C
C $Id: rdbox.F,v 1.3 1998/07/16 16:40:27 jjv5 Exp arjan $
C
C------------------------------------------------------------------------
      SUBROUTINE RDBOX(IERROR)
C
C     READS IN BOX DIMENSIONS FOR PERIODIC BOUNDARY CONDITIONS.
C
C     FOR A BOX THAT IS 15.0 BY 20.0 BY 25.0, THE FORMAT OF THE
C     INPUT WOULD BE:
C
C     BOX
C       XBOX=15.0 YBOX=20.0 ZBOX=25.0
C     END_BOX
C
C     THE ERROR FLAG IS SET TO ONE IF ANY ERRORS ARE ENCOUNTERED WHILE
C     READING THIS INFORMATION.
C
      IMPLICIT DOUBLE PRECISION (A-H,O-Z)
#include "divcon.dim"
#include "divcon.h"
C
C     LOCAL:
C
      CHARACTER LINE*80,BOXSTR(3)*4
      DATA BOXSTR /'XBOX','YBOX','ZBOX'/
      SAVE BOXSTR
      LOGICAL READIT(3)
C
      IERROR = 0
C
C-RDC       WRITE(IOUT,'(//" PBC BOX DIMENSIONS:",
C-RDC      &     /" ------------------"/)')
C
C     RETURN WITH AN ERROR IF THE USER HAS NOT DEFINED RESIDUES.
C
      IF(NRES.EQ.0)THEN
        IERROR = 1
        WRITE(IOUT,
     .       '(/" CANNOT USE PERIODIC BOUNDARY CONDITIONS",
     .                " UNLESS RESIDUES ARE DEFINED")')
        RETURN
      ENDIF
C
C      READIT(1) = .FALSE.
C      READIT(2) = .FALSE.
C      READIT(3) = .FALSE.
C      NREAD = 0
C 100  READ(INPT,FMT='(A80)',END=1000) LINE
C      CALL UPCASE1(LINE,80)
C      IF(INDEX(LINE,'END_BOX').NE.0)THEN
C        IF(NREAD.LT.3)THEN
C          IERROR = 1
C          WRITE(IOUT,
C     .         '(/" SPECIFICATION OF PBC BOX DIMENSIONS",
C     .                  " IS INCOMPLETE")')
C        ELSE
!          WRITE(IOUT,'(" XBOX =",F8.4,
!     .                "  YBOX =",F8.4,
!     .                "  ZBOX =",F8.4)') (DBOX(I),I=1,3)
          DHALF(1) = 0.5D0*DBOX(1)
          DHALF(2) = 0.5D0*DBOX(2)
          DHALF(3) = 0.5D0*DBOX(3)
          bmin = min(dbox(1),dbox(2))
          bmin = min(bmin,dbox(3))
          if (drmc.ge.bmin) then
             write(iout,
     .            '(/" DR FOR MONTE CARLO MOVE IS EQUAL OR GREATER",
     .            " THAN MINIMUM BOXLENGTH")')
             ierror = 1
             return
          endif
C        ENDIF
C        RETURN
C      ELSEIF(INDEX(LINE,'BOX').NE.0.AND.
C     .       INDEX(LINE,'=').EQ.0)THEN
C         write(iout,'(/" ERROR IN BOX SPECIFICATION")')
C         ierror = 1
C         return
C      ELSE
C
C       LOOK FOR BOX DIMENSIONS.
C
C        CALL WDJOIN(LINE,80,'=',IERROR)
C        IF(IERROR.NE.0)THEN
C          WRITE(IOUT,
C     .          '(/" IMPROPER USE OF EQUALS SIGN IN PBC BOX",
C     .                  " DIMENSIONS")')
C          RETURN
C        ENDIF
C
C        ISTART = 1
C 200    CALL RDWORD(LINE,ISTART,ISTOP)
C
C       IF THERE ARE NO MORE WORDS LEFT ON THIS LINE, GO BACK AND
C       READ ANOTHER LINE.
C
C        IF(ISTART.EQ.0) GO TO 100
C
C       LOOK FOR 'XBOX=', 'YBOX=', 'ZBOX=' STRINGS IN CURRENT WORD.
C
C        DO 300 IBOX=1,3
C          IF(INDEX(LINE(ISTART:ISTOP),BOXSTR(IBOX)).NE.0)THEN
C            IF(READIT(IBOX)) GO TO 200
C            CALL RDNUM(LINE,ISTART,DBOX(IBOX),IERROR)
C            IF(IERROR.NE.0) GO TO 2000
C            NREAD = NREAD + 1
C            READIT(IBOX) = .TRUE.
C            IF(NREAD.LT.3)THEN
C              ISTART = ISTOP + 1
C              GO TO 200
C            ELSE
C              GO TO 100
C            ENDIF
C          ENDIF
C 300    CONTINUE
C
C       UNRECOGNIZED SPECIFICATION IF NONE OF THE CORRECT STRINGS
C       WAS FOUND.
C
C        IERROR = 1
C        WRITE(IOUT,
C     .       '(/" UNRECOGNIZED PBC BOX SPECIFICATION: ",
C     .        80A1)') (LINE(I:I),I=ISTART,ISTOP)
C        RETURN
C      ENDIF
C
C 1000 IERROR = 1
C      WRITE(IOUT,
C     .     '(/" END-OF-FILE ENCOUNTERED WHILE READING PBC",
C     .              " BOX DIMENSIONS")')
C      RETURN
C 2000 IERROR = 1
C      WRITE(IOUT,
C     .     '(/" ERROR READING PBC BOX DIMENSIONS")')
C      RETURN

      END