+char *validate_seed(game_params *params, char *seed)
+{
+ char *p, *err;
+ int i, area;
+ int *used;
+
+ area = params->w * params->h;
+ p = seed;
+ err = NULL;
+
+ used = snewn(area, int);
+ for (i = 0; i < area; i++)
+ used[i] = FALSE;
+
+ for (i = 0; i < area; i++) {
+ char *q = p;
+ int n;
+
+ if (*p < '0' || *p > '9') {
+ err = "Not enough numbers in string";
+ goto leave;
+ }
+ while (*p >= '0' && *p <= '9')
+ p++;
+ if (i < area-1 && *p != ',') {
+ err = "Expected comma after number";
+ goto leave;
+ }
+ else if (i == area-1 && *p) {
+ err = "Excess junk at end of string";
+ goto leave;
+ }
+ n = atoi(q);
+ if (n < 0 || n >= area) {
+ err = "Number out of range";
+ goto leave;
+ }
+ if (used[n]) {
+ err = "Number used twice";
+ goto leave;
+ }
+ used[n] = TRUE;
+
+ if (*p) p++; /* eat comma */
+ }
+
+ leave:
+ sfree(used);
+ return err;
+}
+