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midi.c

/*         ______   ___    ___ 
 *        /\  _  \ /\_ \  /\_ \ 
 *        \ \ \L\ \\//\ \ \//\ \      __     __   _ __   ___ 
 *         \ \  __ \ \ \ \  \ \ \   /'__`\ /'_ `\/\`'__\/ __`\
 *          \ \ \/\ \ \_\ \_ \_\ \_/\  __//\ \L\ \ \ \//\ \L\ \
 *           \ \_\ \_\/\____\/\____\ \____\ \____ \ \_\\ \____/
 *            \/_/\/_/\/____/\/____/\/____/\/___L\ \/_/ \/___/
 *                                           /\____/
 *                                           \_/__/
 *
 *      The core MIDI file player.
 *
 *      By Shawn Hargreaves.
 *
 *      Pause and seek functions by George Foot.
 *
 *      get_midi_length by Elias Pschernig.
 *
 *      See readme.txt for copyright information.
 */


#include <limits.h>
#include <string.h>

#include "allegro.h"
#include "allegro/internal/aintern.h"



/* maximum number of layers in a single voice */
#define MIDI_LAYERS  4

/* how often the midi callback gets called maximally / second */
#define MIDI_TIMER_FREQUENCY 40


00038 typedef struct MIDI_TRACK                       /* a track in the MIDI file */
{
   unsigned char *pos;                          /* position in track data */
   long timer;                                  /* time until next event */
   unsigned char running_status;                /* last MIDI event */
} MIDI_TRACK;


00046 typedef struct MIDI_CHANNEL                     /* a MIDI channel */
{
   int patch;                                   /* current sound */
   int volume;                                  /* volume controller */
   int pan;                                     /* pan position */
   int pitch_bend;                              /* pitch bend position */
   int new_volume;                              /* cached volume change */
   int new_pitch_bend;                          /* cached pitch bend */
   int note[128][MIDI_LAYERS];                  /* status of each note */
} MIDI_CHANNEL;


typedef struct MIDI_VOICE                       /* a voice on the soundcard */
{
   int channel;                                 /* MIDI channel */
   int note;                                    /* note (-1 = off) */
   int volume;                                  /* note velocity */
   long time;                                   /* when note was triggered */
} MIDI_VOICE;


00067 typedef struct WAITING_NOTE                     /* a stored note-on request */
{
   int channel;
   int note;
   int volume;
} WAITING_NOTE;


00075 typedef struct PATCH_TABLE                      /* GM -> external synth */
{
   int bank1;                                   /* controller #0 */
   int bank2;                                   /* controller #32 */
   int prog;                                    /* program change */
   int pitch;                                   /* pitch shift */
} PATCH_TABLE;


volatile long midi_pos = -1;                    /* current position in MIDI file */
volatile long midi_time = 0;                    /* current position in seconds */
static volatile long midi_timers;               /* current position in allegro-timer-ticks */
static long midi_pos_counter;                   /* delta for midi_pos */

volatile long _midi_tick = 0;                   /* counter for killing notes */

static void midi_player(void);                  /* core MIDI player routine */
static void prepare_to_play(MIDI *midi);
static void midi_lock_mem(void);

static MIDI *midifile = NULL;                   /* the file that is playing */

static int midi_loop = 0;                       /* repeat at eof? */

long midi_loop_start = -1;                      /* where to loop back to */
long midi_loop_end = -1;                        /* loop at this position */

static int midi_semaphore = 0;                  /* reentrancy flag */
static int midi_loaded_patches = FALSE;         /* loaded entire patch set? */

static long midi_timer_speed;                   /* midi_player's timer speed */
static int midi_pos_speed;                      /* MIDI delta -> midi_pos */
static int midi_speed;                          /* MIDI delta -> timer */
static int midi_new_speed;                      /* for tempo change events */

static int old_midi_volume = -1;                /* stored global volume */

static int midi_alloc_channel;                  /* so _midi_allocate_voice */
static int midi_alloc_note;                     /* knows which note the */
static int midi_alloc_vol;                      /* sound is associated with */

static MIDI_TRACK midi_track[MIDI_TRACKS];      /* the active tracks */
static MIDI_VOICE midi_voice[MIDI_VOICES];      /* synth voice status */
static MIDI_CHANNEL midi_channel[16];           /* MIDI channel info */
static WAITING_NOTE midi_waiting[MIDI_VOICES];  /* notes still to be played */
static PATCH_TABLE patch_table[128];            /* GM -> external synth */

static int midi_seeking;                        /* set during seeks */
static int midi_looping;                        /* set during loops */

/* hook functions */
void (*midi_msg_callback)(int msg, int byte1, int byte2) = NULL;
void (*midi_meta_callback)(int type, AL_CONST unsigned char *data, int length) = NULL;
void (*midi_sysex_callback)(AL_CONST unsigned char *data, int length) = NULL;



/* lock_midi:
 *  Locks a MIDI file into physical memory. Pretty important, since they
 *  are mostly accessed inside interrupt handlers.
 */
void lock_midi(MIDI *midi)
{
   int c;
   ASSERT(midi);

   LOCK_DATA(midi, sizeof(MIDI));

   for (c=0; c<MIDI_TRACKS; c++) {
      if (midi->track[c].data) {
       LOCK_DATA(midi->track[c].data, midi->track[c].len);
      }
   }
}



