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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <plset.h>
include <imhdr.h>
include <imio.h>
# IMCSSZ -- Compute size of buffer needed to hold the section defined
# by the logical vectors VS and VE. If type conversion is needed,
# must allow space for whichever pixel is largest. If subsampling is
# in use (step size greater than one), must allow extra space for the
# unsampled data.
long procedure imcssz (im, vs, ve, ndim, dtype, npix, rwflag)
pointer im # image descriptor
long vs[ARB], ve[ARB] # endpoints of section
int ndim # dimensionality of section
int dtype # datatype of pixels in section
long npix # number of pixels in section (output)
int rwflag # section is to be read or written
int step, i, sz_pixel, npix_per_line, extra_pix
long buf_size
int sizeof()
begin
sz_pixel = max (sizeof(IM_PIXTYPE(im)), sizeof(dtype))
if (IM_VMAP(im,1) == 1)
step = abs (IM_VSTEP(im,1))
else
step = 1
# Compute the total number of pixels in the subraster.
npix_per_line = abs (ve[1] - vs[1]) + 1
npix = npix_per_line
for (i=2; i <= ndim; i=i+1)
npix = npix * (abs (ve[i] - vs[i]) + 1)
# If the sample step size is greater than one, but less than
# IM_MAXSTEP, allow extra space for the final unsampled line.
# If not subsampling, and the buffer is for writing, add extra
# space so that writes can be an integral number of device
# blocks in size.
extra_pix = 0
if (step != 1) {
if (step <= IM_MAXSTEP && rwflag == IM_READ)
extra_pix = (step - 1) * npix_per_line
} else if (rwflag == IM_WRITE)
extra_pix = (IM_PHYSLEN(im,1) - IM_SVLEN(im,1))
# If accessing a mask image with range list i/o, the maximum size
# range list may be larger than the size of an image line in pixels.
# Allow some extra space to permit such range lists to be read in
# without buffer overflow; a runtime error is still possible if the
# subraster contains multiple lines, and an individual range list
# exceeds the length of the line in which it must be stored.
if (and (IM_PLFLAGS(im), PL_RLIO) != 0)
extra_pix = max (extra_pix, RL_MAXLEN(IM_PL(im)) - npix_per_line)
buf_size = (npix + extra_pix) * sz_pixel # size buf, chars
return (buf_size)
end
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