void dafbbs_c ( SpiceInt handle )
Begin a backward search for arrays in a DAF.
DAF
FILES
Variable I/O Description
-------- --- --------------------------------------------------
handle I Handle of DAF to be searched.
handle is the handle of a DAF on which a backward
search is to be conducted.
None.
None.
1) If the input handle is invalid, the error will be diagnosed
by routines called by this routine.
See argument handle.
The DAF search routines are:
dafbfs_c Begin forward search.
daffna Find next array.
dafbbs_c Begin backward search.
daffpa_c Find previous array.
dafgs_c Get summary.
dafgn_c Get name.
dafgh_c Get handle.
dafcs_c Continue search.
The main function of these entry points is to allow the
contents of any DAF to be examined on an array-by-array
basis.
Conceptually, the arrays in a DAF form a doubly linked list,
which can be searched in either of two directions: forward or
backward. It is possible to search multiple DAFs simultaneously.
dafbfs_c (begin forward search) and daffna are used to search the
arrays in a DAF in forward order. In applications that search a
single DAF at a time, the normal usage is
dafbfs_c ( handle );
daffna_c ( &found );
while ( found )
{
dafgs_c ( sum );
dafgn_c ( name );
.
.
daffna_c ( &found );
}
dafbbs_c (begin backward search) and daffpa_c are used to search the
arrays in a DAF in backward order. In applications that search
a single DAF at a time, the normal usage is
dafbbs_c ( handle );
daffpa_c ( &found );
while ( found )
{
dafgs_c ( sum );
dafgn_c ( name );
.
.
daffpa_c ( &found );
}
In applications that conduct multiple searches simultaneously,
the above usage must be modified to specify the handle of the
file to operate on, in any case where the file may not be the
last one specified by dafbfs_c or dafbbs_c. The routine dafcs_c
(DAF, continue search) is used for this purpose. Below, we
give an example of an interleaved search of two files specified
by the handles handl1 and handl2. The directions of searches
in different DAFs are independent; here we conduct a forward
search on one file and a backward search on the other.
Throughout, we use dafcs to specify which file to operate on,
before calling daffna_c, daffpa_c, dafgs_c, or dafgn_c.
dafbfs_c ( handl1 );
dafbbs_c ( handl2 );
dafcs_c ( handl1 );
daffna_c ( &found1 );
dafcs_c ( handl2 );
daffpa_c ( &found2 );
while ( found1 || found2 )
{
if ( found1 )
{
dafcs_c ( handl1 );
dafgs_c ( sum );
dafgn_c ( name );
.
.
dafcs_c ( &handl1 );
daffna_c ( &found1 );
}
if ( found2 )
{
dafcs_c ( handl2 );
dafgs_c ( sum );
dafgn_c ( name );
.
.
dafcs_c ( handl2 );
daffpa_c ( &found2 );
}
}
At any time, the latest array found (whether by daffna_c or daffpa_c)
is regarded as the "current" array for the file in which the
array was found. The last DAF in which a search was started,
executed, or continued by any of dafbfs_c, dafbbs_c, daffna_c,
daffpa_c or dafcs_c is regarded as the "current" DAF. The summary
and name for the current array in the current DAF can be obtained
separately, as shown above, by calls to DAFGS (get summary) and
dafgn_c (get name). The handle of the current DAF can also be
obtained by calling dafgh_c (get handle).
Once a search has been begun, it may be continued in either
direction. That is, daffpa_c may be used to back up during a
forward search, and daffna_c may be used to advance during a
backward search.
Example (1):
See Particulars.
Example (2):
Use a simple routine to output the double precision and integer
values stored in an SPK's segments descriptors. This function
opens a DAF for read, performs a backwards search for the DAF
arrays, prints segments description for each array found, then
closes the DAF.
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Local constants
./
/.
Define the summary parameters appropriate
for an SPK file.
./
#define ND 2
#define NI 6
#define MAXSUM 125
SpiceInt ic [ NI ];
SpiceInt handle;
SpiceDouble dc [ ND ];
SpiceDouble sum [ MAXSUM ];
SpiceChar * kernel = "/kernels/gen/spk/de421.bsp";
SpiceBoolean found;
/.
Open a DAF for read. Return a handle referring to the file.
./
dafopr_c ( kernel, &handle );
/.
Begin a backward search on the file.
./
dafbbs_c ( handle );
/.
Search until a DAF array is found.
./
daffpa_c ( &found );
/.
Loop while the search finds subsequent DAF arrays.
./
while ( found )
{
dafgs_c ( sum );
dafus_c ( sum, ND, NI, dc, ic );
printf( " Doubles: %f %f \n", dc[0], dc[1] );
printf( "Integers: %d %d %d %d %d %d\n\n",
(int)ic[0], (int)ic[1], (int)ic[2],
(int)ic[3], (int)ic[4], (int)ic[5] );
/.
Check for another segment.
./
daffpa_c ( &found );
}
/.
Safely close the DAF.
./
dafcls_c ( handle );
return ( 0 );
}
The program outouts:
Doubles: -3169195200.000000 1696852800.000000
Integers: 499 4 1 2 2098633 2098644
Doubles: -3169195200.000000 1696852800.000000
Integers: 299 2 1 2 2098621 2098632
Doubles: -3169195200.000000 1696852800.000000
Integers: 199 1 1 2 2098609 2098620
Doubles: -3169195200.000000 1696852800.000000
Integers: 399 3 1 2 1521325 2098608
Doubles: -3169195200.000000 1696852800.000000
Integers: 301 3 1 2 944041 1521324
Doubles: -3169195200.000000 1696852800.000000
Integers: 10 0 1 2 820837 944040
Doubles: -3169195200.000000 1696852800.000000
Integers: 9 0 1 2 785633 820836
Doubles: -3169195200.000000 1696852800.000000
Integers: 8 0 1 2 750429 785632
Doubles: -3169195200.000000 1696852800.000000
Integers: 7 0 1 2 715225 750428
Doubles: -3169195200.000000 1696852800.000000
Integers: 6 0 1 2 674741 715224
Doubles: -3169195200.000000 1696852800.000000
Integers: 5 0 1 2 628977 674740
Doubles: -3169195200.000000 1696852800.000000
Integers: 4 0 1 2 567373 628976
Doubles: -3169195200.000000 1696852800.000000
Integers: 3 0 1 2 423049 567372
Doubles: -3169195200.000000 1696852800.000000
Integers: 2 0 1 2 310405 423048
Doubles: -3169195200.000000 1696852800.000000
Integers: 1 0 1 2 641 310404
Note, the final entries in the integer arrays record the segment
start/end indexes. The output indicates the search proceeded
from the end of the file (high value index) towards the beginning
(low value index).
None.
None.
N.J. Bachman (JPL)
W.L. Taber (JPL)
I.M. Underwood (JPL)
-CSPICE Version 1.0.2, 28-JUN-2016 (EDW)
Edit to Example code, SpiceInts output as ints using
explicit casting.
-CSPICE Version 1.0.1, 10-OCT-2012 (EDW)
Added a functional code example to the Examples section.
Removed the obsolete Reference citation to "NAIF
Document 167.0."
-CSPICE Version 1.0.0, 31-JUL-1999 (NJB) (WLT) (IMU)
begin daf backward search
Link to routine dafbbs_c source file dafbbs_c.c
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