Index Page ekgi_c

A B C D E F G H I J K L M N O P Q R S T U V W X

Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       void ekgi_c ( SpiceInt          selidx,
                     SpiceInt          row,
                     SpiceInt          elment,
                     SpiceInt        * idata,
                     SpiceBoolean    * null,
                     SpiceBoolean    * found  )

#### Abstract

       Return an element of an entry in a column of integer
       type in a specified row.

#### Required_Reading

       EK

#### Keywords

       ASSIGNMENT
       EK

#### Brief_I/O

       Variable  I/O  Description
       --------  ---  --------------------------------------------------
       selidx     I   Index of parent column in SELECT clause.
       row        I   Row to fetch from.
       elment     I   Index of element, within column entry, to fetch.
       idata      O   Integer element of column entry.
       null       O   Flag indicating whether column entry was null.
       found      O   Flag indicating whether column was present in row.

#### Detailed_Input

       selidx         is the SELECT clause index of the column to fetch
                      from.  The range of selidx is from 0 to one less than
                      the number of columns in the SELECT clause.

       row            is the output row containing the entry to fetch
                      from.  The range of row is from 0 to one less than
                      the number of rows satisfying the previous query.

       elment         is the index of the element of the column entry
                      to fetch.  The normal range of elment is from 0 to
                      one less than the size of the column's entry, but
                      elment is allowed to exceed the number of elements in
                      the column entry; if it does, found is returned
                      as SPICEFALSE.  This allows the caller to read data
                      from the column entry in a loop without checking the
                      number of available elements first.

                      Null values in variable-sized columns are
                      considered to have size 1.

#### Detailed_Output

       idata          is the requested element of the specified column
                      entry.  If the entry is null, idata is undefined.

                      If idata is too short to accommodate the requested
                      column entry element, the element is truncated on
                      the right to fit idata.

       null           is a logical flag indicating whether the entry
                      belonging to the specified column in the specified
                      row is null.

       found          is a logical flag indicating whether the specified
                      element was found.  If the element does not exist,
                      found is returned as SPICEFALSE.

#### Parameters

       None.

#### Exceptions

       1)  If the input argument elment is less than 0, found is returned as
           SPICEFALSE, and the error SPICE(INVALIDINDEX) is signalled.
           However, elment is allowed to be greater than or equal to
           the number of elements in the specified column entry; this allows
           the caller to read data from the column entry in a loop without
           checking the number of available elements first.  If elment is
           greater than or equal to the number of available elements, found
           is returned as SPICEFALSE.

       2)  If selidx is outside of the range established by the
           last query passed to eksrch_, the error SPICE(INVALIDINDEX)
           will be signalled.

       3)  If the input argument row is less than 0 or greater than or
           equal to the number of rows matching the query, found is returned
           as SPICEFALSE, and the error SPICE(INVALIDINDEX) is signalled.

       4)  If the specified column does not have integer type, the
           error SPICE(INVALIDTYPE) is signalled.

       5)  If this routine is called when no E-kernels have been loaded,
           the error SPICE(NOLOADEDFILES) is signalled.

#### Files

          The EK "query and fetch" suite of functions reads binary `sequence
          component' EK files.  In order for a binary EK file to be
          accessible to this routine, the file must be `loaded' via a call
          to the function eklef_c.

          Text format EK files cannot be used by this routine; they must
          first be converted by binary format by the NAIF Toolkit utility
          SPACIT.

#### Particulars

       This routine allows retrieval of data from integer columns.

       This routine returns one element at a time in order to save the
       caller from imposing a limit on the size of the column entries
       that can be handled.

#### Examples

       1)  Suppose the EK table TAB contains the following columns:

              Column name   Data Type   Size
              -----------   ---------   ----
              INT_COL_1     INT         1
              INT_COL_2     INT         VARIABLE
              INT_COL_3     INT         10

           Suppose the query

              query = "SELECT INT_COL_1 FROM TAB"

           is issued to ekfind_c via the call

              ekfind_c ( query, lenout, nmrows, error, errmsg );

           To fetch and dump column values from the rows that satisfy the
           query, the loop below could be used.  Note that we don't check
           the found flags returned by ekgi_c since we know that every
           entry in column INT_COL_1 contains one element.

