Index of Functions: A B C D E F G H I J K L M N O P Q R S T U V W X
Index Page dlafps_c
Table of contents
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       dlafps_c ( DLA, find previous segment )

       void dlafps_c ( SpiceInt               handle,
                       ConstSpiceDLADescr   * dladsc,
                       SpiceDLADescr        * prvdsc,
                       SpiceBoolean         * found   )
#### Abstract
       Find the segment preceding a specified segment in a DLA file.
#### Required_Reading
       DAS
       DLA
#### Keywords
       DAS
       DLA
       FILES
       SEARCH
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       handle     I   Handle of open DLA file.
       dladsc     I   Descriptor of a segment in DLA file.
       prvdsc     O   Descriptor of previous segment in DLA file.
       found      O   Flag indicating whether a segment was found.
#### Detailed_Input
       handle      is the integer handle associated with the file to be
                   searched. This handle is used to identify the file in
                   subsequent calls to other DLA or DAS routines.

       dladsc      is the descriptor of a DLA segment in the file
                   associated with `handle'. The descriptor of the
                   segment preceding the one associated with `dladsc'
                   is sought.
#### Detailed_Output
       prvdsc      is the descriptor of the DLA segment preceding the
                   segment associated with the input argument `dladsc'.

                   `prvdsc' is valid only if the output argument `found' is
                   SPICETRUE.

       found       is a logical flag indicating whether the previous
                   segment was found. `found' has the value SPICETRUE if the
                   segment was found; otherwise `found' is SPICEFALSE.
#### Parameters
       None.
#### Exceptions
       1)  If the input file handle is invalid, an error is
           signaled by a routine in the call tree of this routine.

       2)  If a failure occurs while reading the DLA file, an error
           is signaled by a routine in the call tree of this routine.
#### Files
       See description of input argument `handle'.
#### Particulars
       DLA files are built using the DAS low-level format; DLA files are
       a specialized type of DAS file in which data are organized as a
       doubly linked list of segments. Each segment's data belong to
       contiguous components of character, double precision, and integer
       type.

       This routine supports backward traversal of a DLA file's segment
       list. A backward traversal may be started from any segment in
       the file; it is not necessary to call dlabbs_c first. The role of
       dlabbs_c is simply to return the descriptor of the last segment in
       the file.
#### Examples
       The numerical results shown for this example may differ across
       platforms. The results depend on the SPICE kernels used as
       input, the compiler and supporting libraries, and the machine
       specific arithmetic implementation.

       1) Open a DLA file for read access, traverse the segment
          list from back to front, and display segment address
          and size attributes.

          Example code begins here.

          /.
             Program dlafps_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main()
          {
             /.
             Local parameters
             ./
             #define FILSIZ           256

             /.
             Local variables
             ./
             SpiceBoolean            found;
             SpiceChar               fname  [ FILSIZ ];
             SpiceDLADescr           current;
             SpiceDLADescr           dladsc;
             SpiceInt                handle;
             SpiceInt                segno;

             /.
             Prompt for the name of the file to search.
             ./
             prompt_c ( "Name of DLA file > ", FILSIZ, fname );

             /.
             Open the DLA file for read access.  Since DLA
             files use the DAS architecture, we can use DAS
             routines to open and close the file.
             ./
             dasopr_c ( fname, &handle );

             /.
             Begin a backward search. Let `dladsc' contain
             the descriptor of the last segment.
             ./
             segno = 0;

             dlabbs_c ( handle, &dladsc, &found );

             while ( found )
             {
                /.
                Display the contents of the current segment
                descriptor.
                ./

                ++segno;

                printf ( "\n"
                         "Segment number (offset from end of file) = %d\n"
                         "\n"
                         "   Backward segment pointer         = %d\n"
                         "   Forward segment pointer          = %d\n"
                         "   Integer component base address   = %d\n"
                         "   Integer component size           = %d\n"
                         "   D.p. component base address      = %d\n"
                         "   D.p. component size              = %d\n"
                         "   Character component base address = %d\n"
                         "   Character component size         = %d\n"
                         "\n",
                         (int)(segno),
                         (int)(dladsc.bwdptr),
                         (int)(dladsc.fwdptr),
                         (int)(dladsc.ibase),
                         (int)(dladsc.isize),
                         (int)(dladsc.dbase),
                         (int)(dladsc.dsize),
                         (int)(dladsc.cbase),
                         (int)(dladsc.csize)                            );

                /.
                Find the previous segment.
                ./
                current = dladsc;

                dlafps_c ( handle, &current, &dladsc, &found );
             }

             /.
             Close the file using the DAS close routine.
             ./
             dascls_c ( handle );

             return ( 0 );
          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, using the DSK file named phobos512.bds, the output
          was:

          Name of DLA file > phobos512.bds

          Segment number (offset from end of file) = 1

             Backward segment pointer         = -1
             Forward segment pointer          = -1
             Integer component base address   = 11
             Integer component size           = 29692614
             D.p. component base address      = 0
             D.p. component size              = 4737076
             Character component base address = 0
             Character component size         = 0
#### Restrictions
       None.
#### Literature_References
       None.
#### Author_and_Institution
       N.J. Bachman        (JPL)
       J. Diaz del Rio     (ODC Space)
#### Version
       -CSPICE Version 1.1.0, 22-FEB-2021 (JDR)

           Changed the output argument name "descr" to "dladsc" for
           consistency with other routines.

           Edited the header comments to comply with NAIF standard.

       -CSPICE Version 1.0.0, 10-JAN-2017 (NJB)
#### Index_Entries
       find previous segment in DLA file
#### Link to routine dlafps_c source file dlafps_c.c

    Fri Dec 31 18:41:04 2021