musix 0.3.5

/*
 * Load_mod.cpp
 * ------------
 * Purpose: MOD / NST (ProTracker / NoiseTracker), M15 / STK (Ultimate Soundtracker / Soundtracker) and ST26 (SoundTracker 2.6 / Ice Tracker) module loader / saver
 * Notes  : "2000 LOC for processing MOD files?!" you say? Well, this file also contains loaders for some formats that are almost identical to MOD, and extensive
 *          heuristics for more or less broken MOD files and files saved with tons of different trackers, to allow for the most optimal playback.
 * Authors: Olivier Lapicque
 *          OpenMPT Devs
 * The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
 */


#include "stdafx.h"
#include "Loaders.h"
#include "Tables.h"
#ifndef MODPLUG_NO_FILESAVE
#include "../common/mptFileIO.h"
#endif
#ifdef MPT_EXTERNAL_SAMPLES
// For loading external data in Startrekker files
#include "../common/mptPathString.h"
#endif // MPT_EXTERNAL_SAMPLES

OPENMPT_NAMESPACE_BEGIN

void CSoundFile::ConvertModCommand(ModCommand &m)
{
	switch(m.command)
	{
	case 0x00:	if(m.param) m.command = CMD_ARPEGGIO; break;
	case 0x01:	m.command = CMD_PORTAMENTOUP; break;
	case 0x02:	m.command = CMD_PORTAMENTODOWN; break;
	case 0x03:	m.command = CMD_TONEPORTAMENTO; break;
	case 0x04:	m.command = CMD_VIBRATO; break;
	case 0x05:	m.command = CMD_TONEPORTAVOL; break;
	case 0x06:	m.command = CMD_VIBRATOVOL; break;
	case 0x07:	m.command = CMD_TREMOLO; break;
	case 0x08:	m.command = CMD_PANNING8; break;
	case 0x09:	m.command = CMD_OFFSET; break;
	case 0x0A:	m.command = CMD_VOLUMESLIDE; break;
	case 0x0B:	m.command = CMD_POSITIONJUMP; break;
	case 0x0C:	m.command = CMD_VOLUME; break;
	case 0x0D:	m.command = CMD_PATTERNBREAK; m.param = ((m.param >> 4) * 10) + (m.param & 0x0F); break;
	case 0x0E:	m.command = CMD_MODCMDEX; break;
	case 0x0F:
		// For a very long time, this code imported 0x20 as CMD_SPEED for MOD files, but this seems to contradict
		// pretty much the majority of other MOD player out there.
		// 0x20 is Speed: Impulse Tracker, Scream Tracker, old ModPlug
		// 0x20 is Tempo: ProTracker, XMPlay, Imago Orpheus, Cubic Player, ChibiTracker, BeRoTracker, DigiTrakker, DigiTrekker, Disorder Tracker 2, DMP, Extreme's Tracker, ...
		if(m.param < 0x20)
			m.command = CMD_SPEED;
		else
			m.command = CMD_TEMPO;
		break;

	// Extension for XM extended effects
	case 'G' - 55:	m.command = CMD_GLOBALVOLUME; break;		//16
	case 'H' - 55:	m.command = CMD_GLOBALVOLSLIDE; break;
	case 'K' - 55:	m.command = CMD_KEYOFF; break;
	case 'L' - 55:	m.command = CMD_SETENVPOSITION; break;
	case 'P' - 55:	m.command = CMD_PANNINGSLIDE; break;
	case 'R' - 55:	m.command = CMD_RETRIG; break;
	case 'T' - 55:	m.command = CMD_TREMOR; break;
	case 'X' - 55:	m.command = CMD_XFINEPORTAUPDOWN;	break;
	case 'Y' - 55:	m.command = CMD_PANBRELLO; break;			//34
	case 'Z' - 55:	m.command = CMD_MIDI;	break;				//35
	case '\\' - 56:	m.command = CMD_SMOOTHMIDI;	break;		//rewbs.smoothVST: 36 - note: this is actually displayed as "-" in FT2, but seems to be doing nothing.
	//case ':' - 21:	m.command = CMD_DELAYCUT;	break;		//37
	case '#' + 3:	m.command = CMD_XPARAM;	break;			//rewbs.XMfixes - Xm.param is 38
	default:		m.command = CMD_NONE;
	}
}

#ifndef MODPLUG_NO_FILESAVE

void CSoundFile::ModSaveCommand(uint8 &command, uint8 &param, bool toXM, bool compatibilityExport) const
{
	switch(command)
	{
	case CMD_NONE:		command = param = 0; break;
	case CMD_ARPEGGIO:	command = 0; break;
	case CMD_PORTAMENTOUP:
		if (GetType() & (MOD_TYPE_S3M|MOD_TYPE_IT|MOD_TYPE_STM|MOD_TYPE_MPT))
		{
			if ((param & 0xF0) == 0xE0) { command = 0x0E; param = ((param & 0x0F) >> 2) | 0x10; break; }
			else if ((param & 0xF0) == 0xF0) { command = 0x0E; param &= 0x0F; param |= 0x10; break; }
		}
		command = 0x01;
		break;
	case CMD_PORTAMENTODOWN:
		if(GetType() & (MOD_TYPE_S3M|MOD_TYPE_IT|MOD_TYPE_STM|MOD_TYPE_MPT))
		{
			if ((param & 0xF0) == 0xE0) { command = 0x0E; param= ((param & 0x0F) >> 2) | 0x20; break; }
			else if ((param & 0xF0) == 0xF0) { command = 0x0E; param &= 0x0F; param |= 0x20; break; }
		}
		command = 0x02;
		break;
	case CMD_TONEPORTAMENTO:	command = 0x03; break;
	case CMD_VIBRATO:			command = 0x04; break;
	case CMD_TONEPORTAVOL:		command = 0x05; break;
	case CMD_VIBRATOVOL:		command = 0x06; break;
	case CMD_TREMOLO:			command = 0x07; break;
	case CMD_PANNING8:
		command = 0x08;
		if(GetType() & MOD_TYPE_S3M)
		{
			if(param <= 0x80)
			{
				param = MIN(param << 1, 0xFF);
			}
			else if(param == 0xA4)	// surround
			{
				if(compatibilityExport || !toXM)
				{
					command = param = 0;
				}
				else
				{
					command = 'X' - 55;
					param = 91;
				}
			}
		}
		break;
	case CMD_OFFSET:			command = 0x09; break;
	case CMD_VOLUMESLIDE:		command = 0x0A; break;
	case CMD_POSITIONJUMP:		command = 0x0B; break;
	case CMD_VOLUME:			command = 0x0C; break;
	case CMD_PATTERNBREAK:		command = 0x0D; param = ((param / 10) << 4) | (param % 10); break;
	case CMD_MODCMDEX:			command = 0x0E; break;
	case CMD_SPEED:				command = 0x0F; param = std::min<uint8>(param, 0x1F); break;
	case CMD_TEMPO:				command = 0x0F; param = std::max<uint8>(param, 0x20); break;
	case CMD_GLOBALVOLUME:		command = 'G' - 55; break;
	case CMD_GLOBALVOLSLIDE:	command = 'H' - 55; break;
	case CMD_KEYOFF:			command = 'K' - 55; break;
	case CMD_SETENVPOSITION:	command = 'L' - 55; break;
	case CMD_PANNINGSLIDE:		command = 'P' - 55; break;
	case CMD_RETRIG:			command = 'R' - 55; break;
	case CMD_TREMOR:			command = 'T' - 55; break;
	case CMD_XFINEPORTAUPDOWN:	command = 'X' - 55;
		if(compatibilityExport && param >= 0x30)	// X1x and X2x are legit, everything above are MPT extensions, which don't belong here.
			param = 0;	// Don't set command to 0 to indicate that there *was* some X command here...
		break;
	case CMD_PANBRELLO:
		if(compatibilityExport)
			command = param = 0;
		else
			command = 'Y' - 55;
		break;
	case CMD_MIDI:
		if(compatibilityExport)
			command = param = 0;
		else
			command = 'Z' - 55;
		break;
	case CMD_SMOOTHMIDI: //rewbs.smoothVST: 36
		if(compatibilityExport)
			command = param = 0;
		else
			command = '\\' - 56;
		break;
	case CMD_XPARAM: //rewbs.XMfixes - XParam is 38
		if(compatibilityExport)
			command = param = 0;
		else
			command = '#' + 3;
		break;
	case CMD_S3MCMDEX:
		switch(param & 0xF0)
		{
		case 0x10:	command = 0x0E; param = (param & 0x0F) | 0x30; break;
		case 0x20:	command = 0x0E; param = (param & 0x0F) | 0x50; break;
		case 0x30:	command = 0x0E; param = (param & 0x0F) | 0x40; break;
		case 0x40:	command = 0x0E; param = (param & 0x0F) | 0x70; break;
		case 0x90:
			if(compatibilityExport)
				command = param = 0;
			else
				command = 'X' - 55;
			break;
		case 0xB0:	command = 0x0E; param = (param & 0x0F) | 0x60; break;
		case 0xA0:
		case 0x50:
		case 0x70:
		case 0x60:	command = param = 0; break;
		default:	command = 0x0E; break;
		}
		break;
	default:
		command = param = 0;
	}

	// Don't even think about saving XM effects in MODs...
	if(command > 0x0F && !toXM)
	{
		command = param = 0;
	}
}

#endif // MODPLUG_NO_FILESAVE


// File Header
struct MODFileHeader
{
	uint8be numOrders;
	uint8be restartPos;
	uint8be orderList[128];
};

MPT_BINARY_STRUCT(MODFileHeader, 130)


// Sample Header
struct MODSampleHeader
{
	char     name[22];
	uint16be length;
	uint8be  finetune;
	uint8be  volume;
	uint16be loopStart;
	uint16be loopLength;

	// Convert an MOD sample header to OpenMPT's internal sample header.
	void ConvertToMPT(ModSample &mptSmp, bool is4Chn) const
	{
		mptSmp.Initialize(MOD_TYPE_MOD);
		mptSmp.nLength = length * 2;
		mptSmp.nFineTune = MOD2XMFineTune(finetune & 0x0F);
		mptSmp.nVolume = 4u * std::min<uint8>(volume, 64);

		SmpLength lStart = loopStart * 2;
		SmpLength lLength = loopLength * 2;
		// See if loop start is incorrect as words, but correct as bytes (like in Soundtracker modules)
		if(lLength > 2 && (lStart + lLength > mptSmp.nLength)
			&& (lStart / 2 + lLength <= mptSmp.nLength))
		{
			lStart /= 2;
		}

		if(mptSmp.nLength == 2)
		{
			mptSmp.nLength = 0;
		}

		if(mptSmp.nLength)
		{
			mptSmp.nLoopStart = lStart;
			mptSmp.nLoopEnd = lStart + lLength;

			if(mptSmp.nLoopStart >= mptSmp.nLength)
			{
				mptSmp.nLoopStart = mptSmp.nLength - 1;
			}
			if(mptSmp.nLoopStart > mptSmp.nLoopEnd || mptSmp.nLoopEnd < 4 || mptSmp.nLoopEnd - mptSmp.nLoopStart < 4)
			{
				mptSmp.nLoopStart = 0;
				mptSmp.nLoopEnd = 0;
			}

