FUNCTION IREV(N)

C$$$  SUBPROGRAM DOCUMENTATION BLOCK
C
C SUBPROGRAM:    IREV
C   PRGMMR: WOOLLEN          ORG: NP20       DATE: 1994-01-06
C
C ABSTRACT: THIS FUNCTION WILL, WHEN THE LOCAL MACHINE IS "LITTLE-
C   ENDIAN" (I.E., 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 PROGRAM HISTORY LOG:
C 1994-01-06  J. WOOLLEN -- ORIGINAL AUTHOR
C 2003-11-04  J. ATOR    -- ADDED DOCUMENTATION
C 2003-11-04  S. BENDER  -- ADDED REMARKS/BUFRLIB ROUTINE
C                           INTERDEPENDENCIES
C 2003-11-04  D. KEYSER  -- UNIFIED/PORTABLE FOR WRF; ADDED HISTORY
C                           DOCUMENTATION
C 2007-01-19  J. ATOR    -- BIG-ENDIAN VS. LITTLE-ENDIAN IS NOW
C                           DETERMINED AT COMPILE TIME AND CONFIGURED
C                           WITHIN BUFRLIB VIA CONDITIONAL COMPILATION
C                           DIRECTIVES
C
C USAGE:    IREV (N)
C   INPUT ARGUMENT LIST:
C     N        - INTEGER: INTEGER WORD WITH BYTES ORDERED ACCORDING TO
C                THE "BIG-ENDIAN" NUMBERING SCHEME
C
C   OUTPUT ARGUMENT LIST:
C     IREV     - 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 REMARKS:
C    THIS ROUTINE CALLS:        None
C    THIS ROUTINE IS CALLED BY: IPKM     IUPM     PKB      PKC
C                               UPB      UPBB
C                               Normally not called by any application
C                               programs.
C
C ATTRIBUTES:
C   LANGUAGE: FORTRAN 77
C   MACHINE:  PORTABLE TO ALL PLATFORMS
C
C$$$

      COMMON /HRDWRD/ NBYTW,NBITW,NREV,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