mod.c

MIDI解码程序(用VC编写)

	{			/* set reppos or repcnt ? */
	  /* set repcnt, so check if repcnt already is set, which means we
	     are already looping */
	  if (a->pat_repcnt)
	    a->pat_repcnt--;	/* already looping, decrease counter */
	  else
	    {
#if 0
	      /* this would make walker.xm, shipped with Xsoundtracker,
	         play correctly, but it's better to remain compatible
	         with FT2 */
	      if ((!(pf->flags & UF_NOWRAP)) || (a->pat_reppos != POS_NONE))
#endif
		a->pat_repcnt = nib;	/* not yet looping, so set repcnt */
	    }

	  if (a->pat_repcnt)
	    {			/* jump to reppos if repcnt>0 */
	      if (a->pat_reppos == POS_NONE)
		a->pat_reppos = mp.patpos - 1;
	      if (a->pat_reppos == -1)
		{
		  mp.pat_repcrazy = 1;
		  mp.patpos = 0;
		}
	      else
		mp.patpos = a->pat_reppos;
	    }
	  else
	    a->pat_reppos = POS_NONE;
	}
      else
	a->pat_reppos = mp.patpos - 1;	/* set reppos - can be (-1) */
      break;
    case 0x7:			/* set tremolo waveform */
      a->wavecontrol &= 0x0f;
      a->wavecontrol |= nib << 4;
      break;
    case 0x8:			/* set panning */
      if (nib <= 8)
	nib <<= 4;
      else
	nib *= 17;
      a->panning = pf->panning[mp.channel] = nib;
      break;
    case 0x9:			/* retrig note */
      /* only retrigger if data nibble > 0 */
      if (nib)
	{
	  if (!a->retrig)
	    {
	      /* when retrig counter reaches 0, reset counter and restart
	         the sample */
	      if (a->period)
		a->kick = KICK_NOTE;
	      a->retrig = nib;
	    }
	  a->retrig--;		/* countdown */
	}
      break;
    case 0xa:			/* fine volume slide up */
      if (mp.vbtick)
	break;
      a->tmpvolume += nib;
      if (a->tmpvolume > 64)
	a->tmpvolume = 64;
      break;
    case 0xb:			/* fine volume slide dn  */
      if (mp.vbtick)
	break;
      a->tmpvolume -= nib;
      if (a->tmpvolume < 0)
	a->tmpvolume = 0;
      break;
    case 0xc:			/* cut note */
      /* When mp.vbtick reaches the cut-note value, turn the volume to
         zero ( Just like on the amiga) */
      if (mp.vbtick >= nib)
	a->tmpvolume = 0;	/* just turn the volume down */
      break;
    case 0xd:			/* note delay */
      /* delay the start of the sample until mp.vbtick==nib */
      if (!mp.vbtick)
	a->notedelay = nib;
      else if (a->notedelay)
	a->notedelay--;
      break;
    case 0xe:			/* pattern delay */
      if (mp.vbtick)
	break;
      if (!mp.patdly2)
	mp.patdly = nib + 1;	/* only once, when vbtick=0 */
      break;
    case 0xf:			/* invert loop, not supported  */
      break;
    }
}

static void 
DoVibrato (void)
{
  UBYTE q;
  UWORD temp = 0;

  q = (a->vibpos >> 2) & 0x1f;

  switch (a->wavecontrol & 3)
    {
    case 0:			/* sine */
      temp = VibratoTable[q];
      break;
    case 1:			/* ramp down */
      q <<= 3;
      if (a->vibpos < 0)
	q = 255 - q;
      temp = q;
      break;
    case 2:			/* square wave */
      temp = 255;
      break;
    case 3:			/* random wave */
      temp = getrandom (256);
      break;
    }

  temp *= a->vibdepth;
  temp >>= 7;
  temp <<= 2;

  if (a->vibpos >= 0)
    a->period = a->tmpperiod + temp;
  else
    a->period = a->tmpperiod - temp;

  if (mp.vbtick)
    a->vibpos += a->vibspd;
}

static void 
DoTremolo (void)
{
  UBYTE q;
  UWORD temp = 0;

  q = (a->trmpos >> 2) & 0x1f;

  switch ((a->wavecontrol >> 4) & 3)
    {
    case 0:			/* sine */
      temp = VibratoTable[q];
      break;
    case 1:			/* ramp down */
      q <<= 3;
      if (a->trmpos < 0)
	q = 255 - q;
      temp = q;
      break;
    case 2:			/* square wave */
      temp = 255;
      break;
    case 3:			/* random wave */
      temp = getrandom (256);
      break;
    }
  temp *= a->trmdepth;
  temp >>= 6;

