Optionally check a binary hack against an expected sequence of bytes.

This can be used to selectively disable certain binary hacks if they would crash a particular variety of a game build.

... well, *actually* this should have been the job of the SHA-256 hash. However, it turns out that certain other patches (*cough*gensokyo.org*cough*) have statically modified the binary to such an extent as to make unpatching their modifications annoying enough.

thcrap/src/binhack.c

@@ -145,14 +145,17 @@ int binhacks_apply(json_t *binhacks)
 	json_object_foreach(binhacks, key, hack) {
 		const char *title = json_object_get_string(hack, "title");
 		const char *code = json_object_get_string(hack, "code");
+		const char *expected = json_object_get_string(hack, "expected");
 		// Addresses can be an array, too
 		json_t *json_addr = json_object_get(hack, "addr");
 		size_t i;
 		json_t *addr_val;
 
 		// calculated byte size of the hack
 		size_t asm_size = binhack_calc_size(code);
+		size_t exp_size = binhack_calc_size(expected);
 		VLA(BYTE, asm_buf, asm_size);
+		VLA(BYTE, exp_buf, exp_size);
 
 		if(!asm_size) {
 			continue;
@@ -171,10 +174,20 @@ int binhacks_apply(json_t *binhacks)
 			if(binhack_render(asm_buf, addr, code)) {
 				continue;
 			}
-			PatchRegion((void*)addr, NULL, asm_buf, asm_size);
-			log_printf("OK\n");
+			if(exp_size > 0 && exp_size != asm_size) {
+				log_printf("different sizes for expected and new code, skipping verification... ");
+				exp_size = 0;
+			} else if(binhack_render(exp_buf, addr, expected)) {
+				exp_size = 0;
+			}
+			log_printf(
+				PatchRegion((void*)addr, exp_size ? exp_buf : NULL, asm_buf, asm_size)
+				? "OK\n"
+				: "expected bytes not matched, skipping...\n"
+			);
 		}
 		VLA_FREE(asm_buf);
+		VLA_FREE(exp_buf);
 	}
 	log_printf("------------------------\n");
 	return 0;