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include <ctype.h>
# CCD_SECTION -- Parse a 2D image section into its elements.
# 1. The default values must be set by the caller.
# 2. A null image section is OK.
# 3. The first nonwhitespace character must be '['.
# 4. The last interpreted character must be ']'.
#
# This procedure should be replaced with an IMIO procedure at some
# point.
procedure ccd_section (section, x1, x2, xstep, y1, y2, ystep)
char section[ARB] # Image section
int x1, x2, xstep # X image section parameters
int y1, y2, ystep # X image section parameters
int i, ip, a, b, c, temp, ctoi()
define error_ 99
begin
# Decode the section string.
ip = 1
while (IS_WHITE(section[ip]))
ip = ip + 1
if (section[ip] == '[')
ip = ip + 1
else if (section[ip] == EOS)
return
else
goto error_
do i = 1, 2 {
while (IS_WHITE(section[ip]))
ip = ip + 1
# Default values
if (i == 1) {
a = x1
b = x2
c = xstep
} else {
a = y1
b = y2
c = ystep
}
# Get a:b:c. Allow notation such as "-*:c"
# (or even "-:c") where the step is obviously negative.
if (ctoi (section, ip, temp) > 0) { # a
a = temp
if (section[ip] == ':') {
ip = ip + 1
if (ctoi (section, ip, b) == 0) # a:b
goto error_
} else
b = a
} else if (section[ip] == '-') { # -*
temp = a
a = b
b = temp
ip = ip + 1
if (section[ip] == '*')
ip = ip + 1
} else if (section[ip] == '*') # *
ip = ip + 1
if (section[ip] == ':') { # ..:step
ip = ip + 1
if (ctoi (section, ip, c) == 0)
goto error_
else if (c == 0)
goto error_
}
if (a > b && c > 0)
c = -c
if (i == 1) {
x1 = a
x2 = b
xstep = c
} else {
y1 = a
y2 = b
ystep = c
}
while (IS_WHITE(section[ip]))
ip = ip + 1
if (section[ip] == ',')
ip = ip + 1
}
if (section[ip] != ']')
goto error_
return
error_
call error (0, "Error in image section specification")
end
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