asapwriter.fu

// asapwriter.fu - format conversions
//
// Copyright (C) 2011-2023  Piotr Fusik
//
// This file is part of ASAP (Another Slight Atari Player),
// see http://asap.sourceforge.net
//
// ASAP is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published
// by the Free Software Foundation; either version 2 of the License,
// or (at your option) any later version.
//
// ASAP is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty
// of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with ASAP; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

class ASAPNativeModuleWriter
{
	internal ASAPWriter!? Writer;
	internal byte[]? SourceModule;
	internal int SourceOffset;
	int AddressDiff;

	int GetByte(int offset)
		=> SourceModule[SourceOffset + offset];

	internal int GetWord(int offset)
		=> ASAPInfo.GetWord(SourceModule, SourceOffset + offset);

	void Copy(int endOffset)
		throws
	{
		Writer.WriteBytes(SourceModule, SourceOffset + Writer.OutputOffset, SourceOffset + endOffset);
	}

	void RelocateBytes(int lowOffset, int highOffset, int count, int shift)
		throws
	{
		lowOffset += SourceOffset;
		highOffset += SourceOffset;
		for (int i = 0; i < count; i++) {
			int address = SourceModule[lowOffset + i] + (SourceModule[highOffset + i] << 8);
			if (address != 0 && address != 0xffff)
				address += AddressDiff;
			Writer.WriteByte((address >> shift) & 0xff);
		}
	}

	void RelocateLowHigh(int count)
		throws
	{
		int lowOffset = Writer.OutputOffset;
		RelocateBytes(lowOffset, lowOffset + count, count, 0);
		RelocateBytes(lowOffset, lowOffset + count, count, 8);
	}

	void RelocateWords(int count)
		throws
	{
		while (--count >= 0) {
			int address = GetWord(Writer.OutputOffset);
			if (address != 0 && address != 0xffff)
				address += AddressDiff;
			Writer.WriteWord(address);
		}
	}

	internal void Write!(ASAPInfo info, ASAPModuleType type, int moduleLen)
		throws
	{
		int startAddr = GetWord(2);
		AddressDiff = info.GetMusicAddress() < 0 ? 0 : info.GetMusicAddress() - startAddr;
		if (GetWord(4) + AddressDiff > 0xffff)
			throw "Address set too high";
		switch (type) {
		case ASAPModuleType.Cmc:
		case ASAPModuleType.Cm3:
		case ASAPModuleType.Cmr:
		case ASAPModuleType.Cms:
			// * -> CMC
			RelocateWords(3); // DOS header
			Copy(6 + 0x14); // CMC header
			RelocateLowHigh(64); // patterns
			break;
		case ASAPModuleType.Dlt:
			// * -> DLT
			RelocateWords(3); // DOS header
			break;
		case ASAPModuleType.Mpt:
			// * -> MPT
			RelocateWords(3 + 32 + 64); // DOS header, instruments, patterns
			Copy(6 + 64 + 128 + 256); // note lookup tables
			RelocateLowHigh(4); // tracks
			break;
		case ASAPModuleType.Rmt:
			// * -> RMT
			Writer.WriteWord(0xffff); // RMT-generated SAPs have a player before the module
			RelocateWords(2); // DOS header
			Copy(6 + 8); // RMT header
			int patternLowAddress = GetWord(0x10);
			RelocateWords((patternLowAddress - startAddr - 8) >> 1); // 4 pointers, instruments
			RelocateLowHigh(GetWord(0x12) - patternLowAddress); // patterns
			int songOffset = 6 + GetWord(0x14) - startAddr;
			Copy(songOffset);
			int songEnd = 7 + GetWord(4) - startAddr;
			while (songOffset + 3 < songEnd) {
				int nextSongOffset = songOffset + GetByte(9) - '0';
				if (GetByte(songOffset) == 0xfe) {
					// song jump
					Copy(songOffset + 2); // copy 0xfe, line_number
					RelocateWords(1); // relocate jump address
				}
				if (nextSongOffset > songEnd)
					nextSongOffset = songEnd;
				Copy(nextSongOffset);
				songOffset = nextSongOffset;
			}
			Copy(songEnd);
			if (moduleLen >= songEnd + 5)
				RelocateWords(2); // DOS header of text info: title and instrument names
			break;
		case ASAPModuleType.Tmc:
			// * -> TMC
			RelocateWords(3); // DOS header
			Copy(6 + 32); // TMC header
			RelocateLowHigh(64); // instruments
			RelocateLowHigh(128); // patterns
			break;
		case ASAPModuleType.Tm2:
			// * -> TM2
			RelocateWords(3); // DOS header
			Copy(6 + 128); // TM2 header
			RelocateBytes(6 + 128, 6 + 128 + 128 + 512, 128, 0); // instruments/low
			RelocateLowHigh(256); // patterns
			RelocateBytes(6 + 128, 6 + 128 + 128 + 512, 128, 8); // instruments/high
			break;
		default:
			throw "Impossible conversion";
		}
		Copy(moduleLen); // copy remaining bytes
	}
}

