Switches to an attempt to break the .CAS into files ahead of time.

Hopefully the better to insert appropriate lengths of header and gap.

Storage/Tape/Formats/CAS.cpp

@@ -8,6 +8,7 @@
 
 #include "CAS.hpp"
 
+#include <cassert>
 #include <cstring>
 
 using namespace Storage::Tape;
@@ -16,89 +17,157 @@ namespace  {
 	const uint8_t header_signature[8] = {0x1f, 0xa6, 0xde, 0xba, 0xcc, 0x13, 0x7d, 0x74};
 }
 
-CAS::CAS(const char *file_name) :
-	file_(file_name) {
-	file_.read(input_, sizeof(input_));
-	if(std::memcmp(input_, header_signature, sizeof(header_signature))) throw ErrorNotCAS;
+CAS::CAS(const char *file_name) {
+	Storage::FileHolder file(file_name);
+	uint8_t lookahead[8] = {0, 0, 0, 0, 0, 0, 0, 0};
+
+	// Get the first header.
+	get_next(file, lookahead, 8);
+	if(std::memcmp(lookahead, header_signature, sizeof(header_signature))) throw ErrorNotCAS;
+
+	File *active_file = nullptr;
+	while(!file.eof()) {
+		// Just found a header, so flush the lookahead.
+		get_next(file, lookahead, 8);
+
+		// If no file is active, create one, as this must be an identification block.
+		if(!active_file) {
+			// Determine the new file type.
+			Block type;
+			switch(lookahead[0]) {
+				case 0xd3:	type = Block::CSAVE;	break;
+				case 0xd0:	type = Block::BSAVE;	break;
+				case 0xea:	type = Block::ASCII;	break;
+
+				// This implies something has gone wrong with parsing.
+				default: throw ErrorNotCAS;
+			}
+
+			// Set the type and feed in the initial data.
+			files_.emplace_back();
+			active_file = &files_.back();
+			active_file->type = type;
+		}
+
+		// Add a new chunk for the new incoming data.
+		active_file->chunks.emplace_back();
+
+		// Keep going until another header arrives.
+		while(std::memcmp(lookahead, header_signature, sizeof(header_signature)) && !file.eof()) {
+			active_file->chunks.back().push_back(lookahead[0]);
+			get_next(file, lookahead, 1);
+		}
+
+		switch(active_file->type) {
+			case Block::ASCII:
+				// ASCII files have as many chunks as necessary, the final one being back filled
+				// with 0x1a.
+				if(active_file->chunks.size() >= 2) {
+					std::vector<uint8_t> &last_chunk = active_file->chunks.back();
+					if(last_chunk.back() == 0x1a)
+						active_file = nullptr;
+				}
+			break;
+
+			default:
+				// CSAVE and BSAVE files have exactly two chunks, the second being the data.
+				if(active_file->chunks.size() == 2)
+					active_file = nullptr;
+			break;
+		}
+	}
+}
+
+void CAS::get_next(Storage::FileHolder &file, uint8_t (&buffer)[8], std::size_t quantity) {
+	assert(quantity <= 8);
+
+	if(quantity < 8)
+		std::memmove(buffer, &buffer[quantity], 8 - quantity);
+
+	while(quantity--) {
+		buffer[7 - quantity] = file.get8();
+	}
 }
 
 bool CAS::is_at_end() {
-	return file_.eof();
+	return phase_ == Phase::EndOfFile;
 }
 
 void CAS::virtual_reset() {
-	file_.seek(0, SEEK_SET);
-	file_.read(input_, sizeof(input_));
 	phase_ = Phase::Header;
+	file_pointer_ = 0;
+	chunk_pointer_ = 0;
 	distance_into_phase_ = 0;
+	distance_into_bit_ = 0;
 }
 
 Tape::Pulse CAS::virtual_get_next_pulse() {
 	Pulse pulse;
-	switch(phase_) {
-		case Phase::Gap: {
-			// Leave a fixed 0.5 second gap between blocks.
-			pulse.length.length = 2400;
-			pulse.length.clock_rate = 4800;
-			pulse.type = Pulse::Type::Zero;
+	pulse.length.clock_rate = 4800;
 
-			if(!file_.eof()) phase_ = Phase::Header;
-		} break;
+	// If this is a gap, then that terminates a file. If this is already the end
+	// of the file then perpetual gaps await.
+	if(phase_ == Phase::Gap || phase_ == Phase::EndOfFile) {
+		pulse.length.length = pulse.length.clock_rate;
+		pulse.type = Pulse::Type::Zero;
+
+		if(phase_ == Phase::Gap) {
+			phase_ = Phase::Header;
+			file_pointer_ ++;
+			chunk_pointer_ = 0;
+			distance_into_phase_ = 0;
+		}
+
+		return pulse;
+	}
+
+	// Determine which bit is now forthcoming.
+	int bit = 1;
+
+	switch(phase_) {
+		default: break;
 
