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.h

@@ -243,6 +243,19 @@ void obi_column_make_unwritable(OBIDMS_column_p column);
 size_t obi_column_get_line_count(OBIDMS_column_p column);
 
 
+/**
+ * @brief Recovers the number of lines used in an OBIDMS column.
+ *
+ * @param column a pointer on an OBIDMS column
+ *
+ * @return the number of lines used in the column
+ *
+ * @since August 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+size_t obi_column_get_nb_lines_used(OBIDMS_column_p column);
+
+
 /**
  * @brief Recovers the data type of an OBIDMS column.
  *