Fix 03cc0d6: Mark level crossings dirty when removing road from them, not from bridge...

[openttd-github.git] / src / music / midifile.cpp

/*
* This file is part of OpenTTD.
* OpenTTD 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, version 2.
* OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/

/* @file midifile.cpp Parser for standard MIDI files */

#include "midifile.hpp"
#include "../fileio_func.h"
#include "../fileio_type.h"
#include "../string_func.h"
#include "../core/endian_func.hpp"
#include "../base_media_base.h"
#include "midi.h"

#include "../console_func.h"
#include "../console_internal.h"

/* SMF reader based on description at: http://www.somascape.org/midi/tech/mfile.html */


static MidiFile *_midifile_instance = nullptr;

/**
 * Retrieve a well-known MIDI system exclusive message.
 * @param msg Which sysex message to retrieve
 * @param[out] length Receives the length of the returned buffer
 * @return Pointer to byte buffer with sysex message
 */
const byte *MidiGetStandardSysexMessage(MidiSysexMessage msg, size_t &length)
{
        static byte reset_gm_sysex[] = { 0xF0, 0x7E, 0x7F, 0x09, 0x01, 0xF7 };
        static byte reset_gs_sysex[] = { 0xF0, 0x41, 0x10, 0x42, 0x12, 0x40, 0x00, 0x7F, 0x00, 0x41, 0xF7 };
        static byte reset_xg_sysex[] = { 0xF0, 0x43, 0x10, 0x4C, 0x00, 0x00, 0x7E, 0x00, 0xF7 };
        static byte roland_reverb_sysex[] = { 0xF0, 0x41, 0x10, 0x42, 0x12, 0x40, 0x01, 0x30, 0x02, 0x04, 0x00, 0x40, 0x40, 0x00, 0x00, 0x09, 0xF7 };

        switch (msg) {
                case MidiSysexMessage::ResetGM:
                        length = lengthof(reset_gm_sysex);
                        return reset_gm_sysex;
                case MidiSysexMessage::ResetGS:
                        length = lengthof(reset_gs_sysex);
                        return reset_gs_sysex;
                case MidiSysexMessage::ResetXG:
                        length = lengthof(reset_xg_sysex);
                        return reset_xg_sysex;
                case MidiSysexMessage::RolandSetReverb:
                        length = lengthof(roland_reverb_sysex);
                        return roland_reverb_sysex;
                default:
                        NOT_REACHED();
        }
}

/**
 * Owning byte buffer readable as a stream.
 * RAII-compliant to make teardown in error situations easier.
 */
class ByteBuffer {
        byte *buf;
        size_t buflen;
        size_t pos;
public:
        /**
         * Construct buffer from data in a file.
         * If file does not have sufficient bytes available, the object is constructed
         * in an error state, that causes all further function calls to fail.
         * @param file file to read from at current position
         * @param len number of bytes to read
         */
        ByteBuffer(FILE *file, size_t len)
        {
                this->buf = MallocT<byte>(len);
                if (fread(this->buf, 1, len, file) == len) {
                        this->buflen = len;
                        this->pos = 0;
                } else {
                        /* invalid state */
                        this->buflen = 0;
                }
        }

        /**
         * Destructor, frees the buffer.
         */
        ~ByteBuffer()
        {
                free(this->buf);
        }

        /**
         * Return whether the buffer was constructed successfully.
         * @return true is the buffer contains data
         */
        bool IsValid() const
        {
                return this->buflen > 0;
        }

        /**
         * Return whether reading has reached the end of the buffer.
         * @return true if there are no more bytes available to read
         */
        bool IsEnd() const
        {
                return this->pos >= this->buflen;
        }

        /**
         * Read a single byte from the buffer.
         * @param[out] b returns the read value
         * @return true if a byte was available for reading
         */
        bool ReadByte(byte &b)
        {
                if (this->IsEnd()) return false;
                b = this->buf[this->pos++];
                return true;
        }

        /**
         * Read a MIDI file variable length value.
         * Each byte encodes 7 bits of the value, most-significant bits are encoded first.
         * If the most significant bit in a byte is set, there are further bytes encoding the value.
         * @param[out] res returns the read value
         * @return true if there was data available
         */
        bool ReadVariableLength(uint32 &res)
        {
                res = 0;
                byte b = 0;
                do {
                        if (this->IsEnd()) return false;
                        b = this->buf[this->pos++];
                        res = (res << 7) | (b & 0x7F);
                } while (b & 0x80);
                return true;
        }

        /**
         * Read bytes into a buffer.
         * @param[out] dest buffer to copy into
         * @param length number of bytes to read
         * @return true if the requested number of bytes were available
         */
        bool ReadBuffer(byte *dest, size_t length)
        {
                if (this->IsEnd()) return false;
                if (this->buflen - this->pos < length) return false;
                memcpy(dest, this->buf + this->pos, length);
                this->pos += length;
                return true;
        }

