readmidi.c

SDL_mixer 是一个基于 SDL 的混音器

static int read_track(int append)
{
  MidiEventList *meep;
  MidiEventList *next, *new;
  int32 len;
  char tmp[4];

  meep=evlist;
  if (append && meep)
    {
      /* find the last event in the list */
      for (; meep->next; meep=meep->next)
	;
      at=meep->event.time;
    }
  else
    at=0;

  /* Check the formalities */
  if ((SDL_RWread(rw,tmp,1,4) != 4) || (SDL_RWread(rw,&len,4,1) != 1))
    {
      ctl->cmsg(CMSG_ERROR, VERB_NORMAL,
	   "%s: Can't read track header.", current_filename);
      return -1;
    }
  len=BE_LONG(len);

  if (memcmp(tmp, "MTrk", 4))
    {
      ctl->cmsg(CMSG_ERROR, VERB_NORMAL,
	   "%s: Corrupt MIDI file.", current_filename);
      return -2;
    }

  for (;;)
    {
      if (!(new=read_midi_event())) /* Some kind of error  */
	return -2;

      if (new==MAGIC_EOT) /* End-of-track Hack. */
	{
	  return 0;
	}

      next=meep->next;
      while (next && (next->event.time < new->event.time))
	{
	  meep=next;
	  next=meep->next;
	}
	  
      new->next=next;
      meep->next=new;

      event_count++; /* Count the event. (About one?) */
      meep=new;
    }
}

/* Free the linked event list from memory. */
static void free_midi_list(void)
{
  MidiEventList *meep, *next;
  if (!(meep=evlist)) return;
  while (meep)
    {
      next=meep->next;
      free(meep);
      meep=next;
    }
  evlist=0;
}


static void xremap_percussion(int *banknumpt, int *this_notept, int this_kit) {
        int i, newmap;
        int banknum = *banknumpt;
        int this_note = *this_notept;
        int newbank, newnote;

        if (this_kit != 127 && this_kit != 126) return;

        for (i = 0; i < XMAPMAX; i++) {
                newmap = xmap[i][0];
                if (!newmap) return;
                if (this_kit == 127 && newmap != XGDRUM) continue;
                if (this_kit == 126 && newmap != SFXDRUM1) continue;
                if (xmap[i][1] != banknum) continue;
                if (xmap[i][3] != this_note) continue;
                newbank = xmap[i][2];
                newnote = xmap[i][4];
                if (newbank == banknum && newnote == this_note) return;
                if (!drumset[newbank]) return;
                *banknumpt = newbank;
                *this_notept = newnote;
                return;
        }
}

/* Allocate an array of MidiEvents and fill it from the linked list of
   events, marking used instruments for loading. Convert event times to
   samples: handle tempo changes. Strip unnecessary events from the list.
   Free the linked list. */
static MidiEvent *groom_list(int32 divisions,int32 *eventsp,int32 *samplesp)
{
  MidiEvent *groomed_list, *lp;
  MidiEventList *meep;
  int32 i, our_event_count, tempo, skip_this_event, new_value;
  int32 sample_cum, samples_to_do, at, st, dt, counting_time;

  int current_bank[MAXCHAN], current_banktype[MAXCHAN], current_set[MAXCHAN],
    current_kit[MAXCHAN], current_program[MAXCHAN];
  /* Or should each bank have its own current program? */
  int dset, dnote, drumsflag, mprog;

  for (i=0; i<MAXCHAN; i++)
    {
      current_bank[i]=0;
      current_banktype[i]=0;
      current_set[i]=0;
      current_kit[i]=channel[i].kit;
      current_program[i]=default_program;
    }

  tempo=500000;
  compute_sample_increment(tempo, divisions);

