CLK/Machines/Apple/AppleIIgs/Sound.hpp

//
//  Sound.hpp
//  Clock Signal
//
//  Created by Thomas Harte on 04/11/2020.
//  Copyright © 2020 Thomas Harte. All rights reserved.
//

#pragma once

#include <atomic>

#include "../../../ClockReceiver/ClockReceiver.hpp"
#include "../../../Concurrency/AsyncTaskQueue.hpp"
#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"

namespace Apple::IIgs::Sound {

class GLU: public Outputs::Speaker::BufferSource<GLU, false> {	// TODO: isn't this stereo?
public:
	GLU(Concurrency::AsyncTaskQueue<false> &audio_queue);

	void set_control(uint8_t);
	uint8_t get_control();
	void set_data(uint8_t);
	uint8_t get_data();
	void set_address_low(uint8_t);
	uint8_t get_address_low();
	void set_address_high(uint8_t);
	uint8_t get_address_high();

	void run_for(Cycles);
	Cycles next_sequence_point() const;
	bool get_interrupt_line();

	// SampleSource.
	template <Outputs::Speaker::Action action>
	void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
	void set_sample_volume_range(std::int16_t range);
	bool is_zero_level() const { return false; }	// TODO.

private:
	Concurrency::AsyncTaskQueue<false> &audio_queue_;

	uint16_t address_ = 0;

	// Use a circular buffer for piping memory alterations onto the audio
	// thread; it would be prohibitive to defer every write individually.
	//
	// Assumed: on most modern architectures, an atomic 64-bit read or
	// write can be achieved locklessly.
	struct MemoryWrite {
		uint32_t time;
		uint16_t address;
		uint8_t value;
		bool enabled;
	};
	static_assert(sizeof(MemoryWrite) == 8);
	constexpr static int StoreBufferSize = 16384;

	std::atomic<MemoryWrite> pending_stores_[StoreBufferSize];
	uint32_t pending_store_read_ = 0, pending_store_read_time_ = 0;
	uint32_t pending_store_write_ = 0, pending_store_write_time_ = 0;

	// Maintain state both 'locally' (i.e. on the emulation thread) and
	// 'remotely' (i.e. on the audio thread).
	struct EnsoniqState {
		uint8_t ram_[65536];
		struct Oscillator {
			uint32_t position;

			// Programmer-set values.
			uint16_t velocity;
			uint8_t volume;
			uint8_t address;
			uint8_t control;
			uint8_t table_size;

			// Derived state.
			uint32_t overflow_mask;			// If a non-zero bit gets anywhere into the overflow mask, this channel
											// has wrapped around. It's a function of table_size.
			bool interrupt_request = false;	// Will be non-zero if this channel would request an interrupt, were
											// it currently enabled to do so.

			uint8_t sample(uint8_t *ram);
			int16_t output(uint8_t *ram);
		} oscillators[32];

		// Some of these aren't actually needed on both threads.
		uint8_t control = 0;
		int oscillator_count = 1;

		void set_register(uint16_t address, uint8_t value);
	} local_, remote_;

	// Functions to update an EnsoniqState; these don't belong to the state itself
	// because they also access the pending stores (inter alia).
	template <Outputs::Speaker::Action action>
	void generate_audio(size_t number_of_samples, Outputs::Speaker::MonoSample *target);
	void skip_audio(EnsoniqState &state, size_t number_of_samples);

	// Audio-thread state.
	int16_t output_range_ = 0;
};

}