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 "../base_media_music.h"
#include "midi.h"
 
#include "../console_func.h"
#include "../console_internal.h"
 
#include "table/strings.h"
 
/* SMF reader based on description at: http://www.somascape.org/midi/tech/mfile.html */
 
 
static MidiFile *_midifile_instance = nullptr;
 
const uint8_t *MidiGetStandardSysexMessage(MidiSysexMessage msg, size_t &length)
{
  static uint8_t reset_gm_sysex[] = { 0xF0, 0x7E, 0x7F, 0x09, 0x01, 0xF7 };
  static uint8_t reset_gs_sysex[] = { 0xF0, 0x41, 0x10, 0x42, 0x12, 0x40, 0x00, 0x7F, 0x00, 0x41, 0xF7 };
  static uint8_t reset_xg_sysex[] = { 0xF0, 0x43, 0x10, 0x4C, 0x00, 0x00, 0x7E, 0x00, 0xF7 };
  static uint8_t 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();
  }
}
 
class ByteBuffer {
  std::vector<uint8_t> buf{};
  size_t pos = 0;
public:
  ByteBuffer(FileHandle &file, size_t len)
  {
    this->buf.resize(len);
    if (fread(this->buf.data(), 1, len, file) != len) {
      /* invalid state */
      this->buf.clear();
    }
  }
 
  bool IsValid() const
  {
    return !this->buf.empty();
  }
 
  bool IsEnd() const
  {
    return this->pos >= this->buf.size();
  }
 
  bool ReadByte(uint8_t &b)
  {
    if (this->IsEnd()) return false;
    b = this->buf[this->pos++];
    return true;
  }
 
  bool ReadVariableLength(uint32_t &res)
  {
    res = 0;
    uint8_t b = 0;
    do {
      if (this->IsEnd()) return false;
      b = this->buf[this->pos++];
      res = (res << 7) | (b & 0x7F);
    } while (b & 0x80);
    return true;
  }
 
  bool ReadBuffer(uint8_t *dest, size_t length)
  {
    if (this->IsEnd()) return false;
    if (this->buf.size() - this->pos < length) return false;
    std::copy(std::begin(this->buf) + this->pos, std::begin(this->buf) + this->pos + length, dest);
    this->pos += length;
    return true;
  }
 
  bool ReadDataBlock(MidiFile::DataBlock *dest, size_t length)
  {
    if (this->IsEnd()) return false;
    if (this->buf.size() - this->pos < length) return false;
    dest->data.insert(dest->data.end(), std::begin(this->buf) + this->pos, std::begin(this->buf) + this->pos + length);
    this->pos += length;
    return true;
  }
 
  bool Skip(size_t count)
  {
    if (this->IsEnd()) return false;
    if (this->buf.size() - this->pos < count) return false;
    this->pos += count;
    return true;
  }
 
  bool Rewind(size_t count)
  {
    if (count > this->pos) return false;
    this->pos -= count;
    return true;
  }
};
 
static bool ReadTrackChunk(FileHandle &file, MidiFile &target)
{
  uint8_t buf[4];
 
  const uint8_t 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_t chunk_length;
  if (fread(&chunk_length, 1, 4, file) != 4) {
    return false;
  }
  chunk_length = FROM_BE32(chunk_length);
 
  /* Limit chunk size to 1 MiB. */
  if (chunk_length > 1024 * 1024) return false;
 
  ByteBuffer chunk(file, chunk_length);
  if (!chunk.IsValid()) {
    return false;
  }
 
  MidiFile::DataBlock *block = &target.blocks.emplace_back();
 
  uint8_t last_status = 0;
  bool running_sysex = false;
  while (!chunk.IsEnd()) {
    /* Read deltatime for event, start new block */
    uint32_t deltatime = 0;
    if (!chunk.ReadVariableLength(deltatime)) {
      return false;
    }
    if (deltatime > 0) {
      block = &target.blocks.emplace_back(block->ticktime + deltatime);
    }
 