 		case Phase::Header: {
-			// 1 bits are two complete cycle at 2400 hz
-			pulse.length.length = 1;
-			pulse.length.clock_rate = 4800;
-			pulse.type = (distance_into_phase_&1) ? Pulse::Type::Low : Pulse::Type::High;
-
-			distance_into_phase_++;
-			if(distance_into_phase_ == 7936*4) {
-				distance_into_phase_ = 0;
-				phase_ = Phase::Bytes;
-
-				for(int c = 1; c < 8; c++) {
-					input_[c] = file_.get8();
+			distance_into_bit_++;
+			if(distance_into_bit_ == 2) {
+				distance_into_phase_++;
+				if(distance_into_phase_ == (chunk_pointer_ ? 15360 : 3840)) {
+					phase_ = Phase::Bytes;
+					distance_into_phase_ = 0;
+					distance_into_bit_ = 0;
 				}
 			}
 		} break;
 
 		case Phase::Bytes: {
-			unsigned int bit;
-			const int bit_offset = distance_into_phase_ >> 2;
+			int byte_value = files_[file_pointer_].chunks[chunk_pointer_][distance_into_phase_ / 11];
+			int bit_offset = distance_into_phase_ % 11;
 			switch(bit_offset) {
 				case 0:		bit = 0;									break;
-				default:	bit = (input_[0] >> (bit_offset - 1)) & 1;	break;
+				default:	bit = (byte_value >> (bit_offset - 1)) & 1;	break;
 				case 9:
 				case 10:	bit = 1;									break;
 			}
 
-			// 1 bits are two complete cycle at 2400 hz; 0 bits are one complete cycle at 1200 hz
-			pulse.length.length = 2 - bit;
-			pulse.length.clock_rate = 4800;
-			pulse.type = distance_into_phase_ ? Pulse::Type::High : Pulse::Type::Low;
-
-			int adder = 1;
-			if(!bit && ((distance_into_phase_&3) == 1)) adder = 3;
-			distance_into_phase_ = (distance_into_phase_ + adder) % (11 * 4);
+			distance_into_bit_++;
+			if(distance_into_bit_ == (bit ? 4 : 2)) {
+				distance_into_bit_ = 0;
+				distance_into_phase_++;
+				if(distance_into_phase_ == files_[file_pointer_].chunks[chunk_pointer_].size() * 11) {
+					distance_into_phase_ = 0;
+					chunk_pointer_++;
+					if(chunk_pointer_ == files_[file_pointer_].chunks.size()) {
+						chunk_pointer_ = 0;
+						file_pointer_++;
+						phase_ = (chunk_pointer_ == files_.size()) ? Phase::EndOfFile : Phase::Gap;
+					}
+				}
+			}
 		} break;
 	}
 
-//	if(pulse.type == Pulse::Type::Zero) printf("\n---\n");
-//	else {
-//		if(pulse.length.length == 1) printf(".");
-//		else if(pulse.length.length == 2) printf("+");
-//		else printf("?");
-//	}
-
-	if(!distance_into_phase_ && phase_ == Phase::Bytes) {
-		std::memmove(input_, &input_[1], 7);
-		input_[7] = file_.get8();
-		if(!is_at_end()) {
-			if(!std::memcmp(input_, header_signature, sizeof(header_signature))) {
-				phase_ = Phase::Header;//Gap;
-			}
-		}
-	}
+	pulse.length.length = static_cast<unsigned int>(2 - bit);
+	pulse.type = (distance_into_bit_ & 1) ? Pulse::Type::High : Pulse::Type::Low;
 
 	return pulse;
 }

Storage/Tape/Formats/CAS.hpp

@@ -12,6 +12,9 @@
 #include "../Tape.hpp"
 #include "../../FileHolder.hpp"
 
+#include <cstdint>
+#include <vector>
+
 namespace Storage {
 namespace Tape {
 
@@ -35,19 +38,35 @@ class CAS: public Tape {
 		bool is_at_end();
 
 	private:
-		Storage::FileHolder file_;
-
 		void virtual_reset();
 		Pulse virtual_get_next_pulse();
 
-		uint8_t input_[8] = {0, 0, 0, 0, 0, 0, 0, 0};
+		// Helper for populating the file list, below.
+		void get_next(Storage::FileHolder &file, uint8_t (&buffer)[8], std::size_t quantity);
 
+		// Storage for the array of files to transcribe into audio.
+		enum class Block {
+			BSAVE,
+			CSAVE,
+			ASCII
+		};
+		struct File {
+			Block type;
+			std::vector<std::vector<std::uint8_t>> chunks;
+		};
+		std::vector<File> files_;
+
+		// Tracker for active state within the file list.
+		std::size_t file_pointer_ = 0;
+		std::size_t chunk_pointer_ = 0;
 		enum class Phase {
 			Header,
 			Bytes,
-			Gap
+			Gap,
+			EndOfFile
 		} phase_ = Phase::Header;
-		int distance_into_phase_ = 0;
+		std::size_t distance_into_phase_ = 0;
+		std::size_t distance_into_bit_ = 0;
 };
 
 }