			// Fix for most likely broken sample loops. This fixes super_sufm_-_new_life.mod (M.K.) which has a long sample which is looped from 0 to 4.
			// This module also has notes outside of the Amiga frequency range, so we cannot say that it should be played using ProTracker one-shot loops.
			// On the other hand, "Crew Generation" by Necros (6CHN) has a sample with a similar loop, which is supposed to be played.
			// To be able to correctly play both modules, we will draw a somewhat arbitrary line here and trust the loop points in MODs with more than
			// 4 channels, even if they are tiny and at the very beginning of the sample.
			if(mptSmp.nLoopEnd <= 8 && mptSmp.nLoopStart == 0 && mptSmp.nLength > mptSmp.nLoopEnd && is4Chn)
			{
				mptSmp.nLoopEnd = 0;
			}
			if(mptSmp.nLoopEnd > mptSmp.nLoopStart)
			{
				mptSmp.uFlags.set(CHN_LOOP);
			}
		}
	}

	// Convert OpenMPT's internal sample header to a MOD sample header.
	SmpLength ConvertToMOD(const ModSample &mptSmp)
	{
		SmpLength writeLength = mptSmp.HasSampleData() ? mptSmp.nLength : 0;
		// If the sample size is odd, we have to add a padding byte, as all sample sizes in MODs are even.
		if((writeLength % 2u) != 0)
		{
			writeLength++;
		}
		LimitMax(writeLength, SmpLength(0x1FFFE));

		length = static_cast<uint16>(writeLength / 2u);

		if(mptSmp.RelativeTone < 0)
		{
			finetune = 0x08;
		} else if(mptSmp.RelativeTone > 0)
		{
			finetune = 0x07;
		} else
		{
			finetune = XM2MODFineTune(mptSmp.nFineTune);
		}
		volume = static_cast<uint8>(mptSmp.nVolume / 4u);

		loopStart = 0;
		loopLength = 1;
		if(mptSmp.uFlags[CHN_LOOP] && (mptSmp.nLoopStart + 2u) < writeLength)
		{
			const SmpLength loopEnd = Clamp(mptSmp.nLoopEnd, (mptSmp.nLoopStart & ~1) + 2u, writeLength) & ~1;
			loopStart = static_cast<uint16>(mptSmp.nLoopStart / 2u);
			loopLength = static_cast<uint16>((loopEnd - (mptSmp.nLoopStart & ~1)) / 2u);
		}

		return writeLength;
	}

	// Compute a "rating" of this sample header by counting invalid header data to ultimately reject garbage files.
	uint32 GetInvalidByteScore() const
	{
		return ((volume > 64) ? 1 : 0)
			+ ((finetune > 15) ? 1 : 0)
			+ ((loopStart > length * 2) ? 1 : 0);
	}

	// Suggested threshold for rejecting invalid files based on cumulated score returned by GetInvalidByteScore
	enum : uint32 { INVALID_BYTE_THRESHOLD = 40 };
	
	// This threshold is used for files where the file magic only gives a
	// fragile result which alone would lead to too many false positives.
	// In particular, the files from Inconexia demo by Iguana
	// (https://www.pouet.net/prod.php?which=830) which have 3 \0 bytes in
	// the file magic tend to cause misdetection of random files.
	enum : uint32 { INVALID_BYTE_FRAGILE_THRESHOLD = 1 };

	// Retrieve the internal sample format flags for this sample.
	static SampleIO GetSampleFormat()
	{
		return SampleIO(
			SampleIO::_8bit,
			SampleIO::mono,
			SampleIO::bigEndian,
			SampleIO::signedPCM);
	}
};

MPT_BINARY_STRUCT(MODSampleHeader, 30)

// Synthesized StarTrekker instruments
struct AMInstrument
{
	char     am[2];			// "AM"
	char     zero[4];
	uint16be startLevel;	// Start level
	uint16be attack1Level;	// Attack 1 level
	uint16be attack1Speed;	// Attack 1 speed
	uint16be attack2Level;	// Attack 2 level
	uint16be attack2Speed;	// Attack 2 speed
	uint16be sustainLevel;	// Sustain level
	uint16be decaySpeed;	// Decay speed
	uint16be sustainTime;	// Sustain time
	uint16be nt;			// ?
	uint16be releaseSpeed;	// Release speed
	uint16be waveform;		// Waveform
	int16be  pitchFall;		// Pitch fall
	uint16be vibAmp;		// Vibrato amplitude
	uint16be vibSpeed;		// Vibrato speed
	uint16be octave;		// Base frequency

	void ConvertToMPT(ModSample &sample, ModInstrument &ins, mpt::fast_prng &rng) const
	{
		sample.nLength = waveform == 3 ? 1024 : 32;
		sample.nLoopStart = 0;
		sample.nLoopEnd = sample.nLength;
		sample.uFlags.set(CHN_LOOP);
		sample.nVolume = 256;	// prelude.mod has volume 0 in sample header
		sample.nVibDepth = mpt::saturate_cast<uint8>(vibAmp * 2);
		sample.nVibRate = static_cast<uint8>(vibSpeed);
		sample.nVibType = VIB_SINE;
		sample.RelativeTone = static_cast<int8>(-12 * octave);
		if(sample.AllocateSample())
		{
			for(SmpLength i = 0; i < sample.nLength; i++)
			{
				switch(waveform)
				{
				default:
				case 0: sample.sample8()[i] = ModSinusTable[i * 2];				break;	// Sine
				case 1: sample.sample8()[i] = static_cast<int8>(-128 + i * 8);	break;	// Saw
				case 2: sample.sample8()[i] = i < 16 ? -128 : 127;				break;	// Square
				case 3: sample.sample8()[i] = mpt::random<int8>(rng);			break;	// Noise
				}
			}
		}

		InstrumentEnvelope &volEnv = ins.VolEnv;
		volEnv.dwFlags.set(ENV_ENABLED);
		volEnv.reserve(6);
		volEnv.push_back(0, static_cast<EnvelopeNode::value_t>(startLevel / 4));

		const struct
		{
			uint16 level, speed;
		} points[] = { { startLevel, 0 }, { attack1Level, attack1Speed }, { attack2Level, attack2Speed }, { sustainLevel, decaySpeed }, { sustainLevel, sustainTime }, { 0, releaseSpeed } };

		for(uint8 i = 1; i < CountOf(points); i++)
		{
			int duration = std::min(points[i].speed, uint16(256));
			// Sustain time is already in ticks, no need to compute the segment duration.
			if(i != 4)
			{
				if(duration == 0)
				{
					volEnv.dwFlags.set(ENV_LOOP);
					volEnv.nLoopStart = volEnv.nLoopEnd = static_cast<uint8>(volEnv.size() - 1);
					break;
				}

				// Startrekker increments / decrements the envelope level by the stage speed
				// until it reaches the next stage level.
				int a, b;
				if(points[i].level > points[i - 1].level)
				{
					a = points[i].level - points[i - 1].level;
					b = 256 - points[i - 1].level;
				} else
				{
					a = points[i - 1].level - points[i].level;
					b = points[i - 1].level;
				}
				// Release time is again special.
				if(i == 5)
					b = 256;
				else if(b == 0)
					b = 1;
				duration = std::max((256 * a) / (duration * b), 1);
			}
			if(duration > 0)
			{
				volEnv.push_back(volEnv.back().tick + static_cast<EnvelopeNode::tick_t>(duration), static_cast<EnvelopeNode::value_t>(points[i].level / 4));
			}
		}

		if(pitchFall)
		{
			InstrumentEnvelope &pitchEnv = ins.PitchEnv;
			pitchEnv.dwFlags.set(ENV_ENABLED);
			pitchEnv.reserve(2);
			pitchEnv.push_back(0, ENVELOPE_MID);
			pitchEnv.push_back(static_cast<EnvelopeNode::tick_t>(1024 / abs(pitchFall)), pitchFall > 0 ? ENVELOPE_MIN : ENVELOPE_MAX);
		}
	}
};

MPT_BINARY_STRUCT(AMInstrument, 36)

struct PT36IffChunk
{
	// IFF chunk names
	enum ChunkIdentifiers
	{
		idVERS	= MagicBE("VERS"),
		idINFO	= MagicBE("INFO"),
		idCMNT	= MagicBE("CMNT"),
		idPTDT	= MagicBE("PTDT"),
	};

	uint32be signature;	// IFF chunk name
	uint32be chunksize;	// chunk size without header
};

MPT_BINARY_STRUCT(PT36IffChunk, 8)

struct PT36InfoChunk
{
	char     name[32];
	uint16be numSamples;
	uint16be numOrders;
	uint16be numPatterns;
	uint16be volume;
	uint16be tempo;
	uint16be flags;
	uint16be dateDay;
	uint16be dateMonth;
	uint16be dateYear;
	uint16be dateHour;
	uint16be dateMinute;
	uint16be dateSecond;
	uint16be playtimeHour;
	uint16be playtimeMinute;
	uint16be playtimeSecond;
	uint16be playtimeMsecond;
};

MPT_BINARY_STRUCT(PT36InfoChunk, 64)


// Check if header magic equals a given string.
static bool IsMagic(const char *magic1, const char *magic2)
{
	return std::memcmp(magic1, magic2, 4) == 0;
}


static uint32 ReadSample(FileReader &file, MODSampleHeader &sampleHeader, ModSample &sample, char (&sampleName)[MAX_SAMPLENAME], bool is4Chn)
{
	file.ReadStruct(sampleHeader);
	sampleHeader.ConvertToMPT(sample, is4Chn);

	mpt::String::Read<mpt::String::spacePadded>(sampleName, sampleHeader.name);
	// Get rid of weird characters in sample names.
	for(auto &c : sampleName)
	{
		if(c > 0 && c < ' ')
		{
			c = ' ';
		}
	}
	// Check for invalid values
	return sampleHeader.GetInvalidByteScore();
}


// Parse the order list to determine how many patterns are used in the file.
static PATTERNINDEX GetNumPatterns(FileReader &file, ModSequence &Order, ORDERINDEX numOrders, SmpLength totalSampleLen, CHANNELINDEX &numChannels, bool checkForWOW)
{
	PATTERNINDEX numPatterns = 0;			// Total number of patterns in file (determined by going through the whole order list) with pattern number < 128
	PATTERNINDEX officialPatterns = 0;		// Number of patterns only found in the "official" part of the order list (i.e. order positions < claimed order length)
	PATTERNINDEX numPatternsIllegal = 0;	// Total number of patterns in file, also counting in "invalid" pattern indexes >= 128

	for(ORDERINDEX ord = 0; ord < 128; ord++)
	{
		PATTERNINDEX pat = Order[ord];
		if(pat < 128 && numPatterns <= pat)
		{
			numPatterns = pat + 1;
			if(ord < numOrders)
			{
				officialPatterns = numPatterns;
			}
		}
		if(pat >= numPatternsIllegal)
		{
			numPatternsIllegal = pat + 1;
		}
	}

