C---------------------------------------------------------------------- subroutine ftpcks(iunit,status) C Create or update the checksum keywords in the CHU. These keywords C provide a checksum verification of the FITS HDU based on the ASCII C coded 1's complement checksum algorithm developed by Rob Seaman at NOAO. C iunit i fortran unit number C status i output error status C C written by Wm Pence, HEASARC/GSFC, Sept, 1994 integer iunit,status C-------COMMON BLOCK DEFINITIONS:-------------------------------------------- integer nf,nb,ne parameter (nf = 3000) 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 integer tfield,tstart,tbcol,rowlen,tdtype,trept,tnull,scount integer theap,nxheap double precision tscale,tzero common/ft0002/tfield(nb),tstart(nb),tbcol(nf),rowlen(nb), & tdtype(nf),trept(nf),tscale(nf),tzero(nf),tnull(nf),scount(nb) & ,theap(nb),nxheap(nb) C-------END OF COMMON BLOCK DEFINITIONS----------------------------------- double precision sum,dsum,odsum integer ibuff,nrec,dd,mm,yy,dummy,i,tstat character datstr*8,string*16,comm*40,oldcks*16,datsum*20 logical complm if (status .gt. 0)return ibuff=bufnum(iunit) C generate current date string to put into the keyword comment call ftgsdt(dd,mm,yy,status) if (status .gt. 0)return datstr=' / / ' write(datstr(1:2),1001)dd write(datstr(4:5),1001)mm write(datstr(7:8),1001)yy 1001 format(i2) C replace blank with leading 0 in each field if required if (datstr(1:1) .eq. ' ')datstr(1:1)='0' if (datstr(4:4) .eq. ' ')datstr(4:4)='0' if (datstr(7:7) .eq. ' ')datstr(7:7)='0' C get the checksum keyword, if it exists, otherwise initialize it tstat=status call ftgkys(iunit,'CHECKSUM',oldcks,comm,status) if (status .eq. 202)then status=tstat oldcks=' ' comm='encoded HDU checksum updated on '//datstr call ftpkys(iunit,'CHECKSUM','0000000000000000',comm,status) end if C get the DATASUM keyword and convert it to a double precision value C if it exists, otherwise initialize it tstat=status call ftgkys(iunit,'DATASUM',datsum,comm,status) if (status .eq. 202)then status=tstat odsum=0. C set the CHECKSUM keyword as undefined oldcks=' ' comm='data unit checksum updated on '//datstr call ftpkys(iunit,'DATASUM',' 0',comm,status) else C decode the datasum into a double precision variable do 10 i=1,20 if (datsum(i:i) .ne. ' ')then call ftc2dd(datsum(i:20),odsum,status) if (status .eq. 409)then C couldn't read the keyword; assume it is out of date status=tstat odsum=-1. end if go to 15 end if 10 continue odsum=0. end if C rewrite the header END card, and following blank fill 15 call ftwend(iunit,status) if (status .gt. 0)return C now re-read the required keywords to determine the structure call ftrhdu(iunit,dummy,status) C write the correct data fill values, if they are not already correct call ftpdfl(iunit,status) C calc. checksum of the data records; first, calc number of data records nrec=(hdstrt(ibuff,chdu(ibuff)+1)-dtstrt(ibuff))/2880 dsum=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,dsum,status) end if if (dsum .ne. odsum)then C modify the DATASUM keyword with the correct value comm='data unit checksum updated on '//datstr C write the datasum into an I10 integer string write(datsum,2000)dsum 2000 format(f11.0) call ftmkys(iunit,'DATASUM',datsum(1:10),comm,status) C set the CHECKSUM keyword as undefined oldcks=' ' end if C if DATASUM was correct, check if CHECKSUM is still OK if (oldcks .ne. ' ')then C move to the start of the header call ftmbyt(iunit,hdstrt(ibuff,chdu(ibuff)),.true.,status) C accumulate the header checksum into the previous data checksum nrec= (dtstrt(ibuff)-hdstrt(ibuff,chdu(ibuff)))/2880 sum=dsum call ftcsum(iunit,nrec,sum,status) C encode the COMPLEMENT of the checksum into a 16-character string complm=.true. call ftesum(sum,complm,string) C return if the checksum is correct if (string .eq. '0000000000000000')then return else if (oldcks .eq. '0000000000000000')then C update the CHECKSUM keyword value with the checksum string call ftmkys(iunit,'CHECKSUM',string,'&',status) return end if end if C Zero the checksum and compute the new value comm='encoded HDU checksum updated on '//datstr call ftmkys(iunit,'CHECKSUM','0000000000000000',comm,status) C move to the start of the header call ftmbyt(iunit,hdstrt(ibuff,chdu(ibuff)),.true.,status) C accumulate the header checksum into the previous data checksum nrec= (dtstrt(ibuff)-hdstrt(ibuff,chdu(ibuff)))/2880 sum=dsum call ftcsum(iunit,nrec,sum,status) C encode the COMPLEMENT of the checksum into a 16-character string complm=.true. call ftesum(sum,complm,string) C update the CHECKSUM keyword value with the checksum string call ftmkys(iunit,'CHECKSUM',string,'&',status) end