/// Static methods for writing modules in different formats.
public class ASAPWriter
{
	/// Maximum number of extensions returned by `GetSaveExts`.
	public const int MaxSaveExts = 3;

	public ASAPWriter()
	{
	}

	/// Enumerates possible file types the given module can be written as.
	/// Returns the number of extensions written to `exts`.
	public static int GetSaveExts(
		/// Receives filename extensions without the leading dot.
		/// Must be `MaxSaveExts` long.
		string[]! exts,
		/// File information.
		ASAPInfo info,
		/// Contents of the file.
		byte[] module,
		/// Length of the file.
		int moduleLen)
	{
		int i = 0;
		switch (info.Type) {
		case ASAPModuleType.SapB:
		case ASAPModuleType.SapC:
			exts[i++] = "sap";
			string? ext = info.GetOriginalModuleExt(module, moduleLen);
			if (ext != null)
				exts[i++] = ext;
			exts[i++] = "xex";
			break;
		case ASAPModuleType.SapD:
			exts[i++] = "sap";
			if (info.GetPlayerRateScanlines() == 312)
				exts[i++] = "xex";
			break;
		case ASAPModuleType.SapS:
			exts[i++] = "sap";
			break;
		default:
			exts[i++] = info.GetOriginalModuleExt(module, moduleLen);
			exts[i++] = "sap";
			exts[i++] = "xex";
			break;
		}
		return i;
	}

	static void TwoDigitsToString(byte[]! result, int offset, int value)
	{
		result[offset] = '0' + value / 10;
		result[offset + 1] = '0' + value % 10;
	}

	static bool SecondsToString(byte[]! result, int offset, int value)
	{
		if (value < 0 || value >= 100 * 60 * 1000)
			return false;
		value /= 1000;
		TwoDigitsToString(result, offset, value / 60);
		result[offset + 2] = ':';
		TwoDigitsToString(result, offset + 3, value % 60);
		return true;
	}

	/// Maximum length of text representation of a duration.
	/// Corresponds to the longest format which is `"mm:ss.xxx"`.
	public const int MaxDurationLength = 9;

	/// Writes text representation of the given duration.
	/// Returns the number of bytes written to `result`.
	public static int DurationToString(
		/// The output buffer.
		byte[]! result,
		/// Number of milliseconds.
		int value)
	{
		if (!SecondsToString(result, 0, value))
			return 0;
		value %= 1000;
		if (value == 0)
			return 5;
		result[5] = '.';
		TwoDigitsToString(result, 6, value / 10);
		value %= 10;
		if (value == 0)
			return 8;
		result[8] = '0' + value;
		return 9;
	}

	internal byte[]! Output;
	internal int OutputOffset;
	int OutputEnd;

	/// Sets the destination array for `Write`.
	public void SetOutput!(
		/// The destination array.
		byte[]! output,
		/// The array offset to start writing at.
		int startIndex,
		/// The array offset to finish writing before.
		int endIndex)
	{
		Output = output;
		OutputOffset = startIndex;
		OutputEnd = endIndex;
	}

	internal void WriteByte!(int value)
		throws
	{
		if (OutputOffset >= OutputEnd)
			throw "Output full";
		Output[OutputOffset++] = value;
	}

	internal void WriteWord!(int value)
		throws
	{
		WriteByte(value & 0xff);
		WriteByte(value >> 8);
	}

