midi.c

   1 /*
   2    Cantaveria - action adventure platform game
   3    Copyright (C) 2009 2010 Evan Rinehart
   4
   5    This program is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU General Public License
   7    as published by the Free Software Foundation; either version 2
   8    of the License, or (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to
  17
  18    The Free Software Foundation, Inc.
  19    51 Franklin Street, Fifth Floor
  20    Boston, MA  02110-1301, USA
  21
  22    evanrinehart@gmail.com
  23 */
  24
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28
  29 #include <list.h>
  30 #include <util.h>
  31 #include <loader.h>
  32 #include <midi.h>
  33
  34
  35 static event* make_event(int tick, int type, int chan, int val1, int val2){
  36         event* e = malloc(sizeof(event));
  37         e->tick = tick;
  38         e->type = type;
  39         e->chan = chan;
  40         e->val1 = val1;
  41         e->val2 = val2;
  42         return e;
  43 }
  44
  45 void free_events(list* events){
  46         list* ptr = events->next;
  47
  48         while(ptr){
  49                 free(ptr->item);
  50                 ptr = ptr->next;
  51         }
  52 }
  53
  54 int value_of_type(int type){
  55         switch(type){
  56                 case 0x80: return -2;
  57                 case EVX_LOOPSTART: return -1;
  58                 case EVX_LOOPEND: return 1;
  59                 case 0x90: return 2;
  60                 default: return 0;
  61         }
  62 }
  63
  64 int compare_event(void* v1, void* v2){
  65         event* e1 = v1;
  66         event* e2 = v2;
  67         int d1, d2;
  68
  69         if(e1->tick < e2->tick) return 1;
  70         if(e1->tick > e2->tick) return -1;
  71
  72         d1 = value_of_type(e1->type);
  73         d2 = value_of_type(e2->type);
  74
  75         return d2 - d1;
  76 }
  77
  78 /* read a midi variable length quantity */
  79 /* returns number of bytes read or 0 for error */
  80 /* fills in buf with bytes read */
  81 int read_deltaenough(reader* r, unsigned char buf[4]){
  82         int bytes[4];
  83         int i;
  84
  85         for(i=0; i<4; i++){
  86                 if(read_byte(r, &bytes[i])) return 0;
  87                 if(!(bytes[i] & 0x80)){
  88                         buf[0] = bytes[0];
  89                         buf[1] = bytes[1];
  90                         buf[2] = bytes[2];
  91                         buf[3] = bytes[3];
  92                         return i+1;
  93                 }
  94         }
  95
  96         error_msg("midi_load: invalid delta encountered\n");
  97         return 0;
  98 }
  99
 100 /* converts midi variable length quantity x int a normal quantity */
 101 /* count should be number of bytes of data in x */
 102 int conv_delta(unsigned char x[4], int count){
 103         switch(count){
 104         case 1: return x[0];
 105         case 2: return ((x[0] & 0x7f) << 7) | x[1];
 106         case 3: return ((x[0] & 0x7f) << 14) | ((x[1] & 0x7f) << 7) | x[2];
 107         case 4: return ((x[0] & 0x7f) << 21) | ((x[1] & 0x7f) << 14) | ((x[2] & 0x7f) << 7) | x[3];
 108         default: error_msg("conv_delta: wrong count (%d)\n", count); return 0;
 109         }
 110 }
 111
 112 int conv_divisions(int divraw){
 113         if(divraw > 0){
 114                 return divraw;
 115         }
 116         else{
 117                 printf("midi_load: time division is given in frames per second, expect breakage without further support\n");
 118                 return abs(divraw>>8);
 119         }
 120 }
 121
 122 /* read a midi variable length quantity from r */
 123 /* 0 for success, -1 for error. out is filled in with quantity */
 124 int read_delta(reader* r, int* out){
 125         unsigned char buf[4];
 126         int count = read_deltaenough(r, buf);
 127
 128         if(count == 0){
 129                 return -1;
 130         }
 131         else{
 132                 *out = conv_delta(buf, count);
 133                 return 0;
 134         }
 135 }
 136
 137
 138
 139 event* meta_endoftrack(reader* r, int tick){
 140         int zero;
 141         if(read_delta(r, &zero)) return NULL;
 142         if(zero != 0){
 143                 error_msg("midi_load: end of track event not followed by zero\n");
 144                 return NULL;
 145         }
 146         return make_event(tick, EVX_ENDOFTRACK, 0, 0, 0);
 147 }
 148
 149 event* meta_tempochange(reader* r, int tick){
 150         unsigned char bytes[3];
 151         int three;
 152         int uspqn;
 153         int bpm;
 154
 155         if(read_delta(r, &three)) return NULL;
 156         if(read_bytes(r, bytes, 3)) return NULL;
 157         uspqn = (bytes[0] << 16) | (bytes[1] << 8) | bytes[0];
 158         bpm = 60000000 / uspqn;
 159
 160         return make_event(tick, EVX_TEMPOCHANGE, 0, bpm, 0);
 161 }
 162
 163 event* meta_possibleloop(reader* r, int tick){
 164 printf("ERR meta_possibleloop not done\n");
 165         return NULL;
 166 }
 167
 168 event* meta_dummy(reader* r, int tick){
 169         int len;
 170         int foo;
 171
 172         if(read_delta(r, &len)) return NULL;
 173
 174         /* FIXME need a skip routine */
 175         for(; len > 0; len--){
 176                 if(read_byte(r, &foo)) return NULL;
 177         }
 178
 179         return make_event(tick, EVX_META, 0, 0, 0);
 180 }
 181
 182 event* skip_sys(reader* r, int tick){
