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midiparser_s1d.cpp

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2001-2004 The ScummVM project
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.

 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * $Header: /cvsroot/scummvm/scummvm/simon/midiparser_s1d.cpp,v 1.9 2004/01/06 12:45:31 fingolfin Exp $
 *
 */

#include "stdafx.h"
#include "sound/midiparser.h"
#include "sound/mididrv.h"
#include "common/util.h"

#include <stdio.h>

namespace Simon {

/**
 * Simon 1 Demo version of MidiParser.
 *
 * This parser is the result of eyeballing the one MUS file that's included
 * with simon1demo. So there might be some things missing. I've tried to notate
 * question-mark areas where they occur.
 */
00038 class MidiParser_S1D : public MidiParser {
protected:
      byte *_data;
      bool _no_delta;

protected:
      void parseNextEvent (EventInfo &info);
      void resetTracking();
      uint32 readVLQ2(byte * &data);

public:
      MidiParser_S1D() : _data(0), _no_delta(false) {}

      bool loadMusic(byte *data, uint32 size);
};


// The VLQs for simon1demo seem to be
// in Little Endian format.
uint32 MidiParser_S1D::readVLQ2(byte * &data) {
      byte str;
      uint32 value = 0;
      int i;

      for (i = 0; i < 4; ++i) {
            str = data[0];
            ++data;
            value |= (str & 0x7F) << (i * 7);
            if (!(str & 0x80))
                  break;
      }
      return value;
}

void MidiParser_S1D::parseNextEvent(EventInfo &info) {
      info.start = _position._play_pos;
      info.delta = _no_delta ? 0 : readVLQ2(_position._play_pos);

      _no_delta = false;
      info.event = *(_position._play_pos++);
      if (info.command() < 0x8) {
            _no_delta = true;
            info.event += 0x80;
      }

      switch (info.command()) {
      case 0x8:
            info.basic.param1 = *(_position._play_pos++);
            info.basic.param2 = 0;
            info.length = 0;
            break;

      case 0x9:
            info.basic.param1 = *(_position._play_pos++);
            info.basic.param2 = *(_position._play_pos++); // I'm ASSUMING this byte is velocity!
            info.length = 0;
            break;

      case 0xC:
            info.basic.param1 = *(_position._play_pos++);
            info.basic.param2 = 0;
            ++_position._play_pos; // I have NO IDEA what the second byte is for.
            break;

      case 0xF:
            if (info.event == 0xFC) {
                  // This means End of Track.
                  // Rewrite in SMF (MIDI transmission) form.
                  info.event = 0xFF;
                  info.ext.type = 0x2F;
                  info.length = 0;
                  break;
            }
            // OTherwise fall through to default.

      default:
            printf ("MidiParser_S1D: Warning! Unexpected byte 0x%02X found!\n", (int) info.event);
            _abort_parse = true;
            _position._play_pos = 0;
      }
}

bool MidiParser_S1D::loadMusic(byte *data, uint32 size) {
      unloadMusic();

      byte *pos = data;
      if (*(pos++) != 0xFC) {
            printf ("Warning: Expected 0xFC header but found 0x%02X instead\n", (int) *pos);
            return false;
      }

      // The next 3 bytes MIGHT be tempo, but we skip them and use the default.
//    setTempo (*(pos++) | (*(pos++) << 8) | (*(pos++) << 16));
      pos += 3;

      // And now we're at the actual data. Only one track.
      _num_tracks = 1;
      _data = pos;
      _tracks[0] = pos;

      // Note that we assume the original data passed in
      // will persist beyond this call, i.e. we do NOT
      // copy the data to our own buffer. Take warning....
      resetTracking();
      setTempo(500000);
      setTrack(0);
      return true;
}

void MidiParser_S1D::resetTracking() {
      MidiParser::resetTracking();
      _no_delta = false;
}

MidiParser *MidiParser_createS1D() { return new MidiParser_S1D; }

} // End of namespace Simon

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