mfmidi.cpp

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/*
 * Read a Standard MIDI File.  Externally-assigned function pointers are
 * called upon recognizing things in the file.  See midifile(3).
 */

/*****************************************************************************
*       Change Log
*       Date    | who : Change
*-----------+-----------------------------------------------------------------
*  2-Mar-92 | GWL : created changelog; MIDIFILE_ERROR to satisfy compiler
*****************************************************************************/

#include "stdio.h"
#include "mfmidi.h"
#include "string.h"

#define MIDIFILE_ERROR -1

/* public stuff */
extern int abort_flag;


void Midifile_reader::midifile()
{
	int ntrks;
	midifile_error = 0;

	ntrks = readheader();
	if (midifile_error) return;
	if ( ntrks <= 0 ) {
		mferror("No tracks!");
		/* no need to return since midifile_error is set */
	}
	while (ntrks-- > 0 && !midifile_error) readtrack();
}

int Midifile_reader::readmt(char *s, int skip)
    /* read through the "MThd" or "MTrk" header string */
    /* if skip == 1, we attempt to skip initial garbage. */
{
	int nread = 0;
	char b[4];
	char buff[32];
	int c;
	char *errmsg = "expecting ";

    retry:
	while ( nread<4 ) {
		c = Mf_getc();
		if ( c == EOF ) {
			errmsg = "EOF while expecting ";
			goto err;
		}
		b[nread++] = c;
	}
	/* See if we found the 4 characters we're looking for */
	if ( s[0]==b[0] && s[1]==b[1] && s[2]==b[2] && s[3]==b[3] )
		return(0);
	if ( skip ) {
		/* If we are supposed to skip initial garbage, */
		/* try again with the next character. */
		b[0]=b[1];
		b[1]=b[2];
		b[2]=b[3];
		nread = 3;
		goto retry;
	}
    err:
	(void) strcpy(buff,errmsg);
	(void) strcat(buff,s);
	mferror(buff);
	return(0);
}

int Midifile_reader::egetc()
    /* read a single character and abort on EOF */
{
	int c = Mf_getc();

	if ( c == EOF ) {
		mferror("premature EOF");
		return EOF;
	}
	Mf_toberead--;
	return(c);
}

int Midifile_reader::readheader()
    /* read a header chunk */
{
	int format, ntrks, division;

	if ( readmt("MThd",Mf_skipinit) == EOF )
		return(0);

	Mf_toberead = read32bit();
	if (midifile_error) return MIDIFILE_ERROR;
	format = read16bit();
	if (midifile_error) return MIDIFILE_ERROR;
	ntrks = read16bit();
	if (midifile_error) return MIDIFILE_ERROR;
	division = read16bit();
	if (midifile_error) return MIDIFILE_ERROR;

	Mf_header(format,ntrks,division);

	/* flush any extra stuff, in case the length of header is not 6 */
	while ( Mf_toberead > 0 && !midifile_error)
		(void) egetc();
	return(ntrks);
}

void Midifile_reader::readtrack()
    /* read a track chunk */
{
	/* This array is indexed by the high half of a status byte.  It's */
	/* value is either the number of bytes needed (1 or 2) for a channel */
	/* message, or 0 (meaning it's not  a channel message). */
	static int chantype[] = {
		0, 0, 0, 0, 0, 0, 0, 0,         /* 0x00 through 0x70 */
		2, 2, 2, 2, 1, 1, 2, 0          /* 0x80 through 0xf0 */
	};
	long lookfor, lng;
	int c, c1, type;
	int sysexcontinue = 0;  /* 1 if last message was an unfinished sysex */
	int running = 0;        /* 1 when running status used */
	int status = 0;         /* (possibly running) status byte */
	int needed;

	if ( readmt("MTrk",0) == EOF )
		return;

	Mf_toberead = read32bit();

	if (midifile_error) return;

	Mf_currtime = 0L;

    Mf_starttrack();

    while ( Mf_toberead > 0 ) {

		Mf_currtime += readvarinum();   /* delta time */
		if (midifile_error) return;

		c = egetc();
        if (midifile_error) return;

		if ( sysexcontinue && c != 0xf7 ) {
			mferror("didn't find expected continuation of a sysex");
			return;
		}
		if ( (c & 0x80) == 0 ) {         /* running status? */
			if ( status == 0 ) {
				mferror("unexpected running status");
				return;
			}
			running = 1;
        } else {
			status = c;
			running = 0;
		}

		needed = chantype[ (status>>4) & 0xf ];

		if ( needed ) {         /* ie. is it a channel message? */

			if ( running )
				c1 = c;
			else {
				c1 = egetc();
				if (midifile_error) return;
			}
			chanmessage( status, c1, (needed>1) ? egetc() : 0 );
			if (midifile_error) return;
			continue;;
		}

		switch ( c ) {

		case 0xff:                      /* meta event */

			type = egetc();
			if (midifile_error) return;
			/* watch out - Don't combine the next 2 statements */
			lng = readvarinum();
			if (midifile_error) return;
			lookfor = Mf_toberead - lng;
			msginit();

			while ( Mf_toberead > lookfor ) {
				char c = egetc();
				if (midifile_error) return;
				msgadd(c);
			}
			metaevent(type);
			break;

		case 0xf0:              /* start of system exclusive */

			/* watch out - Don't combine the next 2 statements */
			lng = readvarinum();
			if (midifile_error) return;
			lookfor = Mf_toberead - lng;
			msginit();
			msgadd(0xf0);

			while ( Mf_toberead > lookfor ) {
				c = egetc();
				if (midifile_error) return;
				msgadