status.i4.v = sr_snapshot_header_c(device_index.i4.v, data_source.i4.v,
					   file_number.i4.v [,case_number.i4.v]

	This routine returns information about a snapshot taken by either
	SDA or the detached snapshot manager.

	device_index	device index
	data_source	source of data
			(SRMNGR_SDA_DATA -> SDA data,
			 SRMNGR_SNAP_DATA -> detached snapshot manager data,
			 CLIB_DEFAULT_ARG -> last selected data source)
	file_number	file number from which to retrieve data
			(This is the subsystem number or user key 1 for
			 detached snapshot manager data.)
	[case_number]	SDA case number  (This is the record number or
			user key 2 for detached snapshot data.)
			(default is SDA_DEFAULT_CASE_NUMBER for SDA data and
			 0 for detached snapshot data)
	[snapshot_info]	returned snapshot information
			(structure of type SR_SNAPSHOT_HEADER)
			(default is NULL)
	[subcase_num]	SDA subcase number (This argument only
			has meaning if the data source is SDA.)
	[sda_usage]	null terminated SDA usage string (This argument only
			has meaning if the data source is SDA.)
			(default is NULL which results in Collider shot access)

	This function returns status values as follows:

	OK			success
	DIO_BADARG		invalid data source or case number
	DIO_MEMFAIL		memory allocation failure
	DIO_INVLEN		too much data requested

	This function requires the following include files:

	cbslib_h, cns_data_structs_h, acnet_errors_h

	Related functions:

	sr_snapshot_info_c, sr_snapshot_info_list_c, sr_get_snapshot_c,
	sr_read_snapshot_c, sr_sda_snapshot_stats_c, sr_snap_directory_info_c,
	sr_snap_date_to_file_info_c, sr_snap_active_devices_c, sr_set_source_c,
	sr_get_device_c, sr_get_device_raw_c, sr_data_length_c,
	sr_sda_cases_present_c, sr_sda_num_subcases_c,
	sr_sda_subcases_present_c, sr_sda_case_times_c, sr_disconnect

	C/C++ usage:

	char	*sda_usage = (char *) NULL;
	int	status;
	int	device_index = 27235;
	int	data_source = SRMNGR_SDA_DATA;
	int	file_number = 0;
	int	case_number = SDA_DEFAULT_CASE_NUMBER;
	int	subcase_num = SDA_DEFAULT_SUBCASE_NUMBER;
	SR_SNAPSHOT_HEADER	snapshot_info;

	status = sr_snapshot_header_c(device_index,data_source,file_number,