        /**
         * Read bytes into a MidiFile::DataBlock.
         * @param[out] dest DataBlock to copy into
         * @param length number of bytes to read
         * @return true if the requested number of bytes were available
         */
        bool ReadDataBlock(MidiFile::DataBlock *dest, size_t length)
        {
                if (this->IsEnd()) return false;
                if (this->buflen - this->pos < length) return false;
                dest->data.insert(dest->data.end(), this->buf + this->pos, this->buf + this->pos + length);
                this->pos += length;
                return true;
        }

        /**
         * Skip over a number of bytes in the buffer.
         * @param count number of bytes to skip over
         * @return true if there were enough bytes available
         */
        bool Skip(size_t count)
        {
                if (this->IsEnd()) return false;
                if (this->buflen - this->pos < count) return false;
                this->pos += count;
                return true;
        }

        /**
         * Go a number of bytes back to re-read.
         * @param count number of bytes to go back
         * @return true if at least count bytes had been read previously
         */
        bool Rewind(size_t count)
        {
                if (count > this->pos) return false;
                this->pos -= count;
                return true;
        }
};

static bool ReadTrackChunk(FILE *file, MidiFile &target)
{
        byte buf[4];

        const byte magic[] = { 'M', 'T', 'r', 'k' };
        if (fread(buf, sizeof(magic), 1, file) != 1) {
                return false;
        }
        if (memcmp(magic, buf, sizeof(magic)) != 0) {
                return false;
        }

        /* Read chunk length and then the whole chunk */
        uint32 chunk_length;
        if (fread(&chunk_length, 1, 4, file) != 4) {
                return false;
        }
        chunk_length = FROM_BE32(chunk_length);

        ByteBuffer chunk(file, chunk_length);
        if (!chunk.IsValid()) {
                return false;
        }

        target.blocks.push_back(MidiFile::DataBlock());
        MidiFile::DataBlock *block = &target.blocks.back();

        byte last_status = 0;
        bool running_sysex = false;
        while (!chunk.IsEnd()) {
                /* Read deltatime for event, start new block */
                uint32 deltatime = 0;
                if (!chunk.ReadVariableLength(deltatime)) {
                        return false;
                }
                if (deltatime > 0) {
                        target.blocks.push_back(MidiFile::DataBlock(block->ticktime + deltatime));
                        block = &target.blocks.back();
                }

                /* Read status byte */
                byte status;
                if (!chunk.ReadByte(status)) {
                        return false;
                }

                if ((status & 0x80) == 0) {
                        /* High bit not set means running status message, status is same as last
                         * convert to explicit status */
                        chunk.Rewind(1);
                        status = last_status;
                        goto running_status;
                } else if ((status & 0xF0) != 0xF0) {
                        /* Regular channel message */
                        last_status = status;
                running_status:
                        switch (status & 0xF0) {
                                case MIDIST_NOTEOFF:
                                case MIDIST_NOTEON:
                                case MIDIST_POLYPRESS:
                                case MIDIST_CONTROLLER:
                                case MIDIST_PITCHBEND:
                                        /* 3 byte messages */
                                        block->data.push_back(status);
                                        if (!chunk.ReadDataBlock(block, 2)) {
                                                return false;
                                        }
                                        break;
                                case MIDIST_PROGCHG:
                                case MIDIST_CHANPRESS:
                                        /* 2 byte messages */
                                        block->data.push_back(status);
                                        if (!chunk.ReadByte(buf[0])) {
                                                return false;
                                        }
                                        block->data.push_back(buf[0]);
                                        break;
                                default:
                                        NOT_REACHED();
                        }
                } else if (status == MIDIST_SMF_META) {
                        /* Meta event, read event type byte and data length */
                        if (!chunk.ReadByte(buf[0])) {
                                return false;
                        }
                        uint32 length = 0;
                        if (!chunk.ReadVariableLength(length)) {
                                return false;
                        }
                        switch (buf[0]) {
                                case 0x2F:
                                        /* end of track, no more data (length != 0 is illegal) */
                                        return (length == 0);
                                case 0x51:
                                        /* tempo change */
                                        if (length != 3) return false;
                                        if (!chunk.ReadBuffer(buf, 3)) return false;
                                        target.tempos.push_back(MidiFile::TempoChange(block->ticktime, buf[0] << 16 | buf[1] << 8 | buf[2]));
                                        break;
                                default:
                                        /* unimportant meta event, skip over it */
                                        if (!chunk.Skip(length)) {
                                                return false;
                                        }
                                        break;
                        }
                } else if (status == MIDIST_SYSEX || (status == MIDIST_SMF_ESCAPE  && running_sysex)) {
                        /* System exclusive message */
                        uint32 length = 0;
                        if (!chunk.ReadVariableLength(length)) {
                                return false;
                        }
                        block->data.push_back(0xF0);
                        if (!chunk.ReadDataBlock(block, length)) {
                                return false;
                        }
                        if (block->data.back() != 0xF7) {
                                /* Engage Casio weirdo mode - convert to normal sysex */
                                running_sysex = true;
                                block->data.push_back(0xF7);
                        } else {
                                running_sysex = false;
                        }
                } else if (status == MIDIST_SMF_ESCAPE) {
                        /* Escape sequence */
                        uint32 length = 0;
                        if (!chunk.ReadVariableLength(length)) {
                                return false;
                        }
                        if (!chunk.ReadDataBlock(block, length)) {
                                return false;
                        }
                } else {
                        /* Messages undefined in standard midi files:
                         * 0xF1 - MIDI time code quarter frame
                         * 0xF2 - Song position pointer
                         * 0xF3 - Song select
                         * 0xF4 - undefined/reserved
                         * 0xF5 - undefined/reserved
                         * 0xF6 - Tune request for analog synths
                         * 0xF8..0xFE - System real-time messages
                         */
                        return false;
                }
        }