/* load_midi:
 *  Loads a standard MIDI file, returning a pointer to a MIDI structure,
 *  or NULL on error. 
 */
MIDI *load_midi(AL_CONST char *filename)
{
   int c;
   char buf[4];
   long data;
   PACKFILE *fp;
   MIDI *midi;
   int num_tracks;
   ASSERT(filename);

   fp = pack_fopen(filename, F_READ);        /* open the file */
   if (!fp)
      return NULL;

   midi = malloc(sizeof(MIDI));              /* get some memory */
   if (!midi) {
      pack_fclose(fp);
      return NULL;
   }

   for (c=0; c<MIDI_TRACKS; c++) {
      midi->track[c].data = NULL;
      midi->track[c].len = 0;
   }

   pack_fread(buf, 4, fp); /* read midi header */

   /* Is the midi inside a .rmi file? */
   if (memcmp(buf, "RIFF", 4) == 0) { /* check for RIFF header */
      pack_mgetl(fp);

      while (!pack_feof(fp)) {
         pack_fread(buf, 4, fp); /* RMID chunk? */
         if (memcmp(buf, "RMID", 4) == 0) break;

         pack_fseek(fp, pack_igetl(fp)); /* skip to next chunk */
      }

      if (pack_feof(fp)) goto err;

      pack_mgetl(fp);
      pack_mgetl(fp);
      pack_fread(buf, 4, fp); /* read midi header */
   }

   if (memcmp(buf, "MThd", 4))
      goto err;

   pack_mgetl(fp);                           /* skip header chunk length */

   data = pack_mgetw(fp);                    /* MIDI file type */
   if ((data != 0) && (data != 1))
      goto err;

   num_tracks = pack_mgetw(fp);              /* number of tracks */
   if ((num_tracks < 1) || (num_tracks > MIDI_TRACKS))
      goto err;

   data = pack_mgetw(fp);                    /* beat divisions */
   midi->divisions = ABS(data);

   for (c=0; c<num_tracks; c++) {            /* read each track */
      pack_fread(buf, 4, fp);                /* read track header */
      if (memcmp(buf, "MTrk", 4))
       goto err;

      data = pack_mgetl(fp);                 /* length of track chunk */
      midi->track[c].len = data;

      midi->track[c].data = malloc(data);    /* allocate memory */
      if (!midi->track[c].data)
       goto err;
                                   /* finally, read track data */
      if (pack_fread(midi->track[c].data, data, fp) != data)
       goto err;
   }

   pack_fclose(fp);
   lock_midi(midi);
   return midi;

   /* oh dear... */
   err:
   pack_fclose(fp);
   destroy_midi(midi);
   return NULL;
}



/* destroy_midi:
 *  Frees the memory being used by a MIDI file.
 */
void destroy_midi(MIDI *midi)
{
   int c;

   if (midi == midifile)
      stop_midi();

   if (midi) {
      for (c=0; c<MIDI_TRACKS; c++) {
       if (midi->track[c].data) {
          UNLOCK_DATA(midi->track[c].data, midi->track[c].len);
          free(midi->track[c].data);
       }
      }

      UNLOCK_DATA(midi, sizeof(MIDI));
      free(midi);
   }
}



/* parse_var_len:
 *  The MIDI file format is a strange thing. Time offsets are only 32 bits,
 *  yet they are compressed in a weird variable length format. This routine 
 *  reads a variable length integer from a MIDI data stream. It returns the 
 *  number read, and alters the data pointer according to the number of
 *  bytes it used.
 */
static unsigned long parse_var_len(AL_CONST unsigned char **data)
{
   unsigned long val = **data & 0x7F;

   while (**data & 0x80) {
      (*data)++;
      val <<= 7;
      val += (**data & 0x7F);
   }

   (*data)++;
   return val;
}

END_OF_STATIC_FUNCTION(parse_var_len);



/* global_volume_fix:
 *  Converts a note volume, adjusting it according to the global 
 *  _midi_volume variable.
 */
static INLINE int global_volume_fix(int vol)
{
   if (_midi_volume >= 0)
      return (vol * _midi_volume) / 256;

   return vol;
}



/* sort_out_volume:
 *  Converts a note volume, adjusting it according to the channel volume
 *  and the global _midi_volume variable.
 */
static INLINE int sort_out_volume(int c, int vol)
{
   return global_volume_fix((vol * midi_channel[c].volume) / 128);
}



/* raw_program_change:
 *  Sends a program change message to a device capable of handling raw
 *  MIDI data, using patch mapping tables. Assumes that midi_driver->raw_midi
 *  isn't NULL, so check before calling it!
 */
static void raw_program_change(int channel, int patch)
{
   if (channel != 9) {
      /* bank change #1 */
      if (patch_table[patch].bank1 >= 0) {
       midi_driver->raw_midi(0xB0+channel);
       midi_driver->raw_midi(0);
       midi_driver->raw_midi(patch_table[patch].bank1);
      }

      /* bank change #2 */
      if (patch_table[patch].bank2 >= 0) {
       midi_driver->raw_midi(0xB0+channel);
       midi_driver->raw_midi(32);
       midi_driver->raw_midi(patch_table[patch].bank2);
      }

      /* program change */
      midi_driver->raw_midi(0xC0+channel);
      midi_driver->raw_midi(patch_table[patch].prog);

      /* update volume */
      midi_driver->raw_midi(0xB0+channel);
      midi_driver->raw_midi(7);
      midi_driver->raw_midi(global_volume_fix(midi_channel[channel].volume-1));
   }
}

END_OF_STATIC_FUNCTION(raw_program_change);



/* midi_note_off:
 *  Processes a MIDI note-off event.
 */
static void midi_note_off(int channel, int note)
{
   int done = FALSE;
   int voice, layer;
   int c;

   /* can we send raw MIDI data? */
   if (midi_driver->raw_midi) {
      if (channel != 9)
       note += patch_table[midi_channel[channel].patch].pitch;

      midi_driver->raw_midi(0x80+channel);
      midi_driver->raw_midi(note);
      midi_driver->raw_midi(0);
      return;
   }

