midi.c - audio/dosmid - Rivoreo Source Code Repositories

 /*
  * A simple MIDI parsing library
  *
  * Copyright (c) 2014, 2015 Mateusz Viste
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright notice,
  *    this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */

 #include <stdlib.h> /* malloc */
 #include <string.h> /* strcmp() */

 #include "mem.h"
 #include "midi.h"   /* include self for control */


 /* PRIVATE ROUTINES USED FOR INTERNAL PROCESSING ONLY */


 /* fetch a variable length quantity value from a given offset. returns number of bytes read */
 static int midi_fetch_variablelen_fromfile(FILE *fd, unsigned long *result) {
   int bytebuff;
   int offset = 0;
   *result = 0;
   for (;;) {
     bytebuff = fgetc(fd);
     *result <<= 7;
     *result |= (bytebuff & 127);
     if ((bytebuff & 128) == 0) break;
   }
   return(offset);
 }

 /* reads a MIDI file and computes a map of chunks (ie a list of offsets) */
 static int midi_getchunkmap(FILE *fd, struct midi_chunkmap_t *chunklist, int maxchunks) {
   int chunkid, i;
   unsigned char hdr[8];
   unsigned long readres;
   /*unsigned long chunklen;*/
   for (chunkid = 0; chunkid < maxchunks; chunkid++) {
     readres = fread(hdr, 1, 8, fd);
     if (readres != 8) break;
     chunklist[chunkid].offset = ftell(fd);
     /* read chunk's id */
     for (i = 0; i < 4; i++) chunklist[chunkid].id[i] = hdr[i];
     chunklist[chunkid].id[4] = 0; /* string terminator */
     /* compute the length */
     chunklist[chunkid].len = 0;
     for (i = 4; i < 8; i++) {
       chunklist[chunkid].len <<= 8;
       chunklist[chunkid].len |= hdr[i];
     }
     /* skip to next chunk */
     fseek(fd, chunklist[chunkid].len, SEEK_CUR);
   }
   return(chunkid);
 }


 /* PUBLIC INTERFACE */


 struct midi_chunk_t *midi_readchunk(FILE *fd) {
   unsigned char hdr[8];
   unsigned long readres;
   int i;
   unsigned long len = 0;
   struct midi_chunk_t *res;
   readres = fread(hdr, 1, 8, fd);
   if (readres != 8) return(NULL);
   /* compute the length */
   for (i = 4; i < 8; i++) {
     len <<= 8;
     len |= hdr[i];
   }
   res = malloc(sizeof(struct midi_chunk_t) + (unsigned int)len);
   if (res == NULL) return(NULL);
   /* copy the id string */
   res->id[0] = hdr[0];
   res->id[1] = hdr[1];
   res->id[2] = hdr[2];
   res->id[3] = hdr[3];
   res->id[4] = 0;
   /* assign data length */
   res->datalen = len;
   /* copy actual data */
   readres = fread(res->data, 1, (unsigned int)res->datalen, fd);
   if (readres != res->datalen) {
     free(res);
     return(NULL);
   }
   return(res);
 }

 int midi_readhdr(FILE *fd, int *format, int *tracks, unsigned short *timeunitdiv, struct midi_chunkmap_t *chunklist, int maxchunks) {
   struct midi_chunk_t *chunk;
   unsigned char rmidbuff[12];
   /* test for RMID format and rewind if not found */
   /* a RMID file starts with RIFFxxxxRMID (xxxx being the data size) */
   /* read first 12 bytes - if unable, return an error */
   if (fread(rmidbuff, 1, 12, fd) != 12) return(-7);
   /* if no RMID header, then rewind the file assuming it's normal MIDI */
   if ((rmidbuff[0] != 'R') || (rmidbuff[1] != 'I')  || (rmidbuff[2] != 'F') || (rmidbuff[3] != 'F')
    || (rmidbuff[8] != 'R') || (rmidbuff[9] != 'M') || (rmidbuff[10] != 'I') || (rmidbuff[11] != 'D')) {
     rewind(fd);
   }
   /* Read the first chunk of data (should be the MIDI header) */
   chunk = midi_readchunk(fd);
   if (chunk == NULL) {
     return(-6);
   }
   /* check id */
   if (strcmp(chunk->id, "MThd") != 0) {
     free(chunk);
     return(-5);
   }
   /* check len - must be at least 6 bytes */
   if (chunk->datalen < 6) {
     free(chunk);
     return(-4);
   }
   *format = (chunk->data[0] << 8) | chunk->data[1];
   *tracks = (chunk->data[2] << 8) | chunk->data[3];