	// Remove the garbage patterns past the official order end now that we don't need them anymore.
	Order.resize(numOrders);

	const size_t patternStartOffset = file.GetPosition();
	const size_t sizeWithoutPatterns = totalSampleLen + patternStartOffset;

	if(checkForWOW && sizeWithoutPatterns + numPatterns * 8 * 256 == file.GetLength())
	{
		// Check if this is a Mod's Grave WOW file... Never seen one of those, but apparently they *do* exist.
		// WOW files should use the M.K. magic but are actually 8CHN files.
		numChannels = 8;
	} else if(numPatterns != officialPatterns && numChannels == 4 && !checkForWOW)
	{
		// Fix SoundTracker modules where "hidden" patterns should be ignored.
		// razor-1911.mod (MD5 b75f0f471b0ae400185585ca05bf7fe8, SHA1 4de31af234229faec00f1e85e1e8f78f405d454b)
		// and captain_fizz.mod (MD5 55bd89fe5a8e345df65438dbfc2df94e, SHA1 9e0e8b7dc67939885435ea8d3ff4be7704207a43)
		// seem to have the "correct" file size when only taking the "official" patterns into account,
		// but they only play correctly when also loading the inofficial patterns.
		// On the other hand, the SoundTracker module
		// wolf1.mod (MD5 a4983d7a432d324ce8261b019257f4ed, SHA1 aa6b399d02546bcb6baf9ec56a8081730dea3f44),
		// wolf3.mod (MD5 af60840815aa9eef43820a7a04417fa6, SHA1 24d6c2e38894f78f6c5c6a4b693a016af8fa037b)
		// and jean_baudlot_-_bad_dudes_vs_dragonninja-dragonf.mod (MD5 fa48e0f805b36bdc1833f6b82d22d936, SHA1 39f2f8319f4847fe928b9d88eee19d79310b9f91)
		// only play correctly if we ignore the hidden patterns.
		// Hence, we have a peek at the first hidden pattern and check if it contains a lot of illegal data.
		// If that is the case, we assume it's part of the sample data and only consider the "official" patterns.
		file.Seek(patternStartOffset + officialPatterns * 1024);
		int illegalBytes = 0;
		for(int i = 0; i < 256; i++)
		{
			uint8 data[4];
			file.ReadArray(data);
			if(data[0] & 0xE0)
			{
				illegalBytes++;
				if(illegalBytes > 64)
				{
					numPatterns = officialPatterns;
					break;
				}
			}
		}
		file.Seek(patternStartOffset);
	}

#ifdef MPT_BUILD_DEBUG
	// Check if the "hidden" patterns in the order list are actually real, i.e. if they are saved in the file.
	// OpenMPT did this check in the past, but no other tracker appears to do this.
	// Interestingly, (broken) variants of the ProTracker modules
	// "killing butterfly" (MD5 bd676358b1dbb40d40f25435e845cf6b, SHA1 9df4ae21214ff753802756b616a0cafaeced8021),
	// "quartex" by Reflex (MD5 35526bef0fb21cb96394838d94c14bab, SHA1 116756c68c7b6598dcfbad75a043477fcc54c96c),
	// seem to have the "correct" file size when only taking the "official" patterns into account, but they only play
	// correctly when also loading the inofficial patterns.
	// See also the above check for ambiguities with SoundTracker modules.
	// Keep this assertion in the code to find potential other broken MODs.
	if(numPatterns != officialPatterns && sizeWithoutPatterns + officialPatterns * numChannels * 256 == file.GetLength())
	{
		MPT_ASSERT(false);
		//numPatterns = officialPatterns;
	} else
#endif
	if(numPatternsIllegal > numPatterns && sizeWithoutPatterns + numPatternsIllegal * numChannels * 256 == file.GetLength())
	{
		// Even those illegal pattern indexes (> 128) appear to be valid... What a weird file!
		// e.g. NIETNU.MOD, where the end of the order list is filled with FF rather than 00, and the file actually contains 256 patterns.
		numPatterns = numPatternsIllegal;
	} else if(numPatternsIllegal >= 0xFF)
	{
		// Patterns FE and FF are used with S3M semantics (e.g. some MODs written with old OpenMPT versions)
		Order.Replace(0xFE, Order.GetIgnoreIndex());
		Order.Replace(0xFF, Order.GetInvalidPatIndex());
	}

	return numPatterns;
}


void CSoundFile::ReadMODPatternEntry(FileReader &file, ModCommand &m)
{
	uint8 data[4];
	file.ReadArray(data);
	ReadMODPatternEntry(data, m);
}


void CSoundFile::ReadMODPatternEntry(const uint8 (&data)[4], ModCommand &m)
{
	// Read Period
	uint16 period = (((static_cast<uint16>(data[0]) & 0x0F) << 8) | data[1]);
	size_t note = NOTE_NONE;
	if(period > 0 && period != 0xFFF)
	{
		note = mpt::size(ProTrackerPeriodTable) + 23 + NOTE_MIN;
		for(size_t i = 0; i < mpt::size(ProTrackerPeriodTable); i++)
		{
			if(period >= ProTrackerPeriodTable[i])
			{
				if(period != ProTrackerPeriodTable[i] && i != 0)
				{
					uint16 p1 = ProTrackerPeriodTable[i - 1];
					uint16 p2 = ProTrackerPeriodTable[i];
					if(p1 - period < (period - p2))
					{
						note = i + 23 + NOTE_MIN;
						break;
					}
				}
				note = i + 24 + NOTE_MIN;
				break;
			}
		}
	}
	m.note = static_cast<ModCommand::NOTE>(note);
	// Read Instrument
	m.instr = (data[2] >> 4) | (data[0] & 0x10);
	// Read Effect
	m.command = data[2] & 0x0F;
	m.param = data[3];
}


struct MODMagicResult
{
	const MPT_UCHAR_TYPE *madeWithTracker = nullptr;
	uint32 invalidByteThreshold = MODSampleHeader::INVALID_BYTE_THRESHOLD;
	CHANNELINDEX numChannels    = 0;
	bool isNoiseTracker         = false;
	bool isStartrekker          = false;
	bool isGenericMultiChannel  = false;
	bool setMODVBlankTiming     = false;
};


static bool CheckMODMagic(const char magic[4], MODMagicResult &result)
{
	if(IsMagic(magic, "M.K.")		// ProTracker and compatible
		|| IsMagic(magic, "M!K!")	// ProTracker (>64 patterns)
		|| IsMagic(magic, "PATT")	// ProTracker 3.6
		|| IsMagic(magic, "NSMS")	// kingdomofpleasure.mod by bee hunter
		|| IsMagic(magic, "LARD"))	// judgement_day_gvine.mod by 4-mat
	{
		result.madeWithTracker = UL_("Generic ProTracker or compatible");
		result.numChannels = 4;
	} else if(IsMagic(magic, "M&K!")	// "His Master's Noise" musicdisk
		|| IsMagic(magic, "FEST")		// "His Master's Noise" musicdisk
		|| IsMagic(magic, "N.T."))
	{
		result.madeWithTracker = UL_("NoiseTracker");
		result.isNoiseTracker = true;
		result.numChannels = 4;
	} else if(IsMagic(magic, "OKTA")
		|| IsMagic(magic, "OCTA"))
	{
		// Oktalyzer
		result.madeWithTracker = UL_("Oktalyzer");
		result.numChannels = 8;
	} else if(IsMagic(magic, "CD81")
		|| IsMagic(magic, "CD61"))
	{
		// Octalyser on Atari STe/Falcon
		result.madeWithTracker = UL_("Octalyser (Atari)");
		result.numChannels = magic[2] - '0';
	} else if(IsMagic(magic, "M\0\0\0") || IsMagic(magic, "8\0\0\0"))
	{
		// Inconexia demo by Iguana, delta samples (https://www.pouet.net/prod.php?which=830)
		result.madeWithTracker = UL_("Inconexia demo (delta samples)");
		result.invalidByteThreshold = MODSampleHeader::INVALID_BYTE_FRAGILE_THRESHOLD;
		result.numChannels = (magic[0] == '8') ? 8 : 4;
	} else if(!memcmp(magic, "FA0", 3) && magic[3] >= '4' && magic[3] <= '8')
	{
		// Digital Tracker on Atari Falcon
		result.madeWithTracker = UL_("Digital Tracker");
		result.numChannels = magic[3] - '0';
	} else if((!memcmp(magic, "FLT", 3) || !memcmp(magic, "EXO", 3)) && magic[3] >= '4' && magic[3] <= '9')
	{
		// FLTx / EXOx - Startrekker by Exolon / Fairlight
		result.madeWithTracker = UL_("Startrekker");
		result.isStartrekker = true;
		result.setMODVBlankTiming = true;
		result.numChannels = magic[3] - '0';
	} else if(magic[0] >= '1' && magic[0] <= '9' && !memcmp(magic + 1, "CHN", 3))
	{
		// xCHN - Many trackers
		result.madeWithTracker = UL_("Generic MOD-compatible Tracker");
		result.isGenericMultiChannel = true;
		result.numChannels = magic[0] - '0';
	} else if(magic[0] >= '1' && magic[0] <= '9' && magic[1]>='0' && magic[1] <= '9'
		&& (!memcmp(magic + 2, "CH", 2) || !memcmp(magic + 2, "CN", 2)))
	{
		// xxCN / xxCH - Many trackers
		result.madeWithTracker = UL_("Generic MOD-compatible Tracker");
		result.isGenericMultiChannel = true;
		result.numChannels = (magic[0] - '0') * 10 + magic[1] - '0';
	} else if(!memcmp(magic, "TDZ", 3) && magic[3] >= '4' && magic[3] <= '9')
	{
		// TDZx - TakeTracker
		result.madeWithTracker = UL_("TakeTracker");
		result.numChannels = magic[3] - '0';
	} else
	{
		return false;
	}
	return true;
}


CSoundFile::ProbeResult CSoundFile::ProbeFileHeaderMOD(MemoryFileReader file, const uint64 *pfilesize)
{
	if(!file.CanRead(1080 + 4))
	{
		return ProbeWantMoreData;
	}
	file.Seek(1080);
	char magic[4];
	file.ReadArray(magic);
	MODMagicResult modMagicResult;
	if(!CheckMODMagic(magic, modMagicResult))
	{
		return ProbeFailure;
	}

	file.Seek(20);
	uint32 invalidBytes = 0;
	for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
	{
		MODSampleHeader sampleHeader;
		file.ReadStruct(sampleHeader);
		invalidBytes += sampleHeader.GetInvalidByteScore();
	}
	if(invalidBytes > modMagicResult.invalidByteThreshold)
	{
		return ProbeFailure;
	}

	MPT_UNREFERENCED_PARAMETER(pfilesize);
	return ProbeSuccess;
}


bool CSoundFile::ReadMOD(FileReader &file, ModLoadingFlags loadFlags)
{
	char magic[4];
	if(!file.Seek(1080) || !file.ReadArray(magic))
	{
		return false;
	}

	InitializeGlobals(MOD_TYPE_MOD);

	MODMagicResult modMagicResult;
	if(!CheckMODMagic(magic, modMagicResult)
		|| modMagicResult.numChannels < 1
		|| modMagicResult.numChannels > MAX_BASECHANNELS)
	{
		return false;
	}

	if(loadFlags == onlyVerifyHeader)
	{
		return true;
	}

	m_nChannels = modMagicResult.numChannels;

	bool isNoiseTracker = modMagicResult.isNoiseTracker;
	bool isStartrekker = modMagicResult.isStartrekker;
	bool isGenericMultiChannel = modMagicResult.isGenericMultiChannel;
	bool isInconexia = IsMagic(magic, "M\0\0\0") || IsMagic(magic, "8\0\0\0");
	// A loop length of zero will freeze ProTracker, so assume that modules having such a value were not meant to be played on Amiga. Fixes LHS_MI.MOD
	bool hasRepLen0 = false;
	if(modMagicResult.setMODVBlankTiming)
	{
		m_playBehaviour.set(kMODVBlankTiming);
	}

