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1 files changed, 105 insertions, 0 deletions

diff --git a/noao/nproto/ir/irimisec.x b/noao/nproto/ir/irimisec.x
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+++ b/noao/nproto/ir/irimisec.x
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+include <ctype.h>
+
+# IR_DECODE_SECTION -- Procedure to decode the reference section.
+
+int procedure ir_decode_section (section, ncols, nrows, c1ref, c2ref, l1ref,
+	l2ref)
+
+char	section[ARB]	# reference subraster section
+int	ncols		# number of columns in the image
+int	nrows		# number of rows in the image
+int	c1ref		# initial column
+int	c2ref		# final reference column
+int	l1ref		# initial reference line
+int	l2ref		# final reference line
+
+char	leftbkt
+int	index, ip, step
+int	ir_decode_subscript(), stridx()
+
+begin
+	leftbkt = '['
+	index = stridx (leftbkt, section)
+	if (index == 0)
+	    return (ERR)
+	ip = index + 1
+        if (ir_decode_subscript (section, ip, ncols, c1ref, c2ref, step) == ERR)
+	    return (ERR)
+        if (ir_decode_subscript (section, ip, nrows, l1ref, l2ref, step) == ERR)
+	    return (ERR)
+	return (OK)
+end
+
+
+# IR_DECODE_SUBSCRIPT -- Decode a single subscript expression to produce the
+# range of values for that subscript (X1:X2), and the sampling step size, STEP.
+# Note that X1 may be less than, greater than, or equal to X2, and STEP may
+# be a positive or negative nonzero integer.  Various shorthand notations are
+# permitted, as is embedded whitespace.
+
+int procedure ir_decode_subscript (section, ip, maxnumber, x1, x2, step)
+
+char	section[ARB]
+int	ip
+int	maxnumber
+long	x1, x2, step, temp
+int	ctol()
+
+begin
+	x1 = 1
+	x2 = maxnumber
+	step = 1
+
+	while (IS_WHITE(section[ip]))
+	    ip = ip + 1
+
+	# Get X1, X2.
+	if (ctol (section, ip, temp) > 0) {			# [x1
+	    x1 = temp
+	    if (section[ip] == ':') {	
+		ip = ip + 1
+		if (ctol (section, ip, x2) == 0)		# [x1:x2
+		    return (ERR)
+	    } else
+		x2 = x1
+
+	} else if (section[ip] == '-') {
+	    x1 = maxnumber						# [-*
+	    x2 = 1
+	    ip = ip + 1
+	    if (section[ip] == '*')
+		ip = ip + 1
+
+	} else if (section[ip] == '*')				# [*
+	    ip = ip + 1
+
+	while (IS_WHITE(section[ip]))
+	    ip = ip + 1
+
+	# Get sample step size, if give.
+	if (section[ip] == ':') {				# ..:step
+	    ip = ip + 1
+	    if (ctol (section, ip, step) == 0)
+		return (ERR)
+	    else if (step == 0)
+		return (ERR)
+	}
+
+	# Allow notation such as "-*:5", (or even "-:5") where the step
+	# is obviously supposed to be negative.
+
+	if (x1 > x2 && step > 0)
+	    step = -step
+	
+	while (IS_WHITE(section[ip]))
+	    ip = ip + 1
+
+	if (section[ip] == ',') {
+	    ip = ip + 1
+	    return (OK)
+	} else if (section[ip] == ']')
+	    return (OK)
+	else
+	    return (ERR)
+
+end