internal/poll: make FD.isFile mean whether it isn't socket on Windows

Before this change, if a directory was closed twice on Windows,
the returning error would be "use of closed network connection".

Some code assumes FD.isFile means whether the fd isn't a network
socket, which is true on Unix. But isFile reports whether
the fd is a normal file rather than directory or console on Windows.

With this change, isFile will have the same meaning on different
platforms. And the change adds a new field kind to replace isConsole
and isDir.

Change-Id: Ib12265f1e12fa3d0239ae925291128a84be59cc2
GitHub-Last-Rev: 3f031756de6ce0b96c1f102ad280950f4adbf6c2
GitHub-Pull-Request: golang/go#30589
Reviewed-on: https://go-review.googlesource.com/c/go/+/165257
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/internal/poll/fd_windows.go

@@ -309,7 +309,6 @@ type FD struct {
 	l sync.Mutex
 
 	// For console I/O.
-	isConsole      bool
 	lastbits       []byte   // first few bytes of the last incomplete rune in last write
 	readuint16     []uint16 // buffer to hold uint16s obtained with ReadConsole
 	readbyte       []byte   // buffer to hold decoding of readuint16 from utf16 to utf8
@@ -328,13 +327,23 @@ type FD struct {
 	// message based socket connection.
 	ZeroReadIsEOF bool
 
-	// Whether this is a normal file.
+	// Whether this is a file rather than a network socket.
 	isFile bool
 
-	// Whether this is a directory.
-	isDir bool
+	// The kind of this file.
+	kind fileKind
 }
 
+// fileKind describes the kind of file.
+type fileKind byte
+
+const (
+	kindNet fileKind = iota
+	kindFile
+	kindConsole
+	kindDir
+)
+
 // logInitFD is set by tests to enable file descriptor initialization logging.
 var logInitFD func(net string, fd *FD, err error)
 
@@ -350,18 +359,20 @@ func (fd *FD) Init(net string, pollable bool) (string, error) {
 
 	switch net {
 	case "file":
-		fd.isFile = true
+		fd.kind = kindFile
 	case "console":
-		fd.isConsole = true
+		fd.kind = kindConsole
 	case "dir":
-		fd.isDir = true
-	case "tcp", "tcp4", "tcp6":
-	case "udp", "udp4", "udp6":
-	case "ip", "ip4", "ip6":
-	case "unix", "unixgram", "unixpacket":
+		fd.kind = kindDir
+	case "tcp", "tcp4", "tcp6",
+		"udp", "udp4", "udp6",
+		"ip", "ip4", "ip6",
+		"unix", "unixgram", "unixpacket":
+		fd.kind = kindNet
 	default:
 		return "", errors.New("internal error: unknown network type " + net)
 	}
+	fd.isFile = fd.kind != kindNet
 
 	var err error
 	if pollable {
@@ -430,13 +441,14 @@ func (fd *FD) destroy() error {
 	// so this must be executed before fd.CloseFunc.
 	fd.pd.close()
 	var err error
-	if fd.isFile || fd.isConsole {
-		err = syscall.CloseHandle(fd.Sysfd)
-	} else if fd.isDir {
-		err = syscall.FindClose(fd.Sysfd)
-	} else {
+	switch fd.kind {
+	case kindNet:
 		// The net package uses the CloseFunc variable for testing.
 		err = CloseFunc(fd.Sysfd)
+	case kindDir:
+		err = syscall.FindClose(fd.Sysfd)
+	default:
+		err = syscall.CloseHandle(fd.Sysfd)
 	}
 	fd.Sysfd = syscall.InvalidHandle
 	runtime_Semrelease(&fd.csema)
@@ -485,12 +497,13 @@ func (fd *FD) Read(buf []byte) (int, error) {
 
 	var n int
 	var err error
-	if fd.isFile || fd.isDir || fd.isConsole {
+	if fd.isFile {
 		fd.l.Lock()
 		defer fd.l.Unlock()
-		if fd.isConsole {
+		switch fd.kind {
+		case kindConsole:
 			n, err = fd.readConsole(buf)
-		} else {
+		default:
 			n, err = syscall.Read(fd.Sysfd, buf)
 		}
 		if err != nil {
@@ -669,12 +682,13 @@ func (fd *FD) Write(buf []byte) (int, error) {
 		}
 		var n int
 		var err error
-		if fd.isFile || fd.isDir || fd.isConsole {
+		if fd.isFile {
 			fd.l.Lock()
 			defer fd.l.Unlock()
-			if fd.isConsole {
+			switch fd.kind {
+			case kindConsole:
 				n, err = fd.writeConsole(b)
-			} else {
+			default:
 				n, err = syscall.Write(fd.Sysfd, b)
 			}
 			if err != nil {

src/os/os_test.go

@@ -2279,8 +2279,7 @@ func TestPipeThreads(t *testing.T) {
 	}
 }
 
-func TestDoubleCloseError(t *testing.T) {
-	path := sfdir + "/" + sfname
+func testDoubleCloseError(t *testing.T, path string) {
 	file, err := Open(path)
 	if err != nil {
 		t.Fatal(err)
@@ -2299,6 +2298,11 @@ func TestDoubleCloseError(t *testing.T) {
 	}
 }
 
+func TestDoubleCloseError(t *testing.T) {
+	testDoubleCloseError(t, filepath.Join(sfdir, sfname))
+	testDoubleCloseError(t, sfdir)
+}
+
 func TestUserHomeDir(t *testing.T) {
 	dir, err := UserHomeDir()
 	if dir == "" && err == nil {