Procedure

     DLASSG ( DLA, same segment? )

     LOGICAL FUNCTION DLASSG ( HAN1, HAN2, DSC1, DSC2 )

Abstract

     Return a logical value indicating whether a two DLA
     segments, each identified by DAS handle and DLA descriptor,
     are in fact the same segment.

Required_Reading

     DAS
     DLA

Keywords

     DAS
     DLA
     FILES

Declarations

     IMPLICIT NONE

     INCLUDE 'dla.inc'

     INTEGER               HAN1
     INTEGER               HAN2
     INTEGER               DSC1 ( DLADSZ )
     INTEGER               DSC2 ( DLADSZ )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HAN1       I   Handle of an open DLA file.
     HAN2       I   Handle of a second open DLA file.
     DSC1       I   DLA descriptor of a segment in the first file.
     DSC2       I   DLA descriptor of a segment in the second file.

     The function returns .TRUE. if and only if the DLA segments
     match.

Detailed_Input

     HAN1     is the integer handle associated with a DLA file.
              The file is open for read access.

     HAN2     is the integer handle associated with a second DLA
              file. The file is open for read access.

     DSC1     is the DLA descriptor of a segment in the file
              associated with HAN1.

     DSC2     is the DLA descriptor of a segment in the file
              associated with HAN2.

Detailed_Output

     The function returns .TRUE. if and only if the DLA segments
     match. The segments are considered to match if and only if the
     input handles match and all elements of the DLA descriptors
     match.

Parameters

     None.

Exceptions

     1)  If any of the inputs are invalid, this routine will
         fail in an unspecified manner.

Files

     See description of input arguments HAN1 and HAN2.

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 DLA and DSK routines by enabling
     them to determine whether a given DLA segment matches one
     they've previously examined. This may allow such routines
     to avoid buffering information redundantly.

Examples

     1)  A typical use of this routine is to enable a subroutine
         to determine whether a DLA segment identified by a
         handle and DLA descriptor matches one seen previously.
         The logic of such a test can be implemented as follows:


                   SUBROUTINE SUBA ( HANDLE, DLADSC )
                   IMPLICIT NONE

                   INCLUDE 'dla.inc'

                   INTEGER               HANDLE
                   INTEGER               DLADSC ( * )

             C
             C     SPICELIB functions
             C
                   LOGICAL               DLASSG
                   LOGICAL               FAILED
             C
             C     Local variables
             C
                   INTEGER               PRVDSC ( DLADSZ )
                   INTEGER               PRVHAN

             C
             C     Saved variables
             C
                   SAVE                  PRVDSC
                   SAVE                  PRVHAN

             C
             C     Initial values
             C
                   DATA                  PRVHAN / 0 /

                   ...

                   IF ( .NOT. DLASSG( HANDLE, PRVHAN,
                  .                   DLADSC, PRVDSC ) ) THEN

                      [Examine segment]

                      IF ( .NOT. FAILED() ) THEN
             C
             C           Save values only if no error occurred.
             C
                         CALL MOVEI ( DLADSC, DLADSZ, PRVDSC )
                         PRVHAN = HANDLE

                      END IF

                   END IF

                   [Normal case]

                   ...

                   END

Restrictions

     1)  This routine relies on uniqueness of DAS file handles.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)

Version

    SPICELIB Version 1.0.1, 22-JUL-2020 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.0, 19-MAY-2016 (NJB)