CLK/Machines/Atari/2600/Cartridges/MNetwork.hpp

//
//  CartridgeMNetwork.h
//  Clock Signal
//
//  Created by Thomas Harte on 18/03/2017.
//  Copyright 2017 Thomas Harte. All rights reserved.
//

#pragma once

#include "Cartridge.hpp"

namespace Atari2600::Cartridge {

class MNetwork: public BusExtender {
public:
	MNetwork(const uint8_t *const rom_base, const std::size_t rom_size) : BusExtender(rom_base, rom_size) {
		rom_ptr_[0] = rom_base + rom_size_ - 4096;
		rom_ptr_[1] = rom_ptr_[0] + 2048;
		high_ram_ptr_ = high_ram_;
	}

	void perform_bus_operation(
		const CPU::MOS6502::BusOperation operation,
		uint16_t address,
		uint8_t *const value
	) {
		address &= 0x1fff;
		if(!(address & 0x1000)) return;

		if(address >= 0x1fe0 && address <= 0x1fe6) {
			rom_ptr_[0] = rom_base_ + (address - 0x1fe0) * 2048;
		} else if(address == 0x1fe7) {
			rom_ptr_[0] = nullptr;
		} else if(address >= 0x1ff8 && address <= 0x1ffb) {
			int offset = (address - 0x1ff8) * 256;
			high_ram_ptr_ = &high_ram_[offset];
		}

		if(address & 0x800) {
			if(address < 0x1900) {
				high_ram_ptr_[address & 255] = *value;
			} else if(address < 0x1a00) {
				if(isReadOperation(operation)) *value = high_ram_ptr_[address & 255];
			} else {
				if(isReadOperation(operation)) *value = rom_ptr_[1][address & 2047];
			}
		} else {
			if(rom_ptr_[0]) {
				if(isReadOperation(operation)) *value = rom_ptr_[0][address & 2047];
			} else {
				if(address < 0x1400) {
					low_ram_[address & 1023] = *value;
				} else {
					if(isReadOperation(operation)) *value = low_ram_[address & 1023];
				}
			}
		}
	}

private:
	const uint8_t *rom_ptr_[2];
	uint8_t *high_ram_ptr_;
	uint8_t low_ram_[1024], high_ram_[1024];
};

}