// This code written mainly from information provided at
// http://www.borg.com/~jglatt/tech/midifile/table.htm
// The program has accreted by exploring a few MIDI files.
// if(zz) {It reports details as it reads files.}
// I expect it to accrete more mods.
// In text output the construction "at 0X..." gives a hexadecimal location
// within the input file where something is located.
#include <stdio.h>
#include <stdlib.h>
#define zz 0
#include "h.h"
note * freenote = 0;

static int cc = 0;
static uchar h[16];
static FILE * in;
void ex(int d){printf("Bye %d, at 0X%X\n", d, cc);
  {int j=16; while(j--) printf("%02X ", h[(cc-1-j)&15]);
    // report the last 16 characters that were read.
  printf("\n");
  j=16; while(j--) printf("%02X ", getc(in));}
    // and upcomming 16 too.
   printf("\n"); exit(4);}
static uchar nc(){char x = getc(in);
   if(x == EOF && feof(in)) {printf("Unexpected end of file at 0X%X\n", cc); ex(6);}
  h[cc++&15] = x; return x;}
static ui gvl(){ui x = 0; uchar c;
  do {c = nc(); x = (x<<7) | (c & 0x7f);} while(c & 0x80); return x;}
static void expect(char * s){while (*s) if(*(s++) != nc()) ex(1);}
static void * mal(int k, int p){void * y = malloc(k); if(y) return y;
  printf("Memory allocation failure; wanted %d bytes at %d\n", k, p); ex(65);
  return 0;}
  
static ui gn(int l) {ui k = 0; while(l--) k = (k<<8) | nc(); return k;}
static note* nf(){while(1){note * n = freenote;
if(n) {freenote = n->next; return n;}
  {note* ar =  mal (2000*sizeof(note), 1);
  {int j = 2000; while(j--) {ar[j].next = freenote; freenote = ar+j;}}}}}

note* Read(char * fn, BP* bp){note * music = 0, * playing = 0;
  in = *fn?fopen(fn, "r"):stdin;
  expect("MThd"); if(gn(4) != 6) ex(3);
  // Needs a MThd <http://www.borg.com/~jglatt/tech/midifile/mthd.htm>.
  {int format = gn(2), tc = gn(2);
  bp->trks = tc; bp->den = gn(2); bp->type = format;
  if(0) printf("%d tracks, %d ticks/quarternote\n", tc, bp->den);
  if(!(format == 1 || (format == 0 && tc == 1))) ex(2);
  
