From f984de42a36b39a1c6b677d146e1722b0abd30f0 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 29 Jul 2016 07:31:02 -0400
Subject: [PATCH] Took some small steps towards having a disk drive that at
 least can select a track and pump relevant events into a PLL.

---
 Storage/Disk/DiskDrive.cpp | 66 ++++++++++++++++++++++++++++++++------
 Storage/Disk/DiskDrive.hpp | 17 +++++-----
 Storage/Storage.hpp        |  9 ++++++
 3 files changed, 74 insertions(+), 18 deletions(-)

diff --git a/Storage/Disk/DiskDrive.cpp b/Storage/Disk/DiskDrive.cpp
index de0dda28d..e1e56ead1 100644
--- a/Storage/Disk/DiskDrive.cpp
+++ b/Storage/Disk/DiskDrive.cpp
@@ -13,17 +13,21 @@ using namespace Storage;
 DiskDrive::DiskDrive(unsigned int clock_rate, unsigned int revolutions_per_minute) :
 	_clock_rate(clock_rate),
 	_revolutions_per_minute(revolutions_per_minute),
-	_head_position(0) {}
+	_head_position(0),
+
+	TimedEventLoop(clock_rate)
+{}
 
 void DiskDrive::set_expected_bit_length(Time bit_length)
 {
 	_bit_length = bit_length;
+//	_pll.reset(new DigitalPhaseLockedLoop();
 }
 
 void DiskDrive::set_disk(std::shared_ptr<Disk> disk)
 {
 	_disk = disk;
-//	_track.reset();
+	set_track();
 }
 
 bool DiskDrive::has_disk()
@@ -39,21 +43,65 @@ bool DiskDrive::get_is_track_zero()
 void DiskDrive::step(int direction)
 {
 	_head_position = std::max(_head_position + direction, 0);
-	_track = _disk->get_track_at_position((unsigned int)_head_position);
+	set_track();
 }
 
-void DiskDrive::digital_phase_locked_loop_output_bit(int value)
+void DiskDrive::set_track()
 {
-	process_input_bit(value, _cycles_since_index_hole);
+	_track = _disk->get_track_at_position((unsigned int)_head_position);
+	reset_timer();
+	get_next_event();
 }
 
 void DiskDrive::run_for_cycles(unsigned int number_of_cycles)
 {
 	if(has_disk())
 	{
-		while(number_of_cycles--)
-		{
-
-		}
+		_cycles_since_index_hole += number_of_cycles;
+		TimedEventLoop::run_for_cycles(number_of_cycles);
 	}
 }
+
+#pragma mark - Track timed event loop
+
+void DiskDrive::get_next_event()
+{
+	if(_track)
+		_current_event = _track->get_next_event();
+	else
+	{
+		_current_event.length.length = 1;
+		_current_event.length.clock_rate = 1;
+		_current_event.type = Track::Event::IndexHole;
+	}
+
+	// divide interval, which is in terms of a rotation of the disk, by rotation speed, and
+	// convert it into revolutions per second
+	Time event_interval = _current_event.length;
+	event_interval.length *= 60;
+	event_interval.clock_rate *= _revolutions_per_minute;
+	event_interval.simplify();
+	set_next_event_time_interval(event_interval);
+}
+
+void DiskDrive::process_next_event()
+{
+	switch(_current_event.type)
+	{
+		case Track::Event::FluxTransition:
+			_pll->add_pulse();
+		break;
+		case Track::Event::IndexHole:
+			_cycles_since_index_hole = 0;
+			process_index_hole();
+		break;
+	}
+	get_next_event();
+}
+
+#pragma mark - PLL delegate
+
+void DiskDrive::digital_phase_locked_loop_output_bit(int value)
+{
+	process_input_bit(value, _cycles_since_index_hole);
+}
diff --git a/Storage/Disk/DiskDrive.hpp b/Storage/Disk/DiskDrive.hpp
index c3e857ec8..2e89fe3c6 100644
--- a/Storage/Disk/DiskDrive.hpp
+++ b/Storage/Disk/DiskDrive.hpp
@@ -11,11 +11,11 @@
 
 #include "Disk.hpp"
 #include "DigitalPhaseLockedLoop.hpp"
-#include "../../SignalProcessing/Stepper.hpp"
+#include "../TimedEventLoop.hpp"
 
 namespace Storage {
 
-class DiskDrive: public DigitalPhaseLockedLoop::Delegate {
+class DiskDrive: public DigitalPhaseLockedLoop::Delegate, public TimedEventLoop {
 	public:
 		DiskDrive(unsigned int clock_rate, unsigned int revolutions_per_minute);
 
@@ -37,6 +37,9 @@ class DiskDrive: public DigitalPhaseLockedLoop::Delegate {
 		virtual void process_input_bit(int value, unsigned int cycles_since_index_hole) = 0;
 		virtual void process_index_hole() = 0;
 
+		// for TimedEventLoop
+		virtual void process_next_event();
+
 	private:
 		Time _bit_length;
 		unsigned int _clock_rate;
@@ -47,14 +50,10 @@ class DiskDrive: public DigitalPhaseLockedLoop::Delegate {
 		std::shared_ptr<Track> _track;
 		int _head_position;
 		unsigned int _cycles_since_index_hole;
+		void set_track();
 
-		void install_track();
-
-		struct {
-			Track::Event current_event;
-			std::unique_ptr<SignalProcessing::Stepper> pulse_stepper;
-			uint32_t time_into_pulse;
-		} _input;
+		inline void get_next_event();
+		Track::Event _current_event;
 };
 
 }
diff --git a/Storage/Storage.hpp b/Storage/Storage.hpp
index ac65da093..d4446b537 100644
--- a/Storage/Storage.hpp
+++ b/Storage/Storage.hpp
@@ -9,10 +9,19 @@
 #ifndef Storage_hpp
 #define Storage_hpp
 
+#include "../NumberTheory/Factors.hpp"
+
 namespace Storage {
 
 struct Time {
 	unsigned int length, clock_rate;
+
+	inline void simplify()
+	{
+		unsigned int common_divisor = NumberTheory::greatest_common_divisor(length, clock_rate);
+		length /= common_divisor;
+		clock_rate /= common_divisor;
+	}
 };
 
 }