        NOT_REACHED();
}

template<typename T>
bool TicktimeAscending(const T &a, const T &b)
{
        return a.ticktime < b.ticktime;
}

static bool FixupMidiData(MidiFile &target)
{
        /* Sort all tempo changes and events */
        std::sort(target.tempos.begin(), target.tempos.end(), TicktimeAscending<MidiFile::TempoChange>);
        std::sort(target.blocks.begin(), target.blocks.end(), TicktimeAscending<MidiFile::DataBlock>);

        if (target.tempos.size() == 0) {
                /* No tempo information, assume 120 bpm (500,000 microseconds per beat */
                target.tempos.push_back(MidiFile::TempoChange(0, 500000));
        }
        /* Add sentinel tempo at end */
        target.tempos.push_back(MidiFile::TempoChange(UINT32_MAX, 0));

        /* Merge blocks with identical tick times */
        std::vector<MidiFile::DataBlock> merged_blocks;
        uint32 last_ticktime = 0;
        for (size_t i = 0; i < target.blocks.size(); i++) {
                MidiFile::DataBlock &block = target.blocks[i];
                if (block.data.size() == 0) {
                        continue;
                } else if (block.ticktime > last_ticktime || merged_blocks.size() == 0) {
                        merged_blocks.push_back(block);
                        last_ticktime = block.ticktime;
                } else {
                        merged_blocks.back().data.insert(merged_blocks.back().data.end(), block.data.begin(), block.data.end());
                }
        }
        std::swap(merged_blocks, target.blocks);

        /* Annotate blocks with real time */
        last_ticktime = 0;
        uint32 last_realtime = 0;
        size_t cur_tempo = 0, cur_block = 0;
        while (cur_block < target.blocks.size()) {
                MidiFile::DataBlock &block = target.blocks[cur_block];
                MidiFile::TempoChange &tempo = target.tempos[cur_tempo];
                MidiFile::TempoChange &next_tempo = target.tempos[cur_tempo+1];
                if (block.ticktime <= next_tempo.ticktime) {
                        /* block is within the current tempo */
                        int64 tickdiff = block.ticktime - last_ticktime;
                        last_ticktime = block.ticktime;
                        last_realtime += uint32(tickdiff * tempo.tempo / target.tickdiv);
                        block.realtime = last_realtime;
                        cur_block++;
                } else {
                        /* tempo change occurs before this block */
                        int64 tickdiff = next_tempo.ticktime - last_ticktime;
                        last_ticktime = next_tempo.ticktime;
                        last_realtime += uint32(tickdiff * tempo.tempo / target.tickdiv); // current tempo until the tempo change
                        cur_tempo++;
                }
        }

        return true;
}

/**
 * Read the header of a standard MIDI file.
 * @param[in] filename name of file to read from
 * @param[out] header filled with data read
 * @return true if the file could be opened and contained a header with correct format
 */
bool MidiFile::ReadSMFHeader(const char *filename, SMFHeader &header)
{
        FILE *file = FioFOpenFile(filename, "rb", Subdirectory::BASESET_DIR);
        if (!file) return false;
        bool result = ReadSMFHeader(file, header);
        FioFCloseFile(file);
        return result;
}

/**
 * Read the header of a standard MIDI file.
 * The function will consume 14 bytes from the current file pointer position.
 * @param[in] file open file to read from (should be in binary mode)
 * @param[out] header filled with data read
 * @return true if a header in correct format could be read from the file
 */
bool MidiFile::ReadSMFHeader(FILE *file, SMFHeader &header)
{
        /* Try to read header, fixed size */
        byte buffer[14];
        if (fread(buffer, sizeof(buffer), 1, file) != 1) {
                return false;
        }

        /* Check magic, 'MThd' followed by 4 byte length indicator (always = 6 in SMF) */
        const byte magic[] = { 'M', 'T', 'h', 'd', 0x00, 0x00, 0x00, 0x06 };
        if (MemCmpT(buffer, magic, sizeof(magic)) != 0) {
                return false;
        }

        /* Read the parameters of the file */
        header.format = (buffer[8] << 8) | buffer[9];
        header.tracks = (buffer[10] << 8) | buffer[11];
        header.tickdiv = (buffer[12] << 8) | buffer[13];
        return true;
}

/**
 * Load a standard MIDI file.
 * @param filename name of the file to load
 * @returns true if loaded was successful
 */
bool MidiFile::LoadFile(const char *filename)
{
        _midifile_instance = this;

        this->blocks.clear();
        this->tempos.clear();
        this->tickdiv = 0;

        bool success = false;
        FILE *file = FioFOpenFile(filename, "rb", Subdirectory::BASESET_DIR);
        if (file == nullptr) return false;

