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Index Page dafbbs_c

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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

       dafbbs_c ( DAF, begin backward search )

       void dafbbs_c ( SpiceInt handle )

#### Abstract

       Begin a backward search for arrays in a DAF.

#### Required_Reading

       DAF

#### Keywords

       FILES

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       handle     I   Handle of DAF to be searched.

#### Detailed_Input

       handle      is the handle of a DAF on which a backward
                   search is to be conducted.

#### Detailed_Output

       None.

#### Parameters

       None.

#### Exceptions

       1)  If the input handle is invalid, an error is signaled by a
           routine in the call tree of this routine.

       2)  If the summary record of the last record in the DAF file cannot be
           read, the error SPICE(RECORDNOTFOUND) is signaled by a routine in the
           call tree of this routine.

#### Files

       See argument `handle'.

#### Particulars

       The DAF search routines are:

          dafbfs_c       Begin forward search.
          daffna         Find next array.

          dafbbs_c       Begin backward search.
          daffpa_c       Find previous array.

          dafgs_c        Get summary.
          dafgn_c        Get name.
          dafgh_c        Get handle.

          dafcs_c        Continue search.

       The main function of these entry points is to allow the
       contents of any DAF to be examined on an array-by-array
       basis.

       Conceptually, the arrays in a DAF form a doubly linked list,
       which can be searched in either of two directions: forward or
       backward. It is possible to search multiple DAFs simultaneously.

       dafbfs_c (begin forward search) and daffna are used to search the
       arrays in a DAF in forward order. In applications that search a
       single DAF at a time, the normal usage is

          dafbfs_c ( handle );
          daffna_c ( &found );

          while ( found )
          {
             dafgs_c ( sum  );
             dafgn_c ( name );
              .
              .

             daffna_c ( &found );
          }

       dafbbs_c (begin backward search) and daffpa_c are used to search the
       arrays in a DAF in backward order. In applications that search
       a single DAF at a time, the normal usage is

          dafbbs_c ( handle );
          daffpa_c ( &found );

          while ( found )
          {
             dafgs_c ( sum  );
             dafgn_c ( name );
              .
              .

             daffpa_c ( &found );
          }

       In applications that conduct multiple searches simultaneously,
       the above usage must be modified to specify the handle of the
       file to operate on, in any case where the file may not be the
       last one specified by dafbfs_c or dafbbs_c. The routine dafcs_c
       (DAF, continue search) is used for this purpose. Below, we
       give an example of an interleaved search of two files specified
       by the handles handl1 and handl2. The directions of searches
       in different DAFs are independent; here we conduct a forward
       search on one file and a backward search on the other.
       Throughout, we use dafcs to specify which file to operate on,
       before calling daffna_c, daffpa_c, dafgs_c, or dafgn_c.

          dafbfs_c ( handl1 );
          dafbbs_c ( handl2 );

          dafcs_c  ( handl1  );
          daffna_c ( &found1 );

          dafcs_c  ( handl2  );
          daffpa_c ( &found2 );

          while ( found1 || found2 )
          {
             if ( found1 )
             {
                dafcs_c ( handl1 );
                dafgs_c ( sum    );
                dafgn_c ( name   );
                 .
                 .
                dafcs_c  ( handl1  );
                daffna_c ( &found1 );
             }

             if ( found2 )
             {
                dafcs_c ( handl2 );
                dafgs_c ( sum    );
                dafgn_c ( name   );
                 .
                 .
                dafcs_c  ( handl2  );
                daffpa_c ( &found2 );
             }
          }

       At any time, the latest array found (whether by daffna_c or daffpa_c)
       is regarded as the "current" array for the file in which the
       array was found. The last DAF in which a search was started,
       executed, or continued by any of dafbfs_c, dafbbs_c, daffna_c,
       daffpa_c or dafcs_c is regarded as the "current" DAF. The summary
       and name for the current array in the current DAF can be obtained
       separately, as shown above, by calls to dafgs_c (get summary) and
       dafgn_c (get name). The handle of the current DAF can also be
       obtained by calling dafgh_c (get handle).

