readns.f

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C> @file
C> @brief Read the next data subset from a BUFR file that was
C> previously opened for reading.

C> This subroutine provides a handy way to combine the functionality
C> of subroutines readmg() and readsb() within a single subroutine
C> call.
C>
C> @author J. Woollen
C> @date 1994-01-06
C>
C> @param[in] LUNIT   -- integer: Fortran logical unit number for
C>                       BUFR file
C> @param[out] SUBSET  -- character*8: Table A mnemonic for type of
C>                        data subset that was read
C>                        (see [DX BUFR Tables](@ref dfbftab)
C>                        for further information about Table A mnemonics)
C> @param[out] JDATE   -- integer: Date-time stored within Section 1 of
C>                        BUFR message containing data subset that
C>                        was read, in format of either
C>                        YYMMDDHH or YYYYMMDDHH, depending on the most
C>                        recent call to subroutine datelen()
C> @param[out] IRET    -- integer: return code
C>                           - 0 = new BUFR data subset was successfully
C>                                 read into internal arrays
C>                           - -1 = there are no more BUFR data subsets
C>                                 in the file connected to logical unit
C>                                 LUNIT
C>
C> <p>Logical unit LUNIT should have already been opened for
C> input operations via a previous call to subroutine openbf().
C> But once that is done, the application program can immediately call
C> this subroutine to read each new data subset from the
C> associated BUFR file, and the subroutine will automatically open
C> and close each new BUFR message internally as needed, so that
C> subsequent calls can immediately be made to any of the various
C> [values-reading subroutines](@ref hierarchy).
C>
C> <b>Program history log:</b>
C> | Date | Programmer | Comments |
C> | -----|------------|----------|
C> | 1994-01-06 | J. Woollen | Original author |
C> | 1998-07-08 | J. Woollen | Replaced call to Cray library routine "ABORT" with call to new internal routine bort(); modified to make Y2K compliant |
C> | 1999-11-18 | J. Woollen | The number of BUFR files which can be opened at one time increased from 10 to 32 |
C> | 2003-11-04 | D. Keyser  | MAXJL (maximum number of jump/link entries) increased from 15000 to 16000 |
C> | 2014-12-10 | J. Ator    | Use modules instead of COMMON blocks |
C>
      SUBROUTINE readns(LUNIT,SUBSET,JDATE,IRET)

      USE moda_msgcwd
      USE moda_tables

      CHARACTER*8  subset

C-----------------------------------------------------------------------
C-----------------------------------------------------------------------

C  REFRESH THE SUBSET AND JDATE PARAMETERS
C  ---------------------------------------

      CALL status(lunit,lun,il,im)
      IF(il.EQ.0) goto 900
      IF(il.GT.0) goto 901
      subset = tag(inode(lun))
      jdate  = idate(lun)

C  READ THE NEXT SUBSET IN THE BUFR FILE
C  -------------------------------------

1     CALL readsb(lunit,iret)
      IF(iret.NE.0) THEN
         CALL readmg(lunit,subset,jdate,iret)
         IF(iret.EQ.0) goto 1
      ENDIF

C  EXITS
C  -----

      RETURN
900   CALL bort('BUFRLIB: READNS - INPUT BUFR FILE IS CLOSED, IT MUST'//
     . ' BE OPEN FOR INPUT')
901   CALL bort('BUFRLIB: READNS - INPUT BUFR FILE IS OPEN FOR OUTPUT'//
     . ', IT MUST BE OPEN FOR INPUT')
      END