Go 支持Protocol Buffers的配置

安裝

protoc （The protocol compiler）是由C++寫的，支持的 C++、Java、Python、Objective-C、C#、JavaNano、JavaScript、Ruby、PHP 的實現都在 https://github.com/google/protobuf 這個項目中， 例外的是 Go 的實現是在 https://github.com/golang/protobuf 這里。

所以Go 支持 Protocol Buffers的安裝需要下面三步：

• Install the standard C++ implementation of protocol buffers from https://developers.google.com/protocol-buffers/ 。如果不想源碼編譯的話，可以直接下載對應操作系統對應的 protoc https://github.com/google/protobuf/releases， 參考 ： https://github.com/google/protobuf/releases?
• Of course, install the Go compiler and tools from https://golang.org/ See https://golang.org/doc/install for details or, if you are using gccgo, follow the instructions at https://golang.org/doc/install/gccgo?? 安裝Go的開發編譯環境。
• Grab the code from the repository and install the proto package. The simplest way is to run go get -u github.com/golang/protobuf/{proto,protoc-gen-go}. The compiler plugin, protoc-gen-go, will be installed in $GOBIN, defaulting to $GOPATH/bin. It must be in your $PATH for the protocol compiler, protoc, to find it.通過go get -u github.com/golang/protobuf/{proto,protoc-gen-go}? 獲得go的插件包，并完成 protoc-gen-go 的編譯。protoc-gen-go 默認會編譯到 $GOPATH/bin 目錄下， 這個目錄需要放入$PATH 中，方便 protoc 找到 protoc-gen-go 。

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https://github.com/golang/protobuf 這里其實包含兩部分功能：

• a 'protocol compiler plugin' that generates Go source files that, once compiled, can access and manage protocol buffers;? Protoc編譯插件，產生Go的源碼。
• a library that implements run-time support for encoding (marshaling), decoding (unmarshaling), and accessing protocol buffers. 運行時支持庫，包括編碼、解碼、訪問PB內容的功能庫。

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使用 protoc

把 proto 文件編譯成 go 源碼的命令如下：

$ protoc --go_out=./go/ ./proto/helloworld.proto

參考： http://www.cnblogs.com/ghj1976/p/5435565.html?

如果我們需要生產 gRPC 使用的代碼， 則需要是下面的命令：

$ protoc --go_out=plugins=grpc:./go/ ./proto/helloworld.proto

注意這類表明了 plugins=grpc，

按照這種方式生成的代碼，會多 客戶端和服務器端的通用代碼，方便我們建立客戶端和服務器端的服務。

下面是使用helloworld.proto 產生的 grpc 使用的源碼， 比不帶 grpc的要多一部分代碼。

// Code generated by protoc-gen-go.
// source: proto/helloworld.proto
// DO NOT EDIT!

/*
Package helloworld is a generated protocol buffer package.

It is generated from these files:
??? proto/helloworld.proto

It has these top-level messages:
??? HelloRequest
??? HelloReply
*/
package helloworld

import proto "github.com/golang/protobuf/proto"
import fmt "fmt"
import math "math"

import (
??? context "golang.org/x/net/context"
??? grpc "google.golang.org/grpc"
)

// 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.
const _ = proto.ProtoPackageIsVersion1

// The request message containing the user's name.
type HelloRequest struct {
??? Name string `protobuf:"bytes,1,opt,name=name" json:"name,omitempty"`
}

func (m *HelloRequest) Reset()??????????????????? { *m = HelloRequest{} }
func (m *HelloRequest) String() string??????????? { return proto.CompactTextString(m) }
func (*HelloRequest) ProtoMessage()?????????????? {}
func (*HelloRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }

// The response message containing the greetings
type HelloReply struct {
??? Message string `protobuf:"bytes,1,opt,name=message" json:"message,omitempty"`
}

func (m *HelloReply) Reset()??????????????????? { *m = HelloReply{} }
func (m *HelloReply) String() string??????????? { return proto.CompactTextString(m) }
func (*HelloReply) ProtoMessage()?????????????? {}
func (*HelloReply) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }

func init() {
??? proto.RegisterType((*HelloRequest)(nil), "helloworld.HelloRequest")
??? proto.RegisterType((*HelloReply)(nil), "helloworld.HelloReply")
}

// Reference imports to suppress errors if they are not otherwise used.
var _ context.Context
var _ grpc.ClientConn

// This is a compile-time assertion to ensure that this generated file
// is compatible with the grpc package it is being compiled against.
const _ = grpc.SupportPackageIsVersion2

// Client API for Greeter service

type GreeterClient interface {
??? // Sends a greeting
??? SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error)
}

type greeterClient struct {
??? cc *grpc.ClientConn
}

func NewGreeterClient(cc *grpc.ClientConn) GreeterClient {
??? return &greeterClient{cc}
}

func (c *greeterClient) SayHello(ctx context.Context, in *HelloRequest, opts ...grpc.CallOption) (*HelloReply, error) {
??? out := new(HelloReply)
??? err := grpc.Invoke(ctx, "/helloworld.Greeter/SayHello", in, out, c.cc, opts...)
??? if err != nil {
??????? return nil, err
??? }
??? return out, nil
}

