New OBIDMS method to list the columns of an OBIDMS

src/obidmscolumn.c

@@ -1347,13 +1347,99 @@ OBIType_t obi_column_get_data_type_from_name(OBIDMS_p dms, const char* column_na
 }
 
 
+size_t obi_column_get_line_count_from_name(OBIDMS_p dms, const char* column_name)
+{
+	OBIDMS_column_header_p 		header;
+	OBIDMS_column_directory_p	column_directory;
+	char* 						column_file_name;
+	int 						column_file_descriptor;
+	int							column_dir_file_descriptor;
+	size_t 						header_size;
+	size_t						line_count;
+	obiversion_t	   			version_number;
+
+	// Get the column directory structure associated to the column
+	column_directory = obi_open_column_directory(dms, column_name);
+	if (column_directory == NULL)
+	{
+		obidebug(1, "\nError opening a column directory structure");
+		return -1;
+	}
+
+	// Get the file descriptor associated to the column directory
+	column_dir_file_descriptor = dirfd(column_directory->directory);
+	if (column_dir_file_descriptor < 0)
+	{
+		obi_set_errno(OBICOLDIR_UNKNOWN_ERROR);
+		obidebug(1, "\nError getting the file descriptor of a column directory");
+		obi_close_column_directory(column_directory);
+		return -1;
+	}
+
+	// Calculate the header size
+	header_size = obi_get_platform_header_size();
+
+	// Get the latest version number
+	version_number = obi_get_latest_version_number(column_directory);
+	if (version_number < 0)
+	{
+		obidebug(1, "\nError getting the latest version number in a column directory");
+		return -1;
+	}
+
+	// Get the column file name
+	column_file_name = build_column_file_name(column_name, version_number);
+	if (column_file_name == NULL)
+	{
+		return -1;
+	}
+
+	// Open the column file (READ-ONLY)
+	column_file_descriptor = openat(column_dir_file_descriptor, column_file_name, O_RDONLY);
+	if (column_file_descriptor < 0)
+	{
+		obidebug(1, "\nError opening a column file");
+		obi_set_errno(OBICOL_UNKNOWN_ERROR);
+		free(column_file_name);
+		return -1;
+	}
+
+	// Fill the header structure
+	header = mmap(NULL,
+			 header_size,
+			 PROT_READ,
+			 MAP_SHARED,
+			 column_file_descriptor,
+			 0
+			 );
+
+	if (header == MAP_FAILED)
+	{
+		obi_set_errno(OBICOL_UNKNOWN_ERROR);
+		obidebug(1, "\nError mmapping the header of a column");
+		close(column_file_descriptor);
+		free(column_file_name);
+		return -1;
+	}
+
+	// Check endianness?
+
+	line_count = header->line_count;
+
+	free(column_file_name);
+	close(column_file_descriptor);
+	munmap(header, header_size);
+	return line_count;
+}
+
+
 const char* obi_column_get_elements_names(OBIDMS_column_p column)
 {
 	return (column->header)->elements_names;
 }
 
 
-// to be rewritten in an optimized and safe way
+// TODO to be rewritten in an optimized and safe way
 size_t obi_column_get_element_index_from_name(OBIDMS_column_p column, const char* element_name)
 {
 	char* elements_names;