# PLRSEG.H -- Macros for sequentially reading segments of a range list.
#
#	       plr_init (rl, descriptor)
#      npix = plr_nleft (descriptor)
#      val = plr_getseg (rl, descriptor, npix, value)
#
# plr_init	Initialize descriptor for sequential i/o from the rangelist RL.
# plr_nleft	Number of pixels left in the current line segment of constant
#		  value.  Zero is returned at the EOL.
# plr_getseg	Read NPIX pixels from the current segment, advancing to the
#		  next segment automatically when the the current segment is
#		  exhausted.
#
# The descriptor is an integer array, the contents of which are hidden from
# the application using these macros.

# Range list i/o descriptor.
define	LEN_PLRDES	4
define	rd_nleft	$1[1]
define	rd_value	$1[2]
define	rd_x		$1[3]
define	rd_rn		$1[4]

# PLR_NLEFT -- Number of pixels left in the current segment.
define	plr_nleft	rd_nleft($1)

# PLR_INIT -- Initialize the rangelist descriptor.
#define	(plr_init, {			# $1=rl $2=des
#	rd_x($2) = 1
#	rd_rn($2) = RL_FIRST
#	plr_nextseg ($1, $2)
#})

# PLR_GETSEG -- Read pixels from the current segment.
#define	(plr_getseg, {			# $1=rl $2=des $3=npix $4=value
#	$4 = rd_value($2)
#	rd_x($2) = rd_x($2) + $3
#	rd_nleft($2) = rd_nleft($2) - $3
#	if (rd_nleft($2) <= 0)
#	    plr_nextseg ($1, $2)
#})
	
# PLR_NEXTSEG -- Set up the next segment (internal routine).
#define	(plr_nextseg, {			# $1=rl $2=des
#	if (rd_rn($2) <= RL_LEN($1)) {
#	    if ($1[1,rd_rn($2)] > rd_x($2)) {
#		rd_value($2) = 0
#		rd_nleft($2) = $1[1,rd_x($2)] - rd_x($2)
#	    } else {
#		rd_value($2) = $1[3,rd_rn($2)]
#		rd_nleft($2) = $1[2,rd_rn($2)]
#		rd_rn($2) = rd_rn($2) + 1
#	    }
#	} else if (rd_x($2) <= RL_AXLEN($1)) {
#	    rd_value($2) = 0
#	    rd_nleft($2) = RL_AXLEN($1) - rd_x($2) + 1
#	}
#})


# PLR_INIT -- Initialize the rangelist descriptor.
define	(plr_init, {rd_x($2)=1;rd_rn($2)=RL_FIRST;plr_nextseg($1,$2);})

# PLR_GETSEG -- Read pixels from the current segment.
define	(plr_getseg, {$4=rd_value($2);rd_x($2)=rd_x($2)+$3;rd_nleft($2)=rd_nleft($2)-$3;if(rd_nleft($2) <= 0){plr_nextseg($1,$2)}})
	
# PLR_NEXTSEG -- Set up the next segment (internal routine).
define	(plr_nextseg, {if(rd_rn($2)<=RL_LEN($1)){if($1[1,rd_rn($2)]>rd_x($2)){rd_value($2)=0;rd_nleft($2)=$1[1,rd_x($2)]-rd_x($2);}else{rd_value($2)=$1[3,rd_rn($2)];rd_nleft($2)=$1[2,rd_rn($2)];rd_rn($2)=rd_rn($2)+1;}}else if(rd_x($2)<=RL_AXLEN($1)){rd_value($2)=0;rd_nleft($2)=RL_AXLEN($1)-rd_x($2)+1;}})