Made sufficient changes for the Vic itself to believe it can recast a PRG as a tape and insert it that way. So now the ball is in the court of: how the heck are Commodore tapes encoded?

Machines/Commodore/Vic-20/Vic20.cpp

@@ -9,6 +9,7 @@
 #include "Vic20.hpp"
 
 #include <algorithm>
+#include "../../../Storage/Tape/Formats/TapePRG.hpp"
 
 using namespace Commodore::Vic20;
 
@@ -218,7 +219,7 @@ void Machine::set_rom(ROMSlot slot, size_t length, const uint8_t *data)
 	}
 }
 
-void Machine::add_prg(size_t length, const uint8_t *data)
+void Machine::set_prg(const char *file_name, size_t length, const uint8_t *data)
 {
 	if(length > 2)
 	{
@@ -237,16 +238,8 @@ void Machine::add_prg(size_t length, const uint8_t *data)
 		}
 		else
 		{
-			// TODO: write to virtual media (tape, probably?), load normally.
+			// if it's not a ROM then insert it as a tape
-			data += 2;
+			set_tape(std::shared_ptr<Storage::Tape>(new Storage::TapePRG(file_name)));
-			while(_rom_length)
-			{
-				uint8_t *ram = _processorWriteMemoryMap[_rom_address >> 10];
-				if(ram) ram[_rom_address & 0x3ff] = *data;
-				data++;
-				_rom_length--;
-				_rom_address++;
-			}
 		}
 	}
 }

Machines/Commodore/Vic-20/Vic20.hpp

@@ -260,7 +260,7 @@ class Machine:
 		~Machine();
 
 		void set_rom(ROMSlot slot, size_t length, const uint8_t *data);
-		void add_prg(size_t length, const uint8_t *data);
+		void set_prg(const char *file_name, size_t length, const uint8_t *data);
 		void set_tape(std::shared_ptr<Storage::Tape> tape);
 		void set_disk(std::shared_ptr<Storage::Disk> disk);
 

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -22,6 +22,7 @@
 		4B2A53A11D117D36003C6002 /* CSAtari2600.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A539A1D117D36003C6002 /* CSAtari2600.mm */; };
 		4B2A53A21D117D36003C6002 /* CSElectron.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A539C1D117D36003C6002 /* CSElectron.mm */; };
 		4B2A53A31D117D36003C6002 /* CSVic20.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4B2A539E1D117D36003C6002 /* CSVic20.mm */; };
+		4B2BFC5F1D613E0200BA3AA9 /* TapePRG.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2BFC5D1D613E0200BA3AA9 /* TapePRG.cpp */; };
 		4B2E2D951C399D1200138695 /* ElectronDocument.xib in Resources */ = {isa = PBXBuildFile; fileRef = 4B2E2D931C399D1200138695 /* ElectronDocument.xib */; };
 		4B2E2D9A1C3A06EC00138695 /* Atari2600.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2E2D971C3A06EC00138695 /* Atari2600.cpp */; };
 		4B2E2D9D1C3A070400138695 /* Electron.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2E2D9B1C3A070400138695 /* Electron.cpp */; };
@@ -393,6 +394,8 @@
 		4B2A539C1D117D36003C6002 /* CSElectron.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = CSElectron.mm; sourceTree = "<group>"; };
 		4B2A539D1D117D36003C6002 /* CSVic20.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = CSVic20.h; sourceTree = "<group>"; };
 		4B2A539E1D117D36003C6002 /* CSVic20.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = CSVic20.mm; sourceTree = "<group>"; };
+		4B2BFC5D1D613E0200BA3AA9 /* TapePRG.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = TapePRG.cpp; sourceTree = "<group>"; };
+		4B2BFC5E1D613E0200BA3AA9 /* TapePRG.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = TapePRG.hpp; sourceTree = "<group>"; };
 		4B2E2D941C399D1200138695 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/ElectronDocument.xib; sourceTree = "<group>"; };
 		4B2E2D971C3A06EC00138695 /* Atari2600.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Atari2600.cpp; sourceTree = "<group>"; };
 		4B2E2D981C3A06EC00138695 /* Atari2600.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Atari2600.hpp; sourceTree = "<group>"; };
@@ -1004,6 +1007,8 @@
 				4B69FB431C4D941400B5F0AA /* TapeUEF.hpp */,
 				4BC91B811D1F160E00884B76 /* CommodoreTAP.cpp */,
 				4BC91B821D1F160E00884B76 /* CommodoreTAP.hpp */,
+				4B2BFC5D1D613E0200BA3AA9 /* TapePRG.cpp */,
+				4B2BFC5E1D613E0200BA3AA9 /* TapePRG.hpp */,
 			);
 			path = Formats;
 			sourceTree = "<group>";
@@ -1908,6 +1913,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				4B2BFC5F1D613E0200BA3AA9 /* TapePRG.cpp in Sources */,
 				4BAB62AD1D3272D200DF5BA0 /* Disk.cpp in Sources */,
 				4BC9DF4F1D04691600F44158 /* 6560.cpp in Sources */,
 				4BB697CE1D4BA44400248BDF /* CommodoreGCR.cpp in Sources */,

