protoc-gen-go/grpc/grpc.go - third_party/github.com/golang/protobuf - Git at Google

 // Go support for Protocol Buffers - Google's data interchange format
 //
 // Copyright 2015 The Go Authors.  All rights reserved.
 // https://github.com/golang/protobuf
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
 // in the documentation and/or other materials provided with the
 // distribution.
 //     * Neither the name of Google Inc. nor the names of its
 // contributors may be used to endorse or promote products derived from
 // this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // Package grpc outputs gRPC service descriptions in Go code.
 // It runs as a plugin for the Go protocol buffer compiler plugin.
 // It is linked in to protoc-gen-go.
 package grpc

 import (
 	"fmt"
 	"strconv"
 	"strings"

 	pb "github.com/golang/protobuf/protoc-gen-go/descriptor"
 	"github.com/golang/protobuf/protoc-gen-go/generator"
 )

 // generatedCodeVersion indicates a version of the generated code.
 // It is incremented whenever an incompatibility between the generated code and
 // the grpc package is introduced; the generated code references
 // a constant, grpc.SupportPackageIsVersionN (where N is generatedCodeVersion).
 const generatedCodeVersion = 4

 // Paths for packages used by code generated in this file,
 // relative to the import_prefix of the generator.Generator.
 const (
 	contextPkgPath = "context"
 	grpcPkgPath    = "google.golang.org/grpc"
 	codePkgPath    = "google.golang.org/grpc/codes"
 	statusPkgPath  = "google.golang.org/grpc/status"
 )

 func init() {
 	generator.RegisterPlugin(new(grpc))
 }

 // grpc is an implementation of the Go protocol buffer compiler's
 // plugin architecture.  It generates bindings for gRPC support.
 type grpc struct {
 	gen *generator.Generator
 }

 // Name returns the name of this plugin, "grpc".
 func (g *grpc) Name() string {
 	return "grpc"
 }

 // The names for packages imported in the generated code.
 // They may vary from the final path component of the import path
 // if the name is used by other packages.
 var (
 	contextPkg string
 	grpcPkg    string
 )

 // Init initializes the plugin.
 func (g *grpc) Init(gen *generator.Generator) {
 	g.gen = gen
 }

 // Given a type name defined in a .proto, return its object.
 // Also record that we're using it, to guarantee the associated import.
 func (g *grpc) objectNamed(name string) generator.Object {
 	g.gen.RecordTypeUse(name)
 	return g.gen.ObjectNamed(name)
 }

 // Given a type name defined in a .proto, return its name as we will print it.
 func (g *grpc) typeName(str string) string {
 	return g.gen.TypeName(g.objectNamed(str))
 }

 // P forwards to g.gen.P.
 func (g *grpc) P(args ...interface{}) { g.gen.P(args...) }

 // Generate generates code for the services in the given file.
 func (g *grpc) Generate(file *generator.FileDescriptor) {
 	if len(file.FileDescriptorProto.Service) == 0 {
 		return
 	}

 	contextPkg = string(g.gen.AddImport(contextPkgPath))
 	grpcPkg = string(g.gen.AddImport(grpcPkgPath))

 	g.P("// Reference imports to suppress errors if they are not otherwise used.")
 	g.P("var _ ", contextPkg, ".Context")
 	g.P("var _ ", grpcPkg, ".ClientConn")
 	g.P()

 	// Assert version compatibility.
 	g.P("// This is a compile-time assertion to ensure that this generated file")
 	g.P("// is compatible with the grpc package it is being compiled against.")
 	g.P("const _ = ", grpcPkg, ".SupportPackageIsVersion", generatedCodeVersion)
 	g.P()

 	for i, service := range file.FileDescriptorProto.Service {
 		g.generateService(file, service, i)
 	}
 }

 // GenerateImports generates the import declaration for this file.
 func (g *grpc) GenerateImports(file *generator.FileDescriptor) {
 }

 // reservedClientName records whether a client name is reserved on the client side.
 var reservedClientName = map[string]bool{
 	// TODO: do we need any in gRPC?
 }

 func unexport(s string) string { return strings.ToLower(s[:1]) + s[1:] }

 // deprecationComment is the standard comment added to deprecated
 // messages, fields, enums, and enum values.
 var deprecationComment = "// Deprecated: Do not use."