        SMFHeader header;
        if (!ReadSMFHeader(file, header)) goto cleanup;

        /* Only format 0 (single-track) and format 1 (multi-track single-song) are accepted for now */
        if (header.format != 0 && header.format != 1) goto cleanup;
        /* Doesn't support SMPTE timecode files */
        if ((header.tickdiv & 0x8000) != 0) goto cleanup;

        this->tickdiv = header.tickdiv;

        for (; header.tracks > 0; header.tracks--) {
                if (!ReadTrackChunk(file, *this)) {
                        goto cleanup;
                }
        }

        success = FixupMidiData(*this);

cleanup:
        FioFCloseFile(file);
        return success;
}


/**
 * Decoder for "MPS MIDI" format data.
 * This format for MIDI music is also used in a few other Microprose games contemporary with Transport Tycoon.
 *
 * The song data are usually packed inside a CAT file, with one CAT chunk per song. The song titles are used as names for the CAT chunks.
 *
 * Unlike the Standard MIDI File format, which is based on the IFF structure, the MPS MIDI format is best described as two linked lists of sub-tracks,
 * the first list contains a number of reusable "segments", and the second list contains the "master tracks". Each list is prefixed with a byte
 * giving the number of elements in the list, and the actual list is just a byte count (BE16 format) for the segment/track followed by the actual data,
 * there is no index as such, so the entire data must be seeked through to build an index.
 *
 * The actual MIDI data inside each track is almost standard MIDI, prefixing every event with a delay, encoded using the same variable-length format
 * used in SMF. A few status codes have changed meaning in MPS MIDI: 0xFE changes control from master track to a segment, 0xFD returns from a segment
 * to the master track, and 0xFF is used to end the song. (In Standard MIDI all those values must only occur in real-time data.)
 *
 * As implemented in the original decoder, there is no support for recursively calling segments from segments, i.e. code 0xFE must only occur in
 * a master track, and code 0xFD must only occur in a segment. There are no checks made for this, it's assumed that the only input data will ever
 * be the original game music, not music from other games, or new productions.
 *
 * Additionally, some program change and controller events are given special meaning, see comments in the code.
 */
struct MpsMachine {
        /** Starting parameter and playback status for one channel/track */
        struct Channel {
                byte cur_program;    ///< program selected, used for velocity scaling (lookup into programvelocities array)
                byte running_status; ///< last midi status code seen
                uint16 delay;        ///< frames until next command
                uint32 playpos;      ///< next byte to play this channel from
                uint32 startpos;     ///< start position of master track
                uint32 returnpos;    ///< next return position after playing a segment
                Channel() : cur_program(0xFF), running_status(0), delay(0), playpos(0), startpos(0), returnpos(0) { }
        };
        Channel channels[16];         ///< playback status for each MIDI channel
        std::vector<uint32> segments; ///< pointers into songdata to repeatable data segments
        int16 tempo_ticks;            ///< ticker that increments when playing a frame, decrements before playing a frame
        int16 current_tempo;          ///< threshold for actually playing a frame
        int16 initial_tempo;          ///< starting tempo of song
        bool shouldplayflag;          ///< not-end-of-song flag

        static const int TEMPO_RATE;
        static const byte programvelocities[128];

        const byte *songdata; ///< raw data array
        size_t songdatalen;   ///< length of song data
        MidiFile &target;     ///< recipient of data

        /** Overridden MIDI status codes used in the data format */
        enum MpsMidiStatus {
                MPSMIDIST_SEGMENT_RETURN = 0xFD, ///< resume playing master track from stored position
                MPSMIDIST_SEGMENT_CALL   = 0xFE, ///< store current position of master track playback, and begin playback of a segment
                MPSMIDIST_ENDSONG        = 0xFF, ///< immediately end the song
        };

        static void AddMidiData(MidiFile::DataBlock &block, byte b1, byte b2)
        {
                block.data.push_back(b1);
                block.data.push_back(b2);
        }
        static void AddMidiData(MidiFile::DataBlock &block, byte b1, byte b2, byte b3)
        {
                block.data.push_back(b1);
                block.data.push_back(b2);
                block.data.push_back(b3);
        }

        /**
         * Construct a TTD DOS music format decoder.
         * @param data Buffer of song data from CAT file, ownership remains with caller
         * @param length Length of the data buffer in bytes
         * @param target MidiFile object to add decoded data to
         */
        MpsMachine(const byte *data, size_t length, MidiFile &target)
                : songdata(data), songdatalen(length), target(target)
        {
                uint32 pos = 0;
                int loopmax;
                int loopidx;

                /* First byte is the initial "tempo" */
                this->initial_tempo = this->songdata[pos++];

                /* Next byte is a count of callable segments */
                loopmax = this->songdata[pos++];
                for (loopidx = 0; loopidx < loopmax; loopidx++) {
                        /* Segments form a linked list in the stream,
                         * first two bytes in each is an offset to the next.
                         * Two bytes between offset to next and start of data
                         * are unaccounted for. */
                        this->segments.push_back(pos + 4);
                        pos += FROM_LE16(*(const int16 *)(this->songdata + pos));
                }