   /* oh well, have to do it the long way... */
   for (layer=0; layer<MIDI_LAYERS; layer++) {
      voice = midi_channel[channel].note[note][layer];
      if (voice >= 0) {
       midi_driver->key_off(voice + midi_driver->basevoice);
       midi_voice[voice].note = -1;
       midi_voice[voice].time = _midi_tick;
       midi_channel[channel].note[note][layer] = -1; 
       done = TRUE;
      }
   }

   /* if the note isn't playing, it must still be in the waiting room */
   if (!done) {
      for (c=0; c<MIDI_VOICES; c++) {
       if ((midi_waiting[c].channel == channel) && 
           (midi_waiting[c].note == note)) {
          midi_waiting[c].note = -1;
          break;
       }
      }
   }
}

END_OF_STATIC_FUNCTION(midi_note_off);



/* sort_out_pitch_bend:
 *  MIDI pitch bend range is + or - two semitones. The low-level soundcard
 *  drivers can only handle bends up to +1 semitone. This routine converts
 *  pitch bends from MIDI format to our own format.
 */
static INLINE void sort_out_pitch_bend(int *bend, int *note)
{
   if (*bend == 0x2000) {
      *bend = 0;
      return;
   }

   (*bend) -= 0x2000;

   while (*bend < 0) {
      (*note)--;
      (*bend) += 0x1000;
   }

   while (*bend >= 0x1000) {
      (*note)++;
      (*bend) -= 0x1000;
   }
}



/* _midi_allocate_voice:
 *  Allocates a MIDI voice in the range min-max (inclusive). This is 
 *  intended to be called by the key_on() handlers in the MIDI driver, 
 *  and shouldn't be used by any other code.
 */
int _midi_allocate_voice(int min, int max)
{
   int c;
   int layer;
   int voice = -1;
   long best_time = LONG_MAX;

   if (min < 0)
      min = 0;

   if (max < 0)
      max = midi_driver->voices-1;

   /* which layer can we use? */
   for (layer=0; layer<MIDI_LAYERS; layer++)
      if (midi_channel[midi_alloc_channel].note[midi_alloc_note][layer] < 0)
       break; 

   if (layer >= MIDI_LAYERS)
      return -1;

   /* find a free voice */
   for (c=min; c<=max; c++) {
      if ((midi_voice[c].note < 0) && 
        (midi_voice[c].time < best_time) && 
        ((c < midi_driver->xmin) || (c > midi_driver->xmax))) {
       voice = c;
       best_time = midi_voice[c].time;
      }
   }

   /* if there are no free voices, kill a note to make room */
   if (voice < 0) {
      voice = -1;
      best_time = LONG_MAX;
      for (c=min; c<=max; c++) {
       if ((midi_voice[c].time < best_time) && 
           ((c < midi_driver->xmin) || (c > midi_driver->xmax))) {
          voice = c;
          best_time = midi_voice[c].time;
       }
      }
      if (voice >= 0)
       midi_note_off(midi_voice[voice].channel, midi_voice[voice].note);
      else
       return -1;
   }

   /* ok, we got it... */
   midi_voice[voice].channel = midi_alloc_channel;
   midi_voice[voice].note = midi_alloc_note;
   midi_voice[voice].volume = midi_alloc_vol;
   midi_voice[voice].time = _midi_tick;
   midi_channel[midi_alloc_channel].note[midi_alloc_note][layer] = voice; 

   return voice + midi_driver->basevoice;
}

END_OF_FUNCTION(_midi_allocate_voice);



/* midi_note_on:
 *  Processes a MIDI note-on event. Tries to find a free soundcard voice,
 *  and if it can't either cuts off an existing note, or if 'polite' is
 *  set, just stores the channel, note and volume in the waiting list.
 */
static void midi_note_on(int channel, int note, int vol, int polite)
{
   int c, layer, inst, bend, corrected_note;

   /* it's easy if the driver can handle raw MIDI data */
   if (midi_driver->raw_midi) {
      if (channel != 9)
       note += patch_table[midi_channel[channel].patch].pitch;

      midi_driver->raw_midi(0x90+channel);
      midi_driver->raw_midi(note);
      midi_driver->raw_midi(vol);
      return;
   }

   /* if the note is already on, turn it off */
   for (layer=0; layer<MIDI_LAYERS; layer++) {
      if (midi_channel[channel].note[note][layer] >= 0) {
       midi_note_off(channel, note);
       return;
      }
   }

   /* if zero volume and the note isn't playing, we can just ignore it */
   if (vol == 0)
      return;

   if (channel != 9) {
      /* are there any free voices? */
      for (c=0; c<midi_driver->voices; c++)
       if ((midi_voice[c].note < 0) && 
           ((c < midi_driver->xmin) || (c > midi_driver->xmax)))
          break;

      /* if there are no free voices, remember the note for later */
      if ((c >= midi_driver->voices) && (polite)) {
       for (c=0; c<MIDI_VOICES; c++) {
          if (midi_waiting[c].note < 0) {
             midi_waiting[c].channel = channel;
             midi_waiting[c].note = note;
             midi_waiting[c].volume = vol;
             break;
          }
       }
       return;
      }
   }

   /* drum sound? */
   if (channel == 9) {
      inst = 128+note;
      corrected_note = 60;
      bend = 0;
   }
   else {
      inst = midi_channel[channel].patch;
      corrected_note = note;
      bend = midi_channel[channel].pitch_bend;
      sort_out_pitch_bend(&bend, &corrected_note);
   }

   /* play the note */
   midi_alloc_channel = channel;
   midi_alloc_note = note;
   midi_alloc_vol = vol;

   midi_driver->key_on(inst, corrected_note, bend, 
                   sort_out_volume(channel, vol), 
                   midi_channel[channel].pan);
}

END_OF_STATIC_FUNCTION(midi_note_on);



