docs: protected int getFreeSpace()
      {
          if (tc.isEntryEnabled())
              Tr.entry(tc, "getFreeSpace", this);
  
          final int freeBytes = _activeFile.freeBytes();
  
          if (tc.isEntryEnabled())
              Tr.exit(tc, "getFreeSpace", freeBytes);
  
          return freeBytes;
      }