  if (a->trmpos >= 0)
    {
      a->volume = a->tmpvolume + temp;
      if (a->volume > 64)
	a->volume = 64;
    }
  else
    {
      a->volume = a->tmpvolume - temp;
      if (a->volume < 0)
	a->volume = 0;
    }

  if (mp.vbtick)
    a->trmpos += a->trmspd;
}

static void 
DoVolSlide (UBYTE dat)
{
  if (!mp.vbtick)
    return;

  if (dat & 0xf)
    {
      a->tmpvolume -= (dat & 0x0f);
      if (a->tmpvolume < 0)
	a->tmpvolume = 0;
    }
  else
    {
      a->tmpvolume += (dat >> 4);
      if (a->tmpvolume > 64)
	a->tmpvolume = 64;
    }
}

static void 
DoToneSlide (void)
{
  if (mp.vbtick)
    {
      int dist;

      /* We have to slide a->period towards a->wantedperiod, so compute the
         difference between those two values */
      dist = a->period - a->wantedperiod;

      /* if they are equal or if portamentospeed is too big ... */
      if ((!dist) || a->portspeed > abs (dist))
	/* ...make tmpperiod equal tperiod */
	a->tmpperiod = a->period = a->wantedperiod;
      else if (dist > 0)
	{
	  a->tmpperiod -= a->portspeed;
	  a->period -= a->portspeed;	/* dist>0, slide up */
	}
      else
	{
	  a->tmpperiod += a->portspeed;
	  a->period += a->portspeed;	/* dist<0, slide down */
	}
    }
  else
    a->tmpperiod = a->period;
}

static void 
DoArpeggio (UBYTE dat)
{
  UBYTE note = a->note;

  if (dat)
    {
      switch (mp.vbtick % 3)
	{
	case 1:
	  note += (dat >> 4);
	  break;
	case 2:
	  note += (dat & 0xf);
	  break;
	}
      a->period = GetPeriod ((UWORD) note << 1, a->speed);
      a->ownper = 1;
    }
}

/*========== Scream Tracker effects */

static void 
DoS3MVolSlide (UBYTE inf)
{
  UBYTE lo, hi;

  if (inf)
    a->s3mvolslide = inf;
  else
    inf = a->s3mvolslide;

  lo = inf & 0xf;
  hi = inf >> 4;

  if (!lo)
    {
      if ((mp.vbtick) || (pf->flags & UF_S3MSLIDES))
	a->tmpvolume += hi;
    }
  else if (!hi)
    {
      if ((mp.vbtick) || (pf->flags & UF_S3MSLIDES))
	a->tmpvolume -= lo;
    }
  else if (lo == 0xf)
    {
      if (!mp.vbtick)
	a->tmpvolume += (hi ? hi : 0xf);
    }
  else if (hi == 0xf)
    {
      if (!mp.vbtick)
	a->tmpvolume -= (lo ? lo : 0xf);
    }
  else
    return;

  if (a->tmpvolume < 0)
    a->tmpvolume = 0;
  else if (a->tmpvolume > 64)
    a->tmpvolume = 64;
}

static void 
DoS3MSlideDn (UBYTE inf)
{
  UBYTE hi, lo;

  if (inf)
    a->slidespeed = inf;
  else
    inf = a->slidespeed;

  hi = inf >> 4;
  lo = inf & 0xf;

  if (hi == 0xf)
    {
      if (!mp.vbtick)
	a->tmpperiod += (UWORD) lo << 2;
    }
  else if (hi == 0xe)
    {
      if (!mp.vbtick)
	a->tmpperiod += lo;
    }
  else
    {
      if (mp.vbtick)
	a->tmpperiod += (UWORD) inf << 2;
    }
}

static void 
DoS3MSlideUp (UBYTE inf)
{
  UBYTE hi, lo;

  if (inf)
    a->slidespeed = inf;
  else
    inf = a->slidespeed;

  hi = inf >> 4;
  lo = inf & 0xf;

  if (hi == 0xf)
    {
      if (!mp.vbtick)
	a->tmpperiod -= (UWORD) lo << 2;
    }
  else if (hi == 0xe)
    {
      if (!mp.vbtick)
	a->tmpperiod -= lo;
    }
  else
    {
      if (mp.vbtick)
	a->tmpperiod -= (UWORD) inf << 2;
    }
}

static void 
DoS3MTremor (UBYTE inf)
{
  UBYTE on, off;

  if (inf)
    a->s3mtronof = inf;
  else
    {
      inf = a->s3mtronof;
      if (!inf)
	return;
    }

  if (!mp.vbtick)
    return;

  on = (inf >> 4) + 1;
  off = (inf & 0xf) + 1;
  a->s3mtremor %= (on + off);
  a->volume = (a->s3mtremor < on) ? a->tmpvolume : 0;
  a->s3mtremor++;
}

static void 
DoS3MRetrig (UBYTE inf)
{
  if (inf)
    {
      a->s3mrtgslide = inf >> 4;
      a->s3mrtgspeed = inf & 0xf;
    }