  /* This may allocate a bit more than we need */
  groomed_list=lp=safe_malloc(sizeof(MidiEvent) * (event_count+1));
  meep=evlist;

  our_event_count=0;
  st=at=sample_cum=0;
  counting_time=2; /* We strip any silence before the first NOTE ON. */

  for (i=0; i<event_count; i++)
    {
      skip_this_event=0;
      ctl->cmsg(CMSG_INFO, VERB_DEBUG_SILLY,
		"%6d: ch %2d: event %d (%d,%d)",
		meep->event.time, meep->event.channel + 1,
		meep->event.type, meep->event.a, meep->event.b);

      if (meep->event.type==ME_TEMPO)
	{
	  tempo=
	    meep->event.channel + meep->event.b * 256 + meep->event.a * 65536;
	  compute_sample_increment(tempo, divisions);
	  skip_this_event=1;
	}
      else if ((quietchannels & (1<<meep->event.channel)))
	skip_this_event=1;
      else switch (meep->event.type)
	{
	case ME_PROGRAM:

	  if (current_kit[meep->event.channel])
	    {
	      if (current_kit[meep->event.channel]==126)
		{
		  /* note request for 2nd sfx rhythm kit */
		  if (meep->event.a && drumset[SFXDRUM2])
		  {
			 current_kit[meep->event.channel]=125;
			 current_set[meep->event.channel]=SFXDRUM2;
		         new_value=SFXDRUM2;
		  }
		  else if (!meep->event.a && drumset[SFXDRUM1])
		  {
			 current_set[meep->event.channel]=SFXDRUM1;
		         new_value=SFXDRUM1;
		  }
		  else
		  {
		  	ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		       		"XG SFX drum set is undefined");
			skip_this_event=1;
		  	break;
		  }
		}
	      if (drumset[meep->event.a]) /* Is this a defined drumset? */
		new_value=meep->event.a;
	      else
		{
		  ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		       "Drum set %d is undefined", meep->event.a);
		  if (drumset[0])
		      new_value=meep->event.a=0;
		  else
		    {
			skip_this_event=1;
			break;
		    }
		}
	      if (current_set[meep->event.channel] != new_value)
		current_set[meep->event.channel]=new_value;
	      else 
		skip_this_event=1;
	    }
	  else
	    {
	      new_value=meep->event.a;
	      if ((current_program[meep->event.channel] != SPECIAL_PROGRAM)
		  && (current_program[meep->event.channel] != new_value))
		current_program[meep->event.channel] = new_value;
	      else
		skip_this_event=1;
	    }
	  break;

	case ME_NOTEON:
	  if (counting_time)
	    counting_time=1;

	  drumsflag = current_kit[meep->event.channel];

	  if (drumsflag) /* percussion channel? */
	    {
	      dset = current_set[meep->event.channel];
	      dnote=meep->event.a;
	      if (XG_System_On) xremap_percussion(&dset, &dnote, drumsflag);

	      /*if (current_config_pc42b) pcmap(&dset, &dnote, &mprog, &drumsflag);*/

	     if (drumsflag)
	     {
	      /* Mark this instrument to be loaded */
	      if (!(drumset[dset]->tone[dnote].layer))
	       {
		drumset[dset]->tone[dnote].layer=
		    MAGIC_LOAD_INSTRUMENT;
	       }
	      else drumset[dset]->tone[dnote].last_used
		 = current_tune_number;
	      if (!channel[meep->event.channel].name) channel[meep->event.channel].name=
		    drumset[dset]->name;
	     }
	    }

	  if (!drumsflag) /* not percussion */
	    {
	      int chan=meep->event.channel;
	      int banknum;

	      if (current_banktype[chan]) banknum=SFXBANK;
	      else banknum=current_bank[chan];

	      mprog = current_program[chan];

	      if (mprog==SPECIAL_PROGRAM)
		break;

	      if (XG_System_On && banknum==SFXBANK && !tonebank[SFXBANK] && tonebank[120]) 
		      banknum = 120;

	      /*if (current_config_pc42b) pcmap(&banknum, &dnote, &mprog, &drumsflag);*/

	     if (drumsflag)
	     {
	      /* Mark this instrument to be loaded */
	      if (!(drumset[dset]->tone[dnote].layer))
	       {
		drumset[dset]->tone[dnote].layer=MAGIC_LOAD_INSTRUMENT;
	       }
	      else drumset[dset]->tone[dnote].last_used = current_tune_number;
	      if (!channel[meep->event.channel].name) channel[meep->event.channel].name=
		    drumset[dset]->name;
	     }
	     if (!drumsflag)
	     {
	      /* Mark this instrument to be loaded */
	      if (!(tonebank[banknum]->tone[mprog].layer))
		{
		  tonebank[banknum]->tone[mprog].layer=MAGIC_LOAD_INSTRUMENT;
		}
	      else tonebank[banknum]->tone[mprog].last_used = current_tune_number;
	      if (!channel[meep->event.channel].name) channel[meep->event.channel].name=
		    tonebank[banknum]->tone[mprog].name;
	     }
	    }
	  break;

