From c257e7f58d51e64dd68d61eec1d2f23c9776296b Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 7 Nov 2016 20:17:06 -0500
Subject: [PATCH] Implemented better sync-to-zero and discovered a header
 counting bug plus, probably, a misleading representation of gaps in the Oric
 TAP decoder.

---
 StaticAnalyser/Oric/Tape.cpp     |  4 ++--
 Storage/Tape/Formats/OricTAP.cpp |  4 ++--
 Storage/Tape/Parsers/Oric.cpp    | 36 +++++++++++++++++++++++++-------
 Storage/Tape/Parsers/Oric.hpp    |  2 ++
 4 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/StaticAnalyser/Oric/Tape.cpp b/StaticAnalyser/Oric/Tape.cpp
index 17662734f..155103e29 100644
--- a/StaticAnalyser/Oric/Tape.cpp
+++ b/StaticAnalyser/Oric/Tape.cpp
@@ -49,7 +49,7 @@ std::list<File> StaticAnalyser::Oric::GetFiles(const std::shared_ptr<Storage::Ta
 		}
 		switch(parser.get_next_byte(tape, is_fast))
 		{
-			case 0x80:	new_file.launch_type = File::ProgramType::BASIC;			break;
+			case 0x80:	new_file.launch_type = File::ProgramType::BASIC;		break;
 			case 0xc7:	new_file.launch_type = File::ProgramType::MachineCode;	break;
 			default:	new_file.launch_type = File::ProgramType::None;			break;
 		}
@@ -60,7 +60,7 @@ std::list<File> StaticAnalyser::Oric::GetFiles(const std::shared_ptr<Storage::Ta
 		new_file.starting_address = (uint16_t)(parser.get_next_byte(tape, is_fast) << 8);
 		new_file.starting_address |= (uint16_t)parser.get_next_byte(tape, is_fast);
 
-		// skip an empty bytes
+		// skip an empty byte
 		parser.get_next_byte(tape, is_fast);
 
 		// read file name, up to 16 characters and null terminated
diff --git a/Storage/Tape/Formats/OricTAP.cpp b/Storage/Tape/Formats/OricTAP.cpp
index 95bbb349f..93360f005 100644
--- a/Storage/Tape/Formats/OricTAP.cpp
+++ b/Storage/Tape/Formats/OricTAP.cpp
@@ -93,11 +93,11 @@ Tape::Pulse OricTAP::virtual_get_next_pulse()
 				if(_phase_counter == 6)	_data_start_address = (uint16_t)(next_byte << 8);
 				if(_phase_counter == 7)	_data_start_address |= next_byte;
 
-				_phase_counter++;
 				if(_phase_counter >= 9 && !next_byte)	// advance after the filename-ending NULL byte
 				{
 					_next_phase = Gap;
 				}
+				_phase_counter++;
 			break;
 
 			case Gap:
@@ -151,7 +151,7 @@ Tape::Pulse OricTAP::virtual_get_next_pulse()
 
 		case Gap:
 			_bit_count = 13;
-			pulse.type = Pulse::Zero;
+			pulse.type = (_phase_counter&1) ? Pulse::Low : Pulse::High;
 			pulse.length.length = 100;
 		return pulse;
 
diff --git a/Storage/Tape/Parsers/Oric.cpp b/Storage/Tape/Parsers/Oric.cpp
index aa055794c..1995c11f0 100644
--- a/Storage/Tape/Parsers/Oric.cpp
+++ b/Storage/Tape/Parsers/Oric.cpp
@@ -12,20 +12,21 @@ using namespace Storage::Tape::Oric;
 
 int Parser::get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape, bool use_fast_encoding)
 {
-	_detection_mode = use_fast_encoding ? FastData : SlowData;
+	_detection_mode = use_fast_encoding ? FastZero : SlowZero;
 	_cycle_length = 0.0f;
 
 	int result = 0;
 	int bit_count = 0;
-	while(bit_count < 10 && !tape->is_at_end())
+	while(bit_count < 11 && !tape->is_at_end())
 	{
 		SymbolType symbol = get_next_symbol(tape);
 		if(!bit_count && symbol != SymbolType::Zero) continue;
+		_detection_mode = use_fast_encoding ? FastData : SlowData;
 		result |= ((symbol == SymbolType::One) ? 1 : 0) << bit_count;
 		bit_count++;
 	}
 	// TODO: check parity?
-	return tape->is_at_end() ? -1 : (result&0xff);
+	return tape->is_at_end() ? -1 : ((result >> 1)&0xff);
 }
 
 bool Parser::sync_and_get_encoding_speed(const std::shared_ptr<Storage::Tape::Tape> &tape)
@@ -49,15 +50,15 @@ void Parser::process_pulse(Storage::Tape::Tape::Pulse pulse)
 	const float length_threshold = 0.0003125f;
 
 	bool wave_is_high = pulse.type == Storage::Tape::Tape::Pulse::High;
-	bool did_change = (wave_is_high != _wave_was_high && _cycle_length > 0.0f);
-	_wave_was_high = wave_is_high;
-	if(did_change)
+	if(wave_is_high != _wave_was_high && _cycle_length > 0.0f)
 	{
-		if(_cycle_length > 2.0 * length_threshold) push_wave(WaveType::Unrecognised);
+		if(_cycle_length > 2.0 * length_threshold)
+			push_wave(WaveType::Unrecognised);
 		else push_wave(_cycle_length < length_threshold ? WaveType::Short : WaveType::Long);
 
 		_cycle_length = 0.0f;
 	}
+	_wave_was_high = wave_is_high;
 	_cycle_length += pulse.length.get_float();
 }
 
@@ -65,6 +66,15 @@ void Parser::inspect_waves(const std::vector<WaveType> &waves)
 {
 	switch(_detection_mode)
 	{
+		case FastZero:
+			if(waves.size() < 2) return;
+			if(waves[0] == WaveType::Short && waves[1] == WaveType::Long)
+			{
+				push_symbol(SymbolType::Zero, 2);
+				return;
+			}
+		break;
+
 		case FastData:
 			if(waves.size() < 2) return;
 			if(waves[0] == WaveType::Short && waves[1] != WaveType::Unrecognised)
@@ -74,6 +84,18 @@ void Parser::inspect_waves(const std::vector<WaveType> &waves)
 			}
 		break;
 
+		case SlowZero:
+			if(waves.size() < 8) return;
+			if(
+				waves[0] == WaveType::Long && waves[1] == WaveType::Long && waves[2] == WaveType::Long && waves[3] == WaveType::Long &&
+				waves[4] == WaveType::Long && waves[5] == WaveType::Long && waves[6] == WaveType::Long && waves[7] == WaveType::Long
+			)
+			{
+				push_symbol(SymbolType::Zero, 8);
+				return;
+			}
+		break;
+
 		case SlowData:
 #define CHECK_RUN(length, type, symbol)	\
 			if(waves.size() >= length)\
diff --git a/Storage/Tape/Parsers/Oric.hpp b/Storage/Tape/Parsers/Oric.hpp
index cb5ffe96b..f4678e3bb 100644
--- a/Storage/Tape/Parsers/Oric.hpp
+++ b/Storage/Tape/Parsers/Oric.hpp
@@ -35,6 +35,8 @@ class Parser: public Storage::Tape::Parser<WaveType, SymbolType> {
 		enum DetectionMode {
 			FastData,
 			SlowData,
+			FastZero,
+			SlowZero,
 			Sync
 		} _detection_mode;
 		bool _wave_was_high;