	// Startrekker 8 channel mod (needs special treatment, see below)
	const bool isFLT8 = isStartrekker && m_nChannels == 8;
	// Only apply VBlank tests to M.K. (ProTracker) modules.
	const bool isMdKd = IsMagic(magic, "M.K.");
	// Adjust finetune values for modules saved with "His Master's Noisetracker"
	const bool isHMNT = IsMagic(magic, "M&K!") || IsMagic(magic, "FEST");

	// Reading song title
	file.Seek(0);
	file.ReadString<mpt::String::spacePadded>(m_songName, 20);

	// Load Sample Headers
	SmpLength totalSampleLen = 0;
	m_nSamples = 31;
	uint32 invalidBytes = 0;
	for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
	{
		MODSampleHeader sampleHeader;
		invalidBytes += ReadSample(file, sampleHeader, Samples[smp], m_szNames[smp], m_nChannels == 4);
		totalSampleLen += Samples[smp].nLength;

		if(isHMNT)
		{
			Samples[smp].nFineTune = -static_cast<int8>(sampleHeader.finetune << 3);
		} else if(Samples[smp].nLength > 65535)
		{
			isNoiseTracker = false;
		}
		if(sampleHeader.length && !sampleHeader.loopLength)
		{
			hasRepLen0 = true;
		}
	}
	// If there is too much binary garbage in the sample headers, reject the file.
	if(invalidBytes > modMagicResult.invalidByteThreshold)
	{
		return false;
	}

	// Read order information
	MODFileHeader fileHeader;
	file.ReadStruct(fileHeader);
	file.Skip(4);	// Magic bytes (we already parsed these)

	ReadOrderFromArray(Order(), fileHeader.orderList);

	ORDERINDEX realOrders = fileHeader.numOrders;
	if(realOrders > 128)
	{
		// beatwave.mod by Sidewinder claims to have 129 orders. (MD5: 8a029ac498d453beb929db9a73c3c6b4, SHA1: f7b76fb9f477b07a2e78eb10d8624f0df262cde7 - the version from ModArchive, not ModLand)
		realOrders = 128;
	} else if(realOrders == 0)
	{
		// Is this necessary?
		realOrders = 128;
		while(realOrders > 1 && Order()[realOrders - 1] == 0)
		{
			realOrders--;
		}
	}

	// Get number of patterns (including some order list sanity checks)
	PATTERNINDEX numPatterns = GetNumPatterns(file, Order(), realOrders, totalSampleLen, m_nChannels, isMdKd);
	if(isMdKd && GetNumChannels() == 8)
	{
		// M.K. with 8 channels = Grave Composer
		modMagicResult.madeWithTracker = UL_("Mod's Grave");
	}

	if(isFLT8)
	{
		// FLT8 has only even order items, so divide by two.
		for(auto &pat : Order())
		{
			pat /= 2u;
		}
	}
	
	// Restart position sanity checks
	realOrders--;
	Order().SetRestartPos(fileHeader.restartPos);

	// (Ultimate) Soundtracker didn't have a restart position, but instead stored a default tempo in this value.
	// The default value for this is 0x78 (120 BPM). This is probably the reason why some M.K. modules
	// have this weird restart position. I think I've read somewhere that NoiseTracker actually writes 0x78 there.
	// M.K. files that have restart pos == 0x78: action's batman by DJ Uno, VALLEY.MOD, WormsTDC.MOD, ZWARTZ.MOD
	// Files that have an order list longer than 0x78 with restart pos = 0x78: my_shoe_is_barking.mod, papermix.mod
	// - in both cases it does not appear like the restart position should be used.
	MPT_ASSERT(fileHeader.restartPos != 0x78 || fileHeader.restartPos + 1u >= realOrders);
	if(fileHeader.restartPos > realOrders || (fileHeader.restartPos == 0x78 && m_nChannels == 4))
	{
		Order().SetRestartPos(0);
	}

	m_nDefaultSpeed = 6;
	m_nDefaultTempo.Set(125);
	m_nMinPeriod = 14 * 4;
	m_nMaxPeriod = 3424 * 4;
	// Prevent clipping based on number of channels... If all channels are playing at full volume, "256 / #channels"
	// is the maximum possible sample pre-amp without getting distortion (Compatible mix levels given).
	// The more channels we have, the less likely it is that all of them are used at the same time, though, so cap at 32...
	m_nSamplePreAmp = Clamp(256 / m_nChannels, 32, 128);
	m_SongFlags.reset();	// SONG_ISAMIGA will be set conditionally

	// Setup channel pan positions and volume
	SetupMODPanning();

	// Before loading patterns, apply some heuristics:
	// - Scan patterns to check if file could be a NoiseTracker file in disguise.
	//   In this case, the parameter of Dxx commands needs to be ignored.
	// - Use the same code to find notes that would be out-of-range on Amiga.
	// - Detect 7-bit panning.
	bool onlyAmigaNotes = true;
	bool fix7BitPanning = false;
	uint8 maxPanning = 0;	// For detecting 8xx-as-sync
	if(!isNoiseTracker)
	{
		bool leftPanning = false, extendedPanning = false;	// For detecting 800-880 panning
		isNoiseTracker = isMdKd;
		for(PATTERNINDEX pat = 0; pat < numPatterns; pat++)
		{
			uint16 patternBreaks = 0;

			for(uint32 i = 0; i < 256; i++)
			{
				ModCommand m;
				ReadMODPatternEntry(file, m);
				if(!m.IsAmigaNote())
				{
					isNoiseTracker = onlyAmigaNotes = false;
				}
				if((m.command > 0x06 && m.command < 0x0A)
					|| (m.command == 0x0E && m.param > 0x01)
					|| (m.command == 0x0F && m.param > 0x1F)
					|| (m.command == 0x0D && ++patternBreaks > 1))
				{
					isNoiseTracker = false;
				}
				if(m.command == 0x08)
				{
					maxPanning = std::max(maxPanning, m.param);
					if(m.param < 0x80)
						leftPanning = true;
					else if(m.param > 0x8F && m.param != 0xA4)
						extendedPanning = true;
				} else if(m.command == 0x0E && (m.param & 0xF0) == 0x80)
				{
					maxPanning = std::max<uint8>(maxPanning, m.param << 4);
				}
			}
		}
		fix7BitPanning = leftPanning && !extendedPanning;
	}
	file.Seek(1084);

	const CHANNELINDEX readChannels = (isFLT8 ? 4 : m_nChannels); // 4 channels per pattern in FLT8 format.
	if(isFLT8) numPatterns++; // as one logical pattern consists of two real patterns in FLT8 format, the highest pattern number has to be increased by one.
	bool hasTempoCommands = false, definitelyCIA = false;	// for detecting VBlank MODs
	// Heuristic for rejecting E0x commands that are most likely not intended to actually toggle the Amiga LED filter, like in naen_leijasi_ptk.mod by ilmarque
	bool filterState = false;
	int filterTransitions = 0;

	// Reading patterns
	Patterns.ResizeArray(numPatterns);
	for(PATTERNINDEX pat = 0; pat < numPatterns; pat++)
	{
		ModCommand *rowBase = nullptr;

		if(isFLT8)
		{
			// FLT8: Only create "even" patterns and either write to channel 1 to 4 (even patterns) or 5 to 8 (odd patterns).
			PATTERNINDEX actualPattern = pat / 2u;
			if((pat % 2u) == 0 && !Patterns.Insert(actualPattern, 64))
			{
				break;
			}
			rowBase = Patterns[actualPattern].GetpModCommand(0, (pat % 2u) == 0 ? 0 : 4);
		} else
		{
			if(!Patterns.Insert(pat, 64))
			{
				break;
			}
			rowBase = Patterns[pat].GetpModCommand(0, 0);
		}

		if(rowBase == nullptr || !(loadFlags & loadPatternData))
		{
			break;
		}

		// For detecting PT1x mode
		std::vector<ModCommand::INSTR> lastInstrument(GetNumChannels(), 0);
		std::vector<uint8> instrWithoutNoteCount(GetNumChannels(), 0);

		for(ROWINDEX row = 0; row < 64; row++, rowBase += m_nChannels)
		{
			// If we have more than one Fxx command on this row and one can be interpreted as speed
			// and the other as tempo, we can be rather sure that it is not a VBlank mod.
			bool hasSpeedOnRow = false, hasTempoOnRow = false;

			for(CHANNELINDEX chn = 0; chn < readChannels; chn++)
			{
				ModCommand &m = rowBase[chn];
				ReadMODPatternEntry(file, m);

				if(m.command || m.param)
				{
					// No support for Startrekker assembly macros
					if(isStartrekker && m.command == 0x0E)
					{
						m.command = CMD_NONE;
						m.param = 0;
					}
					ConvertModCommand(m);
				}

				// Perform some checks for our heuristics...
				if(m.command == CMD_TEMPO)
				{
					hasTempoOnRow = true;
					if(m.param < 100)
						hasTempoCommands = true;
				} else if(m.command == CMD_SPEED)
				{
					hasSpeedOnRow = true;
				} else if(m.command == CMD_PATTERNBREAK && isNoiseTracker)
				{
					m.param = 0;
				} else if(m.command == CMD_PANNING8 && fix7BitPanning)
				{
					// Fix MODs with 7-bit + surround panning
					if(m.param == 0xA4)
					{
						m.command = CMD_S3MCMDEX;
						m.param = 0x91;
					} else
					{
						m.param = mpt::saturate_cast<ModCommand::PARAM>(m.param * 2);
					}
				} else if(m.command == CMD_MODCMDEX && m.param < 0x10)
				{
					// Count LED filter transitions
					bool newState = !(m.param & 0x01);
					if(newState != filterState)
					{
						filterState = newState;
						filterTransitions++;
					}
				}
				if(m.note == NOTE_NONE && m.instr > 0 && !isFLT8)
				{
					if(lastInstrument[chn] > 0 && lastInstrument[chn] != m.instr)
					{
						// Arbitrary threshold for enabling sample swapping: 4 consecutive "sample swaps" in one pattern.
						if(++instrWithoutNoteCount[chn] >= 4)
						{
							m_playBehaviour.set(kMODSampleSwap);
						}
					}
				} else if(m.note != NOTE_NONE)
				{
					instrWithoutNoteCount[chn] = 0;
				}
				if(m.instr != 0)
				{
					lastInstrument[chn] = m.instr;
				}
			}
			if(hasSpeedOnRow && hasTempoOnRow) definitelyCIA = true;
		}
	}

	if(onlyAmigaNotes && !hasRepLen0 && (IsMagic(magic, "M.K.") || IsMagic(magic, "M!K!") || IsMagic(magic, "PATT")))
	{
		// M.K. files that don't exceed the Amiga note limit (fixes mod.mothergoose)
		m_SongFlags.set(SONG_AMIGALIMITS);
		// Need this for professionaltracker.mod by h0ffman (SHA1: 9a7c52cbad73ed2a198ee3fa18d3704ea9f546ff)
		m_SongFlags.set(SONG_PT_MODE);
		m_playBehaviour.set(kMODSampleSwap);
		m_playBehaviour.set(kMODOutOfRangeNoteDelay);
		m_playBehaviour.set(kMODTempoOnSecondTick);
		// Arbitrary threshold for deciding that 8xx effects are only used as sync markers
		if(maxPanning < 0x20)
		{
			m_playBehaviour.set(kMODIgnorePanning);
			if(fileHeader.restartPos != 0x7F)
			{
				// Don't enable these hacks for ScreamTracker modules (restart position = 0x7F), to fix e.g. sample 10 in BASIC001.MOD (SHA1: 11298a5620e677beaa50bd4ed00c3710b75c81af)
				// Note: restart position = 0x7F can also be found in ProTracker modules, e.g. professionaltracker.mod by h0ffman
				m_playBehaviour.set(kMODOneShotLoops);
			}
		}
	} else if(!onlyAmigaNotes && fileHeader.restartPos == 0x7F && isMdKd && fileHeader.restartPos + 1u >= realOrders)
	{
		modMagicResult.madeWithTracker = UL_("ScreamTracker");
	}

	if(onlyAmigaNotes && !isGenericMultiChannel && filterTransitions < 7)
	{
		m_SongFlags.set(SONG_ISAMIGA);
	}
	if(isInconexia)
	{
		m_playBehaviour.set(kMODIgnorePanning);
	}

