Procedure

     SPKSFS ( S/P Kernel, Select file and segment )

     ENTRY SPKSFS ( BODY, ET, HANDLE, DESCR, IDENT, FOUND )

Abstract

     Search through loaded SPK files to find the highest-priority
     segment applicable to the body and time specified and buffer
     searched segments in the process, to attempt to avoid re-reading
     files.

Required_Reading

     SPK

Keywords

     EPHEMERIS
     FILES

Declarations

    INTEGER               BODY
    DOUBLE PRECISION      ET
    INTEGER               HANDLE
    DOUBLE PRECISION      DESCR  ( * )
    CHARACTER*(*)         IDENT
    LOGICAL               FOUND

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     BODY       I   Body ID.
     ET         I   Ephemeris time.
     HANDLE     O   Handle of file containing the applicable segment.
     DESCR      O   Descriptor of the applicable segment.
     IDENT      O   Identifier of the applicable segment.
     FOUND      O   Indicates whether or not a segment was found.

Detailed_Input

     BODY     is the NAIF integer code of an ephemeris object,
              typically a solar system body.

     ET       is a time, in seconds past the epoch J2000 TDB.

Detailed_Output

     HANDLE   is the handle of the SPK file containing a located
              segment.

     DESCR    is the descriptor of a located segment.

     IDENT    is the identifier of a located segment.

     FOUND    is a logical flag indicating whether a requested segment
              was found or not.

Parameters

     None.

Exceptions

     1)  If an attempt is made to call SPKSFS when there aren't any
         files loaded, the error SPICE(NOLOADEDFILES) is signaled.

     2)  If an error occurs while this routine attempts to extract
         segment descriptors from loaded SPK files, the error is
         signaled by a routine in the call tree of this routine.

         Note however that I/O errors occurring during reads of DAF
         double precision records are NOT treated as SPICE errors
         and are not signaled.

Files

     All SPK files loaded by FURNSH or SPKLEF are potential search
     targets for SPKSFS.

Particulars

     This routine finds the highest-priority segment, in any loaded
     SPK file, such that the segment provides data for the specified
     body and epoch.

Examples

     See $Examples in SPKBSR.

Restrictions

     1)  If Fortran I/O errors occur while searching a loaded SPK
         file, the internal state of this suite of routines may
         be corrupted. It may be possible to correct the state
         by unloading the pertinent SPK files and then re-loading
         them.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     H.A. Neilan        (JPL)
     W.L. Taber         (JPL)
     R.E. Thurman       (JPL)

Version

    SPICELIB Version 4.3.0, 13-OCT-2021 (JDR) (NJB)

        Edited the header to comply with NAIF standard. Improved
        $Abstract description.

        Relocated initialization of FOUND so it is always
        executed, even if an error state is indicated by RETURN().

        Added entry #2 to $Exceptions section. Added reference to
        FURNSH routine in $Files section.

    SPICELIB Version 4.2.1, 15-MAR-2017 (NJB)

        Corrected various spelling errors within comments.

    SPICELIB Version 4.2.0, 01-MAR-2011 (NJB)

        Bug fix:

          In the SPKSFS 'MAKE ROOM' state, when the suspended activity
          is 'ADD TO FRONT' and no segment table room is available,
          the body table's pointer to the current segment list
          is now set to null. Previously the pointer was allowed to go
          stale.

    SPICELIB Version 4.1.0, 08-SEP-2005 (NJB)

        Updated to remove non-standard use of duplicate arguments
        in MOVED call.

    SPICELIB Version 4.0.0, 28-DEC-2001 (NJB)

        Bug fixes:

           1) When a segment list is freed because the entire list
              is contributed by a single SPK file, and the list is
              too large to be buffered, the corresponding body table
              pointer is now set to null.

           2) An algorithm change has eliminated a bug caused by not
              updating the current body index when body table entries
              having empty segment lists were compressed out of the
              body table. Previously the body table pointer BINDEX
              could go stale after the compression.

           3) DAF calls are now followed by tests of FAILED()
              in order to ensure that the main state loop terminates.

           4) A subscript bound violation in a loop termination test
              was corrected.

        The "re-use interval" feature was introduced to improve speed
        in the case where repeated, consecutive requests are satisfied
        by the same segment.

        The segment list cost algorithm was modified slightly:
        the contribution of a file search to the cost of a list
        is included only when the file search is completed. The
        cost of finding the re-use interval is accounted for when
        unbuffered searches are required.

        The file table size has been increased to 1000, in order
        to take advantage of the DAF system's new ability to load
        1000 files.

        The body table size has been increased to 200 in order to
        decrease the chance of thrashing due to swapping segment
        lists for different bodies.

        Various small updates and corrections were made to the
        comments throughout the file.


    SPICELIB Version 3.0.0, 14-AUG-1995 (WLT)

        An interim fix to a bug in SPKBSR was made. The parameters
        STSIZE and BTSIZE were increased to be much larger than before
        (from 100 and 20 to 2000 and 40 respectively). This should
        keep the boundary errors experienced by Cassini users from
        occurring again. Version 4.0.0 with a real fix to the
        boundary problem should be installed in SPICELIB by
        October 1995

    SPICELIB Version 1.1.1, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.1.0, 02-MAY-1990 (RET)

        New error detected.

    SPICELIB Version 1.0.1, 22-MAR-1990 (HAN)

        Literature references added to the header.

    SPICELIB Version 1.0.0, 31-JAN-1990 (RET)