	case ME_TONE_KIT:
	  if (!meep->event.a || meep->event.a == 127)
	    {
	      new_value=meep->event.a;
	      if (current_kit[meep->event.channel] != new_value)
		current_kit[meep->event.channel]=new_value;
	      else 
		skip_this_event=1;
	      break;
	    }
	  else if (meep->event.a == 126)
	    {
	      if (drumset[SFXDRUM1]) /* Is this a defined tone bank? */
	        new_value=meep->event.a;
	      else
		{
	          ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		   "XG rhythm kit %d is undefined", meep->event.a);
	          skip_this_event=1;
	          break;
		}
	      current_set[meep->event.channel]=SFXDRUM1;
	      current_kit[meep->event.channel]=new_value;
	      break;
	    }
	  else if (meep->event.a != SFX_BANKTYPE)
	    {
	      ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		   "XG kit %d is impossible", meep->event.a);
	      skip_this_event=1;
	      break;
	    }

	  if (current_kit[meep->event.channel])
	    {
	      skip_this_event=1;
	      break;
	    }
	  if (tonebank[SFXBANK] || tonebank[120]) /* Is this a defined tone bank? */
	    new_value=SFX_BANKTYPE;
	  else 
	    {
	      ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		   "XG Sfx bank is undefined");
	      skip_this_event=1;
	      break;
	    }
	  if (current_banktype[meep->event.channel]!=new_value)
	    current_banktype[meep->event.channel]=new_value;
	  else
	    skip_this_event=1;
	  break;

	case ME_TONE_BANK:
	  if (current_kit[meep->event.channel])
	    {
	      skip_this_event=1;
	      break;
	    }
	  if (XG_System_On && meep->event.a > 0 && meep->event.a < 48) {
	      channel[meep->event.channel].variationbank=meep->event.a;
	      ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		   "XG variation bank %d", meep->event.a);
	      new_value=meep->event.a=0;
	  }
	  else if (tonebank[meep->event.a]) /* Is this a defined tone bank? */
	    new_value=meep->event.a;
	  else 
	    {
	      ctl->cmsg(CMSG_WARNING, VERB_VERBOSE,
		   "Tone bank %d is undefined", meep->event.a);
	      new_value=meep->event.a=0;
	    }

	  if (current_bank[meep->event.channel]!=new_value)
	    current_bank[meep->event.channel]=new_value;
	  else
	    skip_this_event=1;
	  break;

	case ME_HARMONICCONTENT:
	  channel[meep->event.channel].harmoniccontent=meep->event.a;
	  break;
	case ME_BRIGHTNESS:
	  channel[meep->event.channel].brightness=meep->event.a;
	  break;

	}

      /* Recompute time in samples*/
      if ((dt=meep->event.time - at) && !counting_time)
	{
	  samples_to_do=sample_increment * dt;
	  sample_cum += sample_correction * dt;
	  if (sample_cum & 0xFFFF0000)
	    {
	      samples_to_do += ((sample_cum >> 16) & 0xFFFF);
	      sample_cum &= 0x0000FFFF;
	    }
	  st += samples_to_do;
	}
      else if (counting_time==1) counting_time=0;
      if (!skip_this_event)
	{
	  /* Add the event to the list */
	  *lp=meep->event;
	  lp->time=st;
	  lp++;
	  our_event_count++;
	}
      at=meep->event.time;
      meep=meep->next;
    }
  /* Add an End-of-Track event */
  lp->time=st;
  lp->type=ME_EOT;
  our_event_count++;
  free_midi_list();
  
  *eventsp=our_event_count;
  *samplesp=st;
  return groomed_list;
}

MidiEvent *read_midi_file(SDL_RWops *mrw, int32 *count, int32 *sp)
{
  int32 len, divisions;
  int16 format, tracks, divisions_tmp;
  int i;
  char tmp[4];

  rw = mrw;
  event_count=0;
  at=0;
  evlist=0;