	internal void WriteBytes!(byte[] array, int startIndex, int endIndex)
		throws
	{
		int length = endIndex - startIndex;
		if (OutputOffset + length > OutputEnd)
			throw "Output full";
		array.CopyTo(startIndex, Output, OutputOffset, length);
		OutputOffset += length;
	}

	void WriteString!(string s)
		throws
	{
		foreach (int c in s)
			WriteByte(c);
	}

	void WriteDec!(int value)
		throws
	{
		if (value >= 10) {
			WriteDec(value / 10);
			value %= 10;
		}
		WriteByte('0' + value);
	}

	void WriteTextSapTag!(string tag, string value)
		throws
	{
		WriteString(tag);
		WriteByte('"');
		if (value.Length == 0)
			value = "<?>";
		WriteString(value);
		WriteByte('"');
		WriteByte('\r');
		WriteByte('\n');
	}

	void WriteDecSapTag!(string tag, int value)
		throws
	{
		WriteString(tag);
		WriteDec(value);
		WriteByte('\r');
		WriteByte('\n');
	}

	void WriteHexSapTag!(string tag, int value)
		throws
	{
		if (value < 0)
			return;
		WriteString(tag);
		for (int i = 12; i >= 0; i -= 4) {
			int digit = (value >> i) & 0xf;
			WriteByte(digit + (digit < 10 ? '0' : 'A' - 10));
		}
		WriteByte('\r');
		WriteByte('\n');
	}

	void WriteSapHeader!(ASAPInfo info, int type, int init, int player)
		throws
	{
		WriteString("SAP\r\n");
		WriteTextSapTag("AUTHOR ", info.GetAuthor());
		WriteTextSapTag("NAME ", info.GetTitle());
		WriteTextSapTag("DATE ", info.GetDate());
		if (info.GetSongs() > 1) {
			WriteDecSapTag("SONGS ", info.GetSongs());
			if (info.GetDefaultSong() > 0)
				WriteDecSapTag("DEFSONG ", info.GetDefaultSong());
		}
		if (info.GetChannels() > 1)
			WriteString("STEREO\r\n");
		if (info.IsNtsc())
			WriteString("NTSC\r\n");
		WriteString("TYPE ");
		WriteByte(type);
		WriteByte('\r');
		WriteByte('\n');
		if (info.GetPlayerRateScanlines() != (type == 'S' ? 78 : 312) || info.IsNtsc())
			WriteDecSapTag("FASTPLAY ", info.GetPlayerRateScanlines());
		if (type == 'C')
			WriteHexSapTag("MUSIC ", info.GetMusicAddress());
		WriteHexSapTag("INIT ", init);
		WriteHexSapTag("PLAYER ", player);
		WriteHexSapTag("COVOX ", info.GetCovoxAddress());
		for (int song = 0; song < info.GetSongs(); song++) {
			if (info.GetDuration(song) < 0)
				break;
			WriteString("TIME ");
			byte[MaxDurationLength] s;
			WriteBytes(s, 0, DurationToString(s, info.GetDuration(song)));
			if (info.GetLoop(song))
				WriteString(" LOOP");
			WriteByte('\r');
			WriteByte('\n');
		}
	}

	void WriteExecutableHeader!(int[]!? initAndPlayer, ASAPInfo info, int type, int init, int player)
		throws
	{
		if (initAndPlayer == null)
			WriteSapHeader(info, type, init, player);
		else {
			initAndPlayer[0] = init;
			initAndPlayer[1] = player;
		}
	}

	void WritePlaTaxLda0!()
		throws
	{
		WriteByte(0x68);
		WriteByte(0xaa);
		WriteByte(0xa9);
		WriteByte(0);
	}

	void WriteCmcInit!(int[]!? initAndPlayer, ASAPInfo info)
		throws
	{
		if (initAndPlayer == null)
			return; // to SAP
		const int initCmc = 0xfe0; // cms.obx ends at 0xfbe
		WriteWord(initCmc);
		WriteWord(initCmc + 16);
		WriteByte(0x48); // PHA
		int music = info.GetMusicAddress();
		WriteByte(0xa2); WriteByte(music & 0xff); // LDX #<MUSIC
		WriteByte(0xa0); WriteByte(music >> 8); // LDY #>MUSIC
		WriteByte(0xa9); WriteByte(0x70); // LDA #$70
		WriteByte(0x20); WriteWord(initAndPlayer[1] + 3); // JSR PLAYER+3
		WritePlaTaxLda0(); // PLA; TAX; LDA #0
		WriteByte(0x4c); WriteWord(initAndPlayer[1] + 3); // JMP PLAYER+3
		initAndPlayer[0] = initCmc;
		initAndPlayer[1] += 6;
	}