 // generateService generates all the code for the named service.
 func (g *grpc) generateService(file *generator.FileDescriptor, service *pb.ServiceDescriptorProto, index int) {
 	path := fmt.Sprintf("6,%d", index) // 6 means service.

 	origServName := service.GetName()
 	fullServName := origServName
 	if pkg := file.GetPackage(); pkg != "" {
 		fullServName = pkg + "." + fullServName
 	}
 	servName := generator.CamelCase(origServName)
 	deprecated := service.GetOptions().GetDeprecated()

 	g.P()
 	g.P(fmt.Sprintf(`// %sClient is the client API for %s service.
 //
 // For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.`, servName, servName))

 	// Client interface.
 	if deprecated {
 		g.P("//")
 		g.P(deprecationComment)
 	}
 	g.P("type ", servName, "Client interface {")
 	for i, method := range service.Method {
 		g.gen.PrintComments(fmt.Sprintf("%s,2,%d", path, i)) // 2 means method in a service.
 		if method.GetOptions().GetDeprecated() {
 			g.P("//")
 			g.P(deprecationComment)
 		}
 		g.P(g.generateClientSignature(servName, method))
 	}
 	g.P("}")
 	g.P()

 	// Client structure.
 	g.P("type ", unexport(servName), "Client struct {")
 	g.P("cc *", grpcPkg, ".ClientConn")
 	g.P("}")
 	g.P()

 	// NewClient factory.
 	if deprecated {
 		g.P(deprecationComment)
 	}
 	g.P("func New", servName, "Client (cc *", grpcPkg, ".ClientConn) ", servName, "Client {")
 	g.P("return &", unexport(servName), "Client{cc}")
 	g.P("}")
 	g.P()

 	var methodIndex, streamIndex int
 	serviceDescVar := "_" + servName + "_serviceDesc"
 	// Client method implementations.
 	for _, method := range service.Method {
 		var descExpr string
 		if !method.GetServerStreaming() && !method.GetClientStreaming() {
 			// Unary RPC method
 			descExpr = fmt.Sprintf("&%s.Methods[%d]", serviceDescVar, methodIndex)
 			methodIndex++
 		} else {
 			// Streaming RPC method
 			descExpr = fmt.Sprintf("&%s.Streams[%d]", serviceDescVar, streamIndex)
 			streamIndex++
 		}
 		g.generateClientMethod(servName, fullServName, serviceDescVar, method, descExpr)
 	}

 	// Server interface.
 	serverType := servName + "Server"
 	g.P("// ", serverType, " is the server API for ", servName, " service.")
 	if deprecated {
 		g.P("//")
 		g.P(deprecationComment)
 	}
 	g.P("type ", serverType, " interface {")
 	for i, method := range service.Method {
 		g.gen.PrintComments(fmt.Sprintf("%s,2,%d", path, i)) // 2 means method in a service.
 		if method.GetOptions().GetDeprecated() {
 			g.P("//")
 			g.P(deprecationComment)
 		}
 		g.P(g.generateServerSignature(servName, method))
 	}
 	g.P("}")
 	g.P()

 	// Server Unimplemented struct for forward compatibility.
 	if deprecated {
 		g.P(deprecationComment)
 	}
 	g.generateUnimplementedServer(servName, service)

 	// Server registration.
 	if deprecated {
 		g.P(deprecationComment)
 	}
 	g.P("func Register", servName, "Server(s *", grpcPkg, ".Server, srv ", serverType, ") {")
 	g.P("s.RegisterService(&", serviceDescVar, `, srv)`)
 	g.P("}")
 	g.P()

 	// Server handler implementations.
 	var handlerNames []string
 	for _, method := range service.Method {
 		hname := g.generateServerMethod(servName, fullServName, method)
 		handlerNames = append(handlerNames, hname)
 	}

 	// Service descriptor.
 	g.P("var ", serviceDescVar, " = ", grpcPkg, ".ServiceDesc {")
 	g.P("ServiceName: ", strconv.Quote(fullServName), ",")
 	g.P("HandlerType: (*", serverType, ")(nil),")
 	g.P("Methods: []", grpcPkg, ".MethodDesc{")
 	for i, method := range service.Method {
 		if method.GetServerStreaming() || method.GetClientStreaming() {
 			continue
 		}
 		g.P("{")
 		g.P("MethodName: ", strconv.Quote(method.GetName()), ",")
 		g.P("Handler: ", handlerNames[i], ",")
 		g.P("},")
 	}
 	g.P("},")
 	g.P("Streams: []", grpcPkg, ".StreamDesc{")
 	for i, method := range service.Method {
 		if !method.GetServerStreaming() && !method.GetClientStreaming() {
 			continue
 		}
 		g.P("{")
 		g.P("StreamName: ", strconv.Quote(method.GetName()), ",")
 		g.P("Handler: ", handlerNames[i], ",")
 		if method.GetServerStreaming() {
 			g.P("ServerStreams: true,")
 		}
 		if method.GetClientStreaming() {
 			g.P("ClientStreams: true,")
 		}
 		g.P("},")
 	}
 	g.P("},")
 	g.P("Metadata: \"", file.GetName(), "\",")
 	g.P("}")
 	g.P()
 }

 // generateUnimplementedServer creates the unimplemented server struct
 func (g *grpc) generateUnimplementedServer(servName string, service *pb.ServiceDescriptorProto) {
 	serverType := servName + "Server"
 	g.P("// Unimplemented", serverType, " can be embedded to have forward compatible implementations.")
 	g.P("type Unimplemented", serverType, " struct {")
 	g.P("}")
 	g.P()
 	// Unimplemented<service_name>Server's concrete methods
 	for _, method := range service.Method {
 		g.generateServerMethodConcrete(servName, method)
 	}
 	g.P()
 }

