add windows support

file_unix.go

@@ -0,0 +1,14 @@
+// +build !windows
+
+package write
+
+import (
+	"os"
+)
+
+// replaceFile atomically replaces the destination file or directory with the
+// source.  It is guaranteed to either replace the target file entirely, or not
+// change either file.
+func replaceFile(source, destination string) error {
+	return os.Rename(source, destination)
+}

file_windows.go

@@ -0,0 +1,33 @@
+package write
+
+import (
+	"os"
+	"syscall"
+)
+
+const (
+	movefile_replace_existing = 0x1
+	movefile_write_through    = 0x8
+)
+
+//sys moveFileEx(lpExistingFileName *uint16, lpNewFileName *uint16, dwFlags uint32) (err error) = MoveFileExW
+
+// replaceFile atomically replaces the destination file or directory with the
+// source.  It is guaranteed to either replace the target file entirely, or not
+// change either file.
+func replaceFile(source, destination string) error {
+	src, err := syscall.UTF16PtrFromString(source)
+	if err != nil {
+		return &os.LinkError{"replace", source, destination, err}
+	}
+	dest, err := syscall.UTF16PtrFromString(destination)
+	if err != nil {
+		return &os.LinkError{"replace", source, destination, err}
+	}
+
+	// see http://msdn.microsoft.com/en-us/library/windows/desktop/aa365240(v=vs.85).aspx
+	if err := moveFileEx(src, dest, movefile_replace_existing|movefile_write_through); err != nil {
+		return &os.LinkError{"replace", source, destination, err}
+	}
+	return nil
+}

tempfile.go

@@ -64,7 +64,7 @@ func tempDir(dir, dest string) string {
 	defer os.Remove(testdest.Name())
 	testdest.Close()
 
-	if err := os.Rename(testsrc.Name(), testdest.Name()); err != nil {
+	if err := replaceFile(testsrc.Name(), testdest.Name()); err != nil {
 		return fallback
 	}
 	cleanup = false // testsrc no longer exists
@@ -119,7 +119,7 @@ func (t *PendingFile) CloseAtomicallyReplace() error {
 	if err := t.Close(); err != nil {
 		return err
 	}
-	if err := os.Rename(t.Name(), t.path); err != nil {
+	if err := replaceFile(t.Name(), t.path); err != nil {
 		return err
 	}
 	t.done = true
@@ -164,7 +164,7 @@ func Symlink(oldname, newname string) error {
 		return err
 	}
 
-	if err := os.Rename(symlink, newname); err != nil {
+	if err := replaceFile(symlink, newname); err != nil {
 		return err
 	}
 

zfile_windows.go

@@ -0,0 +1,27 @@
+// mksyscall_windows -l32 file_windows.go
+// MACHINE GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
+
+package write
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var (
+	modkernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+	procMoveFileExW = modkernel32.NewProc("MoveFileExW")
+)
+
+func moveFileEx(lpExistingFileName *uint16, lpNewFileName *uint16, dwFlags uint32) (err error) {
+	r1, _, e1 := syscall.Syscall(procMoveFileExW.Addr(), 3, uintptr(unsafe.Pointer(lpExistingFileName)), uintptr(unsafe.Pointer(lpNewFileName)), uintptr(dwFlags))
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}