              /.
              Since INT_COL_1 was the first column selected,
              the selection index selidx is set to 0.
              The column is scalar, so the element index eltidx
              is set to 0.  The variable nmrows is the number of
              matching rows returned by ekfind_c.
              ./

              selidx = 0;
              eltidx = 0;

              for ( row = 0;  row < nmrows;  row++ )
                 {
                 printf ( "\nRow = %d\n\n", row );

                 /.
                 Fetch values from column INT_COL_1.
                 ./
                 ekgi_c ( selidx,  row,      eltidx,
                          ival,    &isnull,  &found );

                 if ( isnull )
                    {
                    printf ( "%s\n", "<null>" );
                    }
                 else
                    {
                    printf ( "%d\n", ival );
                    }
                 }

       2)  Suppose the EK table TAB is as in example 1, and we issue
           the query

              query = "SELECT INT_COL_1, INT_COL_2, INT_COL_3 FROM TAB"

           to ekfind_c via the call

              ekfind_c ( query, lenout, &nmrows, &error, errmsg );

           To fetch and dump column values from the rows that satisfy the
           query, the loop below could be used.  Note that we don't check
           the found flags returned by ekgi_c since we know in advance how
           many elements are contained in each column entry we fetch.

              for ( row = 0;  row < nmrows;  row++ )
                 {
                 printf ( "\nRow = %d\n\n", row );

                 /.
                 Fetch values from column INT_COL_1.  Since
                 INT_COL_1 was the first column selected, the
                 selection index selidx is set to 0.
                 ./

                 selidx = 0;
                 eltidx = 0;

                 ekgi_c ( selidx,    row,      eltidx,
                          ivals[0],  &isnull,  &found )

                 printf ( "\nColumn = INT_COL_1\n\n" );

                 if ( isnull )
                    {
                    printf ( "%s\n", "<null>" );
                    }
                 else
                    {
                    printf ( "%d\n", ivals[0] );
                    }

                 /.
                 Fetch values from column INT_COL_2 in the current
                 row.  Since INT_COL_2 contains variable-size array
                 entries, we call eknelt_c to determine how many
                 elements to fetch.
                 ./
                 selidx = 1;

                 eknelt_c ( selidx, row, &nelt );

                 eltidx = 0;
                 isnull = SPICEFALSE;

                 while (  ( eltidx < nelt ) && ( !isnull )  )
                    {

                    ekgi_c ( selidx,         row,      eltidx,
                             ivals[eltidx],  &isnull,  &found );

                    eltidx++;

                    /.
                    If the column entry is null, we'll be kicked
                    out of this loop after the first iteration.
                    ./
                    }

                 printf ( "\nColumn = INT_COL_2\n\n" );

                 if ( isnull )
                    {
                    printf ( "%s\n", "<null>" );
                    }
                 else
                    {
                    for ( i = 0;  i < nelt;  i++ )
                       {
                       printf ( "%d\n", ivals[i] );
                       }
                    }

                 /.
                 Fetch values from column INT_COL_3 in the current
                 row.  We need not call eknelt_c since we know how
                 many elements are in each column entry.
                 ./
                 selidx = 2;
                 eltidx = 0;
                 isnull = SPICEFALSE;

                 while (  ( eltidx < 10 ) && ( !isnull )  )
                    {

                    ekgi_c ( selidx,         row,      eltidx,
                             ivals[eltidx],  &isnull,  &found );

                    eltidx++;
                    }

                 printf ( "\nColumn = INT_COL_3\n\n" );

                 if ( isnull )
                    {
                    printf ( "%s\n", "<null>" );
                    }
                 else
                    {
                    for ( i = 0;  i < 10;  i++ )
                       {
                       printf ( "%d\n", ivals[i] );
                       }
                    }

                 }

       3)  See the Examples section of the query routine ekfind_c
           for an example in which the names and data types of the
           columns from which to fetch data are not known in advance.

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman   (JPL)

#### Version

       -CSPICE Version 1.1.1, 09-FEB-2003 (EDW)

           Minor edit to correct typo in header.

       -CSPICE Version 1.1.0, 09-JUL-1998 (NJB)

           Bug fix:  now uses local logical variable to capture the
           error flag value returned by the underlying f2c'd routine.

       -CSPICE Version 1.0.0, 27-MAR-1998

           Based on SPICELIB Version 1.1.0, 07-JUL-1996 (NJB)

#### Index_Entries

       fetch element from integer column entry

#### Link to routine ekgi_c source file ekgi_c.c

    Wed Apr  5 17:54:33 2017