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rpc.go
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rpc.go
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// Derived from the Go net/rpc standard library.
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dilithium
import (
"errors"
"log"
"net/rpc"
"reflect"
"strings"
"sync"
"unicode"
"unicode/utf8"
)
type methodType struct {
method reflect.Method
ArgType reflect.Type
ReplyType reflect.Type
readOnly bool // if false, ReplyType is nil
}
type service struct {
name string
rcvr reflect.Value
typ reflect.Type
methods map[string]*methodType
}
type Server struct {
forwarding *ForwardingTable
mu sync.RWMutex // protects services
services map[string]*service
queryLock sync.Mutex
nextQuery *Query
}
type rpcServer Server
// Precompute the reflect type for error. Can't use error directly
// because Typeof takes an empty interface value. This is annoying.
var typeOfError = reflect.TypeOf((*error)(nil)).Elem()
var typeOfQueryArg = reflect.TypeOf((*QueryArg)(nil)).Elem()
var DefaultServer = NewServer(nil)
func NewServer(forwarding *ForwardingTable) *Server {
if forwarding == nil {
forwarding = &ForwardingTable{}
}
return &Server{forwarding: forwarding, services: make(map[string]*service)}
}
func isExported(name string) bool {
r, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(r)
}
func isExportedOrBuiltinType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
// PkgPath will be non-empty even for an exported type,
// so we need to check the type name as well.
return isExported(t.Name()) || t.PkgPath() == ""
}
func (s *Server) Register(rcvr interface{}) error {
s.mu.Lock()
defer s.mu.Unlock()
service := &service{typ: reflect.TypeOf(rcvr), rcvr: reflect.ValueOf(rcvr)}
name := reflect.Indirect(service.rcvr).Type().Name()
if name == "" {
log.Fatal("dilithium: no service name for type", service.typ.String())
}
if !isExported(name) {
e := "dilithium Register: type " + name + " is not exported"
log.Fatal(s)
return errors.New(e)
}
if _, present := s.services[name]; present {
return errors.New("dilithium: service already defined: " + name)
}
service.name = name
service.methods = make(map[string]*methodType)
for i := 0; i < service.typ.NumMethod(); i++ {
method := service.typ.Method(i)
mtype := method.Type
mname := method.Name
// Method must be exported
if method.PkgPath != "" {
continue
}
// Method needs three or four ins.
// ReadOnly: receiver, *conn, *arg, *reply
// Write: receiver, *conn, *arg
if mtype.NumIn() != 3 && mtype.NumIn() != 4 {
log.Println("method", mname, "has wrong number of ins:", mtype.NumIn())
continue
}
// First arg must be a pointer.
connType := mtype.In(1)
if connType.Kind() != reflect.Ptr {
log.Println("method", mname, "connection type not a pointer:", connType)
continue
}
// Connection type must be exported.
if !isExportedOrBuiltinType(connType) {
log.Println("method", mname, "connection type not exported:", connType)
continue
}
// Second arg need not be a pointer, but must be exported and implement QueryArg.
argType := mtype.In(2)
if !isExportedOrBuiltinType(argType) {
log.Println(mname, "argument type not exported:", argType)
continue
}
if !argType.Implements(typeOfQueryArg) {
log.Println(mname, "argument type does not implement QueryArg:", argType)
continue
}
var replyType reflect.Type
var readOnly bool
if mtype.NumIn() == 4 {
readOnly = true
// Third arg must be a pointer.
replyType = mtype.In(3)
if replyType.Kind() != reflect.Ptr {
log.Println("method", mname, "reply type not a pointer:", replyType)
continue
}
// Reply type must be exported.
if !isExportedOrBuiltinType(replyType) {
log.Println("method", mname, "reply type not exported:", replyType)
continue
}
}
// Method needs one out.
if mtype.NumOut() != 1 {
log.Println("method", mname, "has wrong number of outs:", mtype.NumOut())
continue
}
// The return type of the method must be error.
if returnType := mtype.Out(0); returnType != typeOfError {
log.Println("method", mname, "returns", returnType.String(), "not error")
continue
}
service.methods[mname] = &methodType{method: method, ArgType: argType, ReplyType: replyType.Elem(), readOnly: readOnly}
}
if len(service.methods) == 0 {
e := "dilithium Register: type " + name + " has no exported methods of suitable type"
log.Fatal(e)
return errors.New(e)
}
s.services[service.name] = service
return nil
}
func (s *Server) RegisterWithRPC(r *rpc.Server) {
server := rpcServer(*s)
r.RegisterName("dilithium", &server)
}
func (s *rpcServer) Query(q *Query, reply *interface{}) error {
q.server = s
serviceMethod := strings.Split(q.Method, ".")
if len(serviceMethod) != 2 {
return errors.New("dilithium: query service/method invalid: " + q.Method)
}
s.mu.RLock()
q.service = s.services[serviceMethod[0]]
s.mu.RUnlock()
if q.service == nil {
return errors.New("dilithium: can't find service " + serviceMethod[0])
}
q.method = q.service.methods[serviceMethod[1]]
if q.method == nil {
return errors.New("dilithium: can't find method " + q.Method)
}
err := q.Route()
if err != nil {
return err
}
*reply = q.Reply
return nil
}