smf.c

   1 /*
   2 orgux - a just-for-fun real time synth
   3 Copyright (C) 2009  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 the Free Software
  17 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18 */
  19
  20 /* smf */
  21
  22 #include "orgux.h"
  23
  24 #define STRING_MAX 256
  25
  26 typedef unsigned char octet;
  27 typedef int (*reader)(octet* buf, int count);
  28
  29
  30 extern void orgux_seq_append(orgux_state* S, int tick, int type, int chan, int val1, int val2);
  31 extern void orgux_seq_sort(orgux_state* S);
  32
  33 int bytes2short(octet arr[2]){
  34   return (arr[1]<<8) | arr[0];
  35 }
  36
  37 int bytes2int(octet arr[4]){
  38   return (arr[3]<<24) | (arr[2]<<16) | (arr[1]<<8) | arr[0];
  39 }
  40
  41
  42 /* read a bunch of bytes and discard */
  43 void skip_ahead(reader pull, int count){
  44   const int W = 256;
  45   char buf[W];
  46
  47   int C = count;
  48
  49   while(C > W){
  50     pull(buf,W);
  51     C -= W;
  52   }
  53   pull(buf,C);
  54 }
  55
  56 octet read_one(reader pull){
  57   octet byte[1];
  58   pull(byte,1);
  59   return byte[0];
  60 }
  61
  62 int get_delta(reader pull){
  63   octet a = read_one(pull);
  64   if(a<0x80){return a;}
  65
  66   octet b = read_one(pull);
  67   if(b<0x80){return ((a&0x7f)<<7) | b;}
  68
  69   octet c = read_one(pull);
  70   if(c<0x80){return ((a&0x7f)<<14) | ((b&0x7f)<<7) | c;}
  71
  72   octet d = read_one(pull);
  73   return ((a&0x7f)<<21) | ((b&0x7f)<<14) | ((c&0x7f)<<7) | d;
  74 }
  75
  76
  77 int orgux_load_song(orgux_state* S, int (*pull) (unsigned char* buf, int bytes)){
  78
  79   char buf[16];
  80   char string[STRING_MAX];
  81   int e;
  82   int n;
  83
  84   /*MThd*/
  85   if(pull(buf,4)<0) return -1;
  86
  87   /*0x00000006*/
  88   if(pull(buf,4)<0) return -1;
  89
  90   /*format type: 0x0000 0x0001 or 0x0002*/
  91   if(pull(buf,2)<0) return -1;
  92
  93   /*number of tracks*/
  94   if(pull(buf,2)<0) return -1;
  95   int track_count = bytes2short(buf);
  96
  97   /* time division */
  98   if(pull(buf,2)<0) return -1;
  99   //code to figure out time division
 100
 101   for(int i=0; i<track_count; i++){
 102
 103     /*MTrk*/
 104     if(pull(buf,4)<0) return -1;
 105
 106     /* chunk size */
 107     if(pull(buf,4)<0) return -1;
 108     int chunk_size = bytes2int(buf);
 109
 110     int tick = 0;
 111     int end_of_track = 0;
 112     int last_type = 0x80;
 113     int last_chan = 0;
 114     while(1){
 115       int delta = get_delta(pull);
 116       if(delta < 0) return -1;
 117       tick += delta;
 118
 119       //type and channel
 120       if(pull(buf,1)<0) return -1;
 121       int type = buf[0] & 0xf0;
 122       if(type >= 0x80 && type <= 0xe0){//normal event
 123         last_type = type;
 124         int chan = buf[0] & 0x0f;
 125         last_chan = chan;
 126         if(pull(buf,2)<0) return -1;
 127         int val1 = buf[0];
 128         int val2 = buf[1];
 129
 130         orgux_seq_append(S,tick,type,chan,val1,val2);
 131       }
 132       else if(type < 0x80){//running status
 133         int val1 = buf[0];
 134         if(pull(buf,1)<0) return -1;
 135         int val2 = buf[0];
 136
 137         orgux_seq_append(S,tick,last_type,last_chan,val1,val2);
 138       }
 139       else if(type == 0xff){//meta event
 140         if(pull(buf,1)<0) return -1;
 141         type = buf[0];
 142
 143         int len = get_delta(pull);
 144         if(len < 0) return -1;
 145
 146         switch(type){
 147           case 0x2f: end_of_track = 1; break;
 148           case 0x51: /*tempo change*/ break;
 149           case 0x58: /*time signature*/ break;
 150           case 0x01: /*text*/ break;
 151           default: skip_ahead(pull,len); break;
 152         }
 153       }
 154       else{// sysex and such...
 155
 156       }
 157
 158       if(end_of_track) break;
 159     }
 160
 161   }
 162
 163   orgux_seq_sort(S);
 164   return 0;
 165
 166 }