	// Reading samples
	if(loadFlags & loadSampleData)
	{
		file.Seek(1084 + (readChannels * 64 * 4) * numPatterns);
		for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
		{
			ModSample &sample = Samples[smp];
			if(sample.nLength)
			{
				SampleIO::Encoding encoding = SampleIO::signedPCM;
				if(isInconexia)
					encoding = SampleIO::deltaPCM;
				else if(file.ReadMagic("ADPCM"))
					encoding = SampleIO::ADPCM;

				SampleIO sampleIO(
					SampleIO::_8bit,
					SampleIO::mono,
					SampleIO::littleEndian,
					encoding);

				// Fix sample 6 in MOD.shorttune2, which has a replen longer than the sample itself.
				// ProTracker reads beyond the end of the sample when playing. Normally samples are
				// adjacent in PT's memory, so we simply read into the next sample in the file.
				FileReader::off_t nextSample = file.GetPosition() + sampleIO.CalculateEncodedSize(sample.nLength);
				if(isMdKd && onlyAmigaNotes)
					sample.nLength = std::max(sample.nLength, sample.nLoopEnd);

				sampleIO.ReadSample(sample, file);
				file.Seek(nextSample);
			}
		}
	}

#if defined(MPT_EXTERNAL_SAMPLES) || defined(MPT_BUILD_FUZZER)
	// Detect Startrekker files with external synth instruments.
	// Note: Synthesized AM samples may overwrite existing samples (e.g. sample 1 in fa.worse face.mod),
	// hence they are loaded here after all regular samples have been loaded.
	if((loadFlags & loadSampleData) && isStartrekker)
	{
#ifdef MPT_EXTERNAL_SAMPLES
		InputFile amFile;
		FileReader amData;
		mpt::PathString filename = file.GetFileName();
		if(!filename.empty())
		{
			// Find instrument definition file
			const mpt::PathString exts[] = { P_(".nt"), P_(".NT"), P_(".as"), P_(".AS") };
			for(const auto &ext : exts)
			{
				mpt::PathString infoName = filename + ext;
				char stMagic[16];
				if(infoName.IsFile() && amFile.Open(infoName) && (amData = GetFileReader(amFile)).IsValid() && amData.ReadArray(stMagic))
				{
					if(!memcmp(stMagic, "ST1.2 ModuleINFO", 16))
						modMagicResult.madeWithTracker = UL_("Startrekker 1.2");
					else if(!memcmp(stMagic, "ST1.3 ModuleINFO", 16))
						modMagicResult.madeWithTracker = UL_("Startrekker 1.3");
					else if(!memcmp(stMagic, "AudioSculpture10", 16))
						modMagicResult.madeWithTracker = UL_("AudioSculpture 1.0");
					else
						continue;

					if(amData.Seek(144))
					{
						// Looks like a valid instrument definition file!
						m_nInstruments = 31;
						break;
					}
				}
			}
		}
#elif defined(MPT_BUILD_FUZZER)
		// For fuzzing this part of the code, just take random data from patterns
		FileReader amData = file.GetChunkAt(1084, 31 * 120);
		m_nInstruments = 31;
#endif

		for(SAMPLEINDEX smp = 1; smp <= m_nInstruments; smp++)
		{
			// For Startrekker AM synthesis, we need instrument envelopes.
			ModInstrument *ins = AllocateInstrument(smp, smp);
			if(ins == nullptr)
			{
				break;
			}
			mpt::String::Copy(ins->name, m_szNames[smp]);

			AMInstrument am;
			// Allow partial reads for fa.worse face.mod
			if(amData.ReadStructPartial(am) && !memcmp(am.am, "AM", 2) && am.waveform < 4)
			{
				am.ConvertToMPT(Samples[smp], *ins, AccessPRNG());
			}

			// This extra padding is probably present to have identical block sizes for AM and FM instruments.
			amData.Skip(120 - sizeof(AMInstrument));
		}
	}
#endif // MPT_EXTERNAL_SAMPLES || MPT_BUILD_FUZZER

	// Fix VBlank MODs. Arbitrary threshold: 10 minutes.
	// Basically, this just converts all tempo commands into speed commands
	// for MODs which are supposed to have VBlank timing (instead of CIA timing).
	// There is no perfect way to do this, since both MOD types look the same,
	// but the most reliable way is to simply check for extremely long songs
	// (as this would indicate that e.g. a F30 command was really meant to set
	// the ticks per row to 48, and not the tempo to 48 BPM).
	// In the pattern loader above, a second condition is used: Only tempo commands
	// below 100 BPM are taken into account. Furthermore, only M.K. (ProTracker)
	// modules are checked.
	if(isMdKd && hasTempoCommands && !definitelyCIA)
	{
		const double songTime = GetLength(eNoAdjust).front().duration;
		if(songTime >= 600.0)
		{
			m_playBehaviour.set(kMODVBlankTiming);
			if(GetLength(eNoAdjust, GetLengthTarget(songTime)).front().targetReached)
			{
				// This just makes things worse, song is at least as long as in CIA mode (e.g. in "Stary Hallway" by Neurodancer)
				// Obviously we should keep using CIA timing then...
				m_playBehaviour.reset(kMODVBlankTiming);
			} else
			{
				modMagicResult.madeWithTracker = UL_("ProTracker (VBlank)");
			}
		}
	}

	std::transform(std::begin(magic), std::end(magic), std::begin(magic), [](unsigned char c) -> unsigned char { return (c < ' ') ? ' ' : c; });
	m_modFormat.formatName = mpt::format(U_("ProTracker MOD (%1)"))(mpt::ToUnicode(mpt::CharsetASCII, std::string(std::begin(magic), std::end(magic))));
	m_modFormat.type = U_("mod");
	if(modMagicResult.madeWithTracker) m_modFormat.madeWithTracker = modMagicResult.madeWithTracker;
	m_modFormat.charset = mpt::CharsetISO8859_1;

	return true;
}


// Check if a name string is valid (i.e. doesn't contain binary garbage data)
template<size_t N>
static uint32 CountInvalidChars(const char (&name)[N])
{
	uint32 invalidChars = 0;
	for(int8 c : name)  // char can be signed or unsigned
	{
		// Check for any Extended ASCII and control characters
		if(c != 0 && c < ' ')
			invalidChars++;
	}
	return invalidChars;
}


// We'll have to do some heuristic checks to find out whether this is an old Ultimate Soundtracker module
// or if it was made with the newer Soundtracker versions.
// Thanks for Fraggie for this information! (https://www.un4seen.com/forum/?topic=14471.msg100829#msg100829)
enum STVersions
{
	UST1_00,				// Ultimate Soundtracker 1.0-1.21 (K. Obarski)
	UST1_80,				// Ultimate Soundtracker 1.8-2.0 (K. Obarski)
	ST2_00_Exterminator,	// SoundTracker 2.0 (The Exterminator), D.O.C. Sountracker II (Unknown/D.O.C.)
	ST_III,					// Defjam Soundtracker III (Il Scuro/Defjam), Alpha Flight SoundTracker IV (Alpha Flight), D.O.C. SoundTracker IV (Unknown/D.O.C.), D.O.C. SoundTracker VI (Unknown/D.O.C.)
	ST_IX,					// D.O.C. SoundTracker IX (Unknown/D.O.C.)
	MST1_00,				// Master Soundtracker 1.0 (Tip/The New Masters)
	ST2_00,					// SoundTracker 2.0, 2.1, 2.2 (Unknown/D.O.C.)
};



struct M15FileHeaders
{
	char            songname[20];
	MODSampleHeader sampleHeaders[15];
	MODFileHeader   fileHeader;
};

MPT_BINARY_STRUCT(M15FileHeaders, 20 + 15 * 30 + 130)

typedef uint8 M15PatternData[64][4][4];


static bool ValidateHeader(const M15FileHeaders &fileHeaders)
{
	// In theory, sample and song names should only ever contain printable ASCII chars and null.
	// However, there are quite a few SoundTracker modules in the wild with random
	// characters. To still be able to distguish them from other formats, we just reject
	// files with *too* many bogus characters. Arbitrary threshold: 48 bogus characters in total
	// or more than 5 invalid characters just in the title alone.
	uint32 invalidChars = CountInvalidChars(fileHeaders.songname);
	if(invalidChars > 5)
	{
		return false;
	}

	SmpLength totalSampleLen = 0;
	uint8 allVolumes = 0;

	for(SAMPLEINDEX smp = 0; smp < 15; smp++)
	{
		const MODSampleHeader &sampleHeader = fileHeaders.sampleHeaders[smp];

		invalidChars += CountInvalidChars(sampleHeader.name);

		// Sanity checks - invalid character count adjusted for ata.mod (MD5 937b79b54026fa73a1a4d3597c26eace, SHA1 3322ca62258adb9e0ae8e9afe6e0c29d39add874)
		if(invalidChars > 48
			|| sampleHeader.volume > 64
			|| sampleHeader.finetune != 0
			|| sampleHeader.length > 32768)
		{
			return false;
		}

		totalSampleLen += sampleHeader.length;
		allVolumes |= sampleHeader.volume;

	}

	// Reject any files with no (or only silent) samples at all, as this might just be a random binary file (e.g. ID3 tags with tons of padding)
	if(totalSampleLen == 0 || allVolumes == 0)
	{
		return false;
	}

	// Sanity check: No more than 128 positions. ST's GUI limits tempo to [1, 220].
	// There are some mods with a tempo of 0 (explora3-death.mod) though, so ignore the lower limit.
	if(fileHeaders.fileHeader.numOrders > 128 || fileHeaders.fileHeader.restartPos > 220)
	{
		return false;
	}

	uint8 maxPattern = *std::max_element(std::begin(fileHeaders.fileHeader.orderList), std::end(fileHeaders.fileHeader.orderList));
	// Sanity check: 64 patterns max.
	if(maxPattern > 63)
	{
		return false;
	}
	
