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main.go
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main.go
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package main
import (
"context"
"flag"
"fmt"
"log"
"net"
"os"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/reflect/protodesc"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/reflect/protoregistry"
"google.golang.org/protobuf/types/descriptorpb"
"google.golang.org/protobuf/types/dynamicpb"
)
func main() {
flag.Parse()
if flag.NArg() != 1 {
log.Fatal("Expected exactly one argument with proto file")
}
file := flag.Arg(0)
fd, err := loadFile(file)
if err != nil {
log.Fatal(err)
}
srv := grpc.NewServer()
streamer := &handler{}
for i := 0; i < fd.Services().Len(); i++ {
service := fd.Services().Get(i)
desc := &grpc.ServiceDesc{
ServiceName: string(service.FullName()),
HandlerType: (*interface{})(nil),
}
for j := 0; j < service.Methods().Len(); j++ {
method := service.Methods().Get(j)
desc.Methods = append(desc.Methods, grpc.MethodDesc{
MethodName: string(method.Name()),
Handler: methodHandler(method),
})
}
fmt.Println(desc)
srv.RegisterService(desc, streamer)
}
lis, err := net.Listen("tcp", ":8080")
if err != nil {
log.Fatal(err)
}
log.Fatal(srv.Serve(lis))
}
type handler struct{}
func (s *handler) handler(desc protoreflect.MethodDescriptor) grpc.StreamHandler {
return func(srv interface{}, stream grpc.ServerStream) error {
msg := dynamicpb.NewMessage(desc.Input())
err := stream.RecvMsg(msg)
if err != nil {
return status.Error(codes.Internal, "could not receive msg: "+err.Error())
}
fmt.Printf("%+v\n", msg)
return nil
}
}
func methodHandler(desc protoreflect.MethodDescriptor) func(interface{}, context.Context, func(interface{}) error, grpc.UnaryServerInterceptor) (interface{}, error) {
return func(srv interface{}, ctx context.Context, dec func(interface{}) error, _ grpc.UnaryServerInterceptor) (interface{}, error) {
in := dynamicpb.NewMessage(desc.Input())
if err := dec(in); err != nil {
return nil, err
}
val := in.Get(desc.Input().Fields().ByName("name"))
message := fmt.Sprintf("Hello %s", val.String())
out := dynamicpb.NewMessage(desc.Output())
out.Set(desc.Output().Fields().ByName("message"), protoreflect.ValueOf(message))
return out, nil
}
}
func loadFile(filename string) (protoreflect.FileDescriptor, error) {
protoFile, err := os.ReadFile(filename)
if err != nil {
return nil, err
}
pbSet := new(descriptorpb.FileDescriptorSet)
if err := proto.Unmarshal(protoFile, pbSet); err != nil {
return nil, err
}
// We know protoc was invoked with a single .proto file
pb := pbSet.GetFile()[0]
// Initialize the File descriptor object
fd, err := protodesc.NewFile(pb, protoregistry.GlobalFiles)
if err != nil {
return nil, err
}
err = protoregistry.GlobalFiles.RegisterFile(fd)
if err != nil {
return nil, err
}
// and finally register it.
return fd, nil
}