WSJT-X/libm65/ccf2.f

      subroutine ccf2(ss,nz,nflip,ccfbest,lagpk)

!      parameter (LAGMAX=60)
      parameter (LAGMAX=200)
      real ss(nz)
      real ccf(-LAGMAX:LAGMAX)
      integer npr(126)

C  The JT65 pseudo-random sync pattern:
      data npr/
     + 1,0,0,1,1,0,0,0,1,1,1,1,1,1,0,1,0,1,0,0,
     + 0,1,0,1,1,0,0,1,0,0,0,1,1,1,0,0,1,1,1,1,
     + 0,1,1,0,1,1,1,1,0,0,0,1,1,0,1,0,1,0,1,1,
     + 0,0,1,1,0,1,0,1,0,1,0,0,1,0,0,0,0,0,0,1,
     + 1,0,0,0,0,0,0,0,1,1,0,1,0,0,1,0,1,1,0,1,
     + 0,1,0,1,0,0,1,1,0,0,1,0,0,1,0,0,0,0,1,1,
     + 1,1,1,1,1,1/
      save

      ccfbest=0.
      lag1=-LAGMAX
      lag2=LAGMAX
      do lag=lag1,lag2
         s0=0.
         s1=0.
         do i=1,126
            j=2*(8*i + 43) + lag
            if(j.ge.1 .and. j.le.nz-8) then
               x=ss(j)+ss(j+8)             !Add two half-symbol contributions
               if(npr(i).eq.0) then
                  s0=s0 + x
               else
                  s1=s1 + x
               endif
            endif
         enddo
         ccf(lag)=nflip*(s1-s0)
         if(ccf(lag).gt.ccfbest) then
            ccfbest=ccf(lag)
            lagpk=lag
         endif
      enddo

      return
      end