code: func (tf tFiles) getRange(icmp *iComparer) (imin, imax internalKey) {
  	for i, t := range tf {
  		if i == 0 {
  			imin, imax = t.imin, t.imax
  			continue
  		}
  		if icmp.Compare(t.imin, imin) < 0 {
  			imin = t.imin
  		}
  		if icmp.Compare(t.imax, imax) > 0 {
  			imax = t.imax
  		}
  	}
  
  	return
  }
docs: // Returns tables key range.