/* all_notes_off:
 *  Turns off all active notes.
 */
static void all_notes_off(int channel)
{
   if (midi_driver->raw_midi) {
      midi_driver->raw_midi(0xB0+channel);
      midi_driver->raw_midi(123);
      midi_driver->raw_midi(0);
      return;
   }
   else {
      int note, layer;

      for (note=0; note<128; note++)
       for (layer=0; layer<MIDI_LAYERS; layer++)
          if (midi_channel[channel].note[note][layer] >= 0)
             midi_note_off(channel, note);
   }
}

END_OF_STATIC_FUNCTION(all_notes_off);



/* all_sound_off:
 *  Turns off sound.
 */
static void all_sound_off(int channel)
{
   if (midi_driver->raw_midi) {
      midi_driver->raw_midi(0xB0+channel);
      midi_driver->raw_midi(120);
      midi_driver->raw_midi(0);
      return;
   }
}

END_OF_STATIC_FUNCTION(all_sound_off);



/* reset_controllers:
 *  Resets volume, pan, pitch bend, etc, to default positions.
 */
static void reset_controllers(int channel)
{
   midi_channel[channel].new_volume = 128;
   midi_channel[channel].new_pitch_bend = 0x2000;

   switch (channel % 3) {
      case 0:  midi_channel[channel].pan = ((channel/3) & 1) ? 60 : 68; break;
      case 1:  midi_channel[channel].pan = 104; break;
      case 2:  midi_channel[channel].pan = 24; break;
   }

   if (midi_driver->raw_midi) {
      midi_driver->raw_midi(0xB0+channel);
      midi_driver->raw_midi(10);
      midi_driver->raw_midi(midi_channel[channel].pan);
   }
}

END_OF_STATIC_FUNCTION(reset_controllers);



/* update_controllers:
 *  Checks cached controller information and updates active voices.
 */
static void update_controllers(void)
{
   int c, c2, vol, bend, note;

   for (c=0; c<16; c++) {
      /* check for volume controller change */
      if ((midi_channel[c].volume != midi_channel[c].new_volume) || (old_midi_volume != _midi_volume)) {
       midi_channel[c].volume = midi_channel[c].new_volume;
       if (midi_driver->raw_midi) {
          midi_driver->raw_midi(0xB0+c);
          midi_driver->raw_midi(7);
          midi_driver->raw_midi(global_volume_fix(midi_channel[c].volume-1));
       }
       else {
          for (c2=0; c2<MIDI_VOICES; c2++) {
             if ((midi_voice[c2].channel == c) && (midi_voice[c2].note >= 0)) {
              vol = sort_out_volume(c, midi_voice[c2].volume);
              midi_driver->set_volume(c2 + midi_driver->basevoice, vol);
             }
          }
       }
      }

      /* check for pitch bend change */
      if (midi_channel[c].pitch_bend != midi_channel[c].new_pitch_bend) {
       midi_channel[c].pitch_bend = midi_channel[c].new_pitch_bend;
       if (midi_driver->raw_midi) {
          midi_driver->raw_midi(0xE0+c);
          midi_driver->raw_midi(midi_channel[c].pitch_bend & 0x7F);
          midi_driver->raw_midi(midi_channel[c].pitch_bend >> 7);
       }
       else {
          for (c2=0; c2<MIDI_VOICES; c2++) {
             if ((midi_voice[c2].channel == c) && (midi_voice[c2].note >= 0)) {
              bend = midi_channel[c].pitch_bend;
              note = midi_voice[c2].note;
              sort_out_pitch_bend(&bend, &note);
              midi_driver->set_pitch(c2 + midi_driver->basevoice, note, bend);
             }
          }
       }
      }
   }

   old_midi_volume = _midi_volume;
}

END_OF_STATIC_FUNCTION(update_controllers);



/* process_controller:
 *  Deals with a MIDI controller message on the specified channel.
 */
static void process_controller(int channel, int ctrl, int data)
{
   switch (ctrl) {

      case 7:                                   /* main volume */
       midi_channel[channel].new_volume = data+1;
       break;

      case 10:                                  /* pan */
       midi_channel[channel].pan = data;
       if (midi_driver->raw_midi) {
          midi_driver->raw_midi(0xB0+channel);
          midi_driver->raw_midi(10);
          midi_driver->raw_midi(data);
       }
       break;

      case 120:                                 /* all sound off */
       all_sound_off(channel);
       break;

      case 121:                                 /* reset all controllers */
       reset_controllers(channel);
       break;

      case 123:                                 /* all notes off */
      case 124:                                 /* omni mode off */
      case 125:                                 /* omni mode on */
      case 126:                                 /* poly mode off */
      case 127:                                 /* poly mode on */
       all_notes_off(channel);
       break;

      default:
       if (midi_driver->raw_midi) {
          midi_driver->raw_midi(0xB0+channel);
          midi_driver->raw_midi(ctrl);
          midi_driver->raw_midi(data);
       }
       break;
   }
}

END_OF_STATIC_FUNCTION(process_controller);



/* process_meta_event:
 *  Processes the next meta-event on the specified track.
 */
static void process_meta_event(AL_CONST unsigned char **pos, long *timer)
{
   unsigned char metatype = *((*pos)++);
   long length = parse_var_len(pos);
   long tempo;

   if (midi_meta_callback)
      midi_meta_callback(metatype, *pos, length);

   if (metatype == 0x2F) {                      /* end of track */
      *pos = NULL;
      *timer = LONG_MAX;
      return;
   }

   if (metatype == 0x51) {                      /* tempo change */
      tempo = (*pos)[0] * 0x10000L + (*pos)[1] * 0x100 + (*pos)[2];
      midi_new_speed = (tempo/1000) * (TIMERS_PER_SECOND/1000);
      midi_new_speed /= midifile->divisions;
   }

   (*pos) += length;
}

END_OF_STATIC_FUNCTION(process_meta_event);