                /* After segments follows list of master tracks for each channel,
                 * also prefixed with a byte counting actual tracks. */
                loopmax = this->songdata[pos++];
                for (loopidx = 0; loopidx < loopmax; loopidx++) {
                        /* Similar structure to segments list, but also has
                         * the MIDI channel number as a byte before the offset
                         * to next track. */
                        byte ch = this->songdata[pos++];
                        this->channels[ch].startpos = pos + 4;
                        pos += FROM_LE16(*(const int16 *)(this->songdata + pos));
                }
        }

        /**
         * Read an SMF-style variable length value (note duration) from songdata.
         * @param pos Position to read from, updated to point to next byte after the value read
         * @return Value read from data stream
         */
        uint16 ReadVariableLength(uint32 &pos)
        {
                byte b = 0;
                uint16 res = 0;
                do {
                        b = this->songdata[pos++];
                        res = (res << 7) + (b & 0x7F);
                } while (b & 0x80);
                return res;
        }

        /**
         * Prepare for playback from the beginning. Resets the song pointer for every track to the beginning.
         */
        void RestartSong()
        {
                for (int ch = 0; ch < 16; ch++) {
                        Channel &chandata = this->channels[ch];
                        if (chandata.startpos != 0) {
                                /* Active track, set position to beginning */
                                chandata.playpos = chandata.startpos;
                                chandata.delay = this->ReadVariableLength(chandata.playpos);
                        } else {
                                /* Inactive track, mark as such */
                                chandata.playpos = 0;
                                chandata.delay = 0;
                        }
                }
        }

        /**
         * Play one frame of data from one channel
         */
        uint16 PlayChannelFrame(MidiFile::DataBlock &outblock, int channel)
        {
                uint16 newdelay = 0;
                byte b1, b2;
                Channel &chandata = this->channels[channel];

                do {
                        /* Read command/status byte */
                        b1 = this->songdata[chandata.playpos++];

                        /* Command 0xFE, call segment from master track */
                        if (b1 == MPSMIDIST_SEGMENT_CALL) {
                                b1 = this->songdata[chandata.playpos++];
                                chandata.returnpos = chandata.playpos;
                                chandata.playpos = this->segments[b1];
                                newdelay = this->ReadVariableLength(chandata.playpos);
                                if (newdelay == 0) {
                                        continue;
                                }
                                return newdelay;
                        }

                        /* Command 0xFD, return from segment to master track */
                        if (b1 == MPSMIDIST_SEGMENT_RETURN) {
                                chandata.playpos = chandata.returnpos;
                                chandata.returnpos = 0;
                                newdelay = this->ReadVariableLength(chandata.playpos);
                                if (newdelay == 0) {
                                        continue;
                                }
                                return newdelay;
                        }

                        /* Command 0xFF, end of song */
                        if (b1 == MPSMIDIST_ENDSONG) {
                                this->shouldplayflag = false;
                                return 0;
                        }

                        /* Regular MIDI channel message status byte */
                        if (b1 >= 0x80) {
                                /* Save the status byte as running status for the channel
                                 * and read another byte for first parameter to command */
                                chandata.running_status = b1;
                                b1 = this->songdata[chandata.playpos++];
                        }

                        switch (chandata.running_status & 0xF0) {
                                case MIDIST_NOTEOFF:
                                case MIDIST_NOTEON:
                                        b2 = this->songdata[chandata.playpos++];
                                        if (b2 != 0) {
                                                /* Note on, read velocity and scale according to rules */
                                                int16 velocity;
                                                if (channel == 9) {
                                                        /* Percussion channel, fixed velocity scaling not in the table */
                                                        velocity = (int16)b2 * 0x50;
                                                } else {
                                                        /* Regular channel, use scaling from table */
                                                        velocity = b2 * programvelocities[chandata.cur_program];
                                                }
                                                b2 = (velocity / 128) & 0x00FF;
                                                AddMidiData(outblock, MIDIST_NOTEON + channel, b1, b2);
                                        } else {
                                                /* Note off */
                                                AddMidiData(outblock, MIDIST_NOTEON + channel, b1, 0);
                                        }
                                        break;
                                case MIDIST_CONTROLLER:
                                        b2 = this->songdata[chandata.playpos++];
                                        if (b1 == MIDICT_MODE_MONO) {
                                                /* Unknown what the purpose of this is.
                                                 * Occurs in "Can't get There from Here" and in "Aliens Ate my Railway" a few times each.
                                                 * Possibly intended to give hints to other (non-GM) music drivers decoding the song.
                                                 */
                                                break;
                                        } else if (b1 == 0) {
                                                /* Standard MIDI controller 0 is "bank select", override meaning to change tempo.
                                                 * This is not actually used in any of the original songs. */
                                                if (b2 != 0) {
                                                        this->current_tempo = ((int)b2) * 48 / 60;
                                                }
                                                break;
                                        } else if (b1 == MIDICT_EFFECTS1) {
                                                /* Override value of this controller, default mapping is Reverb Send Level according to MMA RP-023.
                                                 * Unknown what the purpose of this particular value is. */
                                                b2 = 30;
                                        }
                                        AddMidiData(outblock, MIDIST_CONTROLLER + channel, b1, b2);
                                        break;
                                case MIDIST_PROGCHG:
                                        if (b1 == 0x7E) {
                                                /* Program change to "Applause" is originally used
                                                 * to cause the song to loop, but that gets handled
                                                 * separately in the output driver here.
                                                 * Just end the song. */
                                                this->shouldplayflag = false;
                                                break;
                                        }
                                        /* Used for note velocity scaling lookup */
                                        chandata.cur_program = b1;
                                        /* Two programs translated to a third, this is likely to
                                         * provide three different velocity scalings of "brass". */
                                        if (b1 == 0x57 || b1 == 0x3F) {
                                                b1 = 0x3E;
                                        }
                                        AddMidiData(outblock, MIDIST_PROGCHG + channel, b1);
                                        break;
                                case MIDIST_PITCHBEND:
                                        b2 = this->songdata[chandata.playpos++];
                                        AddMidiData(outblock, MIDIST_PITCHBEND + channel, b1, b2);
                                        break;
                                default:
                                        break;
                        }

