code review 2696041: rpc: expose Server type to allow multiple RPC Server in...

src/pkg/rpc/server.go

 // 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.
 
 /*
-        The rpc package provides access to the public methods of an object across a
+        The rpc package provides access to the exported methods of an object across a
         network or other I/O connection.  A server registers an object, making it visible
-        as a service with the name of the type of the object.  After registration, public
+        as a service with the name of the type of the object.  After registration, exported
         methods of the object will be accessible remotely.  A server may register multiple
         objects (services) of different types but it is an error to register multiple
         objects of the same type.
 
         Only methods that satisfy these criteria will be made available for remote access;
         other methods will be ignored:
 
-                - the method receiver and name are publicly visible, that is, begin with an upper case letter.
-                - the method has two arguments, both pointers to publicly visible types.
+                - the method receiver and name are exported, that is, begin with an upper case letter.
+                - the method has two arguments, both pointers to exported types.
                 - the method has return type os.Error.
 
         The method's first argument represents the arguments provided by the caller; the
         second argument represents the result parameters to be returned to the caller.
         The method's return value, if non-nil, is passed back as a string that the client
         sees as an os.ErrorString.
 
         The server may handle requests on a single connection by calling ServeConn.  More
         typically it will create a network listener and call Accept or, for an HTTP
         listener, HandleHTTP and http.Serve.
@@ skipping 88 matching lines @@
         "io"
         "net"
         "os"
         "reflect"
         "strings"
         "sync"
         "unicode"
         "utf8"
 )
 
+const (
+        // Defaults used by HandleHTTP
+        DefaultRPCPath   = "/_goRPC_"
+        DefaultDebugPath = "/debug/rpc"
+)
+
 // Precompute the reflect type for os.Error.  Can't use os.Error directly
 // because Typeof takes an empty interface value.  This is annoying.
 var unusedError *os.Error
 var typeOfOsError = reflect.Typeof(unusedError).(*reflect.PtrType).Elem()
 
 type methodType struct {
         sync.Mutex // protects counters
         method     reflect.Method
         argType    *reflect.PtrType
         replyType  *reflect.PtrType
@@ skipping 23 matching lines @@
         Seq           uint64 // echoes that of the request
         Error         string // error, if any.
 }
 
 // ClientInfo records information about an RPC client connection.
 type ClientInfo struct {
         LocalAddr  string
         RemoteAddr string
 }
 
+// Server represents an RPC Server.
 type Server struct {
         sync.Mutex // protects the serviceMap
         serviceMap map[string]*service
 }
 
+// NewServer returns a new Server.
 func NewServer() *Server {
         return &Server{serviceMap: make(map[string]*service)}
 }
 
 // DefaultServer is the default instance of *Server.
 var DefaultServer = NewServer()
 
-// Is this a publicly visible - upper case - name?
-func isPublic(name string) bool {
+// Is this an exported - upper case - name?
+func isExported(name string) bool {
         rune, _ := utf8.DecodeRuneInString(name)
         return unicode.IsUpper(rune)
 }
 
 // Register publishes in the server the set of methods of the
 // receiver value that satisfy the following conditions:
-//      - public method

[rsc1, 2010/10/24 03:47:23]

s/public/exported/

-//      - two arguments, both pointers to public structs
-//      - one return value of type os.Error

[rsc1, 2010/10/24 03:47:23]

s/value/value,/

-// It returns an error if the receiver is not public or has no

[rsc1, 2010/10/24 03:47:23]

s/public/an exported type/.
I don't remember why that matters, actually.

+//      - exported method
+//      - two arguments, both pointers to exported structs
+//      - one return value, of type os.Error
+// It returns an error if the receiver is not an exported type or has no
 // suitable methods.
 func (server *Server) Register(rcvr interface{}) os.Error {
         server.Lock()
         defer server.Unlock()
         if server.serviceMap == nil {
                 server.serviceMap = make(map[string]*service)
         }
         s := new(service)
         s.typ = reflect.Typeof(rcvr)
         s.rcvr = reflect.NewValue(rcvr)
         sname := reflect.Indirect(s.rcvr).Type().Name()
         if sname == "" {
                 log.Exit("rpc: no service name for type", s.typ.String())
         }
-        if s.typ.PkgPath() != "" && !isPublic(sname) {

[rsc1, 2010/10/24 03:47:23]

i know it says public here but let's fix all these
to say exported.  that's the word in the spec, and
it has the side benefit of not being the word in C++ or Java.

