nep.h File Reference

NetCDF Extension Pack (NEP) - Public API. More...

#include <stdio.h>
#include <netcdf.h>
#include <netcdf_filter.h>

Go to the source code of this file.

Macros
#define	BZIP2_ID   307
#define	LZ4_ID   32004
#define	LZF_ID   32000
#define	NEP_UDF_GEOTIFF_BIGTIFF   NC_UDF0
#define	NEP_UDF_GEOTIFF_STANDARD   NC_UDF1
#define	NEP_UDF_GRIB2   NC_UDF2
#define	NEP_UDF_CDF   NC_UDF4
#define	NEP_UDF_FITS   NC_UDF3
#define	NEP_UDF_PDS4   NC_UDF5
#define	NEP_MAGIC_GEOTIFF_STANDARD   "II*"
#define	NEP_MAGIC_GEOTIFF_BIGTIFF   "II+"
#define	NEP_MAGIC_CDF   "\xCD\xF3\x00\x01"
#define	NEP_MAGIC_GRIB2   "GRIB"
#define	NEP_MAGIC_FITS   "SIMPLE"
#define	NEP_MAGIC_PDS4   "<?xml"
#define	NEP_FORMAT_NAME_GEOTIFF   "GeoTIFF"
#define	NEP_FORMAT_NAME_CDF   "NASA CDF"
#define	NEP_FORMAT_NAME_GRIB2   "GRIB2"
#define	NEP_FORMAT_NAME_FITS   "FITS"
#define	NEP_FORMAT_NAME_PDS4   "PDS4"

Functions
int	nc_def_var_bzip2 (int ncid, int varid, int level)
int	nc_inq_var_bzip2 (int ncid, int varid, int *bzip2p, int *levelp)
int	nc_def_var_lz4 (int ncid, int varid, int level)
int	nc_inq_var_lz4 (int ncid, int varid, int *lz4p, int *levelp)
int	nc_def_var_lzf (int ncid, int varid)
int	nc_inq_var_lzf (int ncid, int varid, int *lzfp)

Detailed Description

NetCDF Extension Pack (NEP) - Public API.

Defines compression filter IDs and API, and the centralized mapping of file formats to NetCDF User-Defined Format (UDF) slot numbers.

UDF Slot Allocation

NetCDF-C 4.10.0+ provides 10 UDF slots (UDF0-UDF9):

• UDF0: GeoTIFF BigTIFF (magic: "II+")
• UDF1: GeoTIFF standard TIFF (magic: "II*")
• UDF2: GRIB2 meteorological data (magic: "GRIB")
• UDF3: FITS astronomical data (magic: "SIMPLE")
• UDF4: NASA CDF format (magic: 0xCDF30001)
• UDF5: PDS4 planetary data system (magic: "<?xml")
• UDF6-UDF9: Reserved for future use

Author

Edward Hartnett

Date

Nov 13, 2025

Copyright

Intelligent Data Design, Inc. All rights reserved.

Macro Definition Documentation

BZIP2_ID

#define BZIP2_ID   307

The filter ID for BZIP2 compression.

LZ4_ID

#define LZ4_ID   32004

The filter ID for LZ4 compression.

LZF_ID

#define LZF_ID   32000

The filter ID for LZF compression.

Function Documentation

nc_def_var_bzip2()

int nc_def_var_bzip2	(	int	ncid,
		int	varid,
		int	level
	)

nep supports compression filters for netCDF/HDF5 files which are not natively supported by the netCDF C library.

BZIP2

Bzip2 is a free and open-source file compression program that uses the Burrows–Wheeler algorithm. For more information see https://www.sourceware.org/bzip2/ and https://en.wikipedia.org/wiki/Bzip2.

In C:

• nc_def_var_bzip2()
• nc_inq_var_bzip2()

In Fortran:

• nf90_def_var_bzip2()
• nf90_inq_var_bzip2() Turn on bzip2 compression for a variable.

Parameters

ncid	File ID.
varid	Variable ID.
level	From 1 to 9. Set the block size to 100k, 200k ... 900k when compressing. (bzip2 default level is 9).

Returns

0 for success, error code otherwise.

Author

Edward Hartnett

nc_def_var_lz4()

int nc_def_var_lz4	(	int	ncid,
		int	varid,
		int	level
	)

Turn on lz4 compression for a variable.

Parameters

ncid	File ID.
varid	Variable ID.
level	From 1 to 9. Set the block size to 100k, 200k ... 900k when compressing. (lz4 default level is 9).

Returns

0 for success, error code otherwise.

Author

Edward Hartnett

nc_def_var_lzf()

int nc_def_var_lzf	(	int	ncid,
		int	varid
	)

nc_inq_var_bzip2()

int nc_inq_var_bzip2	(	int	ncid,
		int	varid,
		int *	bzip2p,
		int *	levelp
	)

Learn whether bzip2 compression is on for a variable, and, if so, the level setting.

Parameters

ncid	File ID.
varid	Variable ID.
bzip2p	Pointer that gets a 0 if bzip2 is not in use for this var, and a 1 if it is. Ignored if NULL.
levelp	Pointer that gets the level setting (from 1 to 9), if bzip2 is in use. Ignored if NULL.

Returns

0 for success, error code otherwise.

Author

Edward Hartnett

nc_inq_var_lz4()

int nc_inq_var_lz4	(	int	ncid,
		int	varid,
		int *	lz4p,
		int *	levelp
	)

Learn whether lz4 compression is on for a variable, and, if so, the level setting.

Parameters

ncid	File ID.
varid	Variable ID.
lz4p	Pointer that gets a 0 if lz4 is not in use for this var, and a 1 if it is. Ignored if NULL.
levelp	Pointer that gets the acceleration setting (from 1 to 9). Ignored if NULL.

Returns

0 for success, error code otherwise.

Author

Edward Hartnett

nc_inq_var_lzf()

int nc_inq_var_lzf	(	int	ncid,
		int	varid,
		int *	lzfp
	)