                        newdelay = this->ReadVariableLength(chandata.playpos);
                } while (newdelay == 0);

                return newdelay;
        }

        /**
         * Play one frame of data into a block.
         */
        bool PlayFrame(MidiFile::DataBlock &block)
        {
                /* Update tempo/ticks counter */
                this->tempo_ticks -= this->current_tempo;
                if (this->tempo_ticks > 0) {
                        return true;
                }
                this->tempo_ticks += TEMPO_RATE;

                /* Look over all channels, play those active */
                for (int ch = 0; ch < 16; ch++) {
                        Channel &chandata = this->channels[ch];
                        if (chandata.playpos != 0) {
                                if (chandata.delay == 0) {
                                        chandata.delay = this->PlayChannelFrame(block, ch);
                                }
                                chandata.delay--;
                        }
                }

                return this->shouldplayflag;
        }

        /**
         * Perform playback of whole song.
         */
        bool PlayInto()
        {
                /* Tempo seems to be handled as TEMPO_RATE = 148 ticks per second.
                 * Use this as the tickdiv, and define the tempo to be somewhat less than one second (1M microseconds) per quarter note.
                 * This value was found experimentally to give a very close approximation of the correct playback speed.
                 * MIDI software loading exported files will show a bogus tempo, but playback will be correct. */
                this->target.tickdiv = TEMPO_RATE;
                this->target.tempos.push_back(MidiFile::TempoChange(0, 980500));

                /* Initialize playback simulation */
                this->RestartSong();
                this->shouldplayflag = true;
                this->current_tempo = (int32)this->initial_tempo * 24 / 60;
                this->tempo_ticks = this->current_tempo;

                /* Always reset percussion channel to program 0 */
                this->target.blocks.push_back(MidiFile::DataBlock());
                AddMidiData(this->target.blocks.back(), MIDIST_PROGCHG+9, 0x00);

                /* Technically should be an endless loop, but having
                 * a maximum (about 10 minutes) avoids getting stuck,
                 * in case of corrupted data. */
                for (uint32 tick = 0; tick < 100000; tick+=1) {
                        this->target.blocks.push_back(MidiFile::DataBlock());
                        auto &block = this->target.blocks.back();
                        block.ticktime = tick;
                        if (!this->PlayFrame(block)) {
                                break;
                        }
                }
                return true;
        }
};
/** Frames/ticks per second for music playback */
const int MpsMachine::TEMPO_RATE = 148;
/** Base note velocities for various GM programs */
const byte MpsMachine::programvelocities[128] = {
        100, 100, 100, 100, 100,  90, 100, 100, 100, 100, 100,  90, 100, 100, 100, 100,
        100, 100,  85, 100, 100, 100, 100, 100, 100, 100, 100, 100,  90,  90, 110,  80,
        100, 100, 100,  90,  70, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
        100, 100,  90, 100, 100, 100, 100, 100, 100, 120, 100, 100, 100, 120, 100, 127,
        100, 100,  90, 100, 100, 100, 100, 100, 100,  95, 100, 100, 100, 100, 100, 100,
        100, 100, 100, 100, 100, 100, 100, 115, 100, 100, 100, 100, 100, 100, 100, 100,
        100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
        100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
};

/**
 * Create MIDI data from song data for the original Microprose music drivers.
 * @param data pointer to block of data
 * @param length size of data in bytes
 * @return true if the data could be loaded
 */
bool MidiFile::LoadMpsData(const byte *data, size_t length)
{
        _midifile_instance = this;

        MpsMachine machine(data, length, *this);
        return machine.PlayInto() && FixupMidiData(*this);
}

bool MidiFile::LoadSong(const MusicSongInfo &song)
{
        switch (song.filetype) {
                case MTT_STANDARDMIDI:
                        return this->LoadFile(song.filename);
                case MTT_MPSMIDI:
                {
                        size_t songdatalen = 0;
                        byte *songdata = GetMusicCatEntryData(song.filename, song.cat_index, songdatalen);
                        if (songdata != nullptr) {
                                bool result = this->LoadMpsData(songdata, songdatalen);
                                free(songdata);
                                return result;
                        } else {
                                return false;
                        }
                }
                default:
                        NOT_REACHED();
        }
}