-                s := "rpc Register: type " + sname + " is not public"
+        if s.typ.PkgPath() != "" && !isExported(sname) {
+                s := "rpc Register: type " + sname + " is not exported"
                 log.Print(s)
                 return os.ErrorString(s)
         }
         if _, present := server.serviceMap[sname]; present {
                 return os.ErrorString("rpc: service already defined: " + sname)
         }
         s.name = sname
         s.method = make(map[string]*methodType)
 
         // Install the methods
         for m := 0; m < s.typ.NumMethod(); m++ {
                 method := s.typ.Method(m)
                 mtype := method.Type
                 mname := method.Name
-                if mtype.PkgPath() != "" || !isPublic(mname) {
+                if mtype.PkgPath() != "" || !isExported(mname) {
                         continue
                 }
                 // Method needs three ins: receiver, *args, *reply.
                 if mtype.NumIn() != 3 {
                         log.Println("method", mname, "has wrong number of ins:", mtype.NumIn())
                         continue
                 }
                 argType, ok := mtype.In(1).(*reflect.PtrType)
                 if !ok {
                         log.Println(mname, "arg type not a pointer:", mtype.In(1))
                         continue
                 }
                 replyType, ok := mtype.In(2).(*reflect.PtrType)
                 if !ok {
                         log.Println(mname, "reply type not a pointer:", mtype.In(2))
                         continue
                 }
-                if argType.Elem().PkgPath() != "" && !isPublic(argType.Elem().Name()) {
-                        log.Println(mname, "argument type not public:", argType)
-                        continue
-                }
-                if replyType.Elem().PkgPath() != "" && !isPublic(replyType.Elem().Name()) {
-                        log.Println(mname, "reply type not public:", replyType)
+                if argType.Elem().PkgPath() != "" && !isExported(argType.Elem().Name()) {
+                        log.Println(mname, "argument type not exported:", argType)
+                        continue
+                }
+                if replyType.Elem().PkgPath() != "" && !isExported(replyType.Elem().Name()) {
+                        log.Println(mname, "reply type not exported:", replyType)
                         continue
                 }
                 if mtype.NumIn() == 4 {
                         t := mtype.In(3)
                         if t != reflect.Typeof((*ClientInfo)(nil)) {
                                 log.Println(mname, "last argument not *ClientInfo")
                                 continue
                         }
                 }
                 // Method needs one out: os.Error.
                 if mtype.NumOut() != 1 {
                         log.Println("method", mname, "has wrong number of outs:", mtype.NumOut())
                         continue
                 }
                 if returnType := mtype.Out(0); returnType != typeOfOsError {
                         log.Println("method", mname, "returns", returnType.String(), "not os.Error")
                         continue
                 }
                 s.method[mname] = &methodType{method: method, argType: argType, replyType: replyType}
         }
 
         if len(s.method) == 0 {
-                s := "rpc Register: type " + sname + " has no public methods of suitable type"
+                s := "rpc Register: type " + sname + " has no exported methods of suitable type"
                 log.Print(s)
                 return os.ErrorString(s)
         }
         server.serviceMap[s.name] = s
         return nil
 }
 
 // A value sent as a placeholder for the response when the server receives an invalid request.
 type InvalidRequest struct {
         marker int
@@ skipping 30 matching lines @@
         function := mtype.method.Func
         // Invoke the method, providing a new value for the reply.
         returnValues := function.Call([]reflect.Value{s.rcvr, argv, replyv})
         // The return value for the method is an os.Error.
         errInter := returnValues[0].Interface()
         errmsg := ""
         if errInter != nil {
                 errmsg = errInter.(os.Error).String()
         }
         sendResponse(sending, req, replyv.Interface(), codec, errmsg)
-}
-
-// A ServerCodec implements reading of RPC requests and writing of

[rsc1, 2010/10/24 03:47:23]

seems like a gratuitous move, but okay

-// RPC responses for the server side of an RPC session.
-// The server calls ReadRequestHeader and ReadRequestBody in pairs
-// to read requests from the connection, and it calls WriteResponse to
-// write a response back.  The server calls Close when finished with the
-// connection.
-type ServerCodec interface {
-        ReadRequestHeader(*Request) os.Error
-        ReadRequestBody(interface{}) os.Error
-        WriteResponse(*Response, interface{}) os.Error
-
-        Close() os.Error
 }
 
 type gobServerCodec struct {
         rwc io.ReadWriteCloser
         dec *gob.Decoder
         enc *gob.Encoder
 }
 
 func (c *gobServerCodec) ReadRequestHeader(r *Request) os.Error {
         return c.dec.Decode(r)
@@ skipping 86 matching lines @@
                 conn, err := lis.Accept()
                 if err != nil {
                         log.Exit("rpc.Serve: accept:", err.String()) // TODO(r): exit?
                 }
                 go server.ServeConn(conn)
         }
 }
 