    /* Read status byte */
    uint8_t 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_t 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_t 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_t 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.empty()) {
    /* 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_t last_ticktime = 0;
  for (size_t i = 0; i < target.blocks.size(); i++) {
    MidiFile::DataBlock &block = target.blocks[i];
    if (block.data.empty()) {
      continue;
    } else if (block.ticktime > last_ticktime || merged_blocks.empty()) {
      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_t 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_t tickdiff = block.ticktime - last_ticktime;
      last_ticktime = block.ticktime;
      last_realtime += uint32_t(tickdiff * tempo.tempo / target.tickdiv);
      block.realtime = last_realtime;
      cur_block++;
    } else {
      /* tempo change occurs before this block */
      int64_t tickdiff = next_tempo.ticktime - last_ticktime;
      last_ticktime = next_tempo.ticktime;
      last_realtime += uint32_t(tickdiff * tempo.tempo / target.tickdiv); // current tempo until the tempo change
      cur_tempo++;
    }
  }
 
  return true;
}
 
bool MidiFile::ReadSMFHeader(const std::string &filename, SMFHeader &header)
{
  auto file = FioFOpenFile(filename, "rb", Subdirectory::BASESET_DIR);
  if (!file.has_value()) return false;
  bool result = ReadSMFHeader(*file, header);
  return result;
}
 
bool MidiFile::ReadSMFHeader(FileHandle &file, SMFHeader &header)
{
  /* Try to read header, fixed size */
  uint8_t 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 uint8_t magic[] = { 'M', 'T', 'h', 'd', 0x00, 0x00, 0x00, 0x06 };
  if (!std::ranges::equal(std::span(buffer, std::size(magic)), magic)) {
    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;
}
 
bool MidiFile::LoadFile(const std::string &filename)
{
  _midifile_instance = this;
 
  this->blocks.clear();
  this->tempos.clear();
  this->tickdiv = 0;
 
  auto file = FioFOpenFile(filename, "rb", Subdirectory::BASESET_DIR);
  if (!file.has_value()) return false;
 
  SMFHeader header;
  if (!ReadSMFHeader(*file, header)) return false;
 
  /* Only format 0 (single-track) and format 1 (multi-track single-song) are accepted for now */
  if (header.format != 0 && header.format != 1) return false;
  /* Doesn't support SMPTE timecode files */
  if ((header.tickdiv & 0x8000) != 0) return false;
  /* Ticks per beat / parts per quarter note should not be zero. */
  if (header.tickdiv == 0) return false;
 
  this->tickdiv = header.tickdiv;
 
  for (; header.tracks > 0; header.tracks--) {
    if (!ReadTrackChunk(*file, *this)) {
      return false;
    }
  }
 
  return FixupMidiData(*this);
}
 
 
struct MpsMachine {
  struct Channel {
    uint8_t cur_program = 0xFF; 
    uint8_t running_status = 0; 
    uint16_t delay = 0; 
    uint32_t playpos = 0; 
    uint32_t startpos = 0; 
    uint32_t returnpos = 0; 
  };
  std::array<Channel, 16> channels{}; 
  std::vector<uint32_t> segments{}; 
  int16_t tempo_ticks = 0; 
  int16_t current_tempo = 0; 
  int16_t initial_tempo = 0; 
  bool shouldplayflag = false; 
 
  static const int TEMPO_RATE;
  static const uint8_t programvelocities[128];
 
  const uint8_t *songdata = nullptr; 
  size_t songdatalen = 0; 
  MidiFile &target; 
 
  enum MpsMidiStatus : uint8_t {
    MPSMIDIST_SEGMENT_RETURN = 0xFD, 
    MPSMIDIST_SEGMENT_CALL   = 0xFE, 
    MPSMIDIST_ENDSONG        = 0xFF, 
  };
 
  static void AddMidiData(MidiFile::DataBlock &block, uint8_t b1, uint8_t b2)
  {
    block.data.push_back(b1);
    block.data.push_back(b2);
  }
  static void AddMidiData(MidiFile::DataBlock &block, uint8_t b1, uint8_t b2, uint8_t b3)
  {
    block.data.push_back(b1);
    block.data.push_back(b2);
    block.data.push_back(b3);
  }
 
