Copy the logo data from the NDS ROM's header to the Boktai stub's header

src/GBACart.cpp

@@ -539,6 +539,57 @@ CartGameSolarSensor::CartGameSolarSensor(std::unique_ptr<u8[]>&& rom, u32 len, s
 {
 }
 
+std::unique_ptr<CartGameSolarSensor> CreateFakeSolarSensorROM(const char* gamecode, const NDSCart::CartCommon& cart, void* userdata) noexcept
+{
+    return CreateFakeSolarSensorROM(gamecode, cart.GetHeader().NintendoLogo, userdata);
+}
+
+std::unique_ptr<CartGameSolarSensor> CreateFakeSolarSensorROM(const char* gamecode, const GBACart::CartGame& cart, void* userdata) noexcept
+{
+    return CreateFakeSolarSensorROM(gamecode, cart.GetHeader().NintendoLogo, userdata);
+}
+
+std::unique_ptr<CartGameSolarSensor> CreateFakeSolarSensorROM(const char* gamecode, const u8* logo, void* userdata) noexcept
+{
+    if (!gamecode)
+        return nullptr;
+
+    if (strnlen(gamecode, sizeof(GBAHeader::GameCode)) > sizeof(GBAHeader::GameCode))
+        return nullptr;
+
+    bool solarsensor = false;
+    for (const char* i : SOLAR_SENSOR_GAMECODES)
+    {
+        if (strcmp(gamecode, i) == 0) {
+            solarsensor = true;
+            break;
+        }
+    }
+
+    if (!solarsensor)
+        return nullptr;
+
+    // just 256 bytes; we don't need a whole ROM!
+    constexpr size_t FAKE_BOKTAI_ROM_LENGTH = 0x100;
+    std::unique_ptr<u8[]> rom = std::make_unique<u8[]>(FAKE_BOKTAI_ROM_LENGTH);
+
+    // create a fake ROM
+    GBAHeader& header = *reinterpret_cast<GBAHeader*>(rom.get());
+    memcpy(header.Title, BOKTAI_STUB_TITLE, strnlen(BOKTAI_STUB_TITLE, sizeof(header.Title)));
+    memcpy(header.GameCode, gamecode, strnlen(gamecode, sizeof(header.GameCode)));
+    header.FixedValue = 0x96;
+    if (logo)
+    {
+        memcpy(header.NintendoLogo, logo, sizeof(header.NintendoLogo));
+    }
+    else
+    {
+        memset(header.NintendoLogo, 0xFF, sizeof(header.NintendoLogo));
+    }
+
+    return std::make_unique<CartGameSolarSensor>(std::move(rom), FAKE_BOKTAI_ROM_LENGTH, nullptr, 0, userdata);
+}
+
 const int CartGameSolarSensor::kLuxLevels[11] = {0, 5, 11, 18, 27, 42, 62, 84, 109, 139, 183};
 
 void CartGameSolarSensor::Reset()
@@ -874,6 +925,18 @@ void GBACartSlot::LoadAddon(void* userdata, int type) noexcept
     case GBAAddon_RumblePak:
         Cart = std::make_unique<CartRumblePak>(userdata);
         break;
+    case GBAAddon_SolarSensorBoktai1:
+        // US Boktai 1
+        Cart = CreateFakeSolarSensorROM("U3IE", nullptr, userdata);
+        break;
+    case GBAAddon_SolarSensorBoktai2:
+        // US Boktai 2
+        Cart = CreateFakeSolarSensorROM("U32E", nullptr, userdata);
+        break;
+    case GBAAddon_SolarSensorBoktai3:
+        // JP Boktai 3
+        Cart = CreateFakeSolarSensorROM("U33J", nullptr, userdata);
+        break;
 
     default:
         Log(LogLevel::Warn, "GBACart: !! invalid addon type %d\n", type);