/**
 * Move data from other to this, and clears other.
 * @param other object containing loaded data to take over
 */
void MidiFile::MoveFrom(MidiFile &other)
{
        std::swap(this->blocks, other.blocks);
        std::swap(this->tempos, other.tempos);
        this->tickdiv = other.tickdiv;

        _midifile_instance = this;

        other.blocks.clear();
        other.tempos.clear();
        other.tickdiv = 0;
}

static void WriteVariableLen(FILE *f, uint32 value)
{
        if (value <= 0x7F) {
                byte tb = value;
                fwrite(&tb, 1, 1, f);
        } else if (value <= 0x3FFF) {
                byte tb[2];
                tb[1] =  value & 0x7F;         value >>= 7;
                tb[0] = (value & 0x7F) | 0x80; value >>= 7;
                fwrite(tb, 1, sizeof(tb), f);
        } else if (value <= 0x1FFFFF) {
                byte tb[3];
                tb[2] =  value & 0x7F;         value >>= 7;
                tb[1] = (value & 0x7F) | 0x80; value >>= 7;
                tb[0] = (value & 0x7F) | 0x80; value >>= 7;
                fwrite(tb, 1, sizeof(tb), f);
        } else if (value <= 0x0FFFFFFF) {
                byte tb[4];
                tb[3] =  value & 0x7F;         value >>= 7;
                tb[2] = (value & 0x7F) | 0x80; value >>= 7;
                tb[1] = (value & 0x7F) | 0x80; value >>= 7;
                tb[0] = (value & 0x7F) | 0x80; value >>= 7;
                fwrite(tb, 1, sizeof(tb), f);
        }
}

/**
 * Write a Standard MIDI File containing the decoded music.
 * @param filename Name of file to write to
 * @return True if the file was written to completion
 */
bool MidiFile::WriteSMF(const char *filename)
{
        FILE *f = FioFOpenFile(filename, "wb", Subdirectory::NO_DIRECTORY);
        if (!f) {
                return false;
        }

        /* SMF header */
        const byte fileheader[] = {
                'M', 'T', 'h', 'd',     // block name
                0x00, 0x00, 0x00, 0x06, // BE32 block length, always 6 bytes
                0x00, 0x00,             // writing format 0 (all in one track)
                0x00, 0x01,             // containing 1 track (BE16)
                (byte)(this->tickdiv >> 8), (byte)this->tickdiv, // tickdiv in BE16
        };
        fwrite(fileheader, sizeof(fileheader), 1, f);

        /* Track header */
        const byte trackheader[] = {
                'M', 'T', 'r', 'k', // block name
                0, 0, 0, 0,         // BE32 block length, unknown at this time
        };
        fwrite(trackheader, sizeof(trackheader), 1, f);
        /* Determine position to write the actual track block length at */
        size_t tracksizepos = ftell(f) - 4;

        /* Write blocks in sequence */
        uint32 lasttime = 0;
        size_t nexttempoindex = 0;
        for (size_t bi = 0; bi < this->blocks.size(); bi++) {
                DataBlock &block = this->blocks[bi];
                TempoChange &nexttempo = this->tempos[nexttempoindex];

                uint32 timediff = block.ticktime - lasttime;

                /* Check if there is a tempo change before this block */
                if (nexttempo.ticktime < block.ticktime) {
                        timediff = nexttempo.ticktime - lasttime;
                }

                /* Write delta time for block */
                lasttime += timediff;
                bool needtime = false;
                WriteVariableLen(f, timediff);

                /* Write tempo change if there is one */
                if (nexttempo.ticktime <= block.ticktime) {
                        byte tempobuf[6] = { MIDIST_SMF_META, 0x51, 0x03, 0, 0, 0 };
                        tempobuf[3] = (nexttempo.tempo & 0x00FF0000) >> 16;
                        tempobuf[4] = (nexttempo.tempo & 0x0000FF00) >>  8;
                        tempobuf[5] = (nexttempo.tempo & 0x000000FF);
                        fwrite(tempobuf, sizeof(tempobuf), 1, f);
                        nexttempoindex++;
                        needtime = true;
                }
                /* If a tempo change occurred between two blocks, rather than
                 * at start of this one, start over with delta time for the block. */
                if (nexttempo.ticktime < block.ticktime) {
                        /* Start loop over at same index */
                        bi--;
                        continue;
                }

                /* Write each block data command */
                byte *dp = block.data.data();
                while (dp < block.data.data() + block.data.size()) {
                        /* Always zero delta time inside blocks */
                        if (needtime) {
                                fputc(0, f);
                        }
                        needtime = true;

                        /* Check message type and write appropriate number of bytes */
                        switch (*dp & 0xF0) {
                                case MIDIST_NOTEOFF:
                                case MIDIST_NOTEON:
                                case MIDIST_POLYPRESS:
                                case MIDIST_CONTROLLER:
                                case MIDIST_PITCHBEND:
                                        fwrite(dp, 1, 3, f);
                                        dp += 3;
                                        continue;
                                case MIDIST_PROGCHG:
                                case MIDIST_CHANPRESS:
                                        fwrite(dp, 1, 2, f);
                                        dp += 2;
                                        continue;
                        }

