readmidi.c

来自「SDL_mixer 是一个基于 SDL 的混音器」· C语言 代码 · 共 189 行

/************************************************************************
   readmidi.c -- last change: 1 Jan 96

   Creates a linked list of each chunk in a midi file.
   ENTIRE MIDI FILE IS RETAINED IN MEMORY so that no additional malloc
   calls need be made to store the data of the events in the midi file.

   Copyright (C) 1995-1996 Nathan I. Laredo

   This program is modifiable/redistributable under the terms
   of the GNU General Public Licence.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   Send your comments and all your spare pocket change to
   [e-mail] (Nathan Laredo) or to PSC 1, BOX 709, 2401
   Kelly Drive, Lackland AFB, TX 78236-5128, USA.
 *************************************************************************/
/*    edited by Peter Kutak           */
/*    email : [e-mail]       */

#if defined(linux) || defined(__FreeBSD__)

#include "playmidi.h"
#include <unistd.h>

int format, ntrks, division;
unsigned char *midifilebuf;

/* the following few lines are needed for dealing with CMF files */
int reloadfm = 0;
extern void loadfm();
extern int seqfd, sb_dev, wantopl3, play_fm, fmloaded[256];
SEQ_USE_EXTBUF();

extern struct miditrack seq[MAXTRKS];
extern unsigned long int default_tempo;

unsigned short Read16()
{
    register unsigned short x;

    x = (*(midifilebuf) << 8) | midifilebuf[1];
    midifilebuf += 2;
    return x;
}

unsigned long Read32()
{
    register unsigned long x;

    x = (*(midifilebuf) << 24) | (midifilebuf[1] << 16) |
	(midifilebuf[2] << 8) | midifilebuf[3];
    midifilebuf += 4;
    return x;
}

int readmidi(filebuf, filelength)
unsigned char *filebuf;
off_t filelength;
{
    unsigned long int i = 0, track, tracklen;

    midifilebuf = filebuf;
    /* allow user to specify header number in from large archive */
#if 0
    while (i != find_header && midifilebuf < (filebuf + filelength - 32)) {
	if (strncmp(midifilebuf, "MThd", 4) == 0) {
	    i++;
	    midifilebuf += 4;
	} else
	    midifilebuf++;
    }
    if (i != find_header) {	/* specified header was not found */
	midifilebuf = filebuf;
	return find_header = 0;
    }
#endif
    if (midifilebuf != filebuf)
	midifilebuf -= 4;
    i = Read32();
    if (i == RIFF) {
	midifilebuf += 16;
	i = Read32();
    }
    if (i == MThd) {
	tracklen = Read32();
	format = Read16();
	ntrks = Read16();
	division = Read16();
    } else if (i == CTMF) {
	/* load a creative labs CMF file, with instruments for fm */
	tracklen = midifilebuf[4] | (midifilebuf[5] << 8);
	format = 0;
	ntrks = 1;
	division = midifilebuf[6] | (midifilebuf[7] << 8);
	default_tempo = 1000000 * division /
		(midifilebuf[8] | (midifilebuf[9] << 8));
	seq[0].data = filebuf + tracklen;
	seq[0].length = filelength - tracklen;
	i = (unsigned long int) (*(short *) &midifilebuf[2]) - 4;
	/* if fm playback is enabled, load all fm patches from file */
	if (play_fm) {
	    struct sbi_instrument instr;
	    int j, k;
	    reloadfm = midifilebuf[32]; /* number of custom patches */
            instr.device = sb_dev;
	    for (j = 0; j < 32; j++)
		instr.operators[j] = 0x3f;
	    instr.key = FM_PATCH;
	    for (j = 0; j < reloadfm && j < 255; j++) {
                instr.channel = j;
		fmloaded[j] = instr.key;
                for (k = 0; k < 16; k++)
		    instr.operators[k] = midifilebuf[i + (16 * j) + k];
		SEQ_WRPATCH(&instr, sizeof(instr));
	    }
	}
	return ntrks;
    } else {
	int found = 0;
	while (!found && midifilebuf < (filebuf + filelength - 8))
	    if (strncmp(midifilebuf, "MThd", 4) == 0)
		found++;
	    else
		midifilebuf++;
	if (found) {
	    midifilebuf += 4;
	    tracklen = Read32();
	    format = Read16();
	    ntrks = Read16();
	    division = Read16();
	} else {
#ifndef DISABLE_RAW_MIDI_FILES
	    /* this allows playing ANY file, so watch out */
	    midifilebuf -= 4;
	    format = 0;		/* assume it's .mus file ? */
	    ntrks = 1;
	    division = 40;
#else
	    return -1;
#endif
	}
    }
    if (ntrks > MAXTRKS) {
	fprintf(stderr, "\nWARNING: %d TRACKS IGNORED!\n", ntrks - MAXTRKS);
	ntrks = MAXTRKS;
    }
    if (play_fm && reloadfm) {
	loadfm();	/* if custom CMF patches loaded, replace */
	reloadfm = 0;
    }
    for (track = 0; track < ntrks; track++) {
	if (Read32() != MTrk) {
	    /* MTrk isn't where it's supposed to be, search rest of file */
	    int fuzz, found = 0;
	    midifilebuf -= 4;
	    if (strncmp(midifilebuf, "MThd", 4) == 0)
		continue;
	    else {
		if (!track) {
		    seq[0].length = filebuf + filelength - midifilebuf;
		    seq[0].data = midifilebuf;
		    continue;	/* assume raw midi data file */
		}
		midifilebuf -= seq[track - 1].length;
		for (fuzz = 0; (fuzz + midifilebuf) <
		     (filebuf + filelength - 8) && !found; fuzz++)
		    if (strncmp(&midifilebuf[fuzz], "MTrk", 4) == 0)
			found++;
		seq[track - 1].length = fuzz;
		midifilebuf += fuzz;
		if (!found)
		    continue;
	    }
	}
	tracklen = Read32();
	if (midifilebuf + tracklen > filebuf + filelength)
	    tracklen = filebuf + filelength - midifilebuf;
	seq[track].length = tracklen;
	seq[track].data = midifilebuf;
	midifilebuf += tracklen;
    }
    ntrks = track;
    return ntrks;
}
#endif /* linux || FreeBSD */