// Server API for Greeter service

type GreeterServer interface {
??? // Sends a greeting
??? SayHello(context.Context, *HelloRequest) (*HelloReply, error)
}

func RegisterGreeterServer(s *grpc.Server, srv GreeterServer) {
??? s.RegisterService(&_Greeter_serviceDesc, srv)
}

func _Greeter_SayHello_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
??? in := new(HelloRequest)
??? if err := dec(in); err != nil {
??????? return nil, err
??? }
??? if interceptor == nil {
??????? return srv.(GreeterServer).SayHello(ctx, in)
??? }
??? info := &grpc.UnaryServerInfo{
??????? Server:???? srv,
??????? FullMethod: "/helloworld.Greeter/SayHello",
??? }
??? handler := func(ctx context.Context, req interface{}) (interface{}, error) {
??????? return srv.(GreeterServer).SayHello(ctx, req.(*HelloRequest))
??? }
??? return interceptor(ctx, in, info, handler)
}

var _Greeter_serviceDesc = grpc.ServiceDesc{
??? ServiceName: "helloworld.Greeter",
??? HandlerType: (*GreeterServer)(nil),
??? Methods: []grpc.MethodDesc{
??????? {
??????????? MethodName: "SayHello",
??????????? Handler:??? _Greeter_SayHello_Handler,
??????? },
??? },
??? Streams: []grpc.StreamDesc{},
}

var fileDescriptor0 = []byte{
??? // 183 bytes of a gzipped FileDescriptorProto
??? 0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0xe2, 0x12, 0x2b, 0x28, 0xca, 0x2f,
??? 0xc9, 0xd7, 0xcf, 0x48, 0xcd, 0xc9, 0xc9, 0x2f, 0xcf, 0x2f, 0xca, 0x49, 0xd1, 0x03, 0x0b, 0x08,
??? 0x71, 0x21, 0x44, 0x94, 0x94, 0xb8, 0x78, 0x3c, 0x40, 0xbc, 0xa0, 0xd4, 0xc2, 0xd2, 0xd4, 0xe2,
??? 0x12, 0x21, 0x21, 0x2e, 0x96, 0xbc, 0xc4, 0xdc, 0x54, 0x09, 0x46, 0x05, 0x46, 0x0d, 0xce, 0x20,
??? 0x30, 0x5b, 0x49, 0x8d, 0x8b, 0x0b, 0xaa, 0xa6, 0x20, 0xa7, 0x52, 0x48, 0x82, 0x8b, 0x3d, 0x37,
??? 0xb5, 0xb8, 0x38, 0x31, 0x1d, 0xa6, 0x08, 0xc6, 0x35, 0xf2, 0xe4, 0x62, 0x77, 0x2f, 0x4a, 0x4d,
??? 0x2d, 0x49, 0x2d, 0x12, 0xb2, 0xe3, 0xe2, 0x08, 0x4e, 0xac, 0x04, 0xeb, 0x12, 0x92, 0xd0, 0x43,
??? 0x72, 0x01, 0xb2, 0x65, 0x52, 0x62, 0x58, 0x64, 0x80, 0x56, 0x28, 0x31, 0x38, 0x99, 0x71, 0x49,
??? 0x67, 0xe6, 0xeb, 0xa5, 0x17, 0x15, 0x24, 0xeb, 0xa5, 0x56, 0x24, 0xe6, 0x16, 0xe4, 0xa4, 0x16,
??? 0x23, 0xa9, 0x75, 0xe2, 0x07, 0x2b, 0x0e, 0x07, 0xb1, 0x03, 0x40, 0x5e, 0x0a, 0x60, 0x5c, 0xc4,
??? 0xc4, 0xec, 0xe1, 0x13, 0x9e, 0xc4, 0x06, 0xf6, 0xa1, 0x31, 0x20, 0x00, 0x00, 0xff, 0xff, 0x3e,
??? 0x3f, 0x8e, 0x69, 0xfb, 0x00, 0x00, 0x00,
}

protoc-gen-go 的一些特有的參數如下：

命令格式：

protoc --go_out=plugins=grpc,import_path=mypackage:. *.proto

• import_prefix=xxx - a prefix that is added onto the beginning of all imports. Useful for things like generating protos in a subdirectory, or regenerating vendored protobufs in-place.??? import 的前綴，當產生protos在一個子目錄時有用。
• import_path=foo/bar - used as the package if no input files declare go_package. If it contains slashes, everything up to the rightmost slash is ignored.沒有定義 go_package 時的包名。?
• plugins=plugin1+plugin2 - specifies the list of sub-plugins to load. The only plugin in this repo is grpc.? 插件名，這里只有一個插件 grpc
• Mfoo/bar.proto=quux/shme - declares that foo/bar.proto is associated with Go package quux/shme. This is subject to the import_prefix parameter. 定義proto文件跟包的映射關系。

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參考資料：

https://github.com/golang/protobuf

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