code: func (c cols2HandleSlice) findHandle(ordinal int32) (int32, bool) {
  	if c == nil || len(c) == 0 {
  		return 0, false
  	}
  	// find the smallest index of the range that its start great than ordinal.
  	// @see https://godoc.org/sort#Search
  	rangeBehindOrdinal := sort.Search(len(c), func(i int) bool { return c[i].start > ordinal })
  	if rangeBehindOrdinal == 0 {
  		return 0, false
  	}
  	return c[rangeBehindOrdinal-1].handleOrdinal, true
  }
docs: // findHandle finds the ordinal of the corresponding handle column.