   *timeunitdiv = chunk->data[4];
   *timeunitdiv <<= 8;
   *timeunitdiv |= chunk->data[5];
   /* timeunitdiv must be a positive number */
   if (*timeunitdiv < 1) {
     free(chunk);
     return(-3);
   }

   /*  default tempo -> quarter note (1 beat) == 500'000 microseconds (0.5s), ie 120 bpm.
       a delta time unit is therefore (0.5s / DIV) long. */
   /* check the timeunit */
   if (chunk->data[4] & 128) {
     free(chunk);
     return(-2);
   }
   /* check format - must be 0, 1 or 2 */
   if ((*format < 0) || (*format > 2)) {
     free(chunk);
     return(-1);
   }
   /* read the chunk map */
   midi_getchunkmap(fd, chunklist, maxchunks);
   return(0);
 }

 /* parse a track object and returns the id of the first events in the linked
  * list. channelsusage contains 16 flags indicating what channels are used. */
 long midi_track2events(FILE *fd, char **title, int titlenodes, int titlemaxlen, char *copyright, int copyrightmaxlen, unsigned short *channelsusage, FILE *logfd) {
   unsigned long deltatime;
   unsigned char statusbyte = 0, tmp;
   struct midi_event_t event;
   long result = -1;
   unsigned long tracklen = 0;
   unsigned long ignoreddeltas = 0;
   unsigned char ubuff[4]; /* micro buffer for loading data */

