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7bbdd50 Aug 17, 2016
@abursavich @moraes @HasMatthew @kisielk
181 lines (165 sloc) 4.97 KB
// Copyright 2009 The Go Authors. All rights reserved.
// Copyright 2012 The Gorilla 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 rpc
import (
"fmt"
"net/http"
"reflect"
"strings"
"sync"
"unicode"
"unicode/utf8"
)
var (
// Precompute the reflect.Type of error and http.Request
typeOfError = reflect.TypeOf((*error)(nil)).Elem()
typeOfRequest = reflect.TypeOf((*http.Request)(nil)).Elem()
)
// ----------------------------------------------------------------------------
// service
// ----------------------------------------------------------------------------
type service struct {
name string // name of service
rcvr reflect.Value // receiver of methods for the service
rcvrType reflect.Type // type of the receiver
methods map[string]*serviceMethod // registered methods
passReq bool
}
type serviceMethod struct {
method reflect.Method // receiver method
argsType reflect.Type // type of the request argument
replyType reflect.Type // type of the response argument
}
// ----------------------------------------------------------------------------
// serviceMap
// ----------------------------------------------------------------------------
// serviceMap is a registry for services.
type serviceMap struct {
mutex sync.Mutex
services map[string]*service
}
// register adds a new service using reflection to extract its methods.
func (m *serviceMap) register(rcvr interface{}, name string, passReq bool) error {
// Setup service.
s := &service{
name: name,
rcvr: reflect.ValueOf(rcvr),
rcvrType: reflect.TypeOf(rcvr),
methods: make(map[string]*serviceMethod),
passReq: passReq,
}
if name == "" {
s.name = reflect.Indirect(s.rcvr).Type().Name()
if !isExported(s.name) {
return fmt.Errorf("rpc: type %q is not exported", s.name)
}
}
if s.name == "" {
return fmt.Errorf("rpc: no service name for type %q",
s.rcvrType.String())
}
// Setup methods.
for i := 0; i < s.rcvrType.NumMethod(); i++ {
method := s.rcvrType.Method(i)
mtype := method.Type
// offset the parameter indexes by one if the
// service methods accept an HTTP request pointer
var paramOffset int
if passReq {
paramOffset = 1
} else {
paramOffset = 0
}
// Method must be exported.
if method.PkgPath != "" {
continue
}
// Method needs four ins: receiver, *http.Request, *args, *reply.
if mtype.NumIn() != 3+paramOffset {
continue
}
// If the service methods accept an HTTP request pointer
if passReq {
// First argument must be a pointer and must be http.Request.
reqType := mtype.In(1)
if reqType.Kind() != reflect.Ptr || reqType.Elem() != typeOfRequest {
continue
}
}
// Next argument must be a pointer and must be exported.
args := mtype.In(1 + paramOffset)
if args.Kind() != reflect.Ptr || !isExportedOrBuiltin(args) {
continue
}
// Next argument must be a pointer and must be exported.
reply := mtype.In(2 + paramOffset)
if reply.Kind() != reflect.Ptr || !isExportedOrBuiltin(reply) {
continue
}
// Method needs one out: error.
if mtype.NumOut() != 1 {
continue
}
if returnType := mtype.Out(0); returnType != typeOfError {
continue
}
s.methods[method.Name] = &serviceMethod{
method: method,
argsType: args.Elem(),
replyType: reply.Elem(),
}
}
if len(s.methods) == 0 {
return fmt.Errorf("rpc: %q has no exported methods of suitable type",
s.name)
}
// Add to the map.
m.mutex.Lock()
defer m.mutex.Unlock()
if m.services == nil {
m.services = make(map[string]*service)
} else if _, ok := m.services[s.name]; ok {
return fmt.Errorf("rpc: service already defined: %q", s.name)
}
m.services[s.name] = s
return nil
}
// get returns a registered service given a method name.
//
// The method name uses a dotted notation as in "Service.Method".
func (m *serviceMap) get(method string) (*service, *serviceMethod, error) {
parts := strings.Split(method, ".")
if len(parts) != 2 {
err := fmt.Errorf("rpc: service/method request ill-formed: %q", method)
return nil, nil, err
}
m.mutex.Lock()
service := m.services[parts[0]]
m.mutex.Unlock()
if service == nil {
err := fmt.Errorf("rpc: can't find service %q", method)
return nil, nil, err
}
serviceMethod := service.methods[parts[1]]
if serviceMethod == nil {
err := fmt.Errorf("rpc: can't find method %q", method)
return nil, nil, err
}
return service, serviceMethod, nil
}
// isExported returns true of a string is an exported (upper case) name.
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(rune)
}
// isExportedOrBuiltin returns true if a type is exported or a builtin.
func isExportedOrBuiltin(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() == ""
}