package mount
 
 import (

 	"golang.org/x/sys/unix"

 )
 

 const (
 	// ptypes is the set propagation types.

 	ptypes = unix.MS_SHARED | unix.MS_PRIVATE | unix.MS_SLAVE | unix.MS_UNBINDABLE

 
 	// pflags is the full set valid flags for a change propagation call.

 	pflags = ptypes | unix.MS_REC | unix.MS_SILENT

 
 	// broflags is the combination of bind and read only

 	broflags = unix.MS_BIND | unix.MS_RDONLY

 )
 
 // isremount returns true if either device name or flags identify a remount request, false otherwise.
 func isremount(device string, flags uintptr) bool {
 	switch {
 	// We treat device "" and "none" as a remount request to provide compatibility with
 	// requests that don't explicitly set MS_REMOUNT such as those manipulating bind mounts.

 	case flags&unix.MS_REMOUNT != 0, device == "", device == "none":

 		return true
 	default:
 		return false
 	}
 }
 
 func mount(device, target, mType string, flags uintptr, data string) error {
 	oflags := flags &^ ptypes

 	if !isremount(device, flags) || data != "" {
 		// Initial call applying all non-propagation flags for mount
 		// or remount with changed data

 		if err := unix.Mount(device, target, mType, oflags, data); err != nil {

 			return err
 		}

 	}
 

 	if flags&ptypes != 0 {
 		// Change the propagation type.

 		if err := unix.Mount("", target, "", flags&pflags, ""); err != nil {

 			return err
 		}

 	}

 
 	if oflags&broflags == broflags {
 		// Remount the bind to apply read only.

 		return unix.Mount("", target, "", oflags|unix.MS_REMOUNT, "")

 	}
 

 	return nil

 }
 
 func unmount(target string, flag int) error {

 	return unix.Unmount(target, flag)

 }