OSBindings/Mac/Clock Signal/Documents/Vic20Document.swift

@@ -47,6 +47,7 @@ class Vic20Document: MachineDocument {
 				case "tap":	vic20.openTAPAtURL(url)
 				case "g64":	vic20.openG64AtURL(url)
 				case "d64":	vic20.openD64AtURL(url)
+				case "prg": vic20.openPRGAtURL(url)
 				default:
 					let fileWrapper = try NSFileWrapper(URL: url, options: NSFileWrapperReadingOptions(rawValue: 0))
 					try self.readFromFileWrapper(fileWrapper, ofType: typeName)
@@ -59,10 +60,6 @@ class Vic20Document: MachineDocument {
 		return dataForResource(name, ofType: "bin", inDirectory: "ROMImages/Vic20")
 	}
 
-	override func readFromData(data: NSData, ofType typeName: String) throws {
-		vic20.setPRG(data)
-	}
-
 	// MARK: automatic loading tick box
 	@IBOutlet var loadAutomaticallyButton: NSButton?
 	var autoloadingUserDefaultsKey: String {

OSBindings/Mac/Clock Signal/Machine/Wrappers/CSVic20.h

@@ -30,7 +30,7 @@ typedef NS_ENUM(NSInteger, CSVic20MemorySize)
 - (void)setCharactersROM:(nonnull NSData *)rom;
 - (void)setDriveROM:(nonnull NSData *)rom;
 
-- (void)setPRG:(nonnull NSData *)prg;
+- (BOOL)openPRGAtURL:(nonnull NSURL *)URL;
 - (BOOL)openTAPAtURL:(nonnull NSURL *)URL;
 - (BOOL)openG64AtURL:(nonnull NSURL *)URL;
 - (BOOL)openD64AtURL:(nonnull NSURL *)URL;

OSBindings/Mac/Clock Signal/Machine/Wrappers/CSVic20.mm

@@ -82,9 +82,15 @@ using namespace Commodore::Vic20;
 	}
 }
 
-- (void)setPRG:(nonnull NSData *)prg {
+- (BOOL)openPRGAtURL:(NSURL *)URL {
+	NSData *prg = [NSData dataWithContentsOfURL:URL];
 	@synchronized(self) {
-		_vic20.add_prg(prg.length, (const uint8_t *)prg.bytes);
+		try {
+			_vic20.set_prg(URL.fileSystemRepresentation, prg.length, (const uint8_t *)prg.bytes);
+			return YES;
+		} catch(...) {
+			return NO;
+		}
 	}
 }
 

Storage/Tape/Formats/TapePRG.cpp

@@ -0,0 +1,49 @@
+//
+//  TapePRG.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/08/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#include "TapePRG.hpp"
+
+#include <sys/stat.h>
+
+using namespace Storage;
+
+TapePRG::TapePRG(const char *file_name) : _file(nullptr)
+{
+	struct stat file_stats;
+	stat(file_name, &file_stats);
+
+	// There's really no way to validate other than that if this file is larger than 64kb,
+	// of if load address + length > 65536 then it's broken.
+	if(file_stats.st_size >= 65538 || file_stats.st_size < 3)
+		throw ErrorBadFormat;
+
+	_file = fopen(file_name, "rb");
+	if(!_file) throw ErrorBadFormat;
+
+	_load_address = (uint16_t)fgetc(_file);
+	_load_address |= (uint16_t)fgetc(_file) << 8;
+
+	if (_load_address + file_stats.st_size >= 65536)
+		throw ErrorBadFormat;
+}
+
+TapePRG::~TapePRG()
+{
+	if(_file) fclose(_file);
+}
+
+Tape::Pulse TapePRG::get_next_pulse()
+{
+	Tape::Pulse pulse;
+	return pulse;
+}
+
+void TapePRG::reset()
+{
+	// TODO
+}

Storage/Tape/Formats/TapePRG.hpp

@@ -0,0 +1,58 @@
+//
+//  TapePRG.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/08/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef TapePRG_hpp
+#define TapePRG_hpp
+
+#include "../Tape.hpp"
+#include <stdint.h>
+
+namespace Storage {
+
+/*!
+	Provides a @c Tape containing a .PRG, which is a direct local file.
+*/
+class TapePRG: public Tape {
+	public:
+		/*!
+			Constructs a @c T64 containing content from the file with name @c file_name, of type @c type.
+
+			@param file_name The name of the file to load.
+			@param type The type of data the file should contain.
+			@throws ErrorBadFormat if this file could not be opened and recognised as the specified type.
+		*/
+		TapePRG(const char *file_name);
+		~TapePRG();
+
+		enum {
+			ErrorBadFormat
+		};
+
+		// implemented to satisfy @c Tape
+		Pulse get_next_pulse();
+		void reset();
+	private:
+		FILE *_file;
+		uint16_t _load_address;
+
+		enum FilePhase {
+			FilePhaseLeadIn,
+			FilePhaseHeader
+		} _filePhase;
+
+		enum BitPhase {
+			BitPhase0,
+			BitPhase1,
+			BitPhase2,
+			BitPhase3
+		} _bitPhase;
+};
+
+}
+
+#endif /* T64_hpp */