void dlafps_c ( SpiceInt handle,
ConstSpiceDLADescr * descr,
SpiceDLADescr * prvdsc,
SpiceBoolean * found )
Find the segment preceding a specified segment in a DLA file.
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.
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'
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
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.
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
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. 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
1) Open a DLA file for read access, traverse the segment
list from back to front, and display segment address
and size attributes.
#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 `descr' contain
the descriptor of the last segment.
segno = 0;
dlabbs_c ( handle, &descr, &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 = descr;
dlafps_c ( handle, ¤t, &descr, &found );
Close the file using the DAS close routine.
dascls_c ( handle );
return ( 0 );
N.J. Bachman (JPL)
-CSPICE Version 1.0.0, 10-JAN-2017 (NJB)
find previous segment in dla file