	// No playable song, and lots of null values => most likely a sparse binary file but not a module
	if(fileHeaders.fileHeader.restartPos == 0 && fileHeaders.fileHeader.numOrders == 0 && maxPattern == 0)
	{
		return false;
	}

	return true;
}


static uint32 CountIllegalM15PatternBytes(const M15PatternData &patternData)
{
	uint32 illegalBytes = 0;
	for(uint8 row = 0; row < 64; ++row)
	{
		for(uint8 channel = 0; channel < 4; ++channel)
		{
			if(patternData[row][channel][0] & 0xF0u)
			{
				illegalBytes++;
			}
		}
	}
	return illegalBytes;
}


template <typename TFileReader>
static bool ValidateFirstM15Pattern(TFileReader &file)
{
	M15PatternData patternData;
	if(!file.ReadArray(patternData))
	{
		return false;
	}
	file.SkipBack(sizeof(patternData));
	uint32 invalidBytes = CountIllegalM15PatternBytes(patternData);
	// [threshold for all patterns combined] / [max patterns] * [margin, do not reject too much]
	if(invalidBytes > 512 / 64 * 2)
	{
		return false;
	}
	return true;
}


CSoundFile::ProbeResult CSoundFile::ProbeFileHeaderM15(MemoryFileReader file, const uint64 *pfilesize)
{
	M15FileHeaders fileHeaders;
	if(!file.ReadStruct(fileHeaders))
	{
		return ProbeWantMoreData;
	}
	if(!ValidateHeader(fileHeaders))
	{
		return ProbeFailure;
	}
	if(!file.CanRead(sizeof(M15PatternData)))
	{
		return ProbeWantMoreData;
	}
	if(!ValidateFirstM15Pattern(file))
	{
		return ProbeFailure;
	}
	MPT_UNREFERENCED_PARAMETER(pfilesize);
	return ProbeSuccess;
}


bool CSoundFile::ReadM15(FileReader &file, ModLoadingFlags loadFlags)
{
	file.Rewind();

	M15FileHeaders fileHeaders;
	if(!file.ReadStruct(fileHeaders))
	{
		return false;
	}
	if(!ValidateHeader(fileHeaders))
	{
		return false;
	}
	if(!ValidateFirstM15Pattern(file))
	{
		return false;
	}

	char songname[20];
	std::memcpy(songname, fileHeaders.songname, 20);

	InitializeGlobals(MOD_TYPE_MOD);
	m_playBehaviour.reset(kMODOneShotLoops);
	m_playBehaviour.set(kMODIgnorePanning);
	m_playBehaviour.set(kMODSampleSwap);	// untested
	m_nChannels = 4;

	STVersions minVersion = UST1_00;

	bool hasDiskNames = true;
	SmpLength totalSampleLen = 0;
	m_nSamples = 15;

	file.Seek(20);
	for(SAMPLEINDEX smp = 1; smp <= 15; smp++)
	{
		MODSampleHeader sampleHeader;
		ReadSample(file, sampleHeader, Samples[smp], m_szNames[smp], true);

		totalSampleLen += Samples[smp].nLength;

		if(m_szNames[smp][0] && ((memcmp(m_szNames[smp], "st-", 3) && memcmp(m_szNames[smp], "ST-", 3)) || m_szNames[smp][5] != ':'))
		{
			// Ultimate Soundtracker 1.8 and D.O.C. SoundTracker IX always have sample names containing disk names.
			hasDiskNames = false;
		}

		// Loop start is always in bytes, not words, so don't trust the auto-fix magic in the sample header conversion (fixes loop of "st-01:asia" in mod.drag 10)
		if(sampleHeader.loopLength > 1)
		{
			Samples[smp].nLoopStart = sampleHeader.loopStart;
			Samples[smp].nLoopEnd = sampleHeader.loopStart + sampleHeader.loopLength * 2;
			Samples[smp].SanitizeLoops();
		}

		// UST only handles samples up to 9999 bytes. Master Soundtracker 1.0 and SoundTracker 2.0 introduce 32KB samples.
		if(sampleHeader.length > 4999 || sampleHeader.loopStart > 9999)
			minVersion = std::max(minVersion, MST1_00);
	}

	MODFileHeader fileHeader;
	file.ReadStruct(fileHeader);

	ReadOrderFromArray(Order(), fileHeader.orderList);
	PATTERNINDEX numPatterns = GetNumPatterns(file, Order(), fileHeader.numOrders, totalSampleLen, m_nChannels, false);

	// Most likely just a file with lots of NULs at the start
	if(fileHeader.restartPos == 0 && fileHeader.numOrders == 0 && numPatterns <= 1)
	{
		return false;
	}

	// Let's see if the file is too small (including some overhead for broken files like sll7.mod or ghostbus.mod)
	if(file.BytesLeft() + 65536 < numPatterns * 64u * 4u * 4u + totalSampleLen)
		return false;

	if(loadFlags == onlyVerifyHeader)
		return true;

	// Now we can be pretty sure that this is a valid Soundtracker file. Set up default song settings.
	// explora3-death.mod has a tempo of 0
	if(!fileHeader.restartPos)
		fileHeader.restartPos = 0x78;
	// jjk55 by Jesper Kyd has a weird tempo set, but it needs to be ignored.
	if(!memcmp(songname, "jjk55", 6))
		fileHeader.restartPos = 0x78;
	// Sample 7 in echoing.mod won't "loop" correctly if we don't convert the VBlank tempo.
	m_nDefaultTempo.Set(fileHeader.restartPos * 25 / 24);
	if(fileHeader.restartPos != 0x78)
	{
		// Convert to CIA timing
		//m_nDefaultTempo = TEMPO(((709378.92 / 50.0) * 125.0) / ((240 - fileHeader.restartPos) * 122.0));
		m_nDefaultTempo.Set((709379 / ((240 - fileHeader.restartPos) * 122)) * 125 / 50);
		if(minVersion > UST1_80)
		{
			// D.O.C. SoundTracker IX re-introduced the variable tempo after some other versions dropped it.
			minVersion = std::max(minVersion, hasDiskNames ? ST_IX : MST1_00);
		} else
		{
			// Ultimate Soundtracker 1.8 adds variable tempo
			minVersion = std::max(minVersion, hasDiskNames ? UST1_80 : ST2_00_Exterminator);
		}
	}
	m_nMinPeriod = 113 * 4;
	m_nMaxPeriod = 856 * 4;
	m_nSamplePreAmp = 64;
	m_SongFlags.set(SONG_PT_MODE);
	mpt::String::Read<mpt::String::spacePadded>(m_songName, songname);

	// Setup channel pan positions and volume
	SetupMODPanning();

	FileReader::off_t patOffset = file.GetPosition();

	// Scan patterns to identify Ultimate Soundtracker modules.
	uint32 illegalBytes = 0;
	for(PATTERNINDEX pat = 0; pat < numPatterns; pat++)
	{
		bool patternInUse = std::find(Order().cbegin(), Order().cend(), pat) != Order().cend();
		uint8 numDxx = 0;
		uint8 emptyCmds = 0;
		M15PatternData patternData;
		file.ReadArray(patternData);
		if(patternInUse)
		{
			illegalBytes += CountIllegalM15PatternBytes(patternData);
			// Reject files that contain a lot of illegal pattern data.
			// STK.the final remix (MD5 5ff13cdbd77211d1103be7051a7d89c9, SHA1 e94dba82a5da00a4758ba0c207eb17e3a89c3aa3)
			// has one illegal byte, so we only reject after an arbitrary threshold has been passed.
			// This also allows to play some rather damaged files like
			// crockets.mod (MD5 995ed9f44cab995a0eeb19deb52e2a8b, SHA1 6c79983c3b7d55c9bc110b625eaa07ce9d75f369)
			// but naturally we cannot recover the broken data.

			// We only check patterns that are actually being used in the order list, because some bad rips of the
			// "operation wolf" soundtrack have 15 patterns for several songs, but the last few patterns are just garbage.
			// Apart from those hidden patterns, the files play fine.
			// Example: operation wolf - wolf1.mod (MD5 739acdbdacd247fbefcac7bc2d8abe6b, SHA1 e6b4813daacbf95f41ce9ec3b22520a2ae07eed8)
			if(illegalBytes > 512)
				return false;
		}
		for(ROWINDEX row = 0; row < 64; row++)
		{
			for(CHANNELINDEX chn = 0; chn < 4; chn++)
			{
				const uint8 (&data)[4] = patternData[row][chn];
				const uint8 eff = data[2] & 0x0F, param = data[3];
				// Check for empty space between the last Dxx command and the beginning of another pattern
				if(emptyCmds != 0 && !memcmp(data, "\0\0\0\0", 4))
				{
					emptyCmds++;
					if(emptyCmds > 32)
					{
						// Since there is a lot of empty space after the last Dxx command,
						// we assume it's supposed to be a pattern break effect.
						minVersion = ST2_00;
					}
				} else
				{
					emptyCmds = 0;
				}

				switch(eff)
				{
				case 1:
				case 2:
					if(param > 0x1F && minVersion == UST1_80)
					{
						// If a 1xx / 2xx effect has a parameter greater than 0x20, it is assumed to be UST.
						minVersion = hasDiskNames ? UST1_80 : UST1_00;
					} else if(eff == 1 && param > 0 && param < 0x03)
					{
						// This doesn't look like an arpeggio.
						minVersion = std::max(minVersion, ST2_00_Exterminator);
					} else if(eff == 1 && (param == 0x37 || param == 0x47) && minVersion <= ST2_00_Exterminator)
					{
						// This suspiciously looks like an arpeggio.
						// Catch sleepwalk.mod by Karsten Obarski, which has a default tempo of 125 rather than 120 in the header, so gets mis-identified as a later tracker version.
						minVersion = hasDiskNames ? UST1_80 : UST1_00;
					}
					break;
				case 0x0B:
					minVersion = ST2_00;
					break;
				case 0x0C:
				case 0x0D:
				case 0x0E:
					minVersion = std::max(minVersion, ST2_00_Exterminator);
					if(eff == 0x0D)
					{
						emptyCmds = 1;
						if(param == 0 && row == 0)
						{
							// Fix a possible tracking mistake in Blood Money title - who wants to do a pattern break on the first row anyway?
							break;
						}
						numDxx++;
					}
					break;
				case 0x0F:
					minVersion = std::max(minVersion, ST_III);
					break;
				}
			}
		}

		if(numDxx > 0 && numDxx < 3)
		{
			// Not many Dxx commands in one pattern means they were probably pattern breaks
			minVersion = ST2_00;
		}
	}

	file.Seek(patOffset);

