Made an attempt to build in Oric slow/fast detection.

Storage/Tape/Parsers/Oric.cpp

@@ -12,7 +12,7 @@ using namespace Storage::Tape::Oric;
 
 int Parser::get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape, bool use_fast_encoding)
 {
-	_use_fast_encoding = use_fast_encoding;
+	_detection_mode = use_fast_encoding ? FastData : SlowData;
 	_cycle_length = 0.0f;
 
 	int result = 0;
@@ -24,57 +24,147 @@ int Parser::get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape, bool
 		result |= ((symbol == SymbolType::One) ? 1 : 0) << bit_count;
 		bit_count++;
 	}
-	// TODO: check parity
+	// TODO: check parity?
 	return tape->is_at_end() ? -1 : (result >> 1);
 }
 
+bool Parser::sync_and_get_encoding_speed(const std::shared_ptr<Storage::Tape::Tape> &tape)
+{
+	_detection_mode = Sync;
+	while(!tape->is_at_end())
+	{
+		SymbolType symbol = get_next_symbol(tape);
+		switch(symbol)
+		{
+			case SymbolType::FoundSlow: return false;
+			case SymbolType::FoundFast: return true;
+			default: break;
+		}
+	}
+	return false;
+}
+
 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);
-	_cycle_length += pulse.length.get_float();
+	_wave_was_high = wave_is_high;
 	if(did_change)
 	{
 		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();
 }
 
 void Parser::inspect_waves(const std::vector<WaveType> &waves)
 {
-	if(_use_fast_encoding)
+	switch(_detection_mode)
 	{
-		if(waves.size() < 2) return;
+		case FastData:
-		if(waves[0] == WaveType::Long && waves[1] != WaveType::Unrecognised)
+			if(waves.size() < 2) return;
+			if(waves[0] == WaveType::Short && waves[1] != WaveType::Unrecognised)
+			{
+				push_symbol((waves[1] == WaveType::Long) ? SymbolType::Zero : SymbolType::One, 2);
+				return;
+			}
+		break;
+
+		case SlowData:
+#define CHECK_RUN(length, type, symbol)	\
+			if(waves.size() >= length)\
+			{\
+				size_t c;\
+				for(c = 0; c < length; c++) if(waves[c] != type) break;\
+				if(c == length)\
+				{\
+					push_symbol(symbol, 8);\
+					return;\
+				}\
+			}
+
+			CHECK_RUN(8, WaveType::Long, SymbolType::Zero);
+			CHECK_RUN(16, WaveType::Short, SymbolType::One);
+#undef CHECK_RUN
+			if(waves.size() < 16) return;	// TODO, maybe: if there are any inconsistencies in the first 8, don't return
+		break;
+
+		case Sync:
 		{
-			push_symbol((waves[1] == WaveType::Long) ? SymbolType::Zero : SymbolType::One, 2);
+			// Sync is 0x16, either encoded fast or slow; i.e. 0 0110 1000 1
+			// So, fast: [short, long]*2, [short, short]*2, [short, long], [short, short], [short, long]*3, [short, short] = 20
+			// [short, short] = 1; [short, long] = 0
+			// Slow: long*16, short*32, long*8, short*16, long*24, short*16 = 112
+			Pattern slow_sync[] =
+			{
+				{.type = WaveType::Long,	16},
+				{.type = WaveType::Short,	32},
+				{.type = WaveType::Long,	8},
+				{.type = WaveType::Short,	16},
+				{.type = WaveType::Long,	24},
+				{.type = WaveType::Short,	16},
+				{.type = WaveType::Unrecognised}
+			};
+			Pattern fast_sync[] =
+			{
+				{.type = WaveType::Short, 1},
+				{.type = WaveType::Long, 1},
+				{.type = WaveType::Short, 1},
+				{.type = WaveType::Long, 1},
+				{.type = WaveType::Short, 5},
+				{.type = WaveType::Long, 1},
+				{.type = WaveType::Short, 3},
+				{.type = WaveType::Long, 1},
+				{.type = WaveType::Short, 1},
+				{.type = WaveType::Long, 1},
+				{.type = WaveType::Short, 1},
+				{.type = WaveType::Long, 1},
+				{.type = WaveType::Short, 2},
+				{.type = WaveType::Unrecognised}
+			};
+
+			size_t slow_sync_matching_depth = pattern_matching_depth(waves, slow_sync);
+			size_t fast_sync_matching_depth = pattern_matching_depth(waves, fast_sync);
+
+			if(slow_sync_matching_depth == 112)
+			{
+				push_symbol(SymbolType::FoundSlow, 112);
+				return;
+			}
+			if(fast_sync_matching_depth == 20)
+			{
+				push_symbol(SymbolType::FoundFast, 20);
+				return;
+			}
+			if(slow_sync_matching_depth < waves.size() && fast_sync_matching_depth < waves.size())
+				remove_waves((int)std::min(slow_sync_matching_depth, fast_sync_matching_depth));
+
 			return;
 		}
-	}
+		break;
-	else
-	{
-		if(waves.size() < 16) return;
-#define CHECK_RUN(length, type, symbol)	\
-		if(waves.size() >= length)\
-		{\
-			size_t c;\
-			for(c = 0; c < length; c++) if(waves[c] != type) break;\
-			if(c == length)\
-			{\
-				push_symbol(symbol, 8);\
-				return;\
-			}\
-		}
-
-		CHECK_RUN(8, WaveType::Long, SymbolType::Zero);
-		CHECK_RUN(16, WaveType::Short, SymbolType::One);
-#undef CHECK_RUN
 	}
 
 	remove_waves(1);
 }
+
+size_t Parser::pattern_matching_depth(const std::vector<WaveType> &waves, Pattern *pattern)
+{
+	size_t depth = 0;
+	int pattern_depth = 0;
+	while(depth < waves.size() && pattern->type != WaveType::Unrecognised)
+	{
+		if(waves[depth] != pattern->type) break;
+		pattern_depth++;
+		if(pattern_depth == pattern->count)
+		{
+			pattern_depth = 0;
+			pattern++;
+		}
+	}
+
+	return depth;
+}

Storage/Tape/Parsers/Oric.hpp

@@ -20,20 +20,32 @@ enum class WaveType {
 };
 
 enum class SymbolType {
-	One, Zero
+	One, Zero, FoundFast, FoundSlow
 };
 
 class Parser: public Storage::Tape::Parser<WaveType, SymbolType> {
 	public:
 		int get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape, bool use_fast_encoding);
+		bool sync_and_get_encoding_speed(const std::shared_ptr<Storage::Tape::Tape> &tape);
 
 	private:
 		void process_pulse(Storage::Tape::Tape::Pulse pulse);
 		void inspect_waves(const std::vector<WaveType> &waves);
 
-		bool _use_fast_encoding;
+		enum DetectionMode {
+			FastData,
+			SlowData,
+			Sync
+		} _detection_mode;
 		bool _wave_was_high;
 		float _cycle_length;
+
+		struct Pattern
+		{
+			WaveType type;
+			int count;
+		};
+		size_t pattern_matching_depth(const std::vector<WaveType> &waves, Pattern *pattern);
 };