   for (;;) {
     /* read the delta time first - variable length */
     midi_fetch_variablelen_fromfile(fd, &deltatime);
     tracklen += deltatime;
     /* check the type of the event */
     /* if it's a byte with MSB set, we are dealing with running status (so it's same status as last time */
     tmp = fgetc(fd);
     if ((tmp & 128) != 0) {
       statusbyte = tmp;
     } else { /* get back one byte */
       fseek(fd, -1, SEEK_CUR);
     }
     event.type = EVENT_NONE;
     event.deltatime = deltatime;
     event.next = -1;
     if (statusbyte == 0xFF) { /* META event */
         unsigned long metalen;
         unsigned long i;
         int subtype, endoftrack = 0;
         subtype = fgetc(fd); /* fetch the META subtype fields */
         midi_fetch_variablelen_fromfile(fd, &metalen);
         /* printf("got META[0x%02X] of %ld bytes\n", subtype, metalen); */
         switch (subtype) {
           case 1: /* text */
             fseek(fd, metalen, SEEK_CUR);
             break;
           case 2: /* copyright notice */
             i = 0;
             if (copyright != NULL) { /* take care, copyright might be NULL */
               for (; i < metalen; i++) {
                 if (i == copyrightmaxlen) break; /* avoid overflow */
                 copyright[i] = fgetc(fd);
               }
               copyright[i] = 0;
             }
             fseek(fd, metalen - i, SEEK_CUR); /* skip the rest, if we had to truncate the string */
             break;
           case 3: /* track name */
             i = 0;
             /* find the first empty track */
             if (title != NULL) { /* title might be NULL */
               int titid = -1, t;
               for (t = 0; t < titlenodes; t++) {
                 if (title[t][0] == 0) {
                   titid = t;
                   break;
                 }
               }
               if (titid >= 0) {
                 for (i = 0; i < metalen; i++) {
                   if (i == titlemaxlen) break; /* avoid overflow */
                   title[titid][i] = fgetc(fd);
                 }
                 title[titid][i] = 0;
               }
             }
             fseek(fd, metalen - i, SEEK_CUR); /* skip the rest, if we had to truncate the string */
             break;
           case 4: /* instrument name */
           case 5: /* lyric */
             fseek(fd, metalen, SEEK_CUR);
             if (logfd != NULL) fprintf(logfd, "%lu: LYRIC EVENT (ignored)\n", tracklen);
             break;
           case 0x21:  /* MIDI port -- no support for multi-MIDI files, I just ignore it */
             fseek(fd, metalen, SEEK_CUR);
             if (logfd != NULL) fprintf(logfd, "%lu: MIDI PORT EVENT (ignored)\n", tracklen);
             break;
           case 0x2F: /* end of track */
             if (logfd != NULL) fprintf(logfd, "%lu: END OF TRACK\n", tracklen);
             endoftrack = 1;
             break;
           case 0x51:  /* set tempo */
             if (metalen != 3) {
               if (logfd != NULL) fprintf(logfd, "%lu: TEMPO ERROR\n", tracklen);
             } else {
               fread(ubuff, 1, 3, fd);
               event.type = EVENT_TEMPO;
               event.data.tempoval = ubuff[0];
               event.data.tempoval <<= 8;
               event.data.tempoval |= ubuff[1];
               event.data.tempoval <<= 8;
               event.data.tempoval |= ubuff[2];
               if (logfd != NULL) fprintf(logfd, "%lu: TEMPO -> %lu\n", tracklen, event.data.tempoval);
             }
             break;
           case 0x54:  /* SMPTE offset -> since I expect only format 0/1 files, I ignore this because I want to start playing asap anyway */
             fseek(fd, metalen, SEEK_CUR);
             if (logfd != NULL) fprintf(logfd, "%lu: SMPTE OFFSET (ignored)\n", tracklen);
             break;
           case 0x58:  /* Time signature */
             if (metalen != 4) {
               if (logfd != NULL) fprintf(logfd, "%lu: INVALID TIME SIGNATURE!\n", tracklen);
               return(-1);
             } else {
               fseek(fd, metalen, SEEK_CUR);
               if (logfd != NULL) fprintf(logfd, "%lu: TIME SIGNATURE (ignored)\n", tracklen);
             }
             break;
           case 0x59:  /* key signature */
             if (metalen != 2) {
               if (logfd != NULL) fprintf(logfd, "%lu: INVALID KEY SIGNATURE!\n", tracklen);
               return(-1);
             } else {
               fseek(fd, metalen, SEEK_CUR);
               if (logfd != NULL) fprintf(logfd, "%lu: KEY SIGNATURE (ignored)\n", tracklen);
             }
             break;
           case 0x7F:  /* proprietary event -> this is non-standard stuff, I ignore it */
             fseek(fd, metalen, SEEK_CUR);
             if (logfd != NULL) fprintf(logfd, "%lu: PROPRIETARY EVENT (ignored)\n", tracklen);
             break;
           default:
             fseek(fd, metalen, SEEK_CUR);  /* skip the meta data */
             if (logfd != NULL) fprintf(logfd, "%lu: UNHANDLED META EVENT [0x%02X] (ignored)\n", tracklen, subtype);
             break;
         }
         if (endoftrack != 0) break;
       } else if ((statusbyte >= 0xF0) && (statusbyte <= 0xF7)) { /* SYSEX event */
         unsigned long sysexlen;
         midi_fetch_variablelen_fromfile(fd, &sysexlen); /* get length */
         if (logfd != NULL) fprintf(logfd, "%lu: SYSEX EVENT OF %ld BYTES (ignored)\n", tracklen, sysexlen);
         fseek(fd, sysexlen, SEEK_CUR);
       } else if ((statusbyte >= 0x80) && (statusbyte <= 0xEF)) { /* else it's a note-related command */
         switch (statusbyte & 0xF0) { /* I care only about NoteOn/NoteOff events */
           case 0x80:  /* Note OFF */
             fread(ubuff, 1, 2, fd);
             event.type = EVENT_NOTEOFF;
             event.data.note.chan = statusbyte & 0x0F;
             event.data.note.note = ubuff[0] & 127; /* a note must be in range 0..127 */
             event.data.note.velocity = ubuff[1];
             break;
           case 0x90:  /* Note ON */
             fread(ubuff, 1, 2, fd);
             *channelsusage |= (1 << event.data.note.chan); /* update the channel usage flags */
             event.type = EVENT_NOTEON;
             event.data.note.chan = statusbyte & 0x0F;
             event.data.note.note = ubuff[0] & 127;
             event.data.note.velocity = ubuff[1];
             if (event.data.note.velocity == 0) event.type = EVENT_NOTEOFF; /* if no velocity, it's in fact a note OFF */
             break;
           case 0xA0:  /* key after-touch */
             /* puts("KEY AFTER-TOUCH"); */
             fread(ubuff, 1, 2, fd);
             event.type = EVENT_KEYPRESSURE;
             event.data.keypressure.chan = statusbyte & 0x0F;
             event.data.keypressure.note = ubuff[0];
             event.data.keypressure.pressure = ubuff[1];
             break;
           case 0xB0:  /* control change */
             /* puts("CONTROL CHANGE"); */
             fread(ubuff, 1, 2, fd);
             event.type = EVENT_CONTROL;
             event.data.control.chan = statusbyte & 0x0F;
             event.data.control.id = ubuff[0];
             event.data.control.val = ubuff[1];
             break;
           case 0xC0:  /* program (patch) change */
             event.type = EVENT_PROGCHAN;
             event.data.prog.chan = statusbyte & 0x0F;
             event.data.prog.prog = fgetc(fd);
             break;
           case 0xD0:  /* channel after-touch (aka "channel pressure") */
             event.type = EVENT_CHANPRESSURE;
             event.data.chanpressure.chan = statusbyte & 0x0F;
             event.data.chanpressure.pressure = fgetc(fd);
             break;
           case 0xE0:  /* pitch wheel change */
             fread(ubuff, 1, 2, fd);
             event.type = EVENT_PITCH;
             event.data.pitch.chan = statusbyte & 0x0F;
             event.data.pitch.wheel = ubuff[1];
             event.data.pitch.wheel <<= 7;
             event.data.pitch.wheel |= ubuff[0];
             break;
           default:
             if (logfd != NULL) fprintf(logfd, "%lu: Unknown note data\n", tracklen);
             return(-1);
             break;
         }
       } else { /* else it's an error - free memory we allocated and return NULL */
         if (logfd != NULL) fprintf(logfd, "Err. at offset %04lX (bytebuff = 0x%02X)\n", ftell(fd), statusbyte);
         return(-1);
     }
     /* add the event to the queue */
     if (event.type == EVENT_NONE) {
       ignoreddeltas += event.deltatime;
     } else {
       event.deltatime += ignoreddeltas; /* add any previously ignored delta times */
       ignoreddeltas = 0;
       /* add the event to the queue */
       if (result < 0) {
         pusheventqueue(&event, &result);
       } else {
         pusheventqueue(&event, NULL);
       }
     }
   }
   if (result >= 0) pusheventqueue(NULL, NULL); /* flush last event in buffer to memory */
   return(result);
 }