 // generateServerMethodConcrete returns unimplemented methods which ensure forward compatibility
 func (g *grpc) generateServerMethodConcrete(servName string, method *pb.MethodDescriptorProto) {
 	header := g.generateServerSignatureWithParamNames(servName, method)
 	g.P("func (*Unimplemented", servName, "Server) ", header, " {")
 	var nilArg string
 	if !method.GetServerStreaming() && !method.GetClientStreaming() {
 		nilArg = "nil, "
 	}
 	methName := generator.CamelCase(method.GetName())
 	statusPkg := string(g.gen.AddImport(statusPkgPath))
 	codePkg := string(g.gen.AddImport(codePkgPath))
 	g.P("return ", nilArg, statusPkg, `.Errorf(`, codePkg, `.Unimplemented, "method `, methName, ` not implemented")`)
 	g.P("}")
 }

 // generateClientSignature returns the client-side signature for a method.
 func (g *grpc) generateClientSignature(servName string, method *pb.MethodDescriptorProto) string {
 	origMethName := method.GetName()
 	methName := generator.CamelCase(origMethName)
 	if reservedClientName[methName] {
 		methName += "_"
 	}
 	reqArg := ", in *" + g.typeName(method.GetInputType())
 	if method.GetClientStreaming() {
 		reqArg = ""
 	}
 	respName := "*" + g.typeName(method.GetOutputType())
 	if method.GetServerStreaming() || method.GetClientStreaming() {
 		respName = servName + "_" + generator.CamelCase(origMethName) + "Client"
 	}
 	return fmt.Sprintf("%s(ctx %s.Context%s, opts ...%s.CallOption) (%s, error)", methName, contextPkg, reqArg, grpcPkg, respName)
 }

 func (g *grpc) generateClientMethod(servName, fullServName, serviceDescVar string, method *pb.MethodDescriptorProto, descExpr string) {
 	sname := fmt.Sprintf("/%s/%s", fullServName, method.GetName())
 	methName := generator.CamelCase(method.GetName())
 	inType := g.typeName(method.GetInputType())
 	outType := g.typeName(method.GetOutputType())

 	if method.GetOptions().GetDeprecated() {
 		g.P(deprecationComment)
 	}
 	g.P("func (c *", unexport(servName), "Client) ", g.generateClientSignature(servName, method), "{")
 	if !method.GetServerStreaming() && !method.GetClientStreaming() {
 		g.P("out := new(", outType, ")")
 		// TODO: Pass descExpr to Invoke.
 		g.P(`err := c.cc.Invoke(ctx, "`, sname, `", in, out, opts...)`)
 		g.P("if err != nil { return nil, err }")
 		g.P("return out, nil")
 		g.P("}")
 		g.P()
 		return
 	}
 	streamType := unexport(servName) + methName + "Client"
 	g.P("stream, err := c.cc.NewStream(ctx, ", descExpr, `, "`, sname, `", opts...)`)
 	g.P("if err != nil { return nil, err }")
 	g.P("x := &", streamType, "{stream}")
 	if !method.GetClientStreaming() {
 		g.P("if err := x.ClientStream.SendMsg(in); err != nil { return nil, err }")
 		g.P("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }")
 	}
 	g.P("return x, nil")
 	g.P("}")
 	g.P()

 	genSend := method.GetClientStreaming()
 	genRecv := method.GetServerStreaming()
 	genCloseAndRecv := !method.GetServerStreaming()

 	// Stream auxiliary types and methods.
 	g.P("type ", servName, "_", methName, "Client interface {")
 	if genSend {
 		g.P("Send(*", inType, ") error")
 	}
 	if genRecv {
 		g.P("Recv() (*", outType, ", error)")
 	}
 	if genCloseAndRecv {
 		g.P("CloseAndRecv() (*", outType, ", error)")
 	}
 	g.P(grpcPkg, ".ClientStream")
 	g.P("}")
 	g.P()

 	g.P("type ", streamType, " struct {")
 	g.P(grpcPkg, ".ClientStream")
 	g.P("}")
 	g.P()

 	if genSend {
 		g.P("func (x *", streamType, ") Send(m *", inType, ") error {")
 		g.P("return x.ClientStream.SendMsg(m)")
 		g.P("}")
 		g.P()
 	}
 	if genRecv {
 		g.P("func (x *", streamType, ") Recv() (*", outType, ", error) {")
 		g.P("m := new(", outType, ")")
 		g.P("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }")
 		g.P("return m, nil")
 		g.P("}")
 		g.P()
 	}
 	if genCloseAndRecv {
 		g.P("func (x *", streamType, ") CloseAndRecv() (*", outType, ", error) {")
 		g.P("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }")
 		g.P("m := new(", outType, ")")
 		g.P("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }")
 		g.P("return m, nil")
 		g.P("}")
 		g.P()
 	}
 }