src/GBACart.h

@@ -39,7 +39,7 @@ enum CartType
 struct GBAHeader
 {
     u32 EntryPoint;
-    u8 NintendoLogo[156];
+    u8 NintendoLogo[156]; // must be valid
     char Title[12];
     char GameCode[4];
     char MakerCode[2];
@@ -111,6 +111,7 @@ public:
     [[nodiscard]] const u8* GetROM() const override { return ROM.get(); }
     [[nodiscard]] u32 GetROMLength() const override { return ROMLength; }
     [[nodiscard]] const GBAHeader& GetHeader() const noexcept { return *reinterpret_cast<const GBAHeader*>(ROM.get()); }
+    [[nodiscard]] GBAHeader& GetHeader() noexcept { return *reinterpret_cast<GBAHeader*>(ROM.get()); }
 
     u8* GetSaveMemory() const override;
     u32 GetSaveMemoryLength() const override;
@@ -329,6 +330,23 @@ std::unique_ptr<CartCommon> ParseROM(const u8* romdata, u32 romlen, const u8* sr
 /// or \c nullptr if there was an error.
 std::unique_ptr<CartCommon> ParseROM(std::unique_ptr<u8[]>&& romdata, u32 romlen, std::unique_ptr<u8[]>&& sramdata, u32 sramlen, void* userdata = nullptr);
 
+/// Creates a solar sensor-enabled GBA cart without needing a real Boktai ROM.
+/// This enables the solar sensor to be used in supported games.
+/// Will not contain any SRAM.
+/// @param gamecode
+/// @param logo The Nintendo logo data embedded in the headers for GBA ROMs and NDS ROMs.
+/// Required for the cart to be recognized as a valid GBA cart.
+/// Overloads that accept cart objects directly exist as well.
+/// If not provided, then it will have to be patched with equivalent data
+/// from a real ROM (NDS or GBA) before booting the emulator.
+/// @param userdata Optional user data to associate with the cart.
+/// @return A CartGameSolarSensor if the ROM was created successfully,
+/// or nullptr if any argument is wrong (e.g. an incorrect game code).
+std::unique_ptr<CartGameSolarSensor> CreateFakeSolarSensorROM(const char* gamecode, const u8* logo, void* userdata = nullptr) noexcept;
+std::unique_ptr<CartGameSolarSensor> CreateFakeSolarSensorROM(const char* gamecode, const NDSCart::CartCommon& cart, void* userdata = nullptr) noexcept;
+std::unique_ptr<CartGameSolarSensor> CreateFakeSolarSensorROM(const char* gamecode, const GBACart::CartGame& cart, void* userdata = nullptr) noexcept;
+
+constexpr const char* BOKTAI_STUB_TITLE = "BOKTAI STUB";
 }
 
 #endif // GBACART_H

src/NDS.cpp

@@ -539,6 +539,26 @@ void NDS::Reset()
 void NDS::Start()
 {
     Running = true;
+
+    if (ConsoleType != 0)
+        return;
+
+    auto* ndscart = NDSCartSlot.GetCart();
+    if (!ndscart)
+        return;
+
+    if (auto* cart = GBACartSlot.GetCart(); cart && cart->Type() == GBACart::CartType::GameSolarSensor)
+    { // If we have a solar sensor cart inserted...
+        auto& solarcart = *static_cast<GBACart::CartGameSolarSensor*>(cart);
+        GBACart::GBAHeader& header = solarcart.GetHeader();
+        if (strncmp(header.Title, GBACart::BOKTAI_STUB_TITLE, sizeof(header.Title)) == 0) {
+            // If this is a stub Boktai cart (so we can use the sensor without a full ROM)...
+
+            // ...then copy the Nintendo logo data from the NDS ROM into the stub GBA ROM.
+            // Otherwise, the GBA cart won't be recognized.
+            memcpy(header.NintendoLogo, ndscart->GetHeader().NintendoLogo, sizeof(header.NintendoLogo));
+        }
+    }
 }
 
 static const char* StopReasonName(Platform::StopReason reason)