 /* merge two MIDI tracks into a single (serialized) one. returns a "pointer"
  * to the unique track. I take care not to allocate/free memory here.
  * All notes are already in RAM after all. totlen is filled with the total
  * time of the merged tracks (in seconds). */
 long midi_mergetrack(long t0, long t1, unsigned long *totlen, unsigned short timeunitdiv) {
   long res = -1, lasteventid = -1, selectedid;
   int selected;
   unsigned long curtempo = 500000l, utotlen = 0;
   struct midi_event_t event[2], lastevent;

   if (totlen != NULL) *totlen = 0;
   /* fetch first events for both tracks */
   if (t0 >= 0) pullevent(t0, &event[0]);
   if (t1 >= 0) pullevent(t1, &event[1]);
   /* start looping */
   while ((t0 >= 0) || (t1 >= 0)) {
     /* compare both tracks, and select the soonest one */
     if (t0 >= 0) {
       if ((t1 >= 0) && (event[1].deltatime < event[0].deltatime)) {
         selected = 1;
         selectedid = t1;
       } else {
         selected = 0;
         selectedid = t0;
       }
     } else {
       selected = 1;
       selectedid = t1;
     }
     /* on first iteration, make sure to assign a result */
     if (lasteventid < 0) {
       res = selectedid;
     } else if (lastevent.next != selectedid) { /* otherwise attach selected */
       lastevent.next = selectedid;             /* track to last note, and   */
       pushevent(&lastevent, lasteventid);      /* update last pointer (if   */
     }                                          /* not good already)         */
     /* save the last event into buffer for later, and remember its id */
     lasteventid = selectedid;
     memcpy(&lastevent, &(event[selected]), sizeof(struct midi_event_t));
     /* increment timer */
     if ((totlen != NULL) && (event[selected].deltatime != 0)) {
       utotlen += event[selected].deltatime * curtempo / timeunitdiv;
       while (utotlen >= 1000000lu) {
         utotlen -= 1000000lu;
         *totlen += 1;
       }
     }
     if (event[selected].type == EVENT_TEMPO) curtempo = event[selected].data.tempoval;
     /* decrement timer on the non-selected track, and synch it to xms if needed */
     /* then move along on the selected track, and fetch it from xms */
     if (selected == 0) {
       if ((t1 >= 0) && (event[0].deltatime != 0)) {
         event[1].deltatime -= event[0].deltatime;
         pushevent(&event[1], t1);
       }
       t0 = event[0].next;
       if (t0 >= 0) pullevent(t0, &event[0]);
     } else { /* selected == 1 */
       if ((t0 >= 0) && (event[1].deltatime != 0)) {
         event[0].deltatime -= event[1].deltatime;
         pushevent(&event[0], t0);
       }
       t1 = event[1].next;
       if (t1 >= 0) pullevent(t1, &event[1]);
     }
   }
   return(res);
 }
	/*
	* A simple MIDI parsing library
	*
	* Copyright (c) 2014, 2015 Mateusz Viste
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	*
	* 1. Redistributions of source code must retain the above copyright notice,
	* this list of conditions and the following disclaimer.
	*
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
	* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	* POSSIBILITY OF SUCH DAMAGE.
	*/