 // generateServerSignatureWithParamNames returns the server-side signature for a method with parameter names.
 func (g *grpc) generateServerSignatureWithParamNames(servName string, method *pb.MethodDescriptorProto) string {
 	origMethName := method.GetName()
 	methName := generator.CamelCase(origMethName)
 	if reservedClientName[methName] {
 		methName += "_"
 	}

 	var reqArgs []string
 	ret := "error"
 	if !method.GetServerStreaming() && !method.GetClientStreaming() {
 		reqArgs = append(reqArgs, "ctx "+contextPkg+".Context")
 		ret = "(*" + g.typeName(method.GetOutputType()) + ", error)"
 	}
 	if !method.GetClientStreaming() {
 		reqArgs = append(reqArgs, "req *"+g.typeName(method.GetInputType()))
 	}
 	if method.GetServerStreaming() || method.GetClientStreaming() {
 		reqArgs = append(reqArgs, "srv "+servName+"_"+generator.CamelCase(origMethName)+"Server")
 	}

 	return methName + "(" + strings.Join(reqArgs, ", ") + ") " + ret
 }

 // generateServerSignature returns the server-side signature for a method.
 func (g *grpc) generateServerSignature(servName string, method *pb.MethodDescriptorProto) string {
 	origMethName := method.GetName()
 	methName := generator.CamelCase(origMethName)
 	if reservedClientName[methName] {
 		methName += "_"
 	}

 	var reqArgs []string
 	ret := "error"
 	if !method.GetServerStreaming() && !method.GetClientStreaming() {
 		reqArgs = append(reqArgs, contextPkg+".Context")
 		ret = "(*" + g.typeName(method.GetOutputType()) + ", error)"
 	}
 	if !method.GetClientStreaming() {
 		reqArgs = append(reqArgs, "*"+g.typeName(method.GetInputType()))
 	}
 	if method.GetServerStreaming() || method.GetClientStreaming() {
 		reqArgs = append(reqArgs, servName+"_"+generator.CamelCase(origMethName)+"Server")
 	}

 	return methName + "(" + strings.Join(reqArgs, ", ") + ") " + ret
 }

 func (g *grpc) generateServerMethod(servName, fullServName string, method *pb.MethodDescriptorProto) string {
 	methName := generator.CamelCase(method.GetName())
 	hname := fmt.Sprintf("_%s_%s_Handler", servName, methName)
 	inType := g.typeName(method.GetInputType())
 	outType := g.typeName(method.GetOutputType())

 	if !method.GetServerStreaming() && !method.GetClientStreaming() {
 		g.P("func ", hname, "(srv interface{}, ctx ", contextPkg, ".Context, dec func(interface{}) error, interceptor ", grpcPkg, ".UnaryServerInterceptor) (interface{}, error) {")
 		g.P("in := new(", inType, ")")
 		g.P("if err := dec(in); err != nil { return nil, err }")
 		g.P("if interceptor == nil { return srv.(", servName, "Server).", methName, "(ctx, in) }")
 		g.P("info := &", grpcPkg, ".UnaryServerInfo{")
 		g.P("Server: srv,")
 		g.P("FullMethod: ", strconv.Quote(fmt.Sprintf("/%s/%s", fullServName, methName)), ",")
 		g.P("}")
 		g.P("handler := func(ctx ", contextPkg, ".Context, req interface{}) (interface{}, error) {")
 		g.P("return srv.(", servName, "Server).", methName, "(ctx, req.(*", inType, "))")
 		g.P("}")
 		g.P("return interceptor(ctx, in, info, handler)")
 		g.P("}")
 		g.P()
 		return hname
 	}
 	streamType := unexport(servName) + methName + "Server"
 	g.P("func ", hname, "(srv interface{}, stream ", grpcPkg, ".ServerStream) error {")
 	if !method.GetClientStreaming() {
 		g.P("m := new(", inType, ")")
 		g.P("if err := stream.RecvMsg(m); err != nil { return err }")
 		g.P("return srv.(", servName, "Server).", methName, "(m, &", streamType, "{stream})")
 	} else {
 		g.P("return srv.(", servName, "Server).", methName, "(&", streamType, "{stream})")
 	}
 	g.P("}")
 	g.P()

 	genSend := method.GetServerStreaming()
 	genSendAndClose := !method.GetServerStreaming()
 	genRecv := method.GetClientStreaming()

 	// Stream auxiliary types and methods.
 	g.P("type ", servName, "_", methName, "Server interface {")
 	if genSend {
 		g.P("Send(*", outType, ") error")
 	}
 	if genSendAndClose {
 		g.P("SendAndClose(*", outType, ") error")
 	}
 	if genRecv {
 		g.P("Recv() (*", inType, ", error)")
 	}
 	g.P(grpcPkg, ".ServerStream")
 	g.P("}")
 	g.P()

 	g.P("type ", streamType, " struct {")
 	g.P(grpcPkg, ".ServerStream")
 	g.P("}")
 	g.P()

