Table of contents
CSPICE_DLAFNS finds the segment following a specified segment in a
DLA file.
Given:
handle the DAS integer handle associated with the file to be searched.
help, handle
LONG = Scalar
This handle is used to identify the file in subsequent calls to
other DLA or DAS routines.
dladsc the descriptor of a DLA segment in the file associated with
`handle'.
help, dladsc
LONG = Array[SPICE_DLA_DSCSIZ]
the call:
cspice_dlafns, handle, dladsc, nxtdsc, found
returns:
nxtdsc the descriptor of the next DLA segment following the segment
associated with the input argument `dladsc'.
help, nxtdsc
LONG = Array[SPICE_DLA_DSCSIZ]
`nxtdsc' is valid only if the output argument `found'
is true.
found a logical flag indicating whether the next segment was found.
help, found
BOOLEAN = Scalar
`found' has the value true if the segment was found; otherwise
`found' is false.
SPICE_DLA_DSCSIZ
is the size of a SPICELIB DLA descriptor, defined in
IcyDLA.pro.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
1) Open a DLA file for read access, traverse the segment
list from front to back, and display segment address
and size attributes.
Example code begins here.
PRO dlafns_ex1
;;
;; Constants
;;
SPICE_DLA_BWDIDX = 0
SPICE_DLA_FWDIDX = 1
SPICE_DLA_IBSIDX = 2
SPICE_DLA_ISZIDX = 3
SPICE_DLA_DBSIDX = 4
SPICE_DLA_DSZIDX = 5
SPICE_DLA_CBSIDX = 6
SPICE_DLA_CSZIDX = 7
;;
;; Local variables
;;
fname = ''
;;
;; Prompt for the name of the file to search.
;;
read, fname, PROMPT='Name of DLA file > '
;;
;; Open the DSK file for read access.
;; We use the DAS-level interface for
;; this function.
;;
cspice_dasopr, fname, handle
;;
;; Begin a forward search through the
;; kernel, treating the file as a DLA.
;; In this example, it's a very short
;; search.
;;
segno = 1L
cspice_dlabfs, handle, dladsc, found
while found do begin
;;
;; Display the contents of the current segment
;; descriptor.
;;
print
print, 'Segment number = ', segno
print
print, ' Backward segment pointer = ', $
dladsc[SPICE_DLA_BWDIDX]
print, ' Forward segment pointer = ', $
dladsc[SPICE_DLA_FWDIDX]
print, ' Integer component base address = ', $
dladsc[SPICE_DLA_IBSIDX]
print, ' Integer component size = ', $
dladsc[SPICE_DLA_ISZIDX]
print, ' D.p. component base address = ', $
dladsc[SPICE_DLA_DBSIDX]
print, ' D.p. component size = ', $
dladsc[SPICE_DLA_DSZIDX]
print, ' Character component base address = ', $
dladsc[SPICE_DLA_CBSIDX]
print, ' Character component size = ', $
dladsc[SPICE_DLA_CSZIDX]
;;
;; Find the next segment.
;;
current = dladsc
segno = segno + 1
cspice_dlafns, handle, current, dladsc, found
end
;;
;; Close file.
;;
cspice_dascls, handle
END
When this program was executed on a Mac/Intel/IDL8.x/64-bit
platform, using the DSK file named phobos512.bds, the output
was:
Name of DLA file > phobos512.bds
Segment number = 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
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 forward traversal of a DLA file's segment
list. A forward traversal may be started from any segment in
the file; it is not necessary to call cspice_dlabfs first. The role
of cspice_dlabfs is simply to return the descriptor of the first
segment in the file.
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.
4) If any of the input arguments, `handle' or `dladsc', is
undefined, an error is signaled by the IDL error handling
system.
5) If any of the input arguments, `handle' or `dladsc', is not of
the expected type, or it does not have the expected dimensions
and size, an error is signaled by the Icy interface.
6) If any of the output arguments, `nxtdsc' or `found', is not a
named variable, an error is signaled by the Icy interface.
See description of input argument `handle'.
None.
DAS.REQ
DLA.REQ
ICY.REQ
None.
J. Diaz del Rio (ODC Space)
M. Liukis (JPL)
E.D. Wright (JPL)
-Icy Version 1.0.1, 19-JUL-2021 (JDR)
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections. Updated
list of Required Readings. Corrected typos in header.
Edited the header to comply with NAIF standard. Modified
code example to prompt for input DLA file.
Removed reference to the routine's corresponding CSPICE header from
-Abstract section.
Added arguments' type and size information in the -I/O section.
-Icy Version 1.0.0, 13-DEC-2016 (ML) (EDW)
find next segment in DLA file
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