                        /* Sysex needs to measure length and write that as well */
                        if (*dp == MIDIST_SYSEX) {
                                fwrite(dp, 1, 1, f);
                                dp++;
                                byte *sysexend = dp;
                                while (*sysexend != MIDIST_ENDSYSEX) sysexend++;
                                ptrdiff_t sysexlen = sysexend - dp;
                                WriteVariableLen(f, sysexlen);
                                fwrite(dp, 1, sysexend - dp, f);
                                dp = sysexend + 1;
                                continue;
                        }

                        /* Fail for any other commands */
                        fclose(f);
                        return false;
                }
        }

        /* End of track marker */
        static const byte track_end_marker[] = { 0x00, MIDIST_SMF_META, 0x2F, 0x00 };
        fwrite(&track_end_marker, sizeof(track_end_marker), 1, f);

        /* Fill out the RIFF block length */
        size_t trackendpos = ftell(f);
        fseek(f, tracksizepos, SEEK_SET);
        uint32 tracksize = (uint32)(trackendpos - tracksizepos - 4); // blindly assume we never produce files larger than 2 GB
        tracksize = TO_BE32(tracksize);
        fwrite(&tracksize, 4, 1, f);

        fclose(f);
        return true;
}

/**
 * Get the name of a Standard MIDI File for a given song.
 * For songs already in SMF format, just returns the original.
 * Otherwise the song is converted, written to a temporary-ish file, and the written filename is returned.
 * @param song Song definition to query
 * @return Full filename string, empty string if failed
 */
std::string MidiFile::GetSMFFile(const MusicSongInfo &song)
{
        if (song.filetype == MTT_STANDARDMIDI) {
                std::string filename = FioFindFullPath(Subdirectory::BASESET_DIR, song.filename);
                if (!filename.empty()) return filename;
                filename = FioFindFullPath(Subdirectory::OLD_GM_DIR, song.filename);
                if (!filename.empty()) return filename;

                return std::string();
        }

        if (song.filetype != MTT_MPSMIDI) return std::string();

        char basename[MAX_PATH];
        {
                const char *fnstart = strrchr(song.filename, PATHSEPCHAR);
                if (fnstart == nullptr) {
                        fnstart = song.filename;
                } else {
                        fnstart++;
                }

                /* Remove all '.' characters from filename */
                char *wp = basename;
                for (const char *rp = fnstart; *rp != '\0'; rp++) {
                        if (*rp != '.') *wp++ = *rp;
                }
                *wp++ = '\0';
        }

        std::string tempdirname = FioGetDirectory(Searchpath::SP_AUTODOWNLOAD_DIR, Subdirectory::BASESET_DIR);
        tempdirname += basename;
        AppendPathSeparator(tempdirname);
        FioCreateDirectory(tempdirname);

        std::string output_filename = tempdirname + std::to_string(song.cat_index) + ".mid";

        if (FileExists(output_filename)) {
                /* If the file already exists, assume it's the correct decoded data */
                return output_filename;
        }

        byte *data;
        size_t datalen;
        data = GetMusicCatEntryData(song.filename, song.cat_index, datalen);
        if (data == nullptr) return std::string();

        MidiFile midifile;
        if (!midifile.LoadMpsData(data, datalen)) {
                free(data);
                return std::string();
        }
        free(data);

        if (midifile.WriteSMF(output_filename.c_str())) {
                return output_filename;
        } else {
                return std::string();
        }
}


static bool CmdDumpSMF(byte argc, char *argv[])
{
        if (argc == 0) {
                IConsolePrint(CC_HELP, "Write the current song to a Standard MIDI File. Usage: 'dumpsmf <filename>'.");
                return true;
        }
        if (argc != 2) {
                IConsolePrint(CC_WARNING, "You must specify a filename to write MIDI data to.");
                return false;
        }

        if (_midifile_instance == nullptr) {
                IConsolePrint(CC_ERROR, "There is no MIDI file loaded currently, make sure music is playing, and you're using a driver that works with raw MIDI.");
                return false;
        }

        char fnbuf[MAX_PATH] = { 0 };
        if (seprintf(fnbuf, lastof(fnbuf), "%s%s", FiosGetScreenshotDir(), argv[1]) >= (int)lengthof(fnbuf)) {
                IConsolePrint(CC_ERROR, "Filename too long.");
                return false;
        }
        IConsolePrint(CC_INFO, "Dumping MIDI to '{}'.", fnbuf);

        if (_midifile_instance->WriteSMF(fnbuf)) {
                IConsolePrint(CC_INFO, "File written successfully.");
                return true;
        } else {
                IConsolePrint(CC_ERROR, "An error occurred writing MIDI file.");
                return false;
        }
}

static void RegisterConsoleMidiCommands()
{
        static bool registered = false;
        if (!registered) {
                IConsole::CmdRegister("dumpsmf", CmdDumpSMF);
                registered = true;
        }
}

MidiFile::MidiFile()
{
        RegisterConsoleMidiCommands();
}

MidiFile::~MidiFile()
{
        if (_midifile_instance == this) {
                _midifile_instance = nullptr;
        }
}