 183 printf("ERR skip_sys not done\n");
 184         return NULL;
 185 }
 186
 187 event* read_normal(reader* r, int tick, int status){
 188         int type = status & 0xf0;
 189         int chan = status & 0x0f;
 190         int val1;
 191         int val2;
 192
 193         if(read_byte(r, &val1) || read_byte(r, &val2))
 194                 return NULL;
 195         else
 196                 return make_event(tick, type, chan, val1, val2);
 197 }
 198
 199 event* read_running(reader* r, int tick, int val1){
 200         int val2;
 201
 202         if(read_byte(r, &val2))
 203                 return NULL;
 204         else
 205                 return make_event(tick, -1, -1, val1, val2);
 206 }
 207
 208 event* read_meta(reader* r, int tick){
 209         int type;
 210
 211
 212         if(read_byte(r, &type))
 213                 return NULL;
 214
 215         switch(type){
 216                 case 0x2f: return meta_endoftrack(r, tick);
 217                 case 0x51: return meta_tempochange(r, tick);
 218                 case 0x01: return meta_possibleloop(r, tick);
 219                 default: return meta_dummy(r, tick);
 220         }
 221 }
 222
 223
 224 event* read_event(reader* r, int tick, int byte0){
 225         if(byte0 >= 0x80 && byte0 <  0xf0)
 226                 return read_normal(r, tick, byte0);
 227         else if(byte0 < 0x80)
 228                 return read_running(r, tick, byte0);
 229         else if(byte0 == 0xff)
 230                 return read_meta(r, tick);
 231         else
 232                 return skip_sys(r, tick);
 233 }
 234
 235 int read_track(reader* r, list* events){
 236         int tick = 0;
 237         int last_type = 0x90;
 238         int last_chan = 0;
 239
 240         unsigned char sig[4];
 241         unsigned chunk_size;
 242
 243         if(read_bytes(r, sig, 4) || read_int(r, (int*)&chunk_size)){
 244                 return -1;
 245         }
 246
 247         if(memcmp(sig, "MTrk", 4) != 0){
 248                 error_msg("midi_load: MTrk not found\n");
 249                 return -1;
 250         }
 251
 252         for(;;){
 253                 int delta;
 254                 int byte0;
 255                 if(read_delta(r, &delta) || read_byte(r, &byte0)){
 256                         return -1;
 257                 }
 258
 259                 tick += delta;
 260
 261                 event* e = read_event(r, tick, byte0);
 262                 if(e == NULL){
 263                         return -1;
 264                 }
 265
 266                 append(events, e);
 267
 268                 if(e->type == -1){ /* running status */
 269                         e->type = last_type;
 270                         e->chan = last_chan;
 271                 }
 272                 else if(e->type == EVX_ENDOFTRACK){ /* end of track */
 273                         break;
 274                 }
 275
 276                 if(e->type == 0x90 && e->val2 == 0){
 277                         e->type = 0x80;
 278                 }
 279
 280                 if(e->type == 0x80 || e->type == 0x90){
 281                         e->val1 -= 57;
 282                 }
 283         }
 284
 285         return 0;
 286 }
 287
 288 int read_header(reader* r, int* format, int* track_count, int* divraw){
 289         char sig[4];
 290         int six;
 291
 292         if(read_bytes(r, (unsigned char*)sig, 4)) return -1;
 293         if(read_int(r, &six)) return -1;
 294         if(read_short(r, format)) return -1;
 295         if(read_short(r, track_count)) return -1;
 296         if(read_short(r, divraw)) return -1;
 297
 298         if(memcmp(sig, "MThd", 4) != 0){
 299                 error_msg("midi_load: MThd not found\n");
 300                 return -1;
 301         }
 302
 303         if(six != 6){
 304                 error_msg("midi_load: number six not found (%d)\n", six);
 305                 return -1;
 306         }
 307
 308         if(*format != 0 && *format != 1){
 309                 error_msg("midi_load: format not supported (%d)\n", *format);
 310                 return -1;
 311         }
 312
 313         return 0;
 314 }
 315
 316 list* midi_load(char* filename){
 317         reader* r;
 318         list* events = empty();
 319
 320         int format;
 321         int track_count;
 322         int divraw;
 323         int i;
 324
 325         r = data_open("music/", filename);
 326         if(r == NULL){
 327                 return NULL;
 328         }
 329
 330         if(read_header(r, &format, &track_count, &divraw) < 0){
 331                 error_msg("midi_load: read error in header\n");
 332                 loader_close(r);
 333                 recycle(events);
 334                 return NULL;
 335         }
 336
 337         push(events, make_event(
 338                 0,
 339                 EVX_TICKSPERBEAT,
 340                 0,
 341                 conv_divisions(divraw),
 342                 0
 343         ));
 344
 345         for(i=0; i<track_count; i++){
 346                 if(read_track(r, events) < 0){
 347                         error_msg("midi_load: read error in track\n");
 348                         loader_close(r);
 349                         free_events(events);
 350                         recycle(events);
 351                         return NULL;
 352                 }
 353         }
 354
 355         sort(events, compare_event);
 356         return events;
 357 }
 358
 359
 360
 361