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C----------------------------------------------------------------------
subroutine ftgcks(iunit,datsum,chksum,status)
C calculate and encode the checksums of the data unit and the total HDU
C iunit i fortran unit number
C datsum d output checksum for the data
C chksum d output checksum for the entire HDU
C status i output error status
C
C written by Wm Pence, HEASARC/GSFC, Sept, 1994
integer iunit,status
double precision datsum,chksum
C-------COMMON BLOCK DEFINITIONS:--------------------------------------------
integer nb,ne
parameter (nb = 20)
parameter (ne = 200)
integer bufnum,chdu,hdutyp,maxhdu,hdstrt,hdend,nxthdr,dtstrt
integer nxtfld
logical wrmode
common/ft0001/bufnum(199),chdu(nb),hdutyp(nb),maxhdu(nb),
& wrmode(nb),hdstrt(nb,ne),hdend(nb),nxthdr(nb),dtstrt(nb),nxtfld
C-------END OF COMMON BLOCK DEFINITIONS:------------------------------------
integer ibuff,nrec
if (status .gt. 0)return
C calculate number of data records
ibuff=bufnum(iunit)
nrec=(hdstrt(ibuff,chdu(ibuff)+1)-dtstrt(ibuff))/2880
datsum=0.
if (nrec .gt. 0)then
C move to the start of the data
call ftmbyt(iunit,dtstrt(ibuff),.true.,status)
C accumulate the 32-bit 1's complement checksum
call ftcsum(iunit,nrec,datsum,status)
end if
C move to the start of the header
call ftmbyt(iunit,hdstrt(ibuff,chdu(ibuff)),.true.,status)
C calculate number of FITS blocks in the header
nrec=(dtstrt(ibuff)-hdstrt(ibuff,chdu(ibuff)))/2880
C accumulate the header into the checksum
chksum=datsum
call ftcsum(iunit,nrec,chksum,status)
end
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