       Once a search has been begun, it may be continued in either
       direction. That is, daffpa_c may be used to back up during a
       forward search, and daffna_c may be used to advance during a
       backward search.

#### Examples

       The numerical results shown for these examples 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) See -Particulars.

       2) Create a simple program to output the double precision and integer
          values stored in an SPK's segments' descriptors. This function
          opens a DAF for read, performs a backwards search for the DAF
          arrays, prints the segment descriptor for each array found, then
          closes the DAF.

          Use the SPK kernel below as input DAF file for the program.

             de421.bsp

          Example code begins here.

          /.
             Program dafbbs_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main()
             {

             /.
             Local constants
             ./

             /.
             Define the summary parameters appropriate
             for an SPK file.
             ./

             #define ND              2
             #define NI              6
             #define MAXSUM          125

             SpiceInt                ic  [ NI ];
             SpiceInt                handle;

             SpiceDouble             dc  [ ND ];
             SpiceDouble             sum [ MAXSUM ];

             SpiceChar             * kernel = "de421.bsp";

             SpiceBoolean            found;

             /.
             Open a DAF for read. Return a handle referring to the file.
             ./
             dafopr_c ( kernel, &handle );

             /.
             Begin a backward search on the file.
             ./
             dafbbs_c ( handle );

             /.
             Search until a DAF array is found.
             ./
             daffpa_c ( &found );

             /.
             Loop while the search finds subsequent DAF arrays.
             ./
             while ( found )
                {

                dafgs_c ( sum );
                dafus_c ( sum, ND, NI, dc, ic );

                printf( " Doubles: %f %f \n", dc[0], dc[1] );
                printf( "Integers: %d %d %d %d %d %d\n\n",
                           (int)ic[0], (int)ic[1], (int)ic[2],
                           (int)ic[3], (int)ic[4], (int)ic[5] );

                /.
                Check for another segment.
                ./
                daffpa_c ( &found );
                }

             /.
             Safely close the DAF.
             ./
             dafcls_c ( handle  );

             return ( 0 );
             }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 499 4 1 2 2098633 2098644

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 299 2 1 2 2098621 2098632

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 199 1 1 2 2098609 2098620

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 399 3 1 2 1521325 2098608

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 301 3 1 2 944041 1521324

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 10 0 1 2 820837 944040

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 9 0 1 2 785633 820836

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 8 0 1 2 750429 785632

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 7 0 1 2 715225 750428

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 6 0 1 2 674741 715224

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 5 0 1 2 628977 674740

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 4 0 1 2 567373 628976

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 3 0 1 2 423049 567372

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 2 0 1 2 310405 423048

           Doubles: -3169195200.000000 1696852800.000000
          Integers: 1 0 1 2 641 310404

          Note, the final entries in the integer arrays contain the segment
          start/end indexes. The output indicates the search proceeded
          from the end of the file (high value index) towards the beginning
          (low value index).

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman        (JPL)
       J. Diaz del Rio     (ODC Space)
       W.L. Taber          (JPL)
       I.M. Underwood      (JPL)
       E.D. Wright         (JPL)

#### Version

       -CSPICE Version 1.0.3, 25-AUG-2021 (JDR)

           Edited the header to comply with NAIF standard. Added
           entry #2 to -Exceptions section.

       -CSPICE Version 1.0.2, 28-JUN-2016 (EDW)

           Edit to Example code, SpiceInts output as ints using
           explicit casting.

       -CSPICE Version 1.0.1, 10-OCT-2012 (EDW)

           Added a functional code example to the -Examples section.

           Removed the obsolete Reference citation to "NAIF
           Document 167.0."

       -CSPICE Version 1.0.0, 31-JUL-1999 (NJB) (WLT) (IMU)

#### Index_Entries

       begin DAF backward search

#### Link to routine dafbbs_c source file dafbbs_c.c

    Fri Dec 31 18:41:03 2021