 	if genSend {
 		g.P("func (x *", streamType, ") Send(m *", outType, ") error {")
 		g.P("return x.ServerStream.SendMsg(m)")
 		g.P("}")
 		g.P()
 	}
 	if genSendAndClose {
 		g.P("func (x *", streamType, ") SendAndClose(m *", outType, ") error {")
 		g.P("return x.ServerStream.SendMsg(m)")
 		g.P("}")
 		g.P()
 	}
 	if genRecv {
 		g.P("func (x *", streamType, ") Recv() (*", inType, ", error) {")
 		g.P("m := new(", inType, ")")
 		g.P("if err := x.ServerStream.RecvMsg(m); err != nil { return nil, err }")
 		g.P("return m, nil")
 		g.P("}")
 		g.P()
 	}

 	return hname
 }
	// Go support for Protocol Buffers - Google's data interchange format
	//
	// Copyright 2015 The Go Authors. All rights reserved.
	// https://github.com/golang/protobuf
	//
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are
	// met:
	//
	// * Redistributions of source code must retain the above copyright
	// notice, this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above
	// copyright notice, this list of conditions and the following disclaimer
	// in the documentation and/or other materials provided with the
	// distribution.
	// * Neither the name of Google Inc. nor the names of its
	// contributors may be used to endorse or promote products derived from
	// this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	// Package grpc outputs gRPC service descriptions in Go code.
	// It runs as a plugin for the Go protocol buffer compiler plugin.
	// It is linked in to protoc-gen-go.
	package grpc

	import (
	"fmt"
	"strconv"
	"strings"

	pb "github.com/golang/protobuf/protoc-gen-go/descriptor"
	"github.com/golang/protobuf/protoc-gen-go/generator"
	)

	// generatedCodeVersion indicates a version of the generated code.
	// It is incremented whenever an incompatibility between the generated code and
	// the grpc package is introduced; the generated code references
	// a constant, grpc.SupportPackageIsVersionN (where N is generatedCodeVersion).
	const generatedCodeVersion = 4

	// Paths for packages used by code generated in this file,
	// relative to the import_prefix of the generator.Generator.
	const (
	contextPkgPath = "context"
	grpcPkgPath = "google.golang.org/grpc"
	codePkgPath = "google.golang.org/grpc/codes"
	statusPkgPath = "google.golang.org/grpc/status"
	)

	func init() {
	generator.RegisterPlugin(new(grpc))
	}

	// grpc is an implementation of the Go protocol buffer compiler's
	// plugin architecture. It generates bindings for gRPC support.
	type grpc struct {
	gen *generator.Generator
	}

	// Name returns the name of this plugin, "grpc".
	func (g *grpc) Name() string {
	return "grpc"
	}

	// The names for packages imported in the generated code.
	// They may vary from the final path component of the import path
	// if the name is used by other packages.
	var (
	contextPkg string
	grpcPkg string
	)

	// Init initializes the plugin.
	func (g grpc) Init(gen generator.Generator) {
	g.gen = gen
	}

	// Given a type name defined in a .proto, return its object.
	// Also record that we're using it, to guarantee the associated import.
	func (g *grpc) objectNamed(name string) generator.Object {
	g.gen.RecordTypeUse(name)
	return g.gen.ObjectNamed(name)
	}

	// Given a type name defined in a .proto, return its name as we will print it.
	func (g *grpc) typeName(str string) string {
	return g.gen.TypeName(g.objectNamed(str))
	}

	// P forwards to g.gen.P.
	func (g *grpc) P(args ...interface{}) { g.gen.P(args...) }

	// Generate generates code for the services in the given file.
	func (g grpc) Generate(file generator.FileDescriptor) {
	if len(file.FileDescriptorProto.Service) == 0 {
	return
	}

	contextPkg = string(g.gen.AddImport(contextPkgPath))
	grpcPkg = string(g.gen.AddImport(grpcPkgPath))

	g.P("// Reference imports to suppress errors if they are not otherwise used.")
	g.P("var _ ", contextPkg, ".Context")
	g.P("var _ ", grpcPkg, ".ClientConn")
	g.P()

	// Assert version compatibility.
	g.P("// This is a compile-time assertion to ensure that this generated file")
	g.P("// is compatible with the grpc package it is being compiled against.")
	g.P("const _ = ", grpcPkg, ".SupportPackageIsVersion", generatedCodeVersion)
	g.P()

	for i, service := range file.FileDescriptorProto.Service {
	g.generateService(file, service, i)
	}
	}

	// GenerateImports generates the import declaration for this file.
	func (g grpc) GenerateImports(file generator.FileDescriptor) {
	}

	// reservedClientName records whether a client name is reserved on the client side.
	var reservedClientName = map[string]bool{
	// TODO: do we need any in gRPC?
	}

	func unexport(s string) string { return strings.ToLower(s[:1]) + s[1:] }

	// deprecationComment is the standard comment added to deprecated
	// messages, fields, enums, and enum values.
	var deprecationComment = "// Deprecated: Do not use."