	void WriteExecutableFromSap!(int[]! initAndPlayer, ASAPInfo info, int type, byte[] module, int moduleLen)
		throws
	{
		WriteExecutableHeader(initAndPlayer, info, type, info.GetInitAddress(), info.Player);
		WriteBytes(module, info.HeaderLen, moduleLen);
	}

	int WriteExecutableHeaderForSongPos!(int[]! initAndPlayer, ASAPInfo info, int player, int codeForOneSong, int codeForManySongs, int playerOffset)
		throws
	{
		if (info.GetSongs() != 1) {
			WriteExecutableHeader(initAndPlayer, info, 'B', player - codeForManySongs, player + playerOffset);
			return player - codeForManySongs - info.GetSongs();
		}
		WriteExecutableHeader(initAndPlayer, info, 'B', player - codeForOneSong, player + playerOffset);
		return player - codeForOneSong;
	}

	internal void WriteExecutable!(int[]!? initAndPlayer, ASAPInfo info, byte[] module, int moduleLen)
		throws
	{
		byte[]? playerRoutine = ASAP6502.GetPlayerRoutine(info);
		int player = -1;
		int playerLastByte = -1;
		int music = info.GetMusicAddress();
		if (playerRoutine != null) {
			player = ASAPInfo.GetWord(playerRoutine, 2);
			playerLastByte = ASAPInfo.GetWord(playerRoutine, 4);
			if (music <= playerLastByte)
				throw "Module address conflicts with the player routine";
		}
		int startAddr;
		switch (info.Type) {
		case ASAPModuleType.SapB:
			WriteExecutableFromSap(initAndPlayer, info, 'B', module, moduleLen);
			break;
		case ASAPModuleType.SapC:
			WriteExecutableFromSap(initAndPlayer, info, 'C', module, moduleLen);
			WriteCmcInit(initAndPlayer, info);
			break;
		case ASAPModuleType.SapD:
			WriteExecutableFromSap(initAndPlayer, info, 'D', module, moduleLen);
			break;
		case ASAPModuleType.SapS:
			WriteExecutableFromSap(initAndPlayer, info, 'S', module, moduleLen);
			break;
		case ASAPModuleType.Cmc:
		case ASAPModuleType.Cm3:
		case ASAPModuleType.Cmr:
		case ASAPModuleType.Cms:
			WriteExecutableHeader(initAndPlayer, info, 'C', -1, player);
			WriteWord(0xffff); // some modules start with zeros
			WriteBytes(module, 2, moduleLen);
			WriteBytes(playerRoutine, 2, playerLastByte - player + 7);
			WriteCmcInit(initAndPlayer, info);
			break;
		case ASAPModuleType.Dlt:
			startAddr = WriteExecutableHeaderForSongPos(initAndPlayer, info, player, 5, 7, 0x103);
			if (moduleLen == 0x2c06) {
				// append zero to the module
				WriteBytes(module, 0, 4);
				WriteWord(0x4c00);
				WriteBytes(module, 6, moduleLen);
				WriteByte(0);
			}
			else
				WriteBytes(module, 0, moduleLen);
			WriteWord(startAddr);
			WriteWord(playerLastByte);
			if (info.GetSongs() != 1) {
				WriteBytes(info.SongPos, 0, info.GetSongs());
				WriteByte(0xaa); // TAX
				WriteByte(0xbc); WriteWord(startAddr); // LDY SONG2POS,X
			}
			else {
				WriteByte(0xa0); WriteByte(0); // LDY #0
			}
			WriteByte(0x4c); WriteWord(player + 0x100); // JMP PLAYER+$100
			WriteBytes(playerRoutine, 6, playerLastByte - player + 7);
			break;
		case ASAPModuleType.Mpt:
			startAddr = WriteExecutableHeaderForSongPos(initAndPlayer, info, player, 13, 17, 3);
			WriteBytes(module, 0, moduleLen);
			WriteWord(startAddr);
			WriteWord(playerLastByte);
			if (info.GetSongs() != 1) {
				WriteBytes(info.SongPos, 0, info.GetSongs());
				WriteByte(0x48); // PHA
			}
			WriteByte(0xa0); WriteByte(music & 0xff); // LDY #<MUSIC
			WriteByte(0xa2); WriteByte(music >> 8); // LDX #>MUSIC
			WriteByte(0xa9); WriteByte(0); // LDA #0
			WriteByte(0x20); WriteWord(player); // JSR PLAYER
			if (info.GetSongs() != 1) {
				WriteByte(0x68); WriteByte(0xa8); // PLA; TAY
				WriteByte(0xbe); WriteWord(startAddr); // LDX SONG2POS,Y
			}
			else {
				WriteByte(0xa2); WriteByte(0); // LDX #0
			}
			WriteByte(0xa9); WriteByte(2); // LDA #2
			WriteBytes(playerRoutine, 6, playerLastByte - player + 7);
