irev.F

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C> @file
C> @brief Return a copy of an input integer word with
C> the bytes reversed.
C>
C> @author Woollen @date 1994-01-06
 
C> This function will, when the local machine is "little-endian" (i.e.,
C> when it uses a right to left scheme for numbering the bytes
C> within a machine word), return a copy of an input integer word with
C> the bytes reversed. Although, by definition (within WMO Manual
C> 306), a BUFR message is a stream of individual octets (i.e., bytes)
C> that is independent of any particular machine representation, the
C> BUFR archive library software often needs to interpret all or parts
C> of two or more adjacent bytes in order to construct an integer
C> word. By default, the software uses the "big-endian" (left to
C> right) scheme for numbering bytes. By reversing the bytes, irev()
C> allows the integer word to be properly read or written (depending
C> on whether input or output operations, respectively, are being
C> performed) on "little-endian" machines. If the local machine is
C> "big-endian", irev() simply returns a copy of the same integer that was
C> input.
C>
C> @param[in] N - integer: integer word with bytes ordered according
C> to the "big-endian" numbering scheme
C>
C> @return - integer: integer word with bytes ordered according to
C> the numbering scheme of the local machine (either
C> "big-endian" or "little-endian"; if "big-endian" then
C> this is just a direct copy of N).
C>
C> @author Woollen @date 1994-01-06
      FUNCTION irev(N)
 
      COMMON /hrdwrd/ nbytw,nbitw,iord(8)
 
      CHARACTER*8 cint,dint
      equivalence(cint,int)
      equivalence(dint,jnt)
 
C----------------------------------------------------------------------
C----------------------------------------------------------------------
 
#ifdef BIG_ENDIAN
      irev = n
#else
      int = n
      DO i=1,nbytw
        dint(i:i) = cint(iord(i):iord(i))
      ENDDO
      irev = jnt
#endif
 
      RETURN
      END