	// generateService generates all the code for the named service.
	func (g grpc) generateService(file generator.FileDescriptor, service *pb.ServiceDescriptorProto, index int) {
	path := fmt.Sprintf("6,%d", index) // 6 means service.

	origServName := service.GetName()
	fullServName := origServName
	if pkg := file.GetPackage(); pkg != "" {
	fullServName = pkg + "." + fullServName
	}
	servName := generator.CamelCase(origServName)
	deprecated := service.GetOptions().GetDeprecated()

	g.P()
	g.P(fmt.Sprintf(`// %sClient is the client API for %s service.
	//
	// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.`, servName, servName))

	// Client interface.
	if deprecated {
	g.P("//")
	g.P(deprecationComment)
	}
	g.P("type ", servName, "Client interface {")
	for i, method := range service.Method {
	g.gen.PrintComments(fmt.Sprintf("%s,2,%d", path, i)) // 2 means method in a service.
	if method.GetOptions().GetDeprecated() {
	g.P("//")
	g.P(deprecationComment)
	}
	g.P(g.generateClientSignature(servName, method))
	}
	g.P("}")
	g.P()

	// Client structure.
	g.P("type ", unexport(servName), "Client struct {")
	g.P("cc *", grpcPkg, ".ClientConn")
	g.P("}")
	g.P()

	// NewClient factory.
	if deprecated {
	g.P(deprecationComment)
	}
	g.P("func New", servName, "Client (cc *", grpcPkg, ".ClientConn) ", servName, "Client {")
	g.P("return &", unexport(servName), "Client{cc}")
	g.P("}")
	g.P()

	var methodIndex, streamIndex int
	serviceDescVar := "_" + servName + "_serviceDesc"
	// Client method implementations.
	for _, method := range service.Method {
	var descExpr string
	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	// Unary RPC method
	descExpr = fmt.Sprintf("&%s.Methods[%d]", serviceDescVar, methodIndex)
	methodIndex++
	} else {
	// Streaming RPC method
	descExpr = fmt.Sprintf("&%s.Streams[%d]", serviceDescVar, streamIndex)
	streamIndex++
	}
	g.generateClientMethod(servName, fullServName, serviceDescVar, method, descExpr)
	}

	// Server interface.
	serverType := servName + "Server"
	g.P("// ", serverType, " is the server API for ", servName, " service.")
	if deprecated {
	g.P("//")
	g.P(deprecationComment)
	}
	g.P("type ", serverType, " interface {")
	for i, method := range service.Method {
	g.gen.PrintComments(fmt.Sprintf("%s,2,%d", path, i)) // 2 means method in a service.
	if method.GetOptions().GetDeprecated() {
	g.P("//")
	g.P(deprecationComment)
	}
	g.P(g.generateServerSignature(servName, method))
	}
	g.P("}")
	g.P()

	// Server Unimplemented struct for forward compatibility.
	if deprecated {
	g.P(deprecationComment)
	}
	g.generateUnimplementedServer(servName, service)

	// Server registration.
	if deprecated {
	g.P(deprecationComment)
	}
	g.P("func Register", servName, "Server(s *", grpcPkg, ".Server, srv ", serverType, ") {")
	g.P("s.RegisterService(&", serviceDescVar, `, srv)`)
	g.P("}")
	g.P()

	// Server handler implementations.
	var handlerNames []string
	for _, method := range service.Method {
	hname := g.generateServerMethod(servName, fullServName, method)
	handlerNames = append(handlerNames, hname)
	}

	// Service descriptor.
	g.P("var ", serviceDescVar, " = ", grpcPkg, ".ServiceDesc {")
	g.P("ServiceName: ", strconv.Quote(fullServName), ",")
	g.P("HandlerType: (*", serverType, ")(nil),")
	g.P("Methods: []", grpcPkg, ".MethodDesc{")
	for i, method := range service.Method {
	if method.GetServerStreaming() \|\| method.GetClientStreaming() {
	continue
	}
	g.P("{")
	g.P("MethodName: ", strconv.Quote(method.GetName()), ",")
	g.P("Handler: ", handlerNames[i], ",")
	g.P("},")
	}
	g.P("},")
	g.P("Streams: []", grpcPkg, ".StreamDesc{")
	for i, method := range service.Method {
	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	continue
	}
	g.P("{")
	g.P("StreamName: ", strconv.Quote(method.GetName()), ",")
	g.P("Handler: ", handlerNames[i], ",")
	if method.GetServerStreaming() {
	g.P("ServerStreams: true,")
	}
	if method.GetClientStreaming() {
	g.P("ClientStreams: true,")
	}
	g.P("},")
	}
	g.P("},")
	g.P("Metadata: \"", file.GetName(), "\",")
	g.P("}")
	g.P()
	}

	// generateUnimplementedServer creates the unimplemented server struct
	func (g grpc) generateUnimplementedServer(servName string, service pb.ServiceDescriptorProto) {
	serverType := servName + "Server"
	g.P("// Unimplemented", serverType, " can be embedded to have forward compatible implementations.")
	g.P("type Unimplemented", serverType, " struct {")
	g.P("}")
	g.P()
	// Unimplemented<service_name>Server's concrete methods
	for _, method := range service.Method {
	g.generateServerMethodConcrete(servName, method)
	}
	g.P()
	}