  /* only retrigger if low nibble > 0 */
  if (a->s3mrtgspeed > 0)
    {
      if (!a->retrig)
	{
	  /* when retrig counter reaches 0, reset counter and restart the
	     sample */
	  if (a->kick != KICK_NOTE)
	    a->kick = KICK_KEYOFF;
	  a->retrig = a->s3mrtgspeed;

	  if ((mp.vbtick) || (pf->flags & UF_S3MSLIDES))
	    {
	      switch (a->s3mrtgslide)
		{
		case 1:
		case 2:
		case 3:
		case 4:
		case 5:
		  a->tmpvolume -= (1 << (a->s3mrtgslide - 1));
		  break;
		case 6:
		  a->tmpvolume = (2 * a->tmpvolume) / 3;
		  break;
		case 7:
		  a->tmpvolume >>= 1;
		  break;
		case 9:
		case 0xa:
		case 0xb:
		case 0xc:
		case 0xd:
		  a->tmpvolume += (1 << (a->s3mrtgslide - 9));
		  break;
		case 0xe:
		  a->tmpvolume = (3 * a->tmpvolume) >> 1;
		  break;
		case 0xf:
		  a->tmpvolume = a->tmpvolume << 1;
		  break;
		}
	      if (a->tmpvolume < 0)
		a->tmpvolume = 0;
	      else if (a->tmpvolume > 64)
		a->tmpvolume = 64;
	    }
	}
      a->retrig--;		/* countdown  */
    }
}

static void 
DoS3MSpeed (UBYTE speed)
{
  if (mp.vbtick || mp.patdly2)
    return;

  if (speed > 128)
    speed -= 128;
  if (speed)
    {
      mp.sngspd = speed;
      mp.vbtick = 0;
    }
}

static void 
DoS3MTempo (UBYTE tempo)
{
  if (mp.vbtick || mp.patdly2)
    return;

  mp.newbpm = (tempo < 32) ? 32 : tempo;
}

static void 
DoS3MFineVibrato (void)
{
  UBYTE q;
  UWORD temp = 0;

  q = (a->vibpos >> 2) & 0x1f;

  switch (a->wavecontrol & 3)
    {
    case 0:			/* sine */
      temp = VibratoTable[q];
      break;
    case 1:			/* ramp down */
      q <<= 3;
      if (a->vibpos < 0)
	q = 255 - q;
      temp = q;
      break;
    case 2:			/* square wave */
      temp = 255;
      break;
    case 3:			/* random */
      temp = getrandom (256);
      break;
    }

  temp *= a->vibdepth;
  temp >>= 8;

  if (a->vibpos >= 0)
    a->period = a->tmpperiod + temp;
  else
    a->period = a->tmpperiod - temp;

  a->vibpos += a->vibspd;
}

static void 
DoS3MTremolo (void)
{
  UBYTE q;
  UWORD temp = 0;

  q = (a->trmpos >> 2) & 0x1f;

  switch ((a->wavecontrol >> 4) & 3)
    {
    case 0:			/* sine */
      temp = VibratoTable[q];
      break;
    case 1:			/* ramp down */
      q <<= 3;
      if (a->trmpos < 0)
	q = 255 - q;
      temp = q;
      break;
    case 2:			/* square wave */
      temp = 255;
      break;
    case 3:			/* random */
      temp = getrandom (256);
      break;
    }

  temp *= a->trmdepth;
  temp >>= 7;

  if (a->trmpos >= 0)
    {
      a->volume = a->tmpvolume + temp;
      if (a->volume > 64)
	a->volume = 64;
    }
  else
    {
      a->volume = a->tmpvolume - temp;
      if (a->volume < 0)
	a->volume = 0;
    }

  if (mp.vbtick)
    a->trmpos += a->trmspd;
}

/*========== Fast Tracker effects */

static void 
DoXMVolSlide (UBYTE inf)
{
  UBYTE lo, hi;

  mp.explicitslides = 2;

  if (inf)
    a->s3mvolslide = inf;
  else
    inf = a->s3mvolslide;

  if (!mp.vbtick)
    return;

  lo = inf & 0xf;
  hi = inf >> 4;

  if (!hi)
    {
      a->tmpvolume -= lo;
      if (a->tmpvolume < 0)
	a->tmpvolume = 0;
    }
  else
    {
      a->tmpvolume += hi;
      if (a->tmpvolume > 64)
	a->tmpvolume = 64;
    }
}

static void