			break;
		case ASAPModuleType.Rmt:
			WriteExecutableHeader(initAndPlayer, info, 'B', ASAPInfo.RmtInit, 0x603);
			WriteBytes(module, 0, ASAPInfo.GetWord(module, 4) - music + 7);
			WriteWord(ASAPInfo.RmtInit);
			if (info.GetSongs() != 1) {
				WriteWord(ASAPInfo.RmtInit + 10 + info.GetSongs());
				WriteByte(0xa8); // TAY
				WriteByte(0xb9); WriteWord(ASAPInfo.RmtInit + 11); // LDA SONG2POS,Y
			}
			else {
				WriteWord(ASAPInfo.RmtInit + 8);
				WriteByte(0xa9); WriteByte(0); // LDA #0
			}
			WriteByte(0xa2); WriteByte(music & 0xff); // LDX #<MUSIC
			WriteByte(0xa0); WriteByte(music >> 8); // LDY #>MUSIC
			WriteByte(0x4c); WriteWord(0x600); // JMP PLAYER
			if (info.GetSongs() != 1)
				WriteBytes(info.SongPos, 0, info.GetSongs());
			WriteBytes(playerRoutine, 2, playerLastByte - player + 7);
			break;
		case ASAPModuleType.Tmc:
			int perFrame = module[0x25];
			const int[4] tmcPlayerOffset = { 3, -9, -10, -10 };
			int player2 = player + tmcPlayerOffset[perFrame - 1];
			const int[4] tmcInitOffset = { -14, -16, -17, -17 };
			startAddr = player2 + tmcInitOffset[perFrame - 1];
			if (info.GetSongs() != 1)
				startAddr -= 3;
			WriteExecutableHeader(initAndPlayer, info, 'B', startAddr, player2);
			WriteBytes(module, 0, moduleLen);
			WriteWord(startAddr);
			WriteWord(playerLastByte);
			if (info.GetSongs() != 1)
				WriteByte(0x48); // PHA
			WriteByte(0xa0); WriteByte(music & 0xff); // LDY #<MUSIC
			WriteByte(0xa2); WriteByte(music >> 8); // LDX #>MUSIC
			WriteByte(0xa9); WriteByte(0x70); // LDA #$70
			WriteByte(0x20); WriteWord(player); // JSR PLAYER
			if (info.GetSongs() != 1)
				WritePlaTaxLda0(); // PLA; TAX; LDA #0
			else {
				WriteByte(0xa9); WriteByte(0x60); // LDA #$60
			}
			switch (perFrame) {
			case 2:
				WriteByte(0x06); WriteByte(0); // ASL 0
				WriteByte(0x4c); WriteWord(player); // JMP PLAYER
				WriteByte(0xa5); WriteByte(0); // LDA 0
				WriteByte(0xe6); WriteByte(0); // INC 0
				WriteByte(0x4a); // LSR @
				WriteByte(0x90); WriteByte(5); // BCC PLAYER+3
				WriteByte(0xb0); WriteByte(6); // BCS PLAYER+6
				break;
			case 3:
			case 4:
				WriteByte(0xa0); WriteByte(1); // LDY #1
				WriteByte(0x84); WriteByte(0); // STY 0
				WriteByte(0xd0); WriteByte(10); // BNE PLAYER
				WriteByte(0xc6); WriteByte(0); // DEC 0
				WriteByte(0xd0); WriteByte(12); // BNE PLAYER+6
				WriteByte(0xa0); WriteByte(perFrame); // LDY #3
				WriteByte(0x84); WriteByte(0); // STY 0
				WriteByte(0xd0); WriteByte(3); // BNE PLAYER+3
				break;
			default:
				break;
			}
			WriteBytes(playerRoutine, 6, playerLastByte - player + 7);
			break;
		case ASAPModuleType.Tm2:
			const int tm2Init = 0x1380;
			WriteExecutableHeader(initAndPlayer, info, 'B', tm2Init, 0x803);
			WriteBytes(module, 0, moduleLen);
			WriteWord(tm2Init);
			if (info.GetSongs() != 1) {
				WriteWord(tm2Init + 16);
				WriteByte(0x48); // PHA
			}
			else
				WriteWord(tm2Init + 14);
			WriteByte(0xa0); WriteByte(music & 0xff); // LDY #<MUSIC
			WriteByte(0xa2); WriteByte(music >> 8); // LDX #>MUSIC
			WriteByte(0xa9); WriteByte(0x70); // LDA #$70
			WriteByte(0x20); WriteWord(0x800); // JSR PLAYER
			if (info.GetSongs() != 1)
				WritePlaTaxLda0(); // PLA; TAX; LDA #0
			else {
				WriteByte(0xa9); WriteByte(0); // LDA #0
				WriteByte(0xaa); // TAX
			}
			WriteByte(0x4c); WriteWord(0x800); // JMP PLAYER
			WriteBytes(playerRoutine, 2, playerLastByte - player + 7);
			break;
		case ASAPModuleType.Fc:
			WriteExecutableHeader(initAndPlayer, info, 'B', player, player + 3);
			WriteWord(0xffff);
			WriteWord(music);
			WriteWord(music + moduleLen - 1);
			WriteBytes(module, 0, moduleLen);
			WriteBytes(playerRoutine, 2, playerLastByte - player + 7);
			break;
		}
	}

