From 17635da81295c15e0b8a47b01361b71178f82bde Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 1 Jun 2019 15:18:27 -0400
Subject: [PATCH] Pushes Mac audio further towards being able to function.

---
 Machines/Apple/Macintosh/Audio.cpp     | 28 +++++++++++++++++++-------
 Machines/Apple/Macintosh/Audio.hpp     |  9 ++++++---
 Machines/Apple/Macintosh/Macintosh.cpp |  2 +-
 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/Machines/Apple/Macintosh/Audio.cpp b/Machines/Apple/Macintosh/Audio.cpp
index 7f476db0b..016c81f73 100644
--- a/Machines/Apple/Macintosh/Audio.cpp
+++ b/Machines/Apple/Macintosh/Audio.cpp
@@ -10,41 +10,55 @@
 
 using namespace Apple::Macintosh;
 
+namespace {
+const HalfCycles sample_length(704);
+}
+
 Audio::Audio(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {}
 
 // MARK: - Inputs
 
 void Audio::post_sample(uint8_t sample) {
+	// Grab the read and write pointers, ensure there's room for a new sample and, if not,
+	// drop this one.
 	const auto write_pointer = sample_queue_.write_pointer.load();
-//	const auto pointers
-
 	const auto read_pointer = sample_queue_.read_pointer.load();
+	const decltype(write_pointer) next_write_pointer = (write_pointer + 1) % sample_queue_.buffer.size();
+	if(next_write_pointer == read_pointer) return;
+
+	sample_queue_.buffer[write_pointer] = sample;
+	sample_queue_.write_pointer.store(next_write_pointer);
 }
 
 void Audio::set_volume(int volume) {
+	// Post the volume change as a deferred event.
 	task_queue_.defer([=] () {
 		volume_ = volume;
 	});
 }
 
 void Audio::set_enabled(bool on) {
+	// Post the enabled mask change as a deferred event.
 	task_queue_.defer([=] () {
-		is_enabled_ = on;
+		enabled_mask_ = on ? 1 : 0;
 	});
 }
 
 // MARK: - Output generation
 
 bool Audio::is_zero_level() {
-	return !volume_ || !is_enabled_;
+	return !volume_ || !enabled_mask_;
 }
 
 void Audio::set_sample_volume_range(std::int16_t range) {
+	// Some underflow here doesn't really matter.
 	volume_multiplier_ = range / 7;
 }
 
 void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
-//	if(is_zero_level()) {
-//		memset(target, 0, number_of_samples * sizeof(int16_t));
-//	}
+	// TODO.
+}
+
+void Audio::skip_samples(std::size_t number_of_samples) {
+	// TODO.
 }
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index ea3c035cb..375d1c247 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -9,9 +9,9 @@
 #ifndef Audio_hpp
 #define Audio_hpp
 
-#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
 #include "../../../Concurrency/AsyncTaskQueue.hpp"
 #include "../../../ClockReceiver/ClockReceiver.hpp"
+#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
 
 #include <array>
 #include <atomic>
@@ -51,6 +51,7 @@ class Audio: public ::Outputs::Speaker::SampleSource {
 
 		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter.
 		void get_samples(std::size_t number_of_samples, int16_t *target);
+		void skip_samples(std::size_t number_of_samples);
 		bool is_zero_level();
 		void set_sample_volume_range(std::int16_t range);
 
@@ -61,15 +62,17 @@ class Audio: public ::Outputs::Speaker::SampleSource {
 		// written to by another.
 		struct {
 			std::array<uint8_t, 2048> buffer;
-			std::atomic<int> read_pointer, write_pointer;
+			std::atomic<unsigned int> read_pointer, write_pointer;
 		} sample_queue_;
 
 		// Stateful variables, modified from the audio generation
 		// thread only.
 		int volume_ = 0;
-		bool is_enabled_ = false;
+		int enabled_mask_ = 0;
 
 		std::int16_t volume_multiplier_ = 0;
+
+		HalfCycles subcycle_offset_;
 };
 
 }
diff --git a/Machines/Apple/Macintosh/Macintosh.cpp b/Machines/Apple/Macintosh/Macintosh.cpp
index 6d1946211..7f282086d 100644
--- a/Machines/Apple/Macintosh/Macintosh.cpp
+++ b/Machines/Apple/Macintosh/Macintosh.cpp
@@ -236,7 +236,7 @@ class ConcreteMachine:
 //			video_.run_for(time_since_video_update_.flush());
 
 			// As above: flush audio after video.
-			audio_.queue.flush();
+			audio_.queue.perform();
 		}
 
 		void set_rom_is_overlay(bool rom_is_overlay) {