  MpsMachine(const uint8_t *data, size_t length, MidiFile &target)
    : songdata(data), songdatalen(length), target(target)
  {
    uint32_t 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_t *)(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. */
      uint8_t ch = this->songdata[pos++];
      this->channels[ch].startpos = pos + 4;
      pos += FROM_LE16(*(const int16_t *)(this->songdata + pos));
    }
  }
 
  uint16_t ReadVariableLength(uint32_t &pos)
  {
    uint8_t b = 0;
    uint16_t res = 0;
    do {
      b = this->songdata[pos++];
      res = (res << 7) + (b & 0x7F);
    } while (b & 0x80);
    return res;
  }
 
  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;
      }
    }
  }
 
  uint16_t PlayChannelFrame(MidiFile::DataBlock &outblock, int channel)
  {
    uint16_t newdelay = 0;
    uint8_t 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_t velocity;
            if (channel == 9) {
              /* Percussion channel, fixed velocity scaling not in the table */
              velocity = (int16_t)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;
  }
 
  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;
  }
 
  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_t)this->initial_tempo * 24 / 60;
    this->tempo_ticks = this->current_tempo;
 
    /* Always reset percussion channel to program 0 */
    auto &data_block = this->target.blocks.emplace_back();
    AddMidiData(data_block, 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_t tick = 0; tick < 100000; tick += 1) {
      auto &block = this->target.blocks.emplace_back();
      block.ticktime = tick;
      if (!this->PlayFrame(block)) {
        break;
      }
    }
    return true;
  }
};
const int MpsMachine::TEMPO_RATE = 148;
const uint8_t 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,
};
 
bool MidiFile::LoadMpsData(const uint8_t *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:
    {
      auto songdata = GetMusicCatEntryData(song.filename, song.cat_index);
      if (songdata.has_value()) {
        bool result = this->LoadMpsData(songdata->data(), songdata->size());
        return result;
      } else {
        return false;
      }
    }
    default:
      NOT_REACHED();
  }
}
 
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(FileHandle &f, uint32_t value)
{
  if (value <= 0x7F) {
    uint8_t tb = value;
    fwrite(&tb, 1, 1, f);
  } else if (value <= 0x3FFF) {
    uint8_t 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) {
    uint8_t 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) {
    uint8_t 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);
  }
}
 
bool MidiFile::WriteSMF(const std::string &filename)
{
  auto of = FioFOpenFile(filename, "wb", Subdirectory::NO_DIRECTORY);
  if (!of.has_value()) return false;
  auto &f = *of;
 
  /* SMF header */
  const uint8_t 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)
    (uint8_t)(this->tickdiv >> 8), (uint8_t)this->tickdiv, // tickdiv in BE16
  };
  fwrite(fileheader, sizeof(fileheader), 1, f);
 
  /* Track header */
  const uint8_t 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_t 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_t 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) {
      uint8_t 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 */
    uint8_t *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++;
        uint8_t *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 */
      return false;
    }
  }
 
  /* End of track marker */
  static const uint8_t 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_t tracksize = (uint32_t)(trackendpos - tracksizepos - 4); // blindly assume we never produce files larger than 2 GB
  tracksize = TO_BE32(tracksize);
  fwrite(&tracksize, 4, 1, f);
 
  return true;
}
 
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.c_str(), PATHSEPCHAR);
    if (fnstart == nullptr) {
      fnstart = song.filename.c_str();
    } 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;
  }
 
  auto songdata = GetMusicCatEntryData(song.filename, song.cat_index);
  if (!songdata.has_value()) return std::string();
 
  MidiFile midifile;
  if (!midifile.LoadMpsData(songdata->data(), songdata->size())) {
    return std::string();
  }
 
  if (midifile.WriteSMF(output_filename)) {
    return output_filename;
  } else {
    return std::string();
  }
}
 
 
static bool CmdDumpSMF(uint8_t 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;
  }
 
  std::string filename = fmt::format("{}{}", FiosGetScreenshotDir(), argv[1]);
  IConsolePrint(CC_INFO, "Dumping MIDI to '{}'.", filename);
 
  if (_midifile_instance->WriteSMF(filename)) {
    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;
  }
}