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 dlabbs_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
       dlabbs_c ( DLA, begin backward search )

       void dlabbs_c ( SpiceInt         handle,
                       SpiceDLADescr  * dladsc,
                       SpiceBoolean   * found  )
#### Abstract
       Begin a backward segment search in a DLA file.
#### Required_Reading
       DAS
       DLA
#### Keywords
       DAS
       DLA
       FILES
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       handle     I   Handle of open DLA file.
       dladsc     O   Descriptor of last 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.
#### Detailed_Output
       dladsc      is the descriptor of the last DLA segment in the
                   file associated with `handle'.

                   The segment descriptor layout is:

                      +---------------+
                      | BACKWARD PTR  | Linked list backward pointer
                      +---------------+
                      | FORWARD PTR   | Linked list forward pointer
                      +---------------+
                      | BASE INT ADDR | Base DAS integer address
                      +---------------+
                      | INT COMP SIZE | Size of integer segment component
                      +---------------+
                      | BASE DP ADDR  | Base DAS d.p. address
                      +---------------+
                      | DP COMP SIZE  | Size of d.p. segment component
                      +---------------+
                      | BASE CHR ADDR | Base DAS character address
                      +---------------+
                      | CHR COMP SIZE | Size of character segment component
                      +---------------+

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

       found       is a logical flag indicating whether a segment was
                   found. `found' has the value SPICETRUE if the file
                   contains at least one segment; 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 an error occurs while reading the DLA file, the error
           is signaled by a routine in the call tree of this routine.

       3)  If the input descriptor is invalid, this routine will
           fail in an unpredictable manner.
#### 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. Note that it is not necessary to call this routine to
       conduct a backward traversal; all that is necessary is to have
       access to the last descriptor in the file, which this routine
       provides.
#### 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 dlabbs_ex1
          ./

          #include "SpiceUsr.h"
          #include "SpiceDLA.h"
          #include <stdio.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
       begin backward search in DLA file
#### Link to routine dlabbs_c source file dlabbs_c.c

    Fri Dec 31 18:41:04 2021