	// generateServerMethodConcrete returns unimplemented methods which ensure forward compatibility
	func (g grpc) generateServerMethodConcrete(servName string, method pb.MethodDescriptorProto) {
	header := g.generateServerSignatureWithParamNames(servName, method)
	g.P("func (*Unimplemented", servName, "Server) ", header, " {")
	var nilArg string
	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	nilArg = "nil, "
	}
	methName := generator.CamelCase(method.GetName())
	statusPkg := string(g.gen.AddImport(statusPkgPath))
	codePkg := string(g.gen.AddImport(codePkgPath))
	g.P("return ", nilArg, statusPkg, `.Errorf(`, codePkg, `.Unimplemented, "method `, methName, ` not implemented")`)
	g.P("}")
	}

	// generateClientSignature returns the client-side signature for a method.
	func (g grpc) generateClientSignature(servName string, method pb.MethodDescriptorProto) string {
	origMethName := method.GetName()
	methName := generator.CamelCase(origMethName)
	if reservedClientName[methName] {
	methName += "_"
	}
	reqArg := ", in *" + g.typeName(method.GetInputType())
	if method.GetClientStreaming() {
	reqArg = ""
	}
	respName := "*" + g.typeName(method.GetOutputType())
	if method.GetServerStreaming() \|\| method.GetClientStreaming() {
	respName = servName + "_" + generator.CamelCase(origMethName) + "Client"
	}
	return fmt.Sprintf("%s(ctx %s.Context%s, opts ...%s.CallOption) (%s, error)", methName, contextPkg, reqArg, grpcPkg, respName)
	}

	func (g grpc) generateClientMethod(servName, fullServName, serviceDescVar string, method pb.MethodDescriptorProto, descExpr string) {
	sname := fmt.Sprintf("/%s/%s", fullServName, method.GetName())
	methName := generator.CamelCase(method.GetName())
	inType := g.typeName(method.GetInputType())
	outType := g.typeName(method.GetOutputType())

	if method.GetOptions().GetDeprecated() {
	g.P(deprecationComment)
	}
	g.P("func (c *", unexport(servName), "Client) ", g.generateClientSignature(servName, method), "{")
	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	g.P("out := new(", outType, ")")
	// TODO: Pass descExpr to Invoke.
	g.P(`err := c.cc.Invoke(ctx, "`, sname, `", in, out, opts...)`)
	g.P("if err != nil { return nil, err }")
	g.P("return out, nil")
	g.P("}")
	g.P()
	return
	}
	streamType := unexport(servName) + methName + "Client"
	g.P("stream, err := c.cc.NewStream(ctx, ", descExpr, `, "`, sname, `", opts...)`)
	g.P("if err != nil { return nil, err }")
	g.P("x := &", streamType, "{stream}")
	if !method.GetClientStreaming() {
	g.P("if err := x.ClientStream.SendMsg(in); err != nil { return nil, err }")
	g.P("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }")
	}
	g.P("return x, nil")
	g.P("}")
	g.P()

	genSend := method.GetClientStreaming()
	genRecv := method.GetServerStreaming()
	genCloseAndRecv := !method.GetServerStreaming()

	// Stream auxiliary types and methods.
	g.P("type ", servName, "_", methName, "Client interface {")
	if genSend {
	g.P("Send(*", inType, ") error")
	}
	if genRecv {
	g.P("Recv() (*", outType, ", error)")
	}
	if genCloseAndRecv {
	g.P("CloseAndRecv() (*", outType, ", error)")
	}
	g.P(grpcPkg, ".ClientStream")
	g.P("}")
	g.P()

	g.P("type ", streamType, " struct {")
	g.P(grpcPkg, ".ClientStream")
	g.P("}")
	g.P()

	if genSend {
	g.P("func (x ", streamType, ") Send(m ", inType, ") error {")
	g.P("return x.ClientStream.SendMsg(m)")
	g.P("}")
	g.P()
	}
	if genRecv {
	g.P("func (x ", streamType, ") Recv() (", outType, ", error) {")
	g.P("m := new(", outType, ")")
	g.P("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }")
	g.P("return m, nil")
	g.P("}")
	g.P()
	}
	if genCloseAndRecv {
	g.P("func (x ", streamType, ") CloseAndRecv() (", outType, ", error) {")
	g.P("if err := x.ClientStream.CloseSend(); err != nil { return nil, err }")
	g.P("m := new(", outType, ")")
	g.P("if err := x.ClientStream.RecvMsg(m); err != nil { return nil, err }")
	g.P("return m, nil")
	g.P("}")
	g.P()
	}
	}

