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