os: windows Rename should overwrite destination file.

Rename now uses MoveFileEx which was previously not available to
use because it is not supported on Windows 2000.

Change-Id: I583d029c4467c9be6d1574a790c423559b441e87
Reviewed-on: https://go-review.googlesource.com/6140
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/internal/syscall/windows/syscall_windows.go

@@ -95,8 +95,8 @@ const (
 )
 
 //sys GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizeOfPointer *uint32) (errcode error) = iphlpapi.GetAdaptersAddresses
-
 //sys	GetComputerNameEx(nameformat uint32, buf *uint16, n *uint32) (err error) = GetComputerNameExW
+//sys	MoveFileEx(from *uint16, to *uint16, flags uint32) (err error) = MoveFileExW
 
 const (
 	ComputerNameNetBIOS                   = 0
@@ -108,4 +108,23 @@ const (
 	ComputerNamePhysicalDnsDomain         = 6
 	ComputerNamePhysicalDnsFullyQualified = 7
 	ComputerNameMax                       = 8
+
+	MOVEFILE_REPLACE_EXISTING      = 0x1
+	MOVEFILE_COPY_ALLOWED          = 0x2
+	MOVEFILE_DELAY_UNTIL_REBOOT    = 0x4
+	MOVEFILE_WRITE_THROUGH         = 0x8
+	MOVEFILE_CREATE_HARDLINK       = 0x10
+	MOVEFILE_FAIL_IF_NOT_TRACKABLE = 0x20
 )
+
+func Rename(oldpath, newpath string) error {
+	from, err := syscall.UTF16PtrFromString(oldpath)
+	if err != nil {
+		return err
+	}
+	to, err := syscall.UTF16PtrFromString(newpath)
+	if err != nil {
+		return err
+	}
+	return MoveFileEx(from, to, MOVEFILE_REPLACE_EXISTING)
+}

src/internal/syscall/windows/zsyscall_windows.go

@@ -13,6 +13,7 @@ var (
 
 	procGetAdaptersAddresses = modiphlpapi.NewProc("GetAdaptersAddresses")
 	procGetComputerNameExW   = modkernel32.NewProc("GetComputerNameExW")
+	procMoveFileExW          = modkernel32.NewProc("MoveFileExW")
 )
 
 func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizeOfPointer *uint32) (errcode error) {
@@ -34,3 +35,15 @@ func GetComputerNameEx(nameformat uint32, buf *uint16, n *uint32) (err error) {
 	}
 	return
 }
+
+func MoveFileEx(from *uint16, to *uint16, flags uint32) (err error) {
+	r1, _, e1 := syscall.Syscall(procMoveFileExW.Addr(), 3, uintptr(unsafe.Pointer(from)), uintptr(unsafe.Pointer(to)), uintptr(flags))
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}

src/os/file_posix.go

@@ -28,14 +28,6 @@ func Readlink(name string) (string, error) {
 	}
 }
 
-func rename(oldname, newname string) error {
-	e := syscall.Rename(oldname, newname)
-	if e != nil {
-		return &LinkError{"rename", oldname, newname, e}
-	}
-	return nil
-}
-
 // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
 func syscallMode(i FileMode) (o uint32) {
 	o |= uint32(i.Perm())

src/os/file_unix.go

@@ -12,6 +12,14 @@ import (
 	"syscall"
 )
 
+func rename(oldname, newname string) error {
+	e := syscall.Rename(oldname, newname)
+	if e != nil {
+		return &LinkError{"rename", oldname, newname, e}
+	}
+	return nil
+}
+
 // File represents an open file descriptor.
 type File struct {
 	*file

src/os/file_windows.go

@@ -5,6 +5,7 @@
 package os
 
 import (
+	"internal/syscall/windows"
 	"io"
 	"runtime"
 	"sync"
@@ -460,6 +461,14 @@ func Remove(name string) error {
 	return &PathError{"remove", name, e}
 }
 
+func rename(oldname, newname string) error {
+	e := windows.Rename(oldname, newname)
+	if e != nil {
+		return &LinkError{"rename", oldname, newname, e}
+	}
+	return nil
+}
+
 // Pipe returns a connected pair of Files; reads from r return bytes written to w.
 // It returns the files and an error, if any.
 func Pipe() (r *File, w *File, err error) {

src/os/os_test.go

@@ -708,13 +708,16 @@ func TestRename(t *testing.T) {
 		defer chtmpdir(t)()
 	}
 	from, to := "renamefrom", "renameto"
-	Remove(to) // Just in case.
+	// Ensure we are not testing the overwrite case here.
+	Remove(from)
+	Remove(to)
+
 	file, err := Create(from)
 	if err != nil {
-		t.Fatalf("open %q failed: %v", to, err)
+		t.Fatalf("open %q failed: %v", from, err)
 	}
 	if err = file.Close(); err != nil {
-		t.Errorf("close %q failed: %v", to, err)
+		t.Errorf("close %q failed: %v", from, err)
 	}
 	err = Rename(from, to)
 	if err != nil {
@@ -727,6 +730,52 @@ func TestRename(t *testing.T) {
 	}
 }
 
+func TestRenameOverwriteDest(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping on plan9")
+	}
+	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm" {
+		defer chtmpdir(t)()
+	}
+	from, to := "renamefrom", "renameto"
+	// Just in case.
+	Remove(from)
+	Remove(to)
+
+	toData := []byte("to")
+	fromData := []byte("from")
+
+	err := ioutil.WriteFile(to, toData, 0777)
+	if err != nil {
+		t.Fatalf("write file %q failed: %v", to, err)
+	}
+
+	err = ioutil.WriteFile(from, fromData, 0777)
+	if err != nil {
+		t.Fatalf("write file %q failed: %v", from, err)
+	}
+	err = Rename(from, to)
+	if err != nil {
+		t.Fatalf("rename %q, %q failed: %v", to, from, err)
+	}
+	defer Remove(to)
+
+	_, err = Stat(from)
+	if err == nil {
+		t.Errorf("from file %q still exists", from)
+	}
+	if err != nil && !IsNotExist(err) {
+		t.Fatalf("stat from: %v", err)
+	}
+	toFi, err := Stat(to)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", to, err)
+	}
+	if toFi.Size() != int64(len(fromData)) {
+		t.Errorf(`"to" size = %d; want %d (old "from" size)`, toFi.Size(), len(fromData))
+	}
+}
+
 func exec(t *testing.T, dir, cmd string, args []string, expect string) {
 	r, w, err := Pipe()
 	if err != nil {