From ec3cccbb0df2942fd3fa8b7e697f3474c354255f Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 20 Feb 2016 22:03:14 -0500
Subject: [PATCH] Working towards HQ UEF support: fixed bug whereby writing to
 tape output would reset input pulse stepper; added support for chunk 0116 and
 approximate support for 0113.

---
 Machines/Electron/Electron.cpp   | 10 +++----
 Machines/Electron/Electron.hpp   |  3 +-
 Storage/Tape/Formats/TapeUEF.cpp | 47 ++++++++++++++++++++++++++++++--
 3 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/Machines/Electron/Electron.cpp b/Machines/Electron/Electron.cpp
index c74948a41..607cc262d 100644
--- a/Machines/Electron/Electron.cpp
+++ b/Machines/Electron/Electron.cpp
@@ -690,9 +690,9 @@ inline void Tape::get_next_tape_pulse()
 {
 	_time_into_pulse = 0;
 	_current_pulse = _tape->get_next_pulse();
-	if(_pulse_stepper == nullptr || _current_pulse.length.clock_rate != _pulse_stepper->get_output_rate())
+	if(_input_pulse_stepper == nullptr || _current_pulse.length.clock_rate != _input_pulse_stepper->get_output_rate())
 	{
-		_pulse_stepper = std::unique_ptr<SignalProcessing::Stepper>(new SignalProcessing::Stepper(_current_pulse.length.clock_rate, 2000000));
+		_input_pulse_stepper = std::unique_ptr<SignalProcessing::Stepper>(new SignalProcessing::Stepper(_current_pulse.length.clock_rate, 2000000));
 	}
 }
 
@@ -762,7 +762,7 @@ inline void Tape::set_is_in_input_mode(bool is_in_input_mode)
 
 inline void Tape::set_counter(uint8_t value)
 {
-	_pulse_stepper = std::unique_ptr<SignalProcessing::Stepper>(new SignalProcessing::Stepper(1200, 2000000));
+	_output_pulse_stepper = std::unique_ptr<SignalProcessing::Stepper>(new SignalProcessing::Stepper(1200, 2000000));
 }
 
 inline void Tape::set_data_register(uint8_t value)
@@ -786,7 +786,7 @@ inline void Tape::run_for_cycles(unsigned int number_of_cycles)
 			{
 				while(number_of_cycles--)
 				{
-					_time_into_pulse += (unsigned int)_pulse_stepper->step();
+					_time_into_pulse += (unsigned int)_input_pulse_stepper->step();
 					if(_time_into_pulse == _current_pulse.length.length)
 					{
 						get_next_tape_pulse();
@@ -826,7 +826,7 @@ inline void Tape::run_for_cycles(unsigned int number_of_cycles)
 		{
 			while(number_of_cycles--)
 			{
-				if(_pulse_stepper->step())
+				if(_output_pulse_stepper->step())
 				{
 					_output_bits_remaining--;
 					if(!_output_bits_remaining)
diff --git a/Machines/Electron/Electron.hpp b/Machines/Electron/Electron.hpp
index d9bca2785..e9fb3c1d0 100644
--- a/Machines/Electron/Electron.hpp
+++ b/Machines/Electron/Electron.hpp
@@ -91,7 +91,8 @@ class Tape {
 		std::shared_ptr<Storage::Tape> _tape;
 
 		Storage::Tape::Pulse _current_pulse;
-		std::unique_ptr<SignalProcessing::Stepper> _pulse_stepper;
+		std::unique_ptr<SignalProcessing::Stepper> _input_pulse_stepper;
+		std::unique_ptr<SignalProcessing::Stepper> _output_pulse_stepper;
 		uint32_t _time_into_pulse;
 
 		bool _is_running;
diff --git a/Storage/Tape/Formats/TapeUEF.cpp b/Storage/Tape/Formats/TapeUEF.cpp
index ba6d4b6de..6796fa5ce 100644
--- a/Storage/Tape/Formats/TapeUEF.cpp
+++ b/Storage/Tape/Formats/TapeUEF.cpp
@@ -8,6 +8,38 @@
 
 #include "TapeUEF.hpp"
 #include <string.h>
+#include <math.h>
+
+static float gzgetfloat(gzFile file)
+{
+	uint8_t bytes[4];
+	bytes[0] = (uint8_t)gzgetc(file);
+	bytes[1] = (uint8_t)gzgetc(file);
+	bytes[2] = (uint8_t)gzgetc(file);
+	bytes[3] = (uint8_t)gzgetc(file);
+
+	/* assume a four byte array named Float exists, where Float[0]
+	was the first byte read from the UEF, Float[1] the second, etc */
+
+	/* decode mantissa */
+	int mantissa;
+	mantissa = bytes[0] | (bytes[1] << 8) | ((bytes[2]&0x7f)|0x80) << 16;
+
+	float result = (float)mantissa;
+	result = (float)ldexp(result, -23);
+
+	/* decode exponent */
+	int exponent;
+	exponent = ((bytes[2]&0x80) >> 7) | (bytes[3]&0x7f) << 1;
+	exponent -= 127;
+	result = (float)ldexp(result, exponent);
+
+	/* flip sign if necessary */
+	if(bytes[3]&0x80)
+		result = -result;
+
+	return result;
+}
 
 Storage::UEF::UEF(const char *file_name) :
 	_chunk_id(0), _chunk_length(0), _chunk_position(0),
@@ -117,18 +149,24 @@ void Storage::UEF::find_next_tape_chunk()
 			continue;
 		}
 
+		printf("Deal with %04x?\n", _chunk_id);
 		switch(_chunk_id)
 		{
 			case 0x0100: case 0x0102: // implicit and explicit bit patterns
 			return;
 
-			case 0x0112:
+			case 0x0112: // integer gap
 				_chunk_duration.length = (uint16_t)gzgetc(_file);
 				_chunk_duration.length |= (uint16_t)(gzgetc(_file) << 8);
 				_chunk_duration.clock_rate = _time_base;
 			return;
 
-			case 0x0116: // gaps
+			case 0x0116: // floating point gap
+			{
+				float length = gzgetfloat(_file);
+				_chunk_duration.length = (unsigned int)(length * 4000000);
+				_chunk_duration.clock_rate = 4000000;
+			}
 			return;
 
 			case 0x0110: // carrier tone
@@ -144,6 +182,11 @@ void Storage::UEF::find_next_tape_chunk()
 			break;
 
 			case 0x113: // change of base rate
+			{
+				// TODO: something smarter than just converting this to an int
+				float new_time_base = gzgetfloat(_file);
+				_time_base = (unsigned int)roundf(new_time_base);
+			}
 			break;
 
 			default: