upds3.f

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C> @file
C> @brief Read data descriptors from Section 3 of a BUFR message.

C> This subroutine returns the sequence of data descriptors
C> contained within Section 3 of a BUFR message.
C>
C> @author J. Ator
C> @date 2003-11-04
C>
C> @param[in]  MBAY    - integer(*): BUFR message
C> @param[in] LCDS3    - integer: Dimensioned size of CDS3;
C>                       used by the subroutine to ensure that
C>                       it doesn't overflow the CDS3 array
C> @param[out] CDS3    - character*6(*): Data descriptor sequence
C>                       within Section 3 of MBAY
C> @param[out] NDS3    - integer: Number of data descriptors in CDS3
C>
C> @remarks
C> - The start of the BUFR message (i.e. the string 'BUFR') must be
C>   aligned on the first 4 bytes of MBAY.
C> - This subroutine does not recursively resolve any Table D
C>   descriptors from within Section 3; rather, what is returned in
C>   CDS3 is the exact list of data descriptors as it appears within
C>   Section 3 of MBAY.
C>
C> <b>Program history log:</b>
C> - 2003-11-04  J. Ator    -- Original author
C> - 2004-08-18  J. Ator    -- Removed IFIRST check, since wrdlen() now
C>                             keeps track of whether it has been called
C> - 2005-11-29  J. Ator    -- Use getlens()
C> - 2009-03-23  J. Ator    -- Added LCDS3 argument and check
C>
      SUBROUTINE upds3(MBAY,LCDS3,CDS3,NDS3)

      dimension mbay(*)

      CHARACTER*6 cds3(*), adn30

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

C     Call subroutine WRDLEN to initialize some important information
C     about the local machine, just in case subroutine OPENBF hasn't
C     been called yet.

      CALL wrdlen

C     Skip to the beginning of Section 3.

      CALL getlens(mbay,3,len0,len1,len2,len3,l4,l5)
      ipt = len0 + len1 + len2

C     Unpack the Section 3 descriptors.

      nds3 = 0
      DO jj = 8,(len3-1),2
         nds3 = nds3 + 1
         IF(nds3.GT.lcds3) goto 900
         cds3(nds3) = adn30(iupb(mbay,ipt+jj,16),6)
      ENDDO

      RETURN
900   CALL bort('BUFRLIB: UPDS3 - OVERFLOW OF OUTPUT DESCRIPTOR '//
     . 'ARRAY; TRY A LARGER DIMENSION FOR THIS ARRAY')
      END