Mesen/Core/BaseFdsChannel.h

#pragma once
#include "stdafx.h"
#include "Snapshotable.h"

class BaseFdsChannel : public Snapshotable
{
protected:
	uint8_t _speed = 0;
	uint8_t _gain = 0;
	bool _envelopeOff = false;
	bool _volumeIncrease = false;
	uint16_t _frequency = 0;

	uint32_t _timer = 0;

	uint8_t _masterSpeed = 0;

	void StreamState(bool saving)
	{
		Stream<uint8_t>(_speed);
		Stream<uint8_t>(_gain);
		Stream<bool>(_envelopeOff);
		Stream<bool>(_volumeIncrease);
		Stream<uint16_t>(_frequency);

		Stream<uint32_t>(_timer);

		Stream<uint8_t>(_masterSpeed);
	}

public:
	void SetMasterEnvelopeSpeed(uint8_t masterSpeed)
	{
		_masterSpeed = masterSpeed;
	}

	virtual void WriteReg(uint16_t addr, uint8_t value)
	{
		switch(addr & 0x03) {
			case 0:
				_speed = value & 0x3F;
				_volumeIncrease = (value & 0x40) == 0x40;
				_envelopeOff = (value & 0x80) == 0x80;

				//"Writing to this register immediately resets the clock timer that ticks the volume envelope (delaying the next tick slightly)."
				_timer = 8 * (_speed + 1) * _masterSpeed;
				break;

			case 2:
				_frequency = (_frequency & 0x0F00) | value;
				break;

			case 3:
				_frequency = (_frequency & 0xFF) | ((value & 0x0F) << 8);
				break;
		}
	}

	void TickEnvelope(bool envelopesDisabled)
	{
		if(_envelopeOff) {
			_gain = _speed;
		} else if(!envelopesDisabled && _speed > 0) {
			if(_timer > 0) {
				_timer--;
			} else {
				_timer = 8 * (_speed + 1) * _masterSpeed;

				if(_volumeIncrease) {
					if(_gain < 32) {
						_gain++;
					}
				} else {
					if(_gain > 0) {
						_gain--;
					}
				}
			}
		}
	}

	uint8_t GetGain()
	{
		return _gain;
	}

	uint16_t GetFrequency()
	{
		return _frequency;
	}
};