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diff --git a/sys/plio/tf/plp2ll.x b/sys/plio/tf/plp2ll.x
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+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<plio.h>
+
+# PL_P2L -- Convert a pixel array to a line list.  The length of the list is
+# returned as the function value.
+
+int procedure pl_p2ll (px_src, xs, ll_dst, npix)
+
+long	px_src[ARB]		#I input pixel array
+int	xs			#I starting index in pixbuf
+short	ll_dst[ARB]		#O destination line list
+int	npix			#I number of pixels to convert
+
+long	hi, pv, nv, zero
+int	xe, x1, iz, ip, op, np, nz, dv, v
+define	done_ 91
+
+begin
+	# No input pixels?
+	if (npix <= 0)
+	    return (0)
+
+	# Initialize the linelist header.
+	LL_VERSION(ll_dst) = LL_CURVERSION
+	LL_HDRLEN(ll_dst) = LL_CURHDRLEN
+	LL_NREFS(ll_dst) = 0
+	LL_SETBLEN(ll_dst,0)
+
+	xe = xs + npix - 1
+	op = LL_CURHDRLEN + 1
+
+	# Pack the pixel array into a line list.  This is done by scanning
+	# the pixel list for successive ranges of pixels of constant nonzero
+	# value, where each range is described as follows:
+
+	zero = 0
+	pv = max (zero, px_src[xs])	# pixel value of current range
+	x1 = xs			# start index of current range
+	iz = xs			# start index of range of zeros
+	hi = 1			# current high value
+
+	# Process the data array.
+	do ip = xs, xe {
+	    if (ip < xe) {
+		# Get the next pixel value, loop again if same as previous one.
+		nv = max (zero, px_src[ip+1])
+		if (nv == pv)
+		    next
+
+		# If current range is zero, loop again to get nonzero range.
+		if (pv == 0) {
+		    pv = nv
+		    x1 = ip + 1
+		    next
+		}
+	    } else if (pv == 0)
+		x1 = xe + 1
+
+	    # Encode an instruction to regenerate the current range I0-IP
+	    # of N data values of nonzero level PV.  In the most complex case
+	    # we must update the high value and output a range of zeros,
+	    # followed by a range of NP high values.  If NP is 1, we can
+	    # probably use a PN or [ID]S instruction to save space.
+
+	    np = ip - x1 + 1
+	    nz = x1 - iz
+
+	    # Change the high value?
+	    if (pv > 0) {
+		dv = pv - hi
+		if (dv != 0) {
+		    # Output IH or DH instruction?
+		    hi = pv
+		    if (abs(dv) > I_DATAMAX) {
+			ll_dst[op] = M_SH + and (int(pv), I_DATAMAX)
+			op = op + 1
+			ll_dst[op] = pv / I_SHIFT
+			op = op + 1
+		    } else {
+			if (dv < 0)
+			    ll_dst[op] = M_DH + (-dv)
+			else
+			    ll_dst[op] = M_IH + dv
+			op = op + 1
+
+			# Convert to IS or DS if range is a single pixel.
+			if (np == 1 && nz == 0) {
+			    v = ll_dst[op-1]
+			    ll_dst[op-1] = or (v, M_MOVE)
+			    goto done_
+			}
+		    }
+		}
+	    }
+
+	    # Output range of zeros to catch up to current range?
+	    # The I_DATAMAX-1 limit is to allow adding M_PN+1 without
+	    # overflowing the range of the data segment.
+	    if (nz > 0) {
+		# Output the ZN instruction.
+		for (;  nz > 0;  nz = nz - (I_DATAMAX-1)) {
+		    ll_dst[op] = M_ZN + min(I_DATAMAX-1,nz)
+		    op = op + 1
+		}
+		# Convert to PN if range is a single pixel.
+		if (np == 1 && pv > 0) {
+		    ll_dst[op-1] = ll_dst[op-1] + M_PN + 1
+		    goto done_
+		}
+	    }
+
+	    # The only thing left is the HN instruction if we get here.
+	    for (;  np > 0;  np = np - I_DATAMAX) {
+		ll_dst[op] = M_HN + min(I_DATAMAX,np)
+		op = op + 1
+	    }
+done_
+	    x1 = ip + 1
+	    iz = x1
+	    pv = nv
+	}
+
+	LL_SETLEN(ll_dst, op - 1)
+	return (op - 1)
+end