main.go
package main

import (
    "fmt"

    "./types"
    "github.com/golang/protobuf/proto"
)

func main() {
    req := &types.Request{Data: "Hello LIB"}

    // Marshal
    encoded, err := proto.Marshal(req)
    if err != nil {
        fmt.Printf("Encode to protobuf data error: %v", err)
    }

    // Unmarshal
    var unmarshaledReq types.Request
    err = proto.Unmarshal(encoded, &unmarshaledReq)
    if err != nil {
        fmt.Printf("Unmarshal to struct error: %v", err)
    }

    fmt.Printf("req: %v\n", req.String())
    fmt.Printf("unmarshaledReq: %v\n", unmarshaledReq.String())
}

➜  helloworld1 git:(master) go run main.go
req: data:"Hello LIB"
unmarshaledReq: data:"Hello LIB"