/* process_midi_event:
 *  Processes the next MIDI event on the specified track.
 */
static void process_midi_event(AL_CONST unsigned char **pos, unsigned char *running_status, long *timer)
{
   unsigned char byte1, byte2; 
   int channel;
   unsigned char event;
   long l;

   event = *((*pos)++); 

   if (event & 0x80) {                          /* regular message */
      /* no running status for sysex and meta-events! */
      if ((event != 0xF0) && (event != 0xF7) && (event != 0xFF))
       *running_status = event;
      byte1 = (*pos)[0];
      byte2 = (*pos)[1];
   }
   else {                                       /* use running status */
      byte1 = event; 
      byte2 = (*pos)[0];
      event = *running_status; 
      (*pos)--;
   }

   /* program callback? */
   if ((midi_msg_callback) && 
       (event != 0xF0) && (event != 0xF7) && (event != 0xFF))
      midi_msg_callback(event, byte1, byte2);

   channel = event & 0x0F;

   switch (event>>4) {

      case 0x08:                                /* note off */
       midi_note_off(channel, byte1);
       (*pos) += 2;
       break;

      case 0x09:                                /* note on */
       midi_note_on(channel, byte1, byte2, 1);
       (*pos) += 2;
       break;

      case 0x0A:                                /* note aftertouch */
       (*pos) += 2;
       break;

      case 0x0B:                                /* control change */
       process_controller(channel, byte1, byte2);
       (*pos) += 2;
       break;

      case 0x0C:                                /* program change */
       midi_channel[channel].patch = byte1;
       if (midi_driver->raw_midi)
          raw_program_change(channel, byte1);
       (*pos) += 1;
       break;

      case 0x0D:                                /* channel aftertouch */
       (*pos) += 1;
       break;

      case 0x0E:                                /* pitch bend */
       midi_channel[channel].new_pitch_bend = byte1 + (byte2<<7);
       (*pos) += 2;
       break;

      case 0x0F:                                /* special event */
       switch (event) {
          case 0xF0:                          /* sysex */
          case 0xF7: 
             l = parse_var_len(pos);
             if (midi_sysex_callback)
              midi_sysex_callback(*pos, l);
             (*pos) += l;
             break;

          case 0xF2:                          /* song position */
             (*pos) += 2;
             break;

          case 0xF3:                          /* song select */
             (*pos)++;
             break;

          case 0xFF:                          /* meta-event */
             process_meta_event(pos, timer);
             break;

          default:
             /* the other special events don't have any data bytes,
              so we don't need to bother skipping past them */
             break;
       }
       break;

      default:
       /* something has gone badly wrong if we ever get to here */
       break;
   }
}

END_OF_STATIC_FUNCTION(process_midi_event);



/* midi_player:
 *  The core MIDI player: to be used as a timer callback.
 */
static void midi_player(void)
{
   int c;
   long l;
   int active;

   if (!midifile)
      return;

   if (midi_semaphore) {
      midi_timer_speed += BPS_TO_TIMER(MIDI_TIMER_FREQUENCY);
      install_int_ex(midi_player, BPS_TO_TIMER(MIDI_TIMER_FREQUENCY));
      return;
   }

   midi_semaphore = TRUE;
   _midi_tick++;

   midi_timers += midi_timer_speed;
   midi_time = midi_timers / TIMERS_PER_SECOND;

   do_it_all_again:

   for (c=0; c<MIDI_VOICES; c++)
      midi_waiting[c].note = -1;

   /* deal with each track in turn... */
   for (c=0; c<MIDI_TRACKS; c++) { 
      if (midi_track[c].pos) {
       midi_track[c].timer -= midi_timer_speed;

       /* while events are waiting, process them */
       while (midi_track[c].timer <= 0) { 
          process_midi_event((AL_CONST unsigned char**) &midi_track[c].pos, 
                         &midi_track[c].running_status,
                         &midi_track[c].timer); 

          /* read next time offset */
          if (midi_track[c].pos) { 
             l = parse_var_len((AL_CONST unsigned char**) &midi_track[c].pos);
             l *= midi_speed;
             midi_track[c].timer += l;
          }
       }
      }
   }

   /* update global position value */
   midi_pos_counter -= midi_timer_speed;
   while (midi_pos_counter <= 0) {
      midi_pos_counter += midi_pos_speed;
      midi_pos++;
   }

   /* tempo change? */
   if (midi_new_speed > 0) {
      for (c=0; c<MIDI_TRACKS; c++) {
       if (midi_track[c].pos) {
          midi_track[c].timer /= midi_speed;
          midi_track[c].timer *= midi_new_speed;
       }
      }
      midi_pos_counter /= midi_speed;
      midi_pos_counter *= midi_new_speed;

      midi_speed = midi_new_speed;
      midi_pos_speed = midi_new_speed * midifile->divisions;
      midi_new_speed = -1;
   }

   /* figure out how long until we need to be called again */
   active = 0;
   midi_timer_speed = LONG_MAX;
   for (c=0; c<MIDI_TRACKS; c++) {
      if (midi_track[c].pos) {
       active = 1;
       if (midi_track[c].timer < midi_timer_speed)
          midi_timer_speed = midi_track[c].timer;
      }
   }

   /* end of the music? */
   if ((!active) || ((midi_loop_end > 0) && (midi_pos >= midi_loop_end))) {
      if ((midi_loop) && (!midi_looping)) {
       if (midi_loop_start > 0) {
          remove_int(midi_player);
          midi_semaphore = FALSE;
          midi_looping = TRUE;
          if (midi_seek(midi_loop_start) != 0) {
             midi_looping = FALSE;
             stop_midi(); 
             return;
          }
          midi_looping = FALSE;
          midi_semaphore = TRUE;
          goto do_it_all_again;
       }
       else {
          for (c=0; c<16; c++) {
             all_notes_off(c);
             all_sound_off(c);
          }
          prepare_to_play(midifile);
          goto do_it_all_again;
       }
      }
      else {
       stop_midi(); 
       midi_semaphore = FALSE;
       return;
      }
   }

