Index Page dlafps_c

A B C D E F G H I J K L M N O P Q R S T U V W X

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

       void dlafps_c ( SpiceInt               handle,
                       ConstSpiceDLADescr   * descr,
                       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.
       descr      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.

       descr       is the descriptor of a DLA segment in the file
                   associated with `handle'. The descriptor of the
                   segment preceding the one associated with `descr'
                   is sought.

#### Detailed_Output

       prvdsc      is the descriptor of the DLA segment preceding the
                   segment associated with the input argument `descr'.

                   `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, the error will be
          diagnosed by routines in the call tree of this routine.

       2) If an error occurs while reading the DLA file, the error
          will be diagnosed by routines 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

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

              #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           descr;
                 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 `descr' contain
                 the descriptor of the last segment.
                 ./
                 segno = 0;

                 dlabbs_c ( handle, &descr, &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)(descr.bwdptr),
                             (int)(descr.fwdptr),
                             (int)(descr.ibase),
                             (int)(descr.isize),
                             (int)(descr.dbase),
                             (int)(descr.dsize),
                             (int)(descr.cbase),
                             (int)(descr.csize)                            );

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

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

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

                 return ( 0 );
              }

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman    (JPL)

#### Version

       -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

    Wed Apr  5 17:54:31 2017