upbb.f

Go to the documentation of this file.

C> @file
C> @brief Decode an integer value from an integer array.
C>
C> @author J. Woollen @date 1994-01-06
 
C> This subroutine decodes an integer value from 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> It is similar to subroutine upb(), except that here IBIT is
C> only an input argument, and the overall order of the arguments
C> is different.
C>
C> @param[in] IBAY  -- integer(*): Array containing encoded value
C> @param[in] IBIT  -- integer: Bit within IBAY after which to begin
C>                     decoding NVAL
C> @param[in] NBITS -- integer: Number of bits to be decoded
C> @param[out] NVAL -- integer: Decoded value
C>
C> @author J. Woollen @date 1994-01-06
      SUBROUTINE upbb(NVAL,NBITS,IBIT,IBAY)
 
      COMMON /hrdwrd/ nbytw,nbitw,iord(8)
 
      dimension ibay(*)
 
C----------------------------------------------------------------------
C----------------------------------------------------------------------
 
C  IF NBITS=0, THEN JUST SET NVAL=0 AND RETURN
C  -------------------------------------------
 
      IF(nbits.EQ.0)THEN
        nval=0
        GOTO 100
      ENDIF
 
      nwd = ibit/nbitw + 1
      nbt = mod(ibit,nbitw)
      int = ishft(irev(ibay(nwd)),nbt)
      int = ishft(int,nbits-nbitw)
      lbt = nbt+nbits
      IF(lbt.GT.nbitw) THEN
         jnt = irev(ibay(nwd+1))
         int = ior(int,ishft(jnt,lbt-2*nbitw))
      ENDIF
      nval = int
 
C  EXIT
C  ----
 
100   RETURN
      END