   /* reprogram the timer */
   if (midi_timer_speed < BPS_TO_TIMER(MIDI_TIMER_FREQUENCY))
      midi_timer_speed = BPS_TO_TIMER(MIDI_TIMER_FREQUENCY);

   if (!midi_seeking) 
      install_int_ex(midi_player, midi_timer_speed);

   /* controller changes are cached and only processed here, so we can 
      condense streams of controller data into just a few voice updates */ 
   update_controllers();

   /* and deal with any notes that are still waiting to be played */
   for (c=0; c<MIDI_VOICES; c++)
      if (midi_waiting[c].note >= 0)
       midi_note_on(midi_waiting[c].channel, midi_waiting[c].note,
                  midi_waiting[c].volume, 0);

   midi_semaphore = FALSE;
}

END_OF_STATIC_FUNCTION(midi_player);



/* midi_init:
 *  Sets up the MIDI player ready for use. Returns non-zero on failure.
 */
static int midi_init(void)
{
   int c, c2, c3;
   char **argv;
   int argc;
   char buf[32], tmp[64];

   midi_loaded_patches = FALSE;

   midi_lock_mem();

   for (c=0; c<16; c++) {
      midi_channel[c].volume = midi_channel[c].new_volume = 128;
      midi_channel[c].pitch_bend = midi_channel[c].new_pitch_bend = 0x2000;

      for (c2=0; c2<128; c2++)
       for (c3=0; c3<MIDI_LAYERS; c3++)
          midi_channel[c].note[c2][c3] = -1;
   }

   for (c=0; c<MIDI_VOICES; c++) {
      midi_voice[c].note = -1;
      midi_voice[c].time = 0;
   }

   for (c=0; c<128; c++) {
      uszprintf(buf, sizeof(buf), uconvert_ascii("p%d", tmp), c+1);
      argv = get_config_argv(uconvert_ascii("midimap", tmp), buf, &argc);

      if ((argv) && (argc == 4)) {
       patch_table[c].bank1 = ustrtol(argv[0], NULL, 0);
       patch_table[c].bank2 = ustrtol(argv[1], NULL, 0);
       patch_table[c].prog  = ustrtol(argv[2], NULL, 0);
       patch_table[c].pitch = ustrtol(argv[3], NULL, 0);
      }
      else {
       patch_table[c].bank1 = -1;
       patch_table[c].bank2 = -1;
       patch_table[c].prog = c;
       patch_table[c].pitch = 0;
      }
   }

   register_datafile_object(DAT_MIDI, NULL, (void (*)(void *))destroy_midi);

   return 0;
}



/* midi_exit:
 *  Turns off all active notes and removes the timer handler.
 */
static void midi_exit(void)
{
   stop_midi();
}



/* load_patches:
 *  Scans through a MIDI file and identifies which patches it uses, passing
 *  them to the soundcard driver so it can load whatever samples are
 *  neccessary.
 */
static int load_patches(MIDI *midi)
{
   char patches[128], drums[128];
   unsigned char *p, *end;
   unsigned char running_status, event;
   long l;
   int c;
   ASSERT(midi);

   for (c=0; c<128; c++)                        /* initialise to unused */
      patches[c] = drums[c] = FALSE;

   patches[0] = TRUE;                           /* always load the piano */

   for (c=0; c<MIDI_TRACKS; c++) {              /* for each track... */
      p = midi->track[c].data;
      end = p + midi->track[c].len;
      running_status = 0;

      while (p < end) {                         /* work through data stream */
#ifdef ALLEGRO_BEOS
         /* Is there a bug in this routine, or in gcc under BeOS/x86? --PW */
         { int i; for (i=1; i; i--); }
#endif
       event = *p; 
       if (event & 0x80) {                    /* regular message */
          p++;
          if ((event != 0xF0) && (event != 0xF7) && (event != 0xFF))
             running_status = event;
       }
       else                                   /* use running status */
          event = running_status; 

       switch (event>>4) {

          case 0x0C:                          /* program change! */
             patches[*p] = TRUE;
             p++;
             break;

          case 0x09:                          /* note on, is it a drum? */
             if ((event & 0x0F) == 9)
              drums[*p] = TRUE;
             p += 2;
             break;

          case 0x08:                          /* note off */
          case 0x0A:                          /* note aftertouch */
          case 0x0B:                          /* control change */
          case 0x0E:                          /* pitch bend */
             p += 2;
             break;

          case 0x0D:                          /* channel aftertouch */
             p += 1;
             break;

          case 0x0F:                          /* special event */
             switch (event) {
              case 0xF0:                    /* sysex */
              case 0xF7: 
                 l = parse_var_len((AL_CONST unsigned char**) &p);
                 p += l;
                 break;

              case 0xF2:                    /* song position */
                 p += 2;
                 break;

              case 0xF3:                    /* song select */
                 p++;
                 break;

              case 0xFF:                    /* meta-event */
                 p++;
                 l = parse_var_len((AL_CONST unsigned char**) &p);
                 p += l;
                 break;

              default:
                 /* the other special events don't have any data bytes,
                  so we don't need to bother skipping past them */
                 break;
             }
             break;

          default:
             /* something has gone badly wrong if we ever get to here */
             break;
       }

       if (p < end)                           /* skip time offset */
          parse_var_len((AL_CONST unsigned char**) &p);
      }
   }

   /* tell the driver to do its stuff */ 
   return midi_driver->load_patches(patches, drums);
}