	// Reading patterns
	if(loadFlags & loadPatternData)
		Patterns.ResizeArray(numPatterns);
	for(PATTERNINDEX pat = 0; pat < numPatterns; pat++)
	{
		M15PatternData patternData;
		file.ReadArray(patternData);

		if(!(loadFlags & loadPatternData) || !Patterns.Insert(pat, 64))
		{
			continue;
		}

		uint8 autoSlide[4] = { 0, 0, 0, 0 };
		for(ROWINDEX row = 0; row < 64; row++)
		{
			PatternRow rowBase = Patterns[pat].GetpModCommand(row, 0);
			for(CHANNELINDEX chn = 0; chn < 4; chn++)
			{
				ModCommand &m = rowBase[chn];
				ReadMODPatternEntry(patternData[row][chn], m);

				if(!m.param || m.command == 0x0E)
				{
					autoSlide[chn] = 0;
				}
				if(m.command || m.param)
				{
					if(autoSlide[chn] != 0)
					{
						if(autoSlide[chn] & 0xF0)
						{
							m.volcmd = VOLCMD_VOLSLIDEUP;
							m.vol = autoSlide[chn] >> 4;
						} else
						{
							m.volcmd = VOLCMD_VOLSLIDEDOWN;
							m.vol = autoSlide[chn] & 0x0F;
						}
					}
					if(m.command == 0x0D)
					{
						if(minVersion != ST2_00)
						{
							// Dxy is volume slide in some Soundtracker versions, D00 is a pattern break in the latest versions.
							m.command = 0x0A;
						} else
						{
							m.param = 0;
						}
					} else if(m.command == 0x0C)
					{
						// Volume is sent as-is to the chip, which ignores the highest bit.
						m.param &= 0x7F;
					} else if(m.command == 0x0E && (m.param > 0x01 || minVersion < ST_IX))
					{
						// Import auto-slides as normal slides and fake them using volume column slides.
						m.command = 0x0A;
						autoSlide[chn] = m.param;
					} else if(m.command == 0x0F)
					{
						// Only the low nibble is evaluated in Soundtracker.
						m.param &= 0x0F;
					}

					if(minVersion <= UST1_80)
					{
						// UST effects
						switch(m.command)
						{
						case 0:
							// jackdance.mod by Karsten Obarski has 0xy arpeggios...
							if(m.param < 0x03)
							{
								m.command = CMD_NONE;
							} else
							{
								m.command = CMD_ARPEGGIO;
							}
							break;
						case 1:
							m.command = CMD_ARPEGGIO;
							break;
						case 2:
							if(m.param & 0x0F)
							{
								m.command = CMD_PORTAMENTOUP;
								m.param &= 0x0F;
							} else if(m.param >> 4)
							{
								m.command = CMD_PORTAMENTODOWN;
								m.param >>= 4;
							}
							break;
						default:
							m.command = CMD_NONE;
							break;
						}
					} else
					{
						ConvertModCommand(m);
					}
				} else
				{
					autoSlide[chn] = 0;
				}
			}
		}
	}

	const MPT_UCHAR_TYPE *madeWithTracker = UL_("");
	switch(minVersion)
	{
	case UST1_00:
		madeWithTracker = UL_("Ultimate Soundtracker 1.0-1.21");
		break;
	case UST1_80:
		madeWithTracker = UL_("Ultimate Soundtracker 1.8-2.0");
		break;
	case ST2_00_Exterminator:
		madeWithTracker = UL_("SoundTracker 2.0 / D.O.C. SoundTracker II");
		break;
	case ST_III:
		madeWithTracker = UL_("Defjam Soundtracker III / Alpha Flight SoundTracker IV / D.O.C. SoundTracker IV / VI");
		break;
	case ST_IX:
		madeWithTracker = UL_("D.O.C. SoundTracker IX");
		break;
	case MST1_00:
		madeWithTracker = UL_("Master Soundtracker 1.0");
		break;
	case ST2_00:
		madeWithTracker = UL_("SoundTracker 2.0 / 2.1 / 2.2");
		break;
	}

	m_modFormat.formatName = U_("Soundtracker");
	m_modFormat.type = U_("stk");
	m_modFormat.madeWithTracker = madeWithTracker;
	m_modFormat.charset = mpt::CharsetISO8859_1;

	// Reading samples
	if(loadFlags & loadSampleData)
	{
		for(SAMPLEINDEX smp = 1; smp <= 15; smp++)
		{
			// Looped samples in (Ultimate) Soundtracker seem to ignore all sample data before the actual loop start.
			// This avoids the clicks in the first sample of pretend.mod by Karsten Obarski.
			file.Skip(Samples[smp].nLoopStart);
			Samples[smp].nLength -= Samples[smp].nLoopStart;
			Samples[smp].nLoopEnd -= Samples[smp].nLoopStart;
			Samples[smp].nLoopStart = 0;
			MODSampleHeader::GetSampleFormat().ReadSample(Samples[smp], file);
		}
	}

	return true;
}


CSoundFile::ProbeResult CSoundFile::ProbeFileHeaderICE(MemoryFileReader file, const uint64 *pfilesize)
{
	if(!file.CanRead(1464 + 4))
	{
		return ProbeWantMoreData;
	}
	file.Seek(1464);
	char magic[4];
	file.ReadArray(magic);
	if(!IsMagic(magic, "MTN\0") && !IsMagic(magic, "IT10"))
	{
		return ProbeFailure;
	}
	file.Seek(20);
	uint32 invalidBytes = 0;
	for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
	{
		MODSampleHeader sampleHeader;
		if(!file.ReadStruct(sampleHeader))
		{
			return ProbeWantMoreData;
		}
		invalidBytes += sampleHeader.GetInvalidByteScore();
	}
	if(invalidBytes > MODSampleHeader::INVALID_BYTE_THRESHOLD)
	{
		return ProbeFailure;
	}
	const uint8 numOrders = file.ReadUint8();
	const uint8 numTracks = file.ReadUint8();
	if(numOrders > 128)
	{
		return ProbeFailure;
	}
	uint8 tracks[128 * 4];
	file.ReadArray(tracks);
	for(auto track : tracks)
	{
		if(track > numTracks)
		{
			return ProbeFailure;
		}
	}
	MPT_UNREFERENCED_PARAMETER(pfilesize);
	return ProbeSuccess;
}


// SoundTracker 2.6 / Ice Tracker variation of the MOD format
// The only real difference to other SoundTracker formats is the way patterns are stored:
// Every pattern consists of four independent, re-usable tracks.
bool CSoundFile::ReadICE(FileReader &file, ModLoadingFlags loadFlags)
{
	char magic[4];
	if(!file.Seek(1464) || !file.ReadArray(magic))
	{
		return false;
	}

	InitializeGlobals(MOD_TYPE_MOD);
	m_playBehaviour.reset(kMODOneShotLoops);
	m_playBehaviour.set(kMODIgnorePanning);
	m_playBehaviour.set(kMODSampleSwap);	// untested

	if(IsMagic(magic, "MTN\0"))
	{
		m_modFormat.formatName = U_("MnemoTroN SoundTracker");
		m_modFormat.type = U_("st26");
		m_modFormat.madeWithTracker = U_("SoundTracker 2.6");
		m_modFormat.charset = mpt::CharsetISO8859_1;
	} else if(IsMagic(magic, "IT10"))
	{
		m_modFormat.formatName = U_("Ice Tracker");
		m_modFormat.type = U_("ice");
		m_modFormat.madeWithTracker = U_("Ice Tracker 1.0 / 1.1");
		m_modFormat.charset = mpt::CharsetISO8859_1;
	} else
	{
		return false;
	}

	// Reading song title
	file.Seek(0);
	file.ReadString<mpt::String::spacePadded>(m_songName, 20);

	// Load Samples
	m_nSamples = 31;
	uint32 invalidBytes = 0;
	for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
	{
		MODSampleHeader sampleHeader;
		invalidBytes += ReadSample(file, sampleHeader, Samples[smp], m_szNames[smp], true);
	}
	if(invalidBytes > MODSampleHeader::INVALID_BYTE_THRESHOLD)
	{
		return false;
	}

	const uint8 numOrders = file.ReadUint8();
	const uint8 numTracks = file.ReadUint8();
	if(numOrders > 128)
	{
		return false;
	}

	uint8 tracks[128 * 4];
	file.ReadArray(tracks);
	for(auto track : tracks)
	{
		if(track > numTracks)
		{
			return false;
		}
	}

	if(loadFlags == onlyVerifyHeader)
	{
		return true;
	}

	// Now we can be pretty sure that this is a valid MOD file. Set up default song settings.
	m_nChannels = 4;
	m_nInstruments = 0;
	m_nDefaultSpeed = 6;
	m_nDefaultTempo.Set(125);
	m_nMinPeriod = 14 * 4;
	m_nMaxPeriod = 3424 * 4;
	m_nSamplePreAmp = 64;
	m_SongFlags.set(SONG_PT_MODE);

	// Setup channel pan positions and volume
	SetupMODPanning();

	// Reading patterns
	Order().resize(numOrders);
	uint8 speed[2] = { 0, 0 }, speedPos = 0;
	Patterns.ResizeArray(numOrders);
	for(PATTERNINDEX pat = 0; pat < numOrders; pat++)
	{
		Order()[pat] = pat;
		if(!Patterns.Insert(pat, 64))
			continue;

		for(CHANNELINDEX chn = 0; chn < 4; chn++)
		{
			file.Seek(1468 + tracks[pat * 4 + chn] * 64u * 4u);
			ModCommand *m = Patterns[pat].GetpModCommand(0, chn);

			for(ROWINDEX row = 0; row < 64; row++, m += 4)
			{
				ReadMODPatternEntry(file, *m);

				if((m->command || m->param)
					&& !(m->command == 0x0E && m->param >= 0x10)	// Exx only sets filter
					&& !(m->command >= 0x05 && m->command <= 0x09))	// These don't exist in ST2.6
				{
					ConvertModCommand(*m);
				} else
				{
					m->command = CMD_NONE;
				}
			}
		}

		// Handle speed command with both nibbles set - this enables auto-swing (alternates between the two nibbles)
		auto m = Patterns[pat].begin();
		for(ROWINDEX row = 0; row < 64; row++)
		{
			for(CHANNELINDEX chn = 0; chn < 4; chn++, m++)
			{
				if(m->command == CMD_SPEED || m->command == CMD_TEMPO)
				{
					m->command = CMD_SPEED;
					speedPos = 0;
					if(m->param & 0xF0)
					{
						if((m->param >> 4) != (m->param & 0x0F) && (m->param & 0x0F) != 0)
						{
							// Both nibbles set
							speed[0] = m->param >> 4;
							speed[1] = m->param & 0x0F;
							speedPos = 1;
						}
						m->param >>= 4;
					}
				}
			}
			if(speedPos)
			{
				Patterns[pat].WriteEffect(EffectWriter(CMD_SPEED, speed[speedPos - 1]).Row(row));
				speedPos++;
				if(speedPos == 3) speedPos = 1;
			}
		}
	}

	// Reading samples
	if(loadFlags & loadSampleData)
	{
		file.Seek(1468 + numTracks * 64u * 4u);
		for(SAMPLEINDEX smp = 1; smp <= 31; smp++) if(Samples[smp].nLength)
		{
			SampleIO(
				SampleIO::_8bit,
				SampleIO::mono,
				SampleIO::littleEndian,
				SampleIO::signedPCM)
				.ReadSample(Samples[smp], file);
		}
	}

	return true;
}



struct PT36Header
{
	char     magicFORM[4]; // "FORM"
	uint32be size;
	char     magicMODL[4]; // "MODL"
};

MPT_BINARY_STRUCT(PT36Header, 12)


static bool ValidateHeader(const PT36Header &fileHeader)
{
	if(std::memcmp(fileHeader.magicFORM, "FORM", 4))
	{
		return false;
	}
	if(std::memcmp(fileHeader.magicMODL, "MODL", 4))
	{
		return false;
	}
	return true;
}


CSoundFile::ProbeResult CSoundFile::ProbeFileHeaderPT36(MemoryFileReader file, const uint64 *pfilesize)
{
	PT36Header fileHeader;
	if(!file.ReadStruct(fileHeader))
	{
		return ProbeWantMoreData;
	}
	if(!ValidateHeader(fileHeader))
	{
		return ProbeFailure;
	}
	MPT_UNREFERENCED_PARAMETER(pfilesize);
	return ProbeSuccess;
}


