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C----------------------------------------------------------------------
subroutine ftvcks(iunit,dataok,hduok,status)
C Verify the HDU by comparing the value of the computed checksums against
C the values of the DATASUM and CHECKSUM keywords if they are present.
C iunit i fortran unit number
C dataok i output verification code for the data unit alone
C hduok i output verification code for the entire HDU
C the code values = 1 verification is correct
C = 0 checksum keyword is not present
C = -1 verification not correct
C status i output error status
C
C written by Wm Pence, HEASARC/GSFC, Dec, 1994
integer iunit,dataok,hduok,status,tstat,i
double precision datsum,chksum,dsum
character keyval*20,comm*8
logical cexist,dexist
if (status .gt. 0)return
C check if the CHECKSUM keyword exists
tstat=status
call ftgkys(iunit,'CHECKSUM',keyval,comm,status)
if (status .le. 0)then
cexist=.true.
else
hduok=0
cexist=.false.
status=tstat
end if
C check if the DATASUM keyword exists and get its value
call ftgkys(iunit,'DATASUM',keyval,comm,status)
if (status .le. 0)then
dexist=.true.
else
dataok=0
dexist=.false.
status=tstat
end if
C return if neither keyword exists
if (.not. cexist .and. .not. dexist)return
C calculate the data checksum and the HDU checksum
call ftgcks(iunit,datsum,chksum,status)
if (status .gt. 0)return
if (dexist)then
C decode the datasum string into a double precision variable
do 10 i=1,20
if (keyval(i:i) .ne. ' ')then
call ftc2dd(keyval(i:20),dsum,status)
if (status .eq. 409)then
C couldn't read the keyword; assume it is out of date
status=tstat
dsum=-1.
end if
go to 15
end if
10 continue
dsum=0.
15 continue
if (dsum .eq. datsum)then
dataok=1
else
dataok=-1
end if
end if
if (cexist)then
if (chksum .eq. 0 .or. chksum .eq. 4.294967295D+09)then
hduok=1
else
hduok=-1
end if
end if
end
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