| eknelt_c |
|
Table of contents
Procedure
eknelt_c ( EK, get number of elements in column entry )
SpiceInt eknelt_c ( SpiceInt selidx,
SpiceInt row )
AbstractReturn the number of elements in a specified column entry in the current row. Required_ReadingEK KeywordsEK Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- selidx I Index of parent column in SELECT clause. row I Row containing element. The function returns the number of elements in entry in current row. Detailed_Input
selidx is the SELECT clause index of the column to
fetch from. The range of selidx is 0 : (nsel-1)
inclusive, where nsel is the number of items in
the SELECT clause of the current query.
row is the index of the row containing the element.
This number refers to a member of the set of rows
matching a query. row must be in the range
0 : nmrows-1
where nmrows is the matching row count returned
by ekfind_c.
Detailed_OutputThe function returns the number of elements in the column entry belonging to the specified column in the current row. Null entries in variable-size columns are considered to have size 1. ParametersNone. Exceptions
1) If this routine is called when no E-kernels have been loaded,
the error SPICE(NOLOADEDFILES) is signaled by a routine in the
call tree of this routine.
2) If `selidx' is outside of the range established by the last query
passed to the EK search engine, the error SPICE(INVALIDINDEX) is
signaled by a routine in the call tree of this routine.
3) If `row' is outside of the range established by the last query passed
to the EK search engine, the error SPICE(INVALIDINDEX) is signaled by
a routine in the call tree of this routine.
FilesAt least one E-kernel must be loaded before queries may be passed to the EK system via ekfind_c. ParticularsThis routine is meant to be used in conjunction with the EK fetch entry points ekgc_c, ekgd_c, and ekgi_c. This routine allows the caller of those routines to determine appropriate loop bounds to use to fetch each column entry in the current row. Examples
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 arithmetic implementation.
1) This example demonstrates how to fetch integer, double
precision and character string values from a column when such
column corresponds to either a variable-size array or to a
static-size array.
Create an EK that contains a table TAB that has the following
columns:
Column name Data Type Size
----------- --------- ----
IARRAY INT 3
DARRAY DP VARIABLE
CARRAY CHR VARIABLE
Issue the following query
query = "SELECT IARRAY, DARRAY, CARRAY FROM TAB"
to fetch and dump column values from the rows that satisfy the
query.
Example code begins here.
/.
Program eknelt_ex1
./
#include <stdio.h>
#include <string.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters
./
#define EKNAME "eknelt_ex1.bdb"
#define TABLE "TAB"
#define CHRSLN 6
#define COL1SZ 3
#define DECLEN 201
#define ERRLEN 1841
#define MXC2SZ 4
#define MXC3SZ 7
#define NCOLS 3
#define NROWS 4
#define STRSIZ 31
/.
Local variables
./
SpiceChar cdecls [NCOLS] [DECLEN];
SpiceChar cnames [NCOLS] [SPICE_EK_CSTRLN];
SpiceChar col3 [MXC3SZ][CHRSLN];
SpiceChar cvals [MXC3SZ][STRSIZ];
SpiceChar errmsg [ERRLEN];
SpiceChar * ifname;
SpiceChar * query;
SpiceDouble col2 [MXC2SZ];
SpiceDouble dvals [MXC2SZ];
SpiceInt col1 [COL1SZ];
SpiceInt eltidx;
SpiceInt handle;
SpiceInt i;
SpiceInt ivals [COL1SZ];
SpiceInt j;
SpiceInt nelt;
SpiceInt nmrows;
SpiceInt nresvc;
SpiceInt recno;
SpiceInt row;
SpiceInt segno;
SpiceInt selidx;
SpiceBoolean error;
SpiceBoolean found;
SpiceBoolean isnull;
/.
Open a new EK file. For simplicity, we will not
reserve any space for the comment area, so the
number of reserved comment characters is zero.
The variable `ifname' is the internal file name.
./
nresvc = 0;
ifname = "Test EK/Created 13-JUN-2019";
ekopn_c ( EKNAME, ifname, nresvc, &handle );
/.
Set up the column names and declarations
for the TAB segment. We'll index all of
the columns.
./
strcpy( cnames[0], "IARRAY" );
strcpy( cdecls[0], "DATATYPE = INTEGER, SIZE = 3" );
strcpy( cnames[1], "DARRAY" );
strcpy( cdecls[1], "DATATYPE = DOUBLE PRECISION, SIZE = VARIABLE" );
strcpy( cnames[2], "CARRAY" );
strcpy( cdecls[2], "DATATYPE = CHARACTER*(5), SIZE = VARIABLE" );
/.
Start the segment.
./
ekbseg_c ( handle, TABLE, NCOLS, SPICE_EK_CSTRLN,
cnames, DECLEN, cdecls, &segno );
/.
At the records to the table.
./
for ( i = 0; i < NROWS; i++ )
{
/.
Append a new record to the EK.
./
ekappr_c ( handle, segno, &recno );
/.
