pkb.f

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C> @file
C> @brief Encode an integer value within an integer array.
C>
C> @author J. Woollen @date 1994-01-06
 
C> This subroutine encodes an integer value within a specified
C> number of bits of an integer array, starting at the bit
C> immediately after a specified bit within the array.
C>
C> @param[in] NVAL    -- integer: Value to be encoded
C> @param[in] NBITS   -- integer: Number of bits of IBAY within
C>                       which to encode NVAL
C> @param[out] IBAY   -- integer(*): Array containing encoded NVAL
C> @param[in,out] IBIT -- integer: Bit pointer within IBAY
C>                        - On input, IBIT points to the bit within
C>                          IBAY after which to begin encoding NVAL.
C>                        - On output, IBIT points to the last bit
C>                          of IBAY which contains the encoded NVAL.
C>
C> @remarks
C> - This subroutine is the logical inverse of subroutine upb().
C> - This subroutine will not work properly if NBITS is greater than
C>   the number of bits in an integer, as determined via
C>   an internal call to subroutine wrdlen().
C>
C> @author J. Woollen @date 1994-01-06
      SUBROUTINE pkb(NVAL,NBITS,IBAY,IBIT)
 
      COMMON /hrdwrd/ nbytw,nbitw,iord(8)
 
      dimension ibay(*)
 
      CHARACTER*156 BORT_STR
 
C----------------------------------------------------------------------
C----------------------------------------------------------------------
 
      IF(nbits.GT.nbitw) GOTO 900
 
      nwd  = ibit/nbitw + 1
      nbt  = mod(ibit,nbitw)
      ival = nval
      IF(ishft(ival,-nbits).GT.0) ival = -1
      int = ishft(ival,nbitw-nbits)
      int = ishft(int,-nbt)
      msk = ishft(  -1,nbitw-nbits)
      msk = ishft(msk,-nbt)
      ibay(nwd) = irev(ior(iand(irev(ibay(nwd)),not(msk)),int))
      IF(nbt+nbits.GT.nbitw) THEN
 
C        There are less than NBITS bits remaining within the current
C        word (i.e. array member) of IBAY, so store as many bits as
C        will fit within the current word and then store the remaining
C        bits within the next word.
 
         int = ishft(ival,2*nbitw-(nbt+nbits))
         msk = ishft(  -1,2*nbitw-(nbt+nbits))
         ibay(nwd+1) = irev(ior(iand(irev(ibay(nwd+1)),not(msk)),int))
      ENDIF
 
      ibit = ibit + nbits
 
      RETURN
900   WRITE(bort_str,'("BUFRLIB: PKB - NUMBER OF BITS BEING PACKED '//
     . ', NBITS (",I4,"), IS > THE INTEGER WORD LENGTH ON THIS '//
     . 'MACHINE, NBITW (",I3,")")')
     . nbits,nbitw
      CALL bort(bort_str)
      END