  while(tc--) {
    int Time=0; // computed by accumulating timing bytes in track.
    expect("MTrk"); {int ts = gn(4), hstrt = cc;
    uchar cst=-1, cchan=0x80;
    void ex2(int j){printf("cst=%d, qn = %10.4f, ",
        cst, Time/(float)bp->den); ex(10000+j);}
    if(zz) printf("Beginning track %d with %d bytes at 0X%X\n", bp->trks-tc, ts, cc);
    while(1){Time += gvl();
      zx:  { // We return to zx when we have seen a status byte
             // which is sort of a message prefix.
        uchar sc = nc();
        if(sc & 0x80) {
        if(sc == 0xFF) {uchar sbtp = nc();
          void Opaque(ui rq){
              note * nn = nf();
              nn->start = Time;
              if(0) nn->chan = (sc&15)+1; // perhaps someone depends on this bogus value.
              nn->trk = bp->trks-tc;
              nn->next = music; music = nn; 
              nn->dur = OpaqueStuff; 
              //nn->o.tempo = gn(3);
              {ui size = gvl(); uchar * stuff = (uchar*)mal(size+1, 2);
              if(size != rq && rq) ex2(11);
              {int j; for(j=0; j< size; ++j) stuff[j] = nc();
              stuff[j] = 0;
              nn->o.opaque.odp = stuff; nn->o.opaque.cc = size;
              nn->o.opaque.subtype = sbtp;}}}
          if(0) printf("0x%02x at 0X%X -> ", sbtp, cc);
          switch(sbtp){
           case 1: // Text
           case 2: // Copyright
           case 3: // Track Name
           case 4: // Instrument name
           case 7: // Cue Point
             Opaque(0); break;
           case 33: Opaque(1); break; // MIDI Port?
           case 47: if(zz) printf("End of Track\n\n");
             if(gvl()) ex2(13);
             if(cc != hstrt+ts) ex2(14); goto endTrk;
           case 81: Opaque(3); break; // Tempo
           case 84: Opaque(5); break; // SMPTE Offset
           case 88: Opaque(4); break; // Time Signature
           case 89: Opaque(2); break; // Key Signature
           default: ex2(9);}}
        else {cst = sc>>4;
     //     if(cst == 11) ex2(53);
         {note* gen(int code){
              note * nn = nf(); cst=-1;
              nn->start = Time; nn->chan = (sc&15)+1; nn->trk = bp->trks-tc;
              nn->next = music; music = nn; 
              nn->dur = code; cst=-1; return nn;}
         switch(cst){
          case 9: case 8: cchan = sc&15; goto zx;
          case 11: {int cn = nc(), v=nc();
             printf("Channel %d controller %d to %d", sc&15, cn, v);
             if(cn) printf(" Unknown effet\n");
             else printf(": Bank Select to %d\n", v);} break;
          case 12: // printf("Channel %d changes to program %d\n", 1+(sc&15), nc());
             {note * nn = gen(ProgramChange); nn->o.prog = nc();} break;
          case 14:
             //printf("Channel %d reports pitch wheel at %04X\n", sc&15, nc() | (nc()<<7));
             {note * nn = gen(PitchWheel); nn->o.pitch = nc() | (nc()<<7);} break;
      // See <www.harfesoft.de/aixphysik/sound/midi/pages/genmidi.html>
      // for meanings.
          default: printf("Status byte = %02X!\n", sc); ex2(17);            
          }}}}
       else {// channel message
         char sb = nc(); // get second byte: message is sc:sb
         if(cchan & 0x80) {
             if(sc == 10 && sb == 0x40 && Time == 0) {
               printf("Ignoring mysterious 0x0A40 in track %d at 0x%x\n",
                 bp->trks-tc, cc); continue;}
             ex2(21);} // Note but no running status.
         if(!(cst == 9 || cst == 8 || cst == 10))
         ex2(39);
         if(sb && cst==9){note * nn = nf();
            nn->start = Time; nn->o.n.freq = sc; nn->o.n.loud = sb; nn->chan = cchan+1;
            nn-> trk = bp->trks-tc; nn->next = playing; playing = nn;}
         else if(cst == 8 || !sb) {
            note * sch = playing; note * * tp = &playing; while(sch){
            if(sc == sch->o.n.freq && cchan+1 == sch->chan){
               int dur = Time - sch->start; if (dur > maxdur) ex2(97);
               sch->dur = dur; sch->o.n.quit = cst==8?sb:64; *tp = sch-> next;
               sch->next = music;
               music = sch; break;}
            else{tp = &sch->next; sch = sch->next;}}
         }}}}
      endTrk: ;}}
   if(getc(in) != EOF || !feof(in)) ex(99);
  if(0) {note * m = music; while(m) {printf("note %d from %d for %d, c=%d, t=%d\n",
     m->o.n.freq, m->start, m->dur, m->chan, m->trk);
       m = m-> next;}}
     if(playing) {printf("Stuck notes\n"); ex(57);}
 fclose(in);    
 return music;}}

void Free(note ** m)
  {while(*m){note* n = (*m)->next; (*m)->next = freenote; freenote = *m; *m=n;}}
void aug(note n, note** m){note * nn = nf(); n.next = *m; *nn = n; *m = nn;}
void scan(seeNote feed, note* mus, int consume){
  while(mus) {note nte = *mus; note * nx = nte.next; nte.next = 0; feed(nte);
    if(consume){mus->next = freenote; freenote = mus;} mus=nx;}}