Merge pull request #150 from ehotinger/ehotinger/fs

Adds a file system helper file for determining the file system type.

pkg/fs/fs_windows.go

@@ -0,0 +1,42 @@
+package fs
+
+import (
+	"errors"
+	"path/filepath"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// GetFileSystemType obtains the type of a file system through GetVolumeInformation.
+// https://msdn.microsoft.com/en-us/library/windows/desktop/aa364993(v=vs.85).aspx
+func GetFileSystemType(path string) (fsType string, hr error) {
+	drive := filepath.VolumeName(path)
+	if len(drive) != 2 {
+		return "", errors.New("getFileSystemType path must start with a drive letter")
+	}
+
+	var (
+		modkernel32              = windows.NewLazySystemDLL("kernel32.dll")
+		procGetVolumeInformation = modkernel32.NewProc("GetVolumeInformationW")
+		buf                      = make([]uint16, 255)
+		size                     = windows.MAX_PATH + 1
+	)
+	drive += `\`
+	n := uintptr(unsafe.Pointer(nil))
+	r0, _, _ := syscall.Syscall9(procGetVolumeInformation.Addr(), 8, uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(drive))), n, n, n, n, n, uintptr(unsafe.Pointer(&buf[0])), uintptr(size), 0)
+	if int32(r0) < 0 {
+		hr = syscall.Errno(win32FromHresult(r0))
+	}
+	fsType = windows.UTF16ToString(buf)
+	return
+}
+
+// win32FromHresult is a helper function to get the win32 error code from an HRESULT.
+func win32FromHresult(hr uintptr) uintptr {
+	if hr&0x1fff0000 == 0x00070000 {
+		return hr & 0xffff
+	}
+	return hr
+}