/* prepare_to_play:
 *  Sets up all the global variables needed to play the specified file.
 */
static void prepare_to_play(MIDI *midi)
{
   int c;
   ASSERT(midi);

   for (c=0; c<16; c++)
      reset_controllers(c);

   update_controllers();

   midifile = midi;
   midi_pos = 0;
   midi_timers = 0;
   midi_time = 0;
   midi_pos_counter = 0;
   midi_speed = TIMERS_PER_SECOND / 2 / midifile->divisions;   /* 120 bpm */
   midi_new_speed = -1;
   midi_pos_speed = midi_speed * midifile->divisions;
   midi_timer_speed = 0;
   midi_seeking = 0;
   midi_looping = 0;

   for (c=0; c<16; c++) {
      midi_channel[c].patch = 0;
      if (midi_driver->raw_midi)
       raw_program_change(c, 0);
   }

   for (c=0; c<MIDI_TRACKS; c++) {
      if (midi->track[c].data) {
       midi_track[c].pos = midi->track[c].data;
       midi_track[c].timer = parse_var_len((AL_CONST unsigned char**) &midi_track[c].pos);
       midi_track[c].timer *= midi_speed;
      }
      else {
       midi_track[c].pos = NULL;
       midi_track[c].timer = LONG_MAX;
      }
      midi_track[c].running_status = 0;
   }
}

END_OF_STATIC_FUNCTION(prepare_to_play);



/* play_midi:
 *  Starts playing the specified MIDI file. If loop is set, the MIDI file 
 *  will be repeated until replaced with something else, otherwise it will 
 *  stop at the end of the file. Passing a NULL MIDI file will stop whatever 
 *  music is currently playing: allegro.h defines the macro stop_midi() to 
 *  be play_midi(NULL, FALSE); Returns non-zero if an error occurs (this
 *  may happen if a patch-caching wavetable driver is unable to load the
 *  required samples).
 */
int play_midi(MIDI *midi, int loop)
{
   int c;

   remove_int(midi_player);

   for (c=0; c<16; c++) {
      all_notes_off(c);
      all_sound_off(c);
   }

   if (midi) {
      if (!midi_loaded_patches)
       if (load_patches(midi) != 0)
          return -1;

      midi_loop = loop;
      midi_loop_start = -1;
      midi_loop_end = -1;

      prepare_to_play(midi);

      /* arbitrary speed, midi_player() will adjust it */
      install_int(midi_player, 20);
   }
   else {
      midifile = NULL;

      if (midi_pos > 0)
       midi_pos = -midi_pos;
      else if (midi_pos == 0)
       midi_pos = -1;
   }

   return 0;
}

END_OF_FUNCTION(play_midi);



/* play_looped_midi:
 *  Like play_midi(), but the file loops from the specified end position
 *  back to the specified start position (the end position can be -1 to 
 *  indicate the end of the file).
 */
int play_looped_midi(MIDI *midi, int loop_start, int loop_end)
{
   if (play_midi(midi, TRUE) != 0)
      return -1;

   midi_loop_start = loop_start;
   midi_loop_end = loop_end;

   return 0;
}



/* stop_midi:
 *  Stops whatever MIDI file is currently playing.
 */
void stop_midi(void)
{
   play_midi(NULL, FALSE);
}

END_OF_FUNCTION(stop_midi);



/* midi_pause:
 *  Pauses the currently playing MIDI file.
 */
void midi_pause(void)
{
   int c;

   if (!midifile)
      return;

   remove_int(midi_player);

   for (c=0; c<16; c++) {
      all_notes_off(c);
      all_sound_off(c);
   }
}

END_OF_FUNCTION(midi_pause);



/* midi_resume:
 *  Resumes playing a paused MIDI file.
 */
void midi_resume(void)
{
   if (!midifile)
      return;

   install_int_ex(midi_player, midi_timer_speed);
}

END_OF_FUNCTION(midi_resume);



/* midi_seek:
 *  Seeks to the given midi_pos in the current MIDI file. If the target 
 *  is earlier in the file than the current midi_pos it seeks from the 
 *  beginning; otherwise it seeks from the current position. Returns zero 
 *  if successful, non-zero if it hit the end of the file (1 means it 
 *  stopped playing, 2 means it looped back to the start).
 */
int midi_seek(int target)
{
   int old_midi_loop;
   MIDI *old_midifile;
   MIDI_DRIVER *old_driver;
   int old_patch[16];
   int old_volume[16];
   int old_pan[16];
   int old_pitch_bend[16];
   int c;

   if (!midifile)
      return -1;

   /* first stop the player */
   midi_pause();

   /* store current settings */
   for (c=0; c<16; c++) {
      old_patch[c] = midi_channel[c].patch;
      old_volume[c] = midi_channel[c].volume;
      old_pan[c] = midi_channel[c].pan;
      old_pitch_bend[c] = midi_channel[c].pitch_bend;
   }

   /* save some variables and give temporary values */
   old_driver = midi_driver;
   midi_driver = &_midi_none;
   old_midi_loop = midi_loop;
   midi_loop = 0;
   old_midifile = midifile;

   /* set flag to tell midi_player not to reinstall itself */
   midi_seeking = 1;

   /* are we seeking backwards? If so, skip back to the start of the file */
   if (target <= midi_pos)
      prepare_to_play(midifile);

   /* now sit back and let midi_player get to the position */
   while ((midi_pos < target) && (midi_pos >= 0)) {
      int mmpc = midi_pos_counter;
      int mmp = midi_pos;

      mmpc -= midi_timer_speed;
      while (mmpc <= 0) {
       mmpc += midi_pos_speed;
       mmp++;
      }

      if (mmp >= target)
       break;

      midi_player();
   }

   /* restore previously saved variables */
   midi_loop = old_midi_loop;
   midi_driver = old_driver;
   midi_seeking = 0;

   if (midi_pos >= 0) {
      /* refresh the driver with any changed parameters */
      if (midi_driver->raw_midi) {
       for (c=0; c<16; c++) {
          /* program change (this sets the volume as well) */
          if ((midi_channel[c].patch != old_patch[c]) ||
            (midi_channel[c].volume != old_volume[c]))
             raw_program_change(c, midi_channel[c].patch);