	const int XexInfoCharactersPerLine = 32;

	static int PadXexInfo(byte[]! dest, int offset, int endColumn)
	{
		while (offset % XexInfoCharactersPerLine != endColumn)
			dest[offset++] = ' ';
		return offset;
	}

	static int FormatXexInfoText(byte[]! dest, int destLen, int endColumn, string src, bool author)
	{
		int srcLen = src.Length;
		for (int srcOffset = 0; srcOffset < srcLen; ) {
			int c = src[srcOffset++];
			if (c == ' ') {
				if (author && srcOffset < srcLen && src[srcOffset] == '&') {
					int authorLen;
					for (authorLen = 1; srcOffset + authorLen < srcLen; authorLen++) {
						if (src[srcOffset + authorLen] == ' ' && srcOffset + authorLen + 1 < srcLen && src[srcOffset + authorLen + 1] == '&')
							break;
					}
					if (authorLen <= XexInfoCharactersPerLine && destLen % XexInfoCharactersPerLine + 1 + authorLen > XexInfoCharactersPerLine) {
						destLen = PadXexInfo(dest, destLen, 1); // align author names after "by" and "&"
						continue;
					}
				}
				int wordLen;
				for (wordLen = 0; srcOffset + wordLen < srcLen && src[srcOffset + wordLen] != ' '; wordLen++) {
				}
				if (wordLen <= XexInfoCharactersPerLine && destLen % XexInfoCharactersPerLine + 1 + wordLen > XexInfoCharactersPerLine) {
					destLen = PadXexInfo(dest, destLen, 0);
					continue;
				}
			}
			dest[destLen++] = c;
		}
		return PadXexInfo(dest, destLen, endColumn);
	}

	void WriteXexInfoTextDl!(int address, int len, int verticalScrollAt)
		throws
	{
		WriteByte(verticalScrollAt == 0 ? 0x62 : 0x42);
		WriteWord(address);
		for (int i = XexInfoCharactersPerLine; i < len; i += XexInfoCharactersPerLine)
			WriteByte(i == verticalScrollAt ? 0x22 : 2);
	}

