code: private String getFilenameInVfs(File res) {
  
          String resname = res.getAbsolutePath();
          if (res.isDirectory()) {
              resname += "/";
          }
          // translate the folder separator if necessary
          resname = resname.replace(File.separatorChar, '/');
          return resname.substring(m_destinationPathInRfs.length());
      }
docs: Gets the corresponding filename of the VFS to a resource in the FS. <p>
  
  @param res the resource in the FS
  @return the corresponding filename in the VFS