// ProTracker 3.6 version of the MOD format
// Basically just a normal ProTracker mod with different magic, wrapped in an IFF file.
// The "PTDT" chunk is passed to the normal MOD loader.
bool CSoundFile::ReadPT36(FileReader &file, ModLoadingFlags loadFlags)
{
	file.Rewind();

	PT36Header fileHeader;
	if(!file.ReadStruct(fileHeader))
	{
		return false;
	}
	if(!ValidateHeader(fileHeader))
	{
		return false;
	}

	bool ok = false, infoOk = false;
	FileReader commentChunk;
	mpt::ustring version;
	PT36InfoChunk info;
	MemsetZero(info);

	// Go through IFF chunks...
	PT36IffChunk iffHead;
	if(!file.ReadStruct(iffHead))
	{
		return false;
	}
	// First chunk includes "MODL" magic in size
	iffHead.chunksize -= 4;
	
	do
	{
		// All chunk sizes include chunk header
		iffHead.chunksize -= 8;
		if(loadFlags == onlyVerifyHeader && iffHead.signature == PT36IffChunk::idPTDT)
		{
			return true;
		}
		
		FileReader chunk = file.ReadChunk(iffHead.chunksize);
		if(!chunk.IsValid())
		{
			break;
		}

		switch(iffHead.signature)
		{
		case PT36IffChunk::idVERS:
			chunk.Skip(4);
			if(chunk.ReadMagic("PT") && iffHead.chunksize > 6)
			{
				chunk.ReadString<mpt::String::maybeNullTerminated>(version, mpt::CharsetISO8859_1, iffHead.chunksize - 6);
			}
			break;
		
		case PT36IffChunk::idINFO:
			infoOk = chunk.ReadStruct(info);
			break;
		
		case PT36IffChunk::idCMNT:
			commentChunk = chunk;
			break;
		
		case PT36IffChunk::idPTDT:
			ok = ReadMOD(chunk, loadFlags);
			break;
		}
	} while(file.ReadStruct(iffHead));

	if(version.empty())
	{
		version = U_("3.6");
	}
	
	// both an info chunk and a module are required
	if(ok && infoOk)
	{
		bool vblank = (info.flags & 0x100) == 0;
		m_playBehaviour.set(kMODVBlankTiming, vblank);
		if(info.volume != 0)
			m_nSamplePreAmp = std::min<uint16>(64, info.volume);
		if(info.tempo != 0 && !vblank)
			m_nDefaultTempo.Set(info.tempo);
	
		if(info.name[0])
			mpt::String::Read<mpt::String::maybeNullTerminated>(m_songName, info.name);
	
		if(IsInRange(info.dateMonth, 1, 12) && IsInRange(info.dateDay, 1, 31) && IsInRange(info.dateHour, 0, 23)
			&& IsInRange(info.dateMinute, 0, 59) && IsInRange(info.dateSecond, 0, 59))
		{
			FileHistory mptHistory;
			mptHistory.loadDate.tm_year = info.dateYear;
			mptHistory.loadDate.tm_mon = info.dateMonth - 1;
			mptHistory.loadDate.tm_mday = info.dateDay;
			mptHistory.loadDate.tm_hour = info.dateHour;
			mptHistory.loadDate.tm_min = info.dateMinute;
			mptHistory.loadDate.tm_sec = info.dateSecond;
			m_FileHistory.push_back(mptHistory);
		}
	}
	if(ok)
	{
		if(commentChunk.IsValid())
		{
			std::string author;
			commentChunk.ReadString<mpt::String::maybeNullTerminated>(author, 32);
			if(author != "UNNAMED AUTHOR")
				m_songArtist = mpt::ToUnicode(mpt::CharsetISO8859_1, author);
			if(!commentChunk.NoBytesLeft())
			{
				m_songMessage.ReadFixedLineLength(commentChunk, commentChunk.BytesLeft(), 40, 0);
			}
		}
		
		m_modFormat.madeWithTracker = U_("ProTracker ") + version;
	}
	m_SongFlags.set(SONG_PT_MODE);
	m_playBehaviour.set(kMODIgnorePanning);
	m_playBehaviour.set(kMODOneShotLoops);
	m_playBehaviour.set(kMODSampleSwap);
	
	return ok;
}


#ifndef MODPLUG_NO_FILESAVE

bool CSoundFile::SaveMod(std::ostream &f) const
{
	if(m_nChannels == 0)
	{
		return false;
	}

	// Write song title
	{
		char name[20];
		mpt::String::Write<mpt::String::maybeNullTerminated>(name, m_songName);
		mpt::IO::Write(f, name);
	}

	std::vector<SmpLength> sampleLength(32, 0);
	std::vector<SAMPLEINDEX> sampleSource(32, 0);

	if(GetNumInstruments())
	{
		INSTRUMENTINDEX lastIns = std::min(INSTRUMENTINDEX(31), GetNumInstruments());
		for(INSTRUMENTINDEX ins = 1; ins <= lastIns; ins++) if (Instruments[ins])
		{
			// Find some valid sample associated with this instrument.
			for(size_t i = 0; i < CountOf(Instruments[ins]->Keyboard); i++)
			{
				if(Instruments[ins]->Keyboard[i] > 0 && Instruments[ins]->Keyboard[i] <= GetNumSamples())
				{
					sampleSource[ins] = Instruments[ins]->Keyboard[i];
					break;
				}
			}
		}
	} else
	{
		for(SAMPLEINDEX i = 1; i <= 31; i++)
		{
			sampleSource[i] = i;
		}
	}

	// Write sample headers
	for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
	{
		MODSampleHeader sampleHeader;
		mpt::String::Write<mpt::String::maybeNullTerminated>(sampleHeader.name, m_szNames[sampleSource[smp]]);
		sampleLength[smp] = sampleHeader.ConvertToMOD(sampleSource[smp] <= GetNumSamples() ? GetSample(sampleSource[smp]) : ModSample(MOD_TYPE_MOD));
		mpt::IO::Write(f, sampleHeader);
	}

	// Write order list
	MODFileHeader fileHeader;
	MemsetZero(fileHeader);

	PATTERNINDEX writePatterns = 0;
	uint8 writtenOrders = 0;
	for(ORDERINDEX ord = 0; ord < Order().GetLength() && writtenOrders < 128; ord++)
	{
		// Ignore +++ and --- patterns in order list, as well as high patterns (MOD officially only supports up to 128 patterns)
		if(ord == Order().GetRestartPos())
		{
			fileHeader.restartPos = writtenOrders;
		}
		if(Order()[ord] < 128)
		{
			fileHeader.orderList[writtenOrders++] = static_cast<uint8>(Order()[ord]);
			if(writePatterns <= Order()[ord])
			{
				writePatterns = Order()[ord] + 1;
			}
		}
	}
	fileHeader.numOrders = writtenOrders;
	mpt::IO::Write(f, fileHeader);

	// Write magic bytes
	char modMagic[4];
	CHANNELINDEX writeChannels = std::min(CHANNELINDEX(99), GetNumChannels());
	if(writeChannels == 4)
	{
		// ProTracker may not load files with more than 64 patterns correctly if we do not specify the M!K! magic.
		if(writePatterns <= 64)
			memcpy(modMagic, "M.K.", 4);
		else
			memcpy(modMagic, "M!K!", 4);
	} else if(writeChannels < 10)
	{
		memcpy(modMagic, "0CHN", 4);
		modMagic[0] += static_cast<char>(writeChannels);
	} else
	{
		memcpy(modMagic, "00CH", 4);
		modMagic[0] += static_cast<char>(writeChannels / 10u);
		modMagic[1] += static_cast<char>(writeChannels % 10u);
	}
	mpt::IO::Write(f, modMagic);

	// Write patterns
	std::vector<uint8> events;
	for(PATTERNINDEX pat = 0; pat < writePatterns; pat++)
	{
		if(!Patterns.IsValidPat(pat))
		{
			// Invent empty pattern
			events.assign(writeChannels * 64 * 4, 0);
			mpt::IO::Write(f, events);
			continue;
		}

		for(ROWINDEX row = 0; row < 64; row++)
		{
			if(row >= Patterns[pat].GetNumRows())
			{
				// Invent empty row
				events.assign(writeChannels * 4, 0);
				mpt::IO::Write(f, events);
				continue;
			}
			PatternRow rowBase = Patterns[pat].GetRow(row);

			events.resize(writeChannels * 4);
			size_t eventByte = 0;
			for(CHANNELINDEX chn = 0; chn < writeChannels; chn++)
			{
				ModCommand &m = rowBase[chn];
				uint8 command = m.command, param = m.param;
				ModSaveCommand(command, param, false, true);

				if(m.volcmd == VOLCMD_VOLUME && !command && !param)
				{
					// Maybe we can save some volume commands...
					command = 0x0C;
					param = MIN(m.vol, 64);
				}

				uint16 period = 0;
				// Convert note to period
				if(m.note >= 24 + NOTE_MIN && m.note < mpt::size(ProTrackerPeriodTable) + 24 + NOTE_MIN)
				{
					period = ProTrackerPeriodTable[m.note - 24 - NOTE_MIN];
				}

				uint8 instr = (m.instr <= 31) ? m.instr : 0;

				events[eventByte++] = ((period >> 8) & 0x0F) | (instr & 0x10);
				events[eventByte++] = period & 0xFF;
				events[eventByte++] = ((instr & 0x0F) << 4) | (command & 0x0F);
				events[eventByte++] = param;
			}
			mpt::IO::WriteRaw(f, mpt::as_span(events.data(), eventByte));
		}
	}

	//Check for unsaved patterns
	for(PATTERNINDEX pat = writePatterns; pat < Patterns.Size(); pat++)
	{
		if(Patterns.IsValidPat(pat))
		{
			AddToLog("Warning: This track contains at least one pattern after the highest pattern number referred to in the sequence. Such patterns are not saved in the MOD format.");
			break;
		}
	}

	// Writing samples
	for(SAMPLEINDEX smp = 1; smp <= 31; smp++)
	{
		if(sampleLength[smp] == 0)
		{
			continue;
		}
		const ModSample &sample = Samples[sampleSource[smp]];

		const mpt::IO::Offset sampleStart = mpt::IO::TellWrite(f);
		const size_t writtenBytes = MODSampleHeader::GetSampleFormat().WriteSample(f, sample, sampleLength[smp]);

		const int8 silence = 0;

		// Write padding byte if the sample size is odd.
		if((writtenBytes % 2u) != 0)
		{
			mpt::IO::Write(f, silence);
		}

		if(!sample.uFlags[CHN_LOOP] && writtenBytes >= 2)
		{
			// First two bytes of oneshot samples have to be 0 due to PT's one-shot loop
			const mpt::IO::Offset sampleEnd = mpt::IO::TellWrite(f);
			mpt::IO::SeekAbsolute(f, sampleStart);
			mpt::IO::Write(f, silence);
			mpt::IO::Write(f, silence);
			mpt::IO::SeekAbsolute(f, sampleEnd);
		}
	}

	return true;
}

#endif // MODPLUG_NO_FILESAVE


OPENMPT_NAMESPACE_END