	// generateServerSignatureWithParamNames returns the server-side signature for a method with parameter names.
	func (g grpc) generateServerSignatureWithParamNames(servName string, method pb.MethodDescriptorProto) string {
	origMethName := method.GetName()
	methName := generator.CamelCase(origMethName)
	if reservedClientName[methName] {
	methName += "_"
	}

	var reqArgs []string
	ret := "error"
	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	reqArgs = append(reqArgs, "ctx "+contextPkg+".Context")
	ret = "(*" + g.typeName(method.GetOutputType()) + ", error)"
	}
	if !method.GetClientStreaming() {
	reqArgs = append(reqArgs, "req *"+g.typeName(method.GetInputType()))
	}
	if method.GetServerStreaming() \|\| method.GetClientStreaming() {
	reqArgs = append(reqArgs, "srv "+servName+"_"+generator.CamelCase(origMethName)+"Server")
	}

	return methName + "(" + strings.Join(reqArgs, ", ") + ") " + ret
	}

	// generateServerSignature returns the server-side signature for a method.
	func (g grpc) generateServerSignature(servName string, method pb.MethodDescriptorProto) string {
	origMethName := method.GetName()
	methName := generator.CamelCase(origMethName)
	if reservedClientName[methName] {
	methName += "_"
	}

	var reqArgs []string
	ret := "error"
	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	reqArgs = append(reqArgs, contextPkg+".Context")
	ret = "(*" + g.typeName(method.GetOutputType()) + ", error)"
	}
	if !method.GetClientStreaming() {
	reqArgs = append(reqArgs, "*"+g.typeName(method.GetInputType()))
	}
	if method.GetServerStreaming() \|\| method.GetClientStreaming() {
	reqArgs = append(reqArgs, servName+"_"+generator.CamelCase(origMethName)+"Server")
	}

	return methName + "(" + strings.Join(reqArgs, ", ") + ") " + ret
	}

	func (g grpc) generateServerMethod(servName, fullServName string, method pb.MethodDescriptorProto) string {
	methName := generator.CamelCase(method.GetName())
	hname := fmt.Sprintf("_%s_%s_Handler", servName, methName)
	inType := g.typeName(method.GetInputType())
	outType := g.typeName(method.GetOutputType())

	if !method.GetServerStreaming() && !method.GetClientStreaming() {
	g.P("func ", hname, "(srv interface{}, ctx ", contextPkg, ".Context, dec func(interface{}) error, interceptor ", grpcPkg, ".UnaryServerInterceptor) (interface{}, error) {")
	g.P("in := new(", inType, ")")
	g.P("if err := dec(in); err != nil { return nil, err }")
	g.P("if interceptor == nil { return srv.(", servName, "Server).", methName, "(ctx, in) }")
	g.P("info := &", grpcPkg, ".UnaryServerInfo{")
	g.P("Server: srv,")
	g.P("FullMethod: ", strconv.Quote(fmt.Sprintf("/%s/%s", fullServName, methName)), ",")
	g.P("}")
	g.P("handler := func(ctx ", contextPkg, ".Context, req interface{}) (interface{}, error) {")
	g.P("return srv.(", servName, "Server).", methName, "(ctx, req.(*", inType, "))")
	g.P("}")
	g.P("return interceptor(ctx, in, info, handler)")
	g.P("}")
	g.P()
	return hname
	}
	streamType := unexport(servName) + methName + "Server"
	g.P("func ", hname, "(srv interface{}, stream ", grpcPkg, ".ServerStream) error {")
	if !method.GetClientStreaming() {
	g.P("m := new(", inType, ")")
	g.P("if err := stream.RecvMsg(m); err != nil { return err }")
	g.P("return srv.(", servName, "Server).", methName, "(m, &", streamType, "{stream})")
	} else {
	g.P("return srv.(", servName, "Server).", methName, "(&", streamType, "{stream})")
	}
	g.P("}")
	g.P()

	genSend := method.GetServerStreaming()
	genSendAndClose := !method.GetServerStreaming()
	genRecv := method.GetClientStreaming()

	// Stream auxiliary types and methods.
	g.P("type ", servName, "_", methName, "Server interface {")
	if genSend {
	g.P("Send(*", outType, ") error")
	}
	if genSendAndClose {
	g.P("SendAndClose(*", outType, ") error")
	}
	if genRecv {
	g.P("Recv() (*", inType, ", error)")
	}
	g.P(grpcPkg, ".ServerStream")
	g.P("}")
	g.P()

	g.P("type ", streamType, " struct {")
	g.P(grpcPkg, ".ServerStream")
	g.P("}")
	g.P()

	if genSend {
	g.P("func (x ", streamType, ") Send(m ", outType, ") error {")
	g.P("return x.ServerStream.SendMsg(m)")
	g.P("}")
	g.P()
	}
	if genSendAndClose {
	g.P("func (x ", streamType, ") SendAndClose(m ", outType, ") error {")
	g.P("return x.ServerStream.SendMsg(m)")
	g.P("}")
	g.P()
	}
	if genRecv {
	g.P("func (x ", streamType, ") Recv() (", inType, ", error) {")
	g.P("m := new(", inType, ")")
	g.P("if err := x.ServerStream.RecvMsg(m); err != nil { return nil, err }")
	g.P("return m, nil")
	g.P("}")
	g.P()
	}

	return hname
	}