	#include <stdlib.h> /* malloc */
	#include <string.h> /* strcmp() */

	#include "mem.h"
	#include "midi.h" /* include self for control */


	/* PRIVATE ROUTINES USED FOR INTERNAL PROCESSING ONLY */


	/* fetch a variable length quantity value from a given offset. returns number of bytes read */
	static int midi_fetch_variablelen_fromfile(FILE fd, unsigned long result) {
	int bytebuff;
	int offset = 0;
	*result = 0;
	for (;;) {
	bytebuff = fgetc(fd);
	*result <<= 7;
	*result \|= (bytebuff & 127);
	if ((bytebuff & 128) == 0) break;
	}
	return(offset);
	}

	/* reads a MIDI file and computes a map of chunks (ie a list of offsets) */
	static int midi_getchunkmap(FILE fd, struct midi_chunkmap_t chunklist, int maxchunks) {
	int chunkid, i;
	unsigned char hdr[8];
	unsigned long readres;
	/unsigned long chunklen;/
	for (chunkid = 0; chunkid < maxchunks; chunkid++) {
	readres = fread(hdr, 1, 8, fd);
	if (readres != 8) break;
	chunklist[chunkid].offset = ftell(fd);
	/* read chunk's id */
	for (i = 0; i < 4; i++) chunklist[chunkid].id[i] = hdr[i];
	chunklist[chunkid].id[4] = 0; /* string terminator */
	/* compute the length */
	chunklist[chunkid].len = 0;
	for (i = 4; i < 8; i++) {
	chunklist[chunkid].len <<= 8;
	chunklist[chunkid].len \|= hdr[i];
	}
	/* skip to next chunk */
	fseek(fd, chunklist[chunkid].len, SEEK_CUR);
	}
	return(chunkid);
	}


	/* PUBLIC INTERFACE */


	struct midi_chunk_t midi_readchunk(FILE fd) {
	unsigned char hdr[8];
	unsigned long readres;
	int i;
	unsigned long len = 0;
	struct midi_chunk_t *res;
	readres = fread(hdr, 1, 8, fd);
	if (readres != 8) return(NULL);
	/* compute the length */
	for (i = 4; i < 8; i++) {
	len <<= 8;
	len \|= hdr[i];
	}
	res = malloc(sizeof(struct midi_chunk_t) + (unsigned int)len);
	if (res == NULL) return(NULL);
	/* copy the id string */
	res->id[0] = hdr[0];
	res->id[1] = hdr[1];
	res->id[2] = hdr[2];
	res->id[3] = hdr[3];
	res->id[4] = 0;
	/* assign data length */
	res->datalen = len;
	/* copy actual data */
	readres = fread(res->data, 1, (unsigned int)res->datalen, fd);
	if (readres != res->datalen) {
	free(res);
	return(NULL);
	}
	return(res);
	}

	int midi_readhdr(FILE fd, int format, int tracks, unsigned short timeunitdiv, struct midi_chunkmap_t *chunklist, int maxchunks) {
	struct midi_chunk_t *chunk;
	unsigned char rmidbuff[12];
	/* test for RMID format and rewind if not found */
	/* a RMID file starts with RIFFxxxxRMID (xxxx being the data size) */
	/* read first 12 bytes - if unable, return an error */
	if (fread(rmidbuff, 1, 12, fd) != 12) return(-7);
	/* if no RMID header, then rewind the file assuming it's normal MIDI */
	if ((rmidbuff[0] != 'R') \|\| (rmidbuff[1] != 'I') \|\| (rmidbuff[2] != 'F') \|\| (rmidbuff[3] != 'F')
	\|\| (rmidbuff[8] != 'R') \|\| (rmidbuff[9] != 'M') \|\| (rmidbuff[10] != 'I') \|\| (rmidbuff[11] != 'D')) {
	rewind(fd);
	}
	/* Read the first chunk of data (should be the MIDI header) */
	chunk = midi_readchunk(fd);
	if (chunk == NULL) {
	return(-6);
	}
	/* check id */
	if (strcmp(chunk->id, "MThd") != 0) {
	free(chunk);
	return(-5);
	}
	/* check len - must be at least 6 bytes */
	if (chunk->datalen < 6) {
	free(chunk);
	return(-4);
	}
	*format = (chunk->data[0] << 8) \| chunk->data[1];
	*tracks = (chunk->data[2] << 8) \| chunk->data[3];

