Core: Add Multitap support

src/core/multitap.h

@@ -0,0 +1,56 @@
+#pragma once
+#include "common/state_wrapper.h"
+#include "common/types.h"
+#include "controller.h"
+#include "memory_card.h"
+#include <array>
+
+class Multitap final
+{
+public:
+  Multitap(u32 index);
+
+  void Reset();
+
+  ALWAYS_INLINE void SetEnable(bool enable) { m_enabled = enable; };
+  ALWAYS_INLINE bool IsEnabled() const { return m_enabled; };
+
+  bool DoState(StateWrapper& sw);
+
+  void ResetTransferState();
+  bool Transfer(const u8 data_in, u8* data_out);
+  ALWAYS_INLINE bool IsReadingMemoryCard() { return m_enabled && m_transfer_state == TransferState::MemoryCard; };
+
+private:
+  ALWAYS_INLINE static constexpr u8 GetMultitapIDByte() { return 0x80; };
+  ALWAYS_INLINE static constexpr u8 GetStatusByte() { return 0x5A; };
+
+  Controller* GetControllerForSlot(u32 slot) const;
+  MemoryCard* GetMemoryCardForSlot(u32 slot) const;
+
+  bool TransferController(u32 slot, const u8 data_in, u8* data_out) const;
+  bool TransferMemoryCard(u32 slot, const u8 data_in, u8* data_out) const;
+
+  enum class TransferState : u8
+  {
+    Idle,
+    MemoryCard,
+    ControllerCommand,
+    SingleController,
+    AllControllers
+  };
+
+  TransferState m_transfer_state = TransferState::Idle;
+  u8 m_selected_slot = 0;
+
+  u32 m_controller_transfer_step = 0;
+
+  bool m_invalid_transfer_all_command = false;
+  bool m_transfer_all_controllers = false;
+  bool m_current_controller_done = false;
+
+  std::array<u8, 32> m_transfer_buffer{};
+
+  u32 m_index;
+  bool m_enabled = false;
+};