Started sketching out the basic form here, albeit that it doesn't yet do _the only thing it advertises itself as useful for_.

Storage/Disk/DigitalPhaseLockedLoop.cpp

@@ -7,3 +7,58 @@
 //
 
 #include "DigitalPhaseLockedLoop.hpp"
+
+using namespace Storage;
+
+DigitalPhaseLockedLoop::DigitalPhaseLockedLoop(unsigned int clocks_per_bit, unsigned int tolerance, unsigned int length_of_history) :
+	_clocks_per_bit(clocks_per_bit),
+	_tolerance(tolerance),
+	_length_of_history(length_of_history),
+	_pulse_history(new unsigned int[length_of_history]),
+	_current_window_length(clocks_per_bit),
+	_next_pulse_time(0),
+	_window_was_filled(false),
+	_window_offset(0) {}
+
+void DigitalPhaseLockedLoop::run_for_cycles(unsigned int number_of_cycles)
+{
+	// check whether this triggers any 0s
+	_window_offset += number_of_cycles;
+	if(_delegate)
+	{
+		while(_window_offset > _current_window_length)
+		{
+			if(!_window_was_filled) _delegate->digital_phase_locked_loop_output_bit(0);
+			_window_was_filled = false;
+			_window_offset -= _current_window_length;
+		}
+	}
+	else
+	{
+		_window_offset %= _current_window_length;
+	}
+
+	// updte timing
+	_next_pulse_time += number_of_cycles;
+}
+
+void DigitalPhaseLockedLoop::add_pulse()
+{
+	// TODO: linear regression to adjust _current_window_length and _next_pulse_time
+
+
+	// therefore, there was a 1 in this window
+	_window_was_filled = true;
+	if(_delegate) _delegate->digital_phase_locked_loop_output_bit(1);
+
+	// shift history one to the left, subtracting the outgoing pulse from
+	unsigned int *const _pulse_history_array = _pulse_history.get();
+	unsigned int outgoing_pulse_time = _pulse_history_array[0];
+
+	for(size_t pulse = 1; pulse < _length_of_history; pulse++)
+	{
+		_pulse_history_array[pulse - 1] = _pulse_history_array[pulse] - outgoing_pulse_time;
+	}
+	_next_pulse_time -= outgoing_pulse_time;
+	_pulse_history_array[_length_of_history-1] = _next_pulse_time;
+}

Storage/Disk/DigitalPhaseLockedLoop.hpp

@@ -9,6 +9,8 @@
 #ifndef DigitalPhaseLockedLoop_hpp
 #define DigitalPhaseLockedLoop_hpp
 
+#include <memory>
+
 namespace Storage {
 
 class DigitalPhaseLockedLoop {
@@ -18,8 +20,9 @@ class DigitalPhaseLockedLoop {
 
 			@param clocks_per_bit The expected number of cycles between each bit of input.
 			@param tolerance The maximum tolerance for bit windows — extremes will be clocks_per_bit ± tolerance.
+			@param length_of_history The number of historic pulses to consider in locking to phase.
 		*/
-		DigitalPhaseLockedLoop(unsigned int clocks_per_bit, unsigned int tolerance);
+		DigitalPhaseLockedLoop(unsigned int clocks_per_bit, unsigned int tolerance, unsigned int length_of_history);
 
 		/*!
 			Runs the loop, impliedly posting no pulses during that period.
@@ -47,6 +50,17 @@ class DigitalPhaseLockedLoop {
 
 	private:
 		Delegate *_delegate;
+
+		std::unique_ptr<unsigned int> _pulse_history;
+		unsigned int _current_window_length;
+		unsigned int _length_of_history;
+
+		unsigned int _next_pulse_time;
+		unsigned int _window_offset;
+		bool _window_was_filled;
+
+		unsigned int _clocks_per_bit;
+		unsigned int _tolerance;
 };
 
 }