smf.c

   1 /* smf */
   2
   3 #include "orgux.h"
   4
   5 #define STRING_MAX 256
   6
   7 typedef unsigned char octet;
   8 typedef int (*reader)(octet* buf, int count);
   9
  10
  11 int bytes2short(octet arr[2]){
  12   return (arr[1]<<8) | arr[0];
  13 }
  14
  15 int bytes2int(octet arr[4]){
  16   return (arr[3]<<24) | (arr[2]<<16) | (arr[1]<<8) | arr[0];
  17 }
  18
  19
  20 /* read a bunch of bytes and discard */
  21 void skip_ahead(reader pull, int count){
  22   const int W = 256;
  23   char buf[W];
  24
  25   int C = count;
  26
  27   while(C > W){
  28     pull(buf,W);
  29     C -= W;
  30   }
  31   pull(buf,C);
  32 }
  33
  34 octet read_one(reader pull){
  35   octet byte[1];
  36   pull(byte,1);
  37   return byte[0];
  38 }
  39
  40 int get_delta(reader pull){
  41   octet a = read_one(pull);
  42   if(a<0x80){return a;}
  43
  44   octet b = read_one(pull);
  45   if(b<0x80){return ((a&0x7f)<<7) | b;}
  46
  47   octet c = read_one(pull);
  48   if(c<0x80){return ((a&0x7f)<<14) | ((b&0x7f)<<7) | c;}
  49
  50   octet d = read_one(pull);
  51   return ((a&0x7f)<<21) | ((b&0x7f)<<14) | ((c&0x7f)<<7) | d;
  52 }
  53
  54
  55 int orgux_load_song(orgux_state* S, int (*pull) (unsigned char* buf, int bytes)){
  56
  57   char buf[16];
  58   char string[STRING_MAX];
  59   int e;
  60   int n;
  61
  62   /*MThd*/
  63   if(pull(buf,4)<0) return -1;
  64
  65   /*0x00000006*/
  66   if(pull(buf,4)<0) return -1;
  67
  68   /*format type: 0x0000 0x0001 or 0x0002*/
  69   if(pull(buf,2)<0) return -1;
  70
  71   /*number of tracks*/
  72   if(pull(buf,2)<0) return -1;
  73   int track_count = bytes2short(buf);
  74
  75   /* time division */
  76   if(pull(buf,2)<0) return -1;
  77   //code to figure out time division
  78
  79   for(int i=0; i<track_count; i++){
  80
  81     /*MTrk*/
  82     if(pull(buf,4)<0) return -1;
  83
  84     /* chunk size */
  85     if(pull(buf,4)<0) return -1;
  86     int chunk_size = bytes2int(buf);
  87
  88     int tick = 0;
  89     while(1){
  90       int delta = get_delta(pull);
  91       if(1) break;
  92     }
  93
  94   }
  95
  96   /* get ticks per beat */
  97   /* get time signature */
  98   /* get us per quarter note */
  99   /* get time format */
 100
 101
 102   /* for each track, each event, append event */
 103
 104   /* check for LoopStart and LoopEnd */
 105
 106   /* sort queue */
 107
 108 }