 // Register publishes in the DefaultServer the set of methods·
 // of the receiver value that satisfy the following conditions:
-//      - public method
-//      - two arguments, both pointers to public structs
-//      - one return value of type os.Error
-// It returns an error if the receiver is not public or has no
+//      - exported method
+//      - two arguments, both pointers to exported structs
+//      - one return value, of type os.Error
+// It returns an error if the receiver is not an exported type or has no
 // suitable methods.
 func Register(rcvr interface{}) os.Error { return DefaultServer.Register(rcvr) }
+
+// A ServerCodec implements reading of RPC requests and writing of
+// RPC responses for the server side of an RPC session.
+// The server calls ReadRequestHeader and ReadRequestBody in pairs
+// to read requests from the connection, and it calls WriteResponse to
+// write a response back.  The server calls Close when finished with the
+// connection.
+type ServerCodec interface {
+        ReadRequestHeader(*Request) os.Error
+        ReadRequestBody(interface{}) os.Error
+        WriteResponse(*Response, interface{}) os.Error
+
+        Close() os.Error
+}
 
 // ServeConn runs the DefaultServer on a single connection.
 // ServeConn blocks, serving the connection until the client hangs up.
 // The caller typically invokes ServeConn in a go statement.
 // ServeConn uses the gob wire format (see package gob) on the
 // connection.  To use an alternate codec, use ServeCodec.
 func ServeConn(conn io.ReadWriteCloser) {
         DefaultServer.ServeConn(conn)
 }
 
 // ServeCodec is like ServeConn but uses the specified codec to
 // decode requests and encode responses.
 func ServeCodec(codec ServerCodec) {
         DefaultServer.ServeCodec(codec)
 }
 
 // Accept accepts connections on the listener and serves requests
 // to DefaultServer for each incoming connection.··
 // Accept blocks; the caller typically invokes it in a go statement.
 func Accept(lis net.Listener) { DefaultServer.Accept(lis) }
 
 // Can connect to RPC service using HTTP CONNECT to rpcPath.
-var rpcPath string = "/_goRPC_"
-var debugPath string = "/debug/rpc"
 var connected = "200 Connected to Go RPC"
 
 // ServeHTTP implements an http.Handler that answers RPC requests.

[rsc1, 2010/10/24 03:47:23]

Probably want to export rpcPath too?
And debugPath?

 func (server *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
         if req.Method != "CONNECT" {
                 w.SetHeader("Content-Type", "text/plain; charset=utf-8")
                 w.WriteHeader(http.StatusMethodNotAllowed)
-                io.WriteString(w, "405 must CONNECT to "+rpcPath+"\n")
+                io.WriteString(w, "405 must CONNECT\n")
                 return
         }
         conn, _, err := w.Hijack()
         if err != nil {
                 log.Print("rpc hijacking ", w.RemoteAddr(), ": ", err.String())
                 return
         }
         io.WriteString(conn, "HTTP/1.0 "+connected+"\n\n")
         server.ServeConn(conn)
 }
 
-// HandleHTTP registers an HTTP handler for RPC messages.
+// HandleHTTP registers an HTTP handler for RPC messages on rpcPath,
+// and a debugging handler on debugPath.
 // It is still necessary to invoke http.Serve(), typically in a go statement.
-func (server *Server) HandleHTTP() {
+func (server *Server) HandleHTTP(rpcPath, debugPath string) {
         http.Handle(rpcPath, server)
         http.Handle(debugPath, debugHTTP{server})
 }
 
-// HandleHTTP registers an HTTP handler for RPC messages to DefaultServer.
+// HandleHTTP registers an HTTP handler for RPC messages to DefaultServer
+// on DefaultRPCPath and a debugging handler on DefaultDebugPath.
 // It is still necessary to invoke http.Serve(), typically in a go statement.
 func HandleHTTP() {
-        DefaultServer.HandleHTTP()
-}
+        DefaultServer.HandleHTTP(DefaultRPCPath, DefaultDebugPath)
+}