4.1 CFITSIO Definitions

Any program that uses the CFITSIO interface must include the fitsio.h header file with the statement

  #include "fitsio.h"

This header file contains the prototypes for all the CFITSIO user interface routines as well as the definitions of various constants used in the interface. It also defines a C structure of type `fitsfile' that is used by CFITSIO to store the relevant parameters that define the format of a particular FITS file. Application programs must define a pointer to this structure for each FITS file that is to be opened. This structure is initialized (i.e., memory is allocated for the structure) when the FITS file is first opened or created with the fits_open_file or fits_create_file routines. This fitsfile pointer is then passed as the first argument to every other CFITSIO routine that operates on the FITS file. Application programs must not directly read or write elements in this fitsfile structure because the definition of the structure may change in future versions of CFITSIO.

A number of symbolic constants are also defined in fitsio.h for the convenience of application programmers. Use of these symbolic constants rather than the actual numeric value will help to make the source code more readable and easier for others to understand.

String Lengths, for use when allocating character arrays:

  #define FLEN_FILENAME 1025 /* max length of a filename                  */
  #define FLEN_KEYWORD   72  /* max length of a keyword                   */
  #define FLEN_CARD      81  /* max length of a FITS header card          */
  #define FLEN_VALUE     71  /* max length of a keyword value string      */
  #define FLEN_COMMENT   73  /* max length of a keyword comment string    */
  #define FLEN_ERRMSG    81  /* max length of a CFITSIO error message     */
  #define FLEN_STATUS    31  /* max length of a CFITSIO status text string */

  Note that FLEN_KEYWORD is longer than the nominal 8-character keyword
  name length because the HIERARCH convention supports longer keyword names.

Access modes when opening a FITS file:

  #define READONLY  0
  #define READWRITE 1

BITPIX data type code values for FITS images:

  #define BYTE_IMG      8  /*  8-bit unsigned integers */
  #define SHORT_IMG    16  /* 16-bit   signed integers */
  #define LONG_IMG     32  /* 32-bit   signed integers */
  #define LONGLONG_IMG 64  /* 64-bit   signed integers */
  #define FLOAT_IMG   -32  /* 32-bit single precision floating point */
  #define DOUBLE_IMG  -64  /* 64-bit double precision floating point */

  The following 4 data type codes are also supported by CFITSIO:
  #define SBYTE_IMG  10      /*  8-bit signed integers, equivalent to */
                             /*  BITPIX = 8, BSCALE = 1, BZERO = -128 */
  #define USHORT_IMG  20     /* 16-bit unsigned integers, equivalent to */
                             /*  BITPIX = 16, BSCALE = 1, BZERO = 32768 */
  #define ULONG_IMG   40     /* 32-bit unsigned integers, equivalent to */
                             /*  BITPIX = 32, BSCALE = 1, BZERO = 2147483648 */
  #define ULONGLONG_IMG  80  /* 64-bit unsigned integers, equivalent to */
                             /*  BITPIX = 64, BSCALE = 1, BZERO = 9223372036854775808*/

Codes for the data type of binary table columns and/or for the
data type of variables when reading or writing keywords or data:

                              DATATYPE               TFORM CODE
  #define TBIT          1  /*                            'X' */
  #define TBYTE        11  /* 8-bit unsigned byte,       'B' */
  #define TLOGICAL     14  /* logicals (int for keywords     */
                           /*  and char for table cols   'L' */
  #define TSTRING      16  /* ASCII string,              'A' */
  #define TSHORT       21  /* signed short,              'I' */
  #define TLONG        41  /* signed long,                   */
  #define TLONGLONG    81  /* 64-bit long signed integer 'K' */
  #define TFLOAT       42  /* single precision float,    'E' */
  #define TDOUBLE      82  /* double precision float,    'D' */
  #define TCOMPLEX     83  /* complex (pair of floats)   'C' */
  #define TDBLCOMPLEX 163  /* double complex (2 doubles) 'M' */

  The following data type codes are also supported by CFITSIO:
  #define TINT         31  /* int                            */
  #define TSBYTE       12  /* 8-bit signed byte,         'S' */
  #define TUINT        30  /* unsigned int               'V' */
  #define TUSHORT      20  /* unsigned short             'U' */
  #define TULONG       40  /* unsigned long                  */
  #define TULONGLONG   80  /* unsigned long long         'W' */

  The following data type code is only for use with fits\_get\_coltype
  #define TINT32BIT    41  /* signed 32-bit int,         'J' */


HDU type code values (value returned when moving to new HDU):

  #define IMAGE_HDU  0  /* Primary Array or IMAGE HDU */
  #define ASCII_TBL  1  /* ASCII  table HDU */
  #define BINARY_TBL 2  /* Binary table HDU */
  #define ANY_HDU   -1  /* matches any type of HDU */

Column name and string matching case-sensitivity:

  #define CASESEN   1   /* do case-sensitive string match */
  #define CASEINSEN 0   /* do case-insensitive string match */

Logical states (if TRUE and FALSE are not already defined):

  #define TRUE 1
  #define FALSE 0

Values to represent undefined floating point numbers:

  #define FLOATNULLVALUE  -9.11912E-36F
  #define DOUBLENULLVALUE -9.1191291391491E-36

Image compression algorithm definitions

  #define RICE_1       11
  #define GZIP_1       21
  #define GZIP_2       22
  #define PLIO_1       31
  #define HCOMPRESS_1  41
  #define NOCOMPRESS  -1

  #define NO_DITHER -1
  #define SUBTRACTIVE_DITHER_1 1
  #define SUBTRACTIVE_DITHER_2 2