	void WriteXexInfo!(ASAPInfo info)
		throws
	{
		byte[256] title;
		int titleLen = FormatXexInfoText(title, 0, 0, info.GetTitle().Length == 0 ? "(untitled)" : info.GetTitle(), false);
		byte[256] author;
		int authorLen;
		if (info.GetAuthor().Length > 0) {
			author[0] = 'b';
			author[1] = 'y';
			author[2] = ' ';
			authorLen = FormatXexInfoText(author, 3, 0, info.GetAuthor(), true);
		}
		else
			authorLen = 0;
		byte[256] other;
		int otherLen = FormatXexInfoText(other, 0, XexInfoCharactersPerLine - 13, info.GetDate(), false);
		otherLen = FormatXexInfoText(other, otherLen, XexInfoCharactersPerLine - 5, info.GetChannels() > 1 ? " STEREO" : "   MONO", false);
		int duration = info.GetDuration(info.GetDefaultSong());
		if (duration > 0 && SecondsToString(other, otherLen, duration + 999)) // round up to full seconds
			otherLen += 5;
		else
			otherLen = PadXexInfo(other, otherLen, 0);

		const int xexInfoDl = 0xfc50; // must match xexinfo.asx
		int totalCharacters = titleLen + authorLen + otherLen;
		int totalLines = totalCharacters / XexInfoCharactersPerLine;
		int otherAddress = xexInfoDl - otherLen;
#if HIDE_AUTHOR
		int authorAddress = otherAddress - authorLen;
		int hiddenAddress = authorAddress - authorLen;
		int titleAddress = hiddenAddress - 8 - titleLen;
#else
		int titleAddress = otherAddress - authorLen - 8 - titleLen;
#endif
		WriteWord(titleAddress);
		WriteBytes(resource<byte[]>("xexinfo.obx"), 4, 6);

		WriteBytes(title, 0, titleLen);
		for (int i = 0; i < 8; i++)
			WriteByte(0x55);
#if HIDE_AUTHOR
		if (authorLen > 0) {
			WriteString("(press space to show author)");
			for (int i = 28; i < authorLen; i++)
				WriteByte(' ');
			WriteBytes(author, 0, authorLen);
		}
#else
		WriteBytes(author, 0, authorLen);
#endif
		WriteBytes(other, 0, otherLen);
		for (int i = totalLines; i < 26; i++)
			WriteByte(0x70);
		WriteByte(0x30);
		WriteXexInfoTextDl(titleAddress, titleLen, titleLen - XexInfoCharactersPerLine);
		WriteByte(8);
		WriteByte(0);
#if HIDE_AUTHOR
		if (authorLen > 0)
			WriteXexInfoTextDl(hiddenAddress, authorLen, -1);
		WriteByte(0x10);
		WriteXexInfoTextDl(otherAddress, otherLen, -1);
		WriteByte(0x41);
		WriteWord(xexInfoDl);
		if (authorLen > 0) {
			int dlAuthor = xexInfoDl + 32 - totalLines + titleLen / XexInfoCharactersPerLine;
			WriteByte(0xa9); WriteByte(authorAddress & 0xff); // LDA #<author
			WriteByte(0x8d); WriteWord(dlAuthor); // STA dl_author
			WriteByte(0xa9); WriteByte(authorAddress >> 8); // LDA #>author
			WriteByte(0x8d); WriteWord(dlAuthor + 1); // STA dl_author+1
		}
		else {
			// pad two bytes because DL is shorter due to no LMS for author
			// show_author is just RTS, pad with more RTSes
			for (int i = 0; i < 12; i++)
				WriteByte(0x60);
		}
#else
		for (int i = 0; i < authorLen; i += XexInfoCharactersPerLine)
			WriteByte(2);
		WriteByte(0x10);
		for (int i = 0; i < otherLen; i += XexInfoCharactersPerLine)
			WriteByte(2);
#endif
		WriteBytes(resource<byte[]>("xexinfo.obx"), 6, resource<byte[]>("xexinfo.obx").Length);
	}

	void WriteNative!(ASAPInfo info, byte[] module, int moduleLen)
		throws
	{
		ASAPNativeModuleWriter() nativeWriter;
		nativeWriter.Writer = this;
		nativeWriter.SourceModule = module;