  GM_System_On=GS_System_On=XG_System_On=0;
  /* vol_table = def_vol_table; */
  XG_System_reverb_type=XG_System_chorus_type=XG_System_variation_type=0;
  memset(&drumvolume,-1,sizeof(drumvolume));
  memset(&drumchorusdepth,-1,sizeof(drumchorusdepth));
  memset(&drumreverberation,-1,sizeof(drumreverberation));
  memset(&drumpanpot,NO_PANNING,sizeof(drumpanpot));

  for (i=0; i<MAXCHAN; i++)
     {
	if (ISDRUMCHANNEL(i)) channel[i].kit = 127;
	else channel[i].kit = 0;
	channel[i].brightness = 64;
	channel[i].harmoniccontent = 64;
	channel[i].variationbank = 0;
	channel[i].chorusdepth = 0;
	channel[i].reverberation = 0;
	channel[i].transpose = 0;
     }

past_riff:

  if ((SDL_RWread(rw,tmp,1,4) != 4) || (SDL_RWread(rw,&len,4,1) != 1))
    {
     /* if (ferror(fp))
	{
	  ctl->cmsg(CMSG_ERROR, VERB_NORMAL, "%s: %s", current_filename, 
	       strerror(errno));
	}
      else*/
	ctl->cmsg(CMSG_ERROR, VERB_NORMAL, 
	     "%s: Not a MIDI file!", current_filename);
      return 0;
    }
  len=BE_LONG(len);

  if (!memcmp(tmp, "RIFF", 4))
    {
      SDL_RWread(rw,tmp,1,12);
      goto past_riff;
    }
  if (memcmp(tmp, "MThd", 4) || len < 6)
    {
      ctl->cmsg(CMSG_ERROR, VERB_NORMAL,
	   "%s: Not a MIDI file!", current_filename);
      return 0;
    }

  SDL_RWread(rw,&format, 2, 1);
  SDL_RWread(rw,&tracks, 2, 1);
  SDL_RWread(rw,&divisions_tmp, 2, 1);
  format=BE_SHORT(format);
  tracks=BE_SHORT(tracks);
  track_info = tracks;
  curr_track = 0;
  curr_title_track = -1;
  divisions_tmp=BE_SHORT(divisions_tmp);

  if (divisions_tmp<0)
    {
      /* SMPTE time -- totally untested. Got a MIDI file that uses this? */
      divisions=
	(int32)(-(divisions_tmp/256)) * (int32)(divisions_tmp & 0xFF);
    }
  else divisions=(int32)(divisions_tmp);

  if (len > 6)
    {
      ctl->cmsg(CMSG_WARNING, VERB_NORMAL, 
	   "%s: MIDI file header size %ld bytes", 
	   current_filename, len);
      SDL_RWseek(rw, len-6, SEEK_CUR); /* skip the excess */
    }
  if (format<0 || format >2)
    {
      ctl->cmsg(CMSG_ERROR, VERB_NORMAL, 
	   "%s: Unknown MIDI file format %d", current_filename, format);
      return 0;
    }
  ctl->cmsg(CMSG_INFO, VERB_VERBOSE, 
       "Format: %d  Tracks: %d  Divisions: %d", format, tracks, divisions);

  /* Put a do-nothing event first in the list for easier processing */
  evlist=safe_malloc(sizeof(MidiEventList));
  evlist->event.time=0;
  evlist->event.type=ME_NONE;
  evlist->next=0;
  event_count++;

  switch(format)
    {
    case 0:
      if (read_track(0))
	{
	  free_midi_list();
	  return 0;
	}
      else curr_track++;
      break;

    case 1:
      for (i=0; i<tracks; i++)
	if (read_track(0))
	  {
	    free_midi_list();
	    return 0;
	  }
      break;

    case 2: /* We simply play the tracks sequentially */
      for (i=0; i<tracks; i++)
	if (read_track(1))
	  {
	    free_midi_list();
	    return 0;
	  }
         else curr_track++;
      break;
    }
  return groom_list(divisions, count, sp);
}