	*timeunitdiv = chunk->data[4];
	*timeunitdiv <<= 8;
	*timeunitdiv \|= chunk->data[5];
	/* timeunitdiv must be a positive number */
	if (*timeunitdiv < 1) {
	free(chunk);
	return(-3);
	}

	/* default tempo -> quarter note (1 beat) == 500'000 microseconds (0.5s), ie 120 bpm.
	a delta time unit is therefore (0.5s / DIV) long. */
	/* check the timeunit */
	if (chunk->data[4] & 128) {
	free(chunk);
	return(-2);
	}
	/* check format - must be 0, 1 or 2 */
	if ((format < 0) \|\| (format > 2)) {
	free(chunk);
	return(-1);
	}
	/* read the chunk map */
	midi_getchunkmap(fd, chunklist, maxchunks);
	return(0);
	}

	/* parse a track object and returns the id of the first events in the linked
	* list. channelsusage contains 16 flags indicating what channels are used. */
	long midi_track2events(FILE fd, char title, int titlenodes, int titlemaxlen, char copyright, int copyrightmaxlen, unsigned short channelsusage, FILE logfd) {
	unsigned long deltatime;
	unsigned char statusbyte = 0, tmp;
	struct midi_event_t event;
	long result = -1;
	unsigned long tracklen = 0;
	unsigned long ignoreddeltas = 0;
	unsigned char ubuff[4]; /* micro buffer for loading data */

