code: @Beta
      public boolean hasValidPointer(DataDirectoryKey dataDirKey) {
          DataDirEntry dataDir = optHeader.getDataDirectory().get(dataDirKey);
          long rva = dataDir.getVirtualAddress();
          long offset = getFileOffset(rva);
          return offset <= file.length() && offset >= 0;
      }
docs: Returns whether the virtual address of the data directory entry is valid.
  TODO remove
  
  @param dataDirKey
  @return true iff virtual address is valid