Add 3 items to IARRAY
./
for ( j = 0; j < COL1SZ; j++ )
{
col1[j] = i+1 + (j+1)*100;
}
ekacei_c ( handle, segno, recno,
cnames[0], COL1SZ, col1, SPICEFALSE );
/.
Add i+1 items to DARRAY
./
for ( j = 0; j <= i; j++ )
{
col2[j] = j+1 + (i+1)*200.0;
}
ekaced_c ( handle, segno, recno,
cnames[1], i+1, col2, SPICEFALSE );
/.
Add 4+i items to CARRAY
./
for ( j = 0; j < 4+i; j++ )
{
repmi_c ( "ST#", "#", j+1 + (i+1)*100, CHRSLN, col3[j] );
}
ekacec_c ( handle, segno, recno, cnames[2],
i+4, CHRSLN, col3, SPICEFALSE );
}
/.
Close the file.
./
ekcls_c ( handle );
/.
Open the created file. Perform the query and show the
results.
./
furnsh_c ( EKNAME );
query = "SELECT IARRAY, DARRAY, CARRAY FROM TAB";
/.
Query the EK system for data rows matching the
SELECT constraints.
./
ekfind_c ( query, ERRLEN, &nmrows, &error, errmsg );
/.
Check whether an error occurred while processing the
SELECT clause. If so, output the error message.
./
if ( error )
{
printf( "SELECT clause error: %s\n", errmsg );
}
else
{
for ( row = 0; row < nmrows; row++ )
{
printf( " \n" );
printf( "ROW = %2d\n", row );
/.
Fetch values from column IARRAY in the current
row. Since IARRAY was the first column selected,
the selection index `selidx' is set to 0.
./
selidx = 0;
eltidx = 0;
isnull = SPICEFALSE;
while ( ( eltidx < COL1SZ ) && ( !isnull ) )
{
/.
If the column entry is null, we'll be kicked
out of this loop after the first iteration.
./
ekgi_c ( selidx, row, eltidx,
ivals+eltidx, &isnull, &found );
eltidx = eltidx + 1;
}
printf( " COLUMN = IARRAY:" );
if ( isnull )
{
printf( "<Null>\n" );
}
else
{
for ( i = 0; i < COL1SZ; i++ )
{
printf( "%6d", ivals[i] );
}
printf( " \n" );
}
/.
Fetch values from column DARRAY in the current
row. Since DARRAY contains variable-size array
elements, we call eknelt_c to determine how many
elements to fetch.
./
selidx = 1;
nelt = eknelt_c ( selidx, row );
eltidx = 0;
isnull = SPICEFALSE;
while ( ( eltidx < nelt ) && ( !isnull ) )
{
ekgd_c ( selidx, row, eltidx,
dvals+eltidx, &isnull, &found );
eltidx = eltidx + 1;
}
printf( " COLUMN = DARRAY:" );
if ( isnull )
{
printf( "<Null>\n" );
}
else
{
for ( i = 0; i < nelt; i++ )
{
printf( "%6.1f", dvals[i] );
}
printf( " \n" );
}
/.
Fetch values from column CARRAY in the current
row.
./
selidx = 2;
nelt = eknelt_c ( selidx, row );
eltidx = 0;
isnull = SPICEFALSE;
while ( ( eltidx < nelt ) && ( !isnull ) )
{
ekgc_c ( selidx, row, eltidx, STRSIZ,
cvals[eltidx], &isnull, &found );
eltidx = eltidx + 1;
}
printf( " COLUMN = CARRAY:" );
if ( isnull )
{
printf( "<Null>\n" );
}
else
{
for ( i = 0; i < nelt; i++ )
{
printf( " %s", cvals[i] );
}
printf( " \n" );
}
}
/.
We either parsed the SELECT clause or had an error.
./
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
ROW = 0
COLUMN = IARRAY: 101 201 301
COLUMN = DARRAY: 201.0
COLUMN = CARRAY: ST101 ST102 ST103 ST104
ROW = 1
COLUMN = IARRAY: 102 202 302
COLUMN = DARRAY: 401.0 402.0
COLUMN = CARRAY: ST201 ST202 ST203 ST204 ST205
ROW = 2
COLUMN = IARRAY: 103 203 303
COLUMN = DARRAY: 601.0 602.0 603.0
COLUMN = CARRAY: ST301 ST302 ST303 ST304 ST305 ST306
ROW = 3
COLUMN = IARRAY: 104 204 304
COLUMN = DARRAY: 801.0 802.0 803.0 804.0
COLUMN = CARRAY: ST401 ST402 ST403 ST404 ST405 ST406 ST407
Note that after run completion, a new EK file exists in the
output directory.
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) Version
-CSPICE Version 1.1.1, 02-AUG-2021 (JDR)
Edited the header to comply with NAIF standard. Added
complete code example based on existing fragment.
-CSPICE Version 1.1.0, 23-JUL-2001 (NJB)
Removed tab characters from source file.
-CSPICE Version 1.0.0, 24-FEB-1999 (NJB)
Index_Entriesreturn the number of elements in a column entry |
Fri Dec 31 18:41:06 2021