Table of contents
dlabbs_c ( DLA, begin backward search )
void dlabbs_c ( SpiceInt handle,
SpiceDLADescr * dladsc,
SpiceBoolean * found )
Begin a backward segment search in a DLA file.
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
handle I Handle of open DLA file.
dladsc O Descriptor of last segment in DLA file.
found O Flag indicating whether a segment was found.
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.
dladsc is the descriptor of the last DLA segment in the
file associated with `handle'.
The segment descriptor layout is:
| BACKWARD PTR | Linked list backward pointer
| FORWARD PTR | Linked list forward pointer
| BASE INT ADDR | Base DAS integer address
| INT COMP SIZE | Size of integer segment component
| BASE DP ADDR | Base DAS d.p. address
| DP COMP SIZE | Size of d.p. segment component
| BASE CHR ADDR | Base DAS character address
| CHR COMP SIZE | Size of character segment component
`dladsc' is valid only if the output argument `found' is
found is a logical flag indicating whether a segment was
found. `found' has the value SPICETRUE if the file
contains at least one segment; otherwise `found' is
1) If the input file handle is invalid, an error is
signaled by a routine in the call tree of this routine.
2) If an error occurs while reading the DLA file, the error
is signaled by a routine in the call tree of this routine.
3) If the input descriptor is invalid, this routine will
fail in an unpredictable manner.
See description of input argument `handle'.
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
This routine supports backward traversal of a DLA file's segment
list. Note that it is not necessary to call this routine to
conduct a backward traversal; all that is necessary is to have
access to the last descriptor in the file, which this routine
The numerical results shown for this example may differ across
platforms. The results depend on the SPICE kernels used as input,
the compiler and supporting libraries, and the machine specific
1) Open a DLA file for read access, traverse the segment
list from back to front, and display segment address
and size attributes.
Example code begins here.
#define FILSIZ 256
SpiceChar fname [ FILSIZ ];
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 `dladsc' contain
the descriptor of the last segment.
segno = 0;
dlabbs_c ( handle, &dladsc, &found );
while ( found )
Display the contents of the current segment
printf ( "\n"
"Segment number (offset from end of file) = %d\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"
Find the previous segment.
current = dladsc;
dlafps_c ( handle, ¤t, &dladsc, &found );
Close the file using the DAS close routine.
dascls_c ( handle );
return ( 0 );
When this program was executed on a Mac/Intel/cc/64-bit
platform, using the DSK file named phobos512.bds, the output
Name of DLA file > phobos512.bds
Segment number (offset from end of file) = 1
Backward segment pointer = -1
Forward segment pointer = -1
Integer component base address = 11
Integer component size = 29692614
D.p. component base address = 0
D.p. component size = 4737076
Character component base address = 0
Character component size = 0
N.J. Bachman (JPL)
J. Diaz del Rio (ODC Space)
-CSPICE Version 1.1.0, 22-FEB-2021 (JDR)
Changed the output argument name "descr" to "dladsc" for
consistency with other routines.
Edited the header comments to comply with NAIF standard.
-CSPICE Version 1.0.0, 10-JAN-2017 (NJB)
begin backward search in DLA file