Automatic Game Pak size detection

source/main.c

@@ -5,9 +5,31 @@
 
 #define GBA_ROM_ADDR 0x08000000
 
+// This works fine on real hardware with all the GBA games I have but most likely will not work in emulators. (It didn't in MelonDS)
+int detectCartSize()
+{
+	char* c = (char*)GBA_ROM_ADDR;
+
+	for (int mbits = 1; mbits < 256; mbits *= 2)
+	{
+		c = (char*) GBA_ROM_ADDR + ((1024 * 128) * mbits) + 1;
+
+		if (c[0] == 0x00)
+		{
+			if (c[1] == 0x01 && c[3] == 0x02 && c[5] == 0x03 && c[7] == 0x04 && c[9] == 0x05 && c[11] == 0x06 && c[13] == 0x07 && c[15] == 0x08)
+			{
+				return mbits;
+			}
+		}
+	}
+
+	return 1;
+}
+
 int main(int argc, char* argv[])
 {
 	char gameID[7];
+	char gameID_old[6];
 	char gameName[13];
 	char path[256];
 
@@ -19,6 +41,8 @@ int main(int argc, char* argv[])
 	sysSetBusOwners(true, true);	// Allow the ARM9 to read from carts.
 	consoleDemoInit();				// Get a simple console to print stuff to.
 
+	cartMbits = detectCartSize();
+
 	if (!fatInitDefault())
 	{
 		printf("Failed to mount SD card!");	
@@ -34,12 +58,20 @@ int main(int argc, char* argv[])
 		memcpy(gameName, (void*)GBA_ROM_ADDR + 0xA0, 12);
 		memcpy(gameID, (void*)GBA_ROM_ADDR + 0xAC, 6);
 
+		if (strncmp(gameID, gameID_old, 6) != 0)
+		{
+			memcpy(gameID_old, gameID, 6);
+			cartMbits = detectCartSize();
+		}
+
 		printf("\x1b[1;1H ----------------------------");
 		printf("\x1b[2;1H  Current Game Pak in SLOT-2");
 		printf("\x1b[3;1H   %s (ID: %s)", gameName, gameID);
 		printf("\x1b[4;1H ----------------------------");
 		printf("\x1b[6;1HCart size: %03d Mbit (%05d KB)", cartMbits, 128 * cartMbits);
 		printf("\x1b[8;0H  Use LEFT/RIGHT to adjust the\n cart size.  If you're not sure\n    use the 256 Mbit option.");
+		printf("\x1b[31;1m\x1b[12;0HAutomatically detected cart size");
+		printf("\x1b[13;0H Don't set a manual cart size\nunless you get a corrupted dump!\x1b[39m");
 		printf("\x1b[18;0H Press START to  dump the game.");
 
 		if (keys & KEY_LEFT && cartMbits > 1)