		ASAPModuleType type = info.Type;
		switch (type) {
		case ASAPModuleType.SapB:
		case ASAPModuleType.SapC:
			// SAP -> native
			int offset = info.GetRmtSapOffset(module, moduleLen);
			if (offset > 0) {
				// RMT-generated SAP -> RMT
				nativeWriter.SourceOffset = offset - 2;
				nativeWriter.Write(info, ASAPModuleType.Rmt, moduleLen - offset + 2);
				return;
			}
			nativeWriter.SourceOffset = info.HeaderLen;
			int blockLen = nativeWriter.GetWord(4) - nativeWriter.GetWord(2) + 7;
			if (blockLen < 7 || info.HeaderLen + blockLen >= moduleLen)
				throw "Cannot extract module from SAP";
			type = info.GetOriginalModuleType(module, moduleLen);
			if (type == ASAPModuleType.Fc)
				WriteBytes(module, info.HeaderLen + 6, info.HeaderLen + blockLen); // SAP -> FC
			else
				nativeWriter.Write(info, type, blockLen); // SAP -> native
			break;
		case ASAPModuleType.Fc:
			// FC -> FC
			WriteBytes(module, 0, moduleLen);
			return;
		default:
			// native -> native
			nativeWriter.SourceOffset = 0;
			nativeWriter.Write(info, type, moduleLen);
			break;
		}
	}

	/// Writes the given module in a possibly different file format.
	public int Write!(
		/// Output filename, used to determine the format.
		string targetFilename,
		/// File information got from the source file with data updated for the output file.
		ASAPInfo info,
		/// Contents of the source file.
		byte[] module,
		/// Length of the source file.
		int moduleLen,
		/// Display information (xex output only).
		bool tag)
		throws
	{
		int destExt = ASAPInfo.GetPackedExt(targetFilename);
		switch (destExt) {
		case ASAPInfo.PackExt("SAP"):
			// * -> SAP
			WriteExecutable(null, info, module, moduleLen);
			return OutputOffset;
		case ASAPInfo.PackExt("XEX"):
			// * -> XEX
			{
				int[2] initAndPlayer;
				WriteExecutable(initAndPlayer, info, module, moduleLen);
				switch (info.Type) {
				case ASAPModuleType.SapD:
					if (info.GetPlayerRateScanlines() != 312)
						throw "Impossible conversion";
					WriteBytes(resource<byte[]>("xexd.obx"), 2, resource<byte[]>("xexd.obx").Length);
					WriteWord(initAndPlayer[0]);
					if (initAndPlayer[1] < 0) {
						WriteByte(0x60); // RTS
						WriteByte(0x60); // don't care
						WriteByte(0x60); // don't care
					}
					else {
						WriteByte(0x4c); // JMP
						WriteWord(initAndPlayer[1]);
					}
					WriteByte(info.GetDefaultSong());
					break;
				case ASAPModuleType.SapS:
					throw "Impossible conversion";
				default:
					WriteBytes(resource<byte[]>("xexb.obx"), 2, resource<byte[]>("xexb.obx").Length);
					WriteWord(initAndPlayer[0]);
					WriteByte(0x4c); // JMP
					WriteWord(initAndPlayer[1]);
					WriteByte(info.GetDefaultSong());
					int fastplay = info.GetPlayerRateScanlines();
					WriteByte(fastplay & 1);
					WriteByte((fastplay >> 1) % 156);
					WriteByte((fastplay >> 1) % 131);
					WriteByte(fastplay / 312);
					WriteByte(fastplay / 262);
					break;
				}
				if (tag)
					WriteXexInfo(info);
				WriteWord(0x2e0);
				WriteWord(0x2e1);
				WriteWord(tag ? 0x100 : 0x124); // must match xexinfo.asx, xexb.asx, xexd.asx
				FlashPack() flashPack;
				flashPack.Compress(this);
				return OutputOffset;
			}
		default:
			string? possibleExt = info.GetOriginalModuleExt(module, moduleLen);
			if (possibleExt != null) {
				int packedPossibleExt = ASAPInfo.PackExt(possibleExt);
				if (destExt == packedPossibleExt
				 || (destExt == ASAPInfo.PackExt("TM8") && packedPossibleExt == ASAPInfo.PackExt("TMC"))) {
					// * -> native
					WriteNative(info, module, moduleLen);
					return OutputOffset;
				}
			}
			throw "Impossible conversion";
		}
	}
}