          /* pan */
          if (midi_channel[c].pan != old_pan[c]) {
             midi_driver->raw_midi(0xB0+c);
             midi_driver->raw_midi(10);
             midi_driver->raw_midi(midi_channel[c].pan);
          }

          /* pitch bend */
          if (midi_channel[c].pitch_bend != old_pitch_bend[c]) {
             midi_driver->raw_midi(0xE0+c);
             midi_driver->raw_midi(midi_channel[c].pitch_bend & 0x7F);
             midi_driver->raw_midi(midi_channel[c].pitch_bend >> 7);
          }
       }
      }

      /* if we didn't hit the end of the file, continue playing */
      if (!midi_looping)
       install_int(midi_player, 20);

      return 0;
   }

   if ((midi_loop) && (!midi_looping)) {  /* was file looped? */
      prepare_to_play(old_midifile);
      install_int(midi_player, 20);
      return 2;                           /* seek past EOF => file restarted */
   }

   return 1;                              /* seek past EOF => file stopped */
}

END_OF_FUNCTION(midi_seek);



/* get_midi_length:
 *  Returns the length, in seconds, of the specified midi. This will stop any
 *  currently playing midi. Don't call it too often, since it simulates playing
 *  all of the midi to get the time even if the midi contains tempo changes.
 */
int get_midi_length(MIDI *midi)
{
    play_midi(midi, 0);
    while (midi_pos < 0); /* Without this, midi_seek won't work. */
    midi_seek(INT_MAX);
    return midi_time;
}



/* midi_out:
 *  Inserts MIDI command bytes into the output stream, in realtime.
 */
void midi_out(unsigned char *data, int length)
{
   unsigned char *pos = data;
   unsigned char running_status = 0;
   long timer = 0;
   ASSERT(data);

   midi_semaphore = TRUE;
   _midi_tick++;

   while (pos < data+length)
      process_midi_event((AL_CONST unsigned char**) &pos, &running_status, &timer);

   update_controllers();

   midi_semaphore = FALSE;
}



/* load_midi_patches:
 *  Tells the MIDI driver to preload the entire sample set.
 */
int load_midi_patches(void)
{
   char patches[128], drums[128];
   int c, ret;

   for (c=0; c<128; c++)
      patches[c] = drums[c] = TRUE;

   midi_semaphore = TRUE;
   ret = midi_driver->load_patches(patches, drums);
   midi_semaphore = FALSE;

   midi_loaded_patches = TRUE;

   return ret;
}



/* midi_lock_mem:
 *  Locks all the memory that the midi player touches inside the timer
 *  interrupt handler (which is most of it).
 */
static void midi_lock_mem(void)
{
   LOCK_VARIABLE(midi_pos);
   LOCK_VARIABLE(midi_time);
   LOCK_VARIABLE(midi_timers);
   LOCK_VARIABLE(midi_pos_counter);
   LOCK_VARIABLE(_midi_tick);
   LOCK_VARIABLE(midifile);
   LOCK_VARIABLE(midi_semaphore);
   LOCK_VARIABLE(midi_loop);
   LOCK_VARIABLE(midi_loop_start);
   LOCK_VARIABLE(midi_loop_end);
   LOCK_VARIABLE(midi_timer_speed);
   LOCK_VARIABLE(midi_pos_speed);
   LOCK_VARIABLE(midi_speed);
   LOCK_VARIABLE(midi_new_speed);
   LOCK_VARIABLE(old_midi_volume);
   LOCK_VARIABLE(midi_alloc_channel);
   LOCK_VARIABLE(midi_alloc_note);
   LOCK_VARIABLE(midi_alloc_vol);
   LOCK_VARIABLE(midi_track);
   LOCK_VARIABLE(midi_voice);
   LOCK_VARIABLE(midi_channel);
   LOCK_VARIABLE(midi_waiting);
   LOCK_VARIABLE(patch_table);
   LOCK_VARIABLE(midi_msg_callback);
   LOCK_VARIABLE(midi_meta_callback);
   LOCK_VARIABLE(midi_sysex_callback);
   LOCK_VARIABLE(midi_seeking);
   LOCK_VARIABLE(midi_looping);
   LOCK_FUNCTION(parse_var_len);
   LOCK_FUNCTION(raw_program_change);
   LOCK_FUNCTION(midi_note_off);
   LOCK_FUNCTION(_midi_allocate_voice);
   LOCK_FUNCTION(midi_note_on);
   LOCK_FUNCTION(all_notes_off);
   LOCK_FUNCTION(all_sound_off);
   LOCK_FUNCTION(reset_controllers);
   LOCK_FUNCTION(update_controllers);
   LOCK_FUNCTION(process_controller);
   LOCK_FUNCTION(process_meta_event);
   LOCK_FUNCTION(process_midi_event);
   LOCK_FUNCTION(midi_player);
   LOCK_FUNCTION(prepare_to_play);
   LOCK_FUNCTION(play_midi);
   LOCK_FUNCTION(stop_midi);
   LOCK_FUNCTION(midi_pause);
   LOCK_FUNCTION(midi_resume);
   LOCK_FUNCTION(midi_seek);
}



/* midi_constructor:
 *  Register my functions with the code in sound.c.
 */
#ifdef ALLEGRO_USE_CONSTRUCTOR
   CONSTRUCTOR_FUNCTION(void _midi_constructor(void));
#endif

static struct _AL_LINKER_MIDI midi_linker = {
   midi_init,
   midi_exit
};

void _midi_constructor(void)
{
   _al_linker_midi = &midi_linker;
}


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