General server cleanups (#103)

- no need to initalise mutexes, their zero value is valid
- make NewServer simpler, 90% of use cases already had an
  io.ReadWriteCloser, in the single case that it it is easy to provide a
  simple wrapper.

client_integration_test.go

@@ -99,11 +99,12 @@ func testClientGoSvr(t testing.TB, readonly bool, delay time.Duration) (*Client,
 		options = append(options, ReadOnly())
 	}
 
-	server, err := NewServer(
-		txPipeRd,
-		rxPipeWr,
-		options...,
-	)
+	rwc := struct {
+		io.Reader
+		io.WriteCloser
+	}{txPipeRd, rxPipeWr}
+
+	server, err := NewServer(rwc, options...)
 	if err != nil {
 		t.Fatal(err)
 	}

examples/sftp-server/main.go

@@ -119,7 +119,6 @@ func main() {
 		}(requests)
 
 		server, err := sftp.NewServer(
-			channel,
 			channel,
 			sftp.WithDebug(debugStream),
 			sftp.ReadOnly(),

server.go

@@ -28,16 +28,15 @@ const (
 type Server struct {
 	in            io.Reader
 	out           io.WriteCloser
-	outMutex      *sync.Mutex
+	outMutex      sync.Mutex
 	debugStream   io.Writer
 	readOnly      bool
 	lastID        uint32
 	pktChan       chan rxPacket
 	openFiles     map[string]*os.File
-	openFilesLock *sync.RWMutex
+	openFilesLock sync.RWMutex
 	handleCount   int
 	maxTxPacket   uint32
-	workerCount   int
 }
 
 func (svr *Server) nextHandle(f *os.File) string {
@@ -78,17 +77,14 @@ type serverRespondablePacket interface {
 // functions may be specified to further configure the Server.
 //
 // A subsequent call to Serve() is required to begin serving files over SFTP.
-func NewServer(in io.Reader, out io.WriteCloser, options ...ServerOption) (*Server, error) {
+func NewServer(rwc io.ReadWriteCloser, options ...ServerOption) (*Server, error) {
 	s := &Server{
-		in:            in,
-		out:           out,
-		outMutex:      &sync.Mutex{},
-		debugStream:   ioutil.Discard,
-		pktChan:       make(chan rxPacket, sftpServerWorkerCount),
-		openFiles:     map[string]*os.File{},
-		openFilesLock: &sync.RWMutex{},
-		maxTxPacket:   1 << 15,
-		workerCount:   sftpServerWorkerCount,
+		in:          rwc.(io.Reader),
+		out:         rwc.(io.WriteCloser),
+		debugStream: ioutil.Discard,
+		pktChan:     make(chan rxPacket, sftpServerWorkerCount),
+		openFiles:   make(map[string]*os.File),
+		maxTxPacket: 1 << 15,
 	}
 
 	for _, o := range options {
@@ -233,10 +229,10 @@ func (svr *Server) sftpServerWorker(doneChan chan error) {
 func (svr *Server) Serve() error {
 	go svr.rxPackets()
 	doneChan := make(chan error)
-	for i := 0; i < svr.workerCount; i++ {
+	for i := 0; i < sftpServerWorkerCount; i++ {
 		go svr.sftpServerWorker(doneChan)
 	}
-	for i := 0; i < svr.workerCount; i++ {
+	for i := 0; i < sftpServerWorkerCount; i++ {
 		if err := <-doneChan; err != nil {
 			// abort early and shut down the session on un-decodable packets
 			break

server_integration_test.go

@@ -295,7 +295,6 @@ func (chsvr *sshSessionChannelServer) handleSubsystem(req *ssh.Request) error {
 	}
 
 	sftpServer, err := NewServer(
-		chsvr.ch,
 		chsvr.ch,
 		WithDebug(sftpServerDebugStream),
 	)

server_standalone/main.go

@@ -6,6 +6,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
 
@@ -28,8 +29,12 @@ func main() {
 	}
 
 	svr, _ := sftp.NewServer(
-		os.Stdin,
-		os.Stdout,
+		struct {
+			io.Reader
+			io.WriteCloser
+		}{os.Stdin,
+			os.Stdout,
+		},
 		sftp.WithDebug(debugStream),
 		sftp.ReadOnly(),
 	)