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/*
* cspgen(image, cycle) - calculate next "cyclic space" generation
*
* The image is considered a torus, with top and bottom connected directly
* and with sides connected using a shift of one row.
*/
/*
* internal buffer layout:
*
* image header
* copy of last row
* original array
* copy of first row
*
* new array is stored atop old array, but directly after the header.
*/
#include <stdlib.h>
#include <string.h>
#include "icall.h"
int cspgen(int argc, descriptor *argv)
{
int ulength, period, i;
char *ustring, *udata, *cycle;
char *old, *new;
char o, x;
int w, h, n; /* width, height, total pixels */
char hbuf[20]; /* image header buffer */
int hlen; /* header length */
static char *ibuf; /* image buffer */
static int ilen; /* buffer length */
int ineed; /* buffer length needed */
static char map[256]; /* mapping from one char to next */
/*
* Get the parameters.
*/
ArgString(1); /* validate types */
ArgString(2);
ustring = StringAddr(argv[1]); /* universe string and length */
ulength = StringLen(argv[1]);
cycle = StringAddr(argv[2]); /* cycle and length */
period = StringLen(argv[2]);
sscanf(ustring, "%d", &w); /* row width */
/*
* Build the generation mapping table.
*/
map[cycle[period-1] & 0xFF] = cycle[0]; /* last maps to first */
for (i = 1; i < period; i++)
map[cycle[i-1] & 0xFF] = cycle[i];
/*
* Copy the image header (through the second comma) to hbuf.
*/
old = ustring;
new = hbuf;
while ((*new++ = *old++) != ',')
;
while ((*new++ = *old++) != ',')
;
udata = old;
hlen = udata - ustring; /* header length */
/*
* Allocate the image buffer.
*/
n = ulength - hlen; /* number of pixels */
if (n % w != 0)
Error(205);
h = n / w; /* image height */
ineed = hlen + n + 2 * w; /* buffer size needed */
if (ilen < ineed)
if (!(ibuf = realloc(ibuf, ilen = ineed)))
Error(305);
/*
* Copy the image into the buffer. Allow for the possibility that
* the image already be *in* the buffer.
*/
new = ibuf + hlen;
old = new + w;
memmove(old, udata, n); /* main image, leaving room */
memcpy(old - w, old + n - w, w); /* dup last row first first */
memcpy(old + n, old, w); /* dup first row beyond last */
/*
* Create the new image.
*/
memcpy(ibuf, hbuf, hlen);
for (i = 0; i < n; i++) {
o = *old;
x = map[o & 0xFF];
if (old[-1] == x || old[1] == x || old[-w] == x || old[w] == x)
o = x;
*new++ = o;
old++;
}
/*
* Return the result.
*/
RetConstStringN(ibuf, ulength);
}
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