	for (;;) {
	/* read the delta time first - variable length */
	midi_fetch_variablelen_fromfile(fd, &deltatime);
	tracklen += deltatime;
	/* check the type of the event */
	/* if it's a byte with MSB set, we are dealing with running status (so it's same status as last time */
	tmp = fgetc(fd);
	if ((tmp & 128) != 0) {
	statusbyte = tmp;
	} else { /* get back one byte */
	fseek(fd, -1, SEEK_CUR);
	}
	event.type = EVENT_NONE;
	event.deltatime = deltatime;
	event.next = -1;
	if (statusbyte == 0xFF) { /* META event */
	unsigned long metalen;
	unsigned long i;
	int subtype, endoftrack = 0;
	subtype = fgetc(fd); /* fetch the META subtype fields */
	midi_fetch_variablelen_fromfile(fd, &metalen);
	/* printf("got META[0x%02X] of %ld bytes\n", subtype, metalen); */
	switch (subtype) {
	case 1: /* text */
	fseek(fd, metalen, SEEK_CUR);
	break;
	case 2: /* copyright notice */
	i = 0;
	if (copyright != NULL) { /* take care, copyright might be NULL */
	for (; i < metalen; i++) {
	if (i == copyrightmaxlen) break; /* avoid overflow */
	copyright[i] = fgetc(fd);
	}
	copyright[i] = 0;
	}
	fseek(fd, metalen - i, SEEK_CUR); /* skip the rest, if we had to truncate the string */
	break;
	case 3: /* track name */
	i = 0;
	/* find the first empty track */
	if (title != NULL) { /* title might be NULL */
	int titid = -1, t;
	for (t = 0; t < titlenodes; t++) {
	if (title[t][0] == 0) {
	titid = t;
	break;
	}
	}
	if (titid >= 0) {
	for (i = 0; i < metalen; i++) {
	if (i == titlemaxlen) break; /* avoid overflow */
	title[titid][i] = fgetc(fd);
	}
	title[titid][i] = 0;
	}
	}
	fseek(fd, metalen - i, SEEK_CUR); /* skip the rest, if we had to truncate the string */
	break;
	case 4: /* instrument name */
	case 5: /* lyric */
	fseek(fd, metalen, SEEK_CUR);
	if (logfd != NULL) fprintf(logfd, "%lu: LYRIC EVENT (ignored)\n", tracklen);
	break;
	case 0x21: /* MIDI port -- no support for multi-MIDI files, I just ignore it */
	fseek(fd, metalen, SEEK_CUR);
	if (logfd != NULL) fprintf(logfd, "%lu: MIDI PORT EVENT (ignored)\n", tracklen);
	break;
	case 0x2F: /* end of track */
	if (logfd != NULL) fprintf(logfd, "%lu: END OF TRACK\n", tracklen);
	endoftrack = 1;
	break;
	case 0x51: /* set tempo */
	if (metalen != 3) {
	if (logfd != NULL) fprintf(logfd, "%lu: TEMPO ERROR\n", tracklen);
	} else {
	fread(ubuff, 1, 3, fd);
	event.type = EVENT_TEMPO;
	event.data.tempoval = ubuff[0];
	event.data.tempoval <<= 8;
	event.data.tempoval \|= ubuff[1];
	event.data.tempoval <<= 8;
	event.data.tempoval \|= ubuff[2];
	if (logfd != NULL) fprintf(logfd, "%lu: TEMPO -> %lu\n", tracklen, event.data.tempoval);
	}
	break;
	case 0x54: /* SMPTE offset -> since I expect only format 0/1 files, I ignore this because I want to start playing asap anyway */
	fseek(fd, metalen, SEEK_CUR);
	if (logfd != NULL) fprintf(logfd, "%lu: SMPTE OFFSET (ignored)\n", tracklen);
	break;
	case 0x58: /* Time signature */
	if (metalen != 4) {
	if (logfd != NULL) fprintf(logfd, "%lu: INVALID TIME SIGNATURE!\n", tracklen);
	return(-1);
	} else {
	fseek(fd, metalen, SEEK_CUR);
	if (logfd != NULL) fprintf(logfd, "%lu: TIME SIGNATURE (ignored)\n", tracklen);
	}
	break;
	case 0x59: /* key signature */
	if (metalen != 2) {
	if (logfd != NULL) fprintf(logfd, "%lu: INVALID KEY SIGNATURE!\n", tracklen);
	return(-1);
	} else {
	fseek(fd, metalen, SEEK_CUR);
	if (logfd != NULL) fprintf(logfd, "%lu: KEY SIGNATURE (ignored)\n", tracklen);
	}
	break;
	case 0x7F: /* proprietary event -> this is non-standard stuff, I ignore it */
	fseek(fd, metalen, SEEK_CUR);
	if (logfd != NULL) fprintf(logfd, "%lu: PROPRIETARY EVENT (ignored)\n", tracklen);
	break;
	default:
	fseek(fd, metalen, SEEK_CUR); /* skip the meta data */
	if (logfd != NULL) fprintf(logfd, "%lu: UNHANDLED META EVENT [0x%02X] (ignored)\n", tracklen, subtype);
	break;
	}
	if (endoftrack != 0) break;
	} else if ((statusbyte >= 0xF0) && (statusbyte <= 0xF7)) { /* SYSEX event */
	unsigned long sysexlen;
	midi_fetch_variablelen_fromfile(fd, &sysexlen); /* get length */
	if (logfd != NULL) fprintf(logfd, "%lu: SYSEX EVENT OF %ld BYTES (ignored)\n", tracklen, sysexlen);
	fseek(fd, sysexlen, SEEK_CUR);
	} else if ((statusbyte >= 0x80) && (statusbyte <= 0xEF)) { /* else it's a note-related command */
	switch (statusbyte & 0xF0) { /* I care only about NoteOn/NoteOff events */
	case 0x80: /* Note OFF */
	fread(ubuff, 1, 2, fd);
	event.type = EVENT_NOTEOFF;
	event.data.note.chan = statusbyte & 0x0F;
	event.data.note.note = ubuff[0] & 127; /* a note must be in range 0..127 */
	event.data.note.velocity = ubuff[1];
	break;
	case 0x90: /* Note ON */
	fread(ubuff, 1, 2, fd);
	channelsusage \|= (1 << event.data.note.chan); / update the channel usage flags */
	event.type = EVENT_NOTEON;
	event.data.note.chan = statusbyte & 0x0F;
	event.data.note.note = ubuff[0] & 127;
	event.data.note.velocity = ubuff[1];
	if (event.data.note.velocity == 0) event.type = EVENT_NOTEOFF; /* if no velocity, it's in fact a note OFF */
	break;
	case 0xA0: /* key after-touch */
	/* puts("KEY AFTER-TOUCH"); */
	fread(ubuff, 1, 2, fd);
	event.type = EVENT_KEYPRESSURE;
	event.data.keypressure.chan = statusbyte & 0x0F;
	event.data.keypressure.note = ubuff[0];
	event.data.keypressure.pressure = ubuff[1];
	break;
	case 0xB0: /* control change */
	/* puts("CONTROL CHANGE"); */
	fread(ubuff, 1, 2, fd);
	event.type = EVENT_CONTROL;
	event.data.control.chan = statusbyte & 0x0F;
	event.data.control.id = ubuff[0];
	event.data.control.val = ubuff[1];
	break;
	case 0xC0: /* program (patch) change */
	event.type = EVENT_PROGCHAN;
	event.data.prog.chan = statusbyte & 0x0F;
	event.data.prog.prog = fgetc(fd);
	break;
	case 0xD0: /* channel after-touch (aka "channel pressure") */
	event.type = EVENT_CHANPRESSURE;
	event.data.chanpressure.chan = statusbyte & 0x0F;
	event.data.chanpressure.pressure = fgetc(fd);
	break;
	case 0xE0: /* pitch wheel change */
	fread(ubuff, 1, 2, fd);
	event.type = EVENT_PITCH;
	event.data.pitch.chan = statusbyte & 0x0F;
	event.data.pitch.wheel = ubuff[1];
	event.data.pitch.wheel <<= 7;
	event.data.pitch.wheel \|= ubuff[0];
	break;
	default:
	if (logfd != NULL) fprintf(logfd, "%lu: Unknown note data\n", tracklen);
	return(-1);
	break;
	}
	} else { /* else it's an error - free memory we allocated and return NULL */
	if (logfd != NULL) fprintf(logfd, "Err. at offset %04lX (bytebuff = 0x%02X)\n", ftell(fd), statusbyte);
	return(-1);
	}
	/* add the event to the queue */
	if (event.type == EVENT_NONE) {
	ignoreddeltas += event.deltatime;
	} else {
	event.deltatime += ignoreddeltas; /* add any previously ignored delta times */
	ignoreddeltas = 0;
	/* add the event to the queue */
	if (result < 0) {
	pusheventqueue(&event, &result);
	} else {
	pusheventqueue(&event, NULL);
	}
	}
	}
	if (result >= 0) pusheventqueue(NULL, NULL); /* flush last event in buffer to memory */
	return(result);
	}

	/* merge two MIDI tracks into a single (serialized) one. returns a "pointer"
	* to the unique track. I take care not to allocate/free memory here.
	* All notes are already in RAM after all. totlen is filled with the total
	* time of the merged tracks (in seconds). */
	long midi_mergetrack(long t0, long t1, unsigned long *totlen, unsigned short timeunitdiv) {
	long res = -1, lasteventid = -1, selectedid;
	int selected;
	unsigned long curtempo = 500000l, utotlen = 0;
	struct midi_event_t event[2], lastevent;

	if (totlen != NULL) *totlen = 0;
	/* fetch first events for both tracks */
	if (t0 >= 0) pullevent(t0, &event[0]);
	if (t1 >= 0) pullevent(t1, &event[1]);
	/* start looping */
	while ((t0 >= 0) \|\| (t1 >= 0)) {
	/* compare both tracks, and select the soonest one */
	if (t0 >= 0) {
	if ((t1 >= 0) && (event[1].deltatime < event[0].deltatime)) {
	selected = 1;
	selectedid = t1;
	} else {
	selected = 0;
	selectedid = t0;
	}
	} else {
	selected = 1;
	selectedid = t1;
	}
	/* on first iteration, make sure to assign a result */
	if (lasteventid < 0) {
	res = selectedid;
	} else if (lastevent.next != selectedid) { /* otherwise attach selected */
	lastevent.next = selectedid; /* track to last note, and */
	pushevent(&lastevent, lasteventid); /* update last pointer (if */
	} /* not good already) */
	/* save the last event into buffer for later, and remember its id */
	lasteventid = selectedid;
	memcpy(&lastevent, &(event[selected]), sizeof(struct midi_event_t));
	/* increment timer */
	if ((totlen != NULL) && (event[selected].deltatime != 0)) {
	utotlen += event[selected].deltatime * curtempo / timeunitdiv;
	while (utotlen >= 1000000lu) {
	utotlen -= 1000000lu;
	*totlen += 1;
	}
	}
	if (event[selected].type == EVENT_TEMPO) curtempo = event[selected].data.tempoval;
	/* decrement timer on the non-selected track, and synch it to xms if needed */
	/* then move along on the selected track, and fetch it from xms */
	if (selected == 0) {
	if ((t1 >= 0) && (event[0].deltatime != 0)) {
	event[1].deltatime -= event[0].deltatime;
	pushevent(&event[1], t1);
	}
	t0 = event[0].next;
	if (t0 >= 0) pullevent(t0, &event[0]);
	} else { /* selected == 1 */
	if ((t0 >= 0) && (event[1].deltatime != 0)) {
	event[0].deltatime -= event[1].deltatime;
	pushevent(&event[0], t0);
	}
	t1 = event[1].next;
	if (t1 >= 0) pullevent(t1, &event[1]);
	}
	}
	return(res);
	}