6.3 Define or Redefine the structure of the CHDU

It should rarely be necessary to call the subroutines in this section. FITSIO internally calls these routines whenever necessary, so any calls to these routines by application programs will likely be redundant.

1

This routine forces FITSIO to scan the current header keywords that define the structure of the HDU (such as the NAXISn, PCOUNT and GCOUNT keywords) so that it can initialize the internal buffers that describe the HDU structure. This routine may be used instead of the more complicated calls to ftpdef, ftadef or ftbdef. This routine is also very useful for reinitializing the structure of an HDU, if the number of rows in a table, as specified by the NAXIS2 keyword, has been modified from its initial value.

        FTRDEF(unit, > status)   (DEPRECATED)

2

Define the structure of the primary array or IMAGE extension. When writing GROUPed FITS files that by convention set the NAXIS1 keyword equal to 0, ftpdef must be called with naxes(1) = 1, NOT 0, otherwise FITSIO will report an error status=308 when trying to write data to a group. Note: it is usually simpler to call FTRDEF rather than this routine.

        FTPDEF(unit,bitpix,naxis,naxes,pcount,gcount, > status)  (DEPRECATED)

3

Define the structure of an ASCII table (TABLE) extension. Note: it is usually simpler to call FTRDEF rather than this routine.

        FTADEF(unit,rowlen,tfields,tbcol,tform,nrows > status) (DEPRECATED)

4

Define the structure of a binary table (BINTABLE) extension. Note: it is usually simpler to call FTRDEF rather than this routine.

        FTBDEF(unit,tfields,tform,varidat,nrows > status) (DEPRECATED)

5

Define the size of the Current Data Unit, overriding the length of the data unit as previously defined by ftpdef, ftadef, or ftbdef. This is useful if one does not know the total size of the data unit until after the data have been written. The size (in bytes) of an ASCII or Binary table is given by NAXIS1 * NAXIS2. (Note that to determine the value of NAXIS1 it is often more convenient to read the value of the NAXIS1 keyword from the output file, rather than computing the row length directly from all the TFORM keyword values). Note: it is usually simpler to call FTRDEF rather than this routine.

        FTDDEF(unit,bytlen, > status) (DEPRECATED)

6

Define the zero indexed byte offset of the 'heap' measured from the start of the binary table data. By default the heap is assumed to start immediately following the regular table data, i.e., at location NAXIS1 x NAXIS2. This routine is only relevant for binary tables which contain variable length array columns (with TFORMn = 'Pt'). This subroutine also automatically writes the value of theap to a keyword in the extension header. This subroutine must be called after the required keywords have been written (with ftphbn) and after the table structure has been defined (with ftbdef) but before any data is written to the table.

        FTPTHP(unit,theap, > status)