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CLK/Machines/Apple/Macintosh/Audio.hpp

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//
// Audio.hpp
// Clock Signal
//
// Created by Thomas Harte on 31/05/2019.
// Copyright © 2019 Thomas Harte. All rights reserved.
//
#pragma once
#include "../../../Concurrency/AsyncTaskQueue.hpp"
#include "../../../ClockReceiver/ClockReceiver.hpp"
#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"
#include <array>
#include <atomic>
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namespace Apple::Macintosh {
/*!
Implements the Macintosh's audio output hardware.
Designed to be clocked at half the rate of the real hardware i.e.
a shade less than 4Mhz.
*/
class Audio: public ::Outputs::Speaker::BufferSource<Audio, false> {
public:
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Audio(Concurrency::AsyncTaskQueue<false> &task_queue);
/*!
Macintosh audio is (partly) sourced by the same scanning
hardware as the video; each line it collects an additional
word of memory, half of which is used for audio output.
Use this method to add a newly-collected sample to the queue.
*/
void post_sample(uint8_t sample);
/*!
Macintosh audio also separately receives an output volume
level, in the range 0 to 7.
Use this method to set the current output volume.
*/
void set_volume(int volume);
/*!
A further factor in audio output is the on-off toggle.
*/
void set_enabled(bool on);
// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter.
template <Outputs::Speaker::Action action>
void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
bool is_zero_level() const;
void set_sample_volume_range(std::int16_t range);
private:
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Concurrency::AsyncTaskQueue<false> &task_queue_;
// A queue of fetched samples; read from by one thread,
// written to by another.
struct {
std::array<std::atomic<uint8_t>, 740> buffer;
size_t read_pointer = 0, write_pointer = 0;
} sample_queue_;
// Emulator-thread stateful variables, to avoid work posting
// deferral updates if possible.
int posted_volume_ = 0;
int posted_enable_mask_ = 0;
// Stateful variables, modified from the audio generation
// thread only.
int volume_ = 0;
int enabled_mask_ = 0;
std::int16_t output_volume_ = 0;
std::int16_t volume_multiplier_ = 0;
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std::size_t subcycle_offset_ = 0;
void set_volume_multiplier();
};
}