Procedure

     EKRCED ( EK, read column entry element, d.p. )

     SUBROUTINE EKRCED ( HANDLE,  SEGNO,  RECNO,  COLUMN,
    .                    NVALS,   DVALS,  ISNULL          )

Abstract

     Read data from a double precision column in a specified EK
     record.

Required_Reading

     EK

Keywords

     EK
     FILES
     UTILITY

Declarations

     IMPLICIT NONE

     INCLUDE 'ekcoldsc.inc'
     INCLUDE 'eksegdsc.inc'
     INCLUDE 'ektype.inc'

     INTEGER               HANDLE
     INTEGER               SEGNO
     INTEGER               RECNO
     CHARACTER*(*)         COLUMN
     INTEGER               NVALS
     DOUBLE PRECISION      DVALS  ( * )
     LOGICAL               ISNULL

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     HANDLE     I   Handle attached to EK file.
     SEGNO      I   Index of segment containing record.
     RECNO      I   Record from which data is to be read.
     COLUMN     I   Column name.
     NVALS      O   Number of values in column entry.
     DVALS      O   D.p. values in column entry.
     ISNULL     O   Flag indicating whether column entry is null.

Detailed_Input

     HANDLE   is an EK file handle. The file may be open for read or
              write access.

     SEGNO    is the index of the segment from which data is to be
              read.

     RECNO    is the index of the record from which data is to be read.
              This record number is relative to the start of the
              segment indicated by SEGNO; the first record in the
              segment has index 1.

     COLUMN   is the name of the column from which data is to be read.

Detailed_Output

     NVALS,
     DVALS    are, respectively, the number of values found in the
              specified column entry and the set of values themselves.

              For columns having fixed-size entries, when column entry
              is null, NVALS is still set to the column entry size. For
              columns having variable- size entries, NVALS is set to 1
              for null entries.

     ISNULL   is a logical flag indicating whether the returned column
              entry is null.

Parameters

     None.

Exceptions

     1)  If HANDLE is invalid, an error is signaled by a routine in the
         call tree of this routine.

     2)  If SEGNO is out of range, an error is signaled by a routine in
         the call tree of this routine.

     3)  If RECNO is out of range, an error is signaled by a routine in
         the call tree of this routine.

     4)  If COLUMN is not the name of a declared column, an error
         is signaled by a routine in the call tree of this routine.

     5)  If COLUMN specifies a column of whose data type is not
         double precision, the error SPICE(WRONGDATATYPE) is signaled.

     6)  If COLUMN specifies a column of whose class is not
         a double precision class known to this routine, the error
         SPICE(NOCLASS) is signaled.

     7)  If an attempt is made to read an uninitialized column entry,
         an error is signaled by a routine in the call tree of this
         routine. A null entry is considered to be initialized, but
         entries do not contain null values by default.

     8)  If an I/O error occurs while reading or writing the indicated
         file, the error is signaled by a routine in the call tree of
         this routine.

Files

     See the EK Required Reading ek.req for a discussion of the EK file
     format.

Particulars

     This routine is a utility that allows an EK file to be read
     directly without using the high-level query interface.

Examples

     1)  Read the value in the third record of the column DCOL in
         the fifth segment of an EK file designated by HANDLE.

            CALL EKRCED ( HANDLE, 5, 3, 'DCOL', N, DVAL, ISNULL )

Restrictions

     1)  EK files open for write access are not necessarily readable.
         In particular, a column entry can be read only if it has been
         initialized. The caller is responsible for determining
         when it is safe to read from files open for write access.

Literature_References

     None.

Author_and_Institution

     N.J. Bachman       (JPL)
     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.3.1, 26-MAY-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.3.0, 06-FEB-2015 (NJB)

        Now uses ERRHAN to insert DAS file name into
        long error messages.

    SPICELIB Version 1.2.0, 20-JUN-1999 (WLT)

        Removed unbalanced call to CHKOUT.

    SPICELIB Version 1.1.0, 28-JUL-1997 (NJB)

        Bug fix: Record number, not record pointer, is now supplied
        to look up data in the class 8 case. Miscellaneous header
        changes were made as well.

    SPICELIB Version 1.0.0, 06-NOV-1995 (NJB)