The number of lines used is updated in the header when a value is set,

and the iteration on the values of a column is done on the number of
lines used (instead of on the total line count).

src/obidmscolumn.c

@@ -1089,6 +1089,12 @@ size_t obi_column_get_line_count(OBIDMS_column_p column)
 }
 
 
+size_t obi_column_get_nb_lines_used(OBIDMS_column_p column)
+{
+	return (column->header)->lines_used;
+}
+
+
 OBIType_t obi_column_get_data_type(OBIDMS_column_p column)
 {
 	return (column->header)->data_type;