+ const char *s = s0;
+ unsigned char *d = (void *)dest;
+ unsigned long a[4] = { 0 };
+ char *z;
+ int i;
+
+ for (i=0; i<4; i++) {
+ a[i] = strtoul(s, &z, 0);
+ if (z==s || (*z && *z != '.') || !isdigit(*s))
+ return 0;
+ if (!*z) break;
+ s=z+1;
+ }
+ if (i==4) return 0;
+ switch (i) {
+ case 0:
+ a[1] = a[0] & 0xffffff;
+ a[0] >>= 24;
+ case 1:
+ a[2] = a[1] & 0xffff;
+ a[1] >>= 16;
+ case 2:
+ a[3] = a[2] & 0xff;
+ a[2] >>= 8;
+ }
+ for (i=0; i<4; i++) {
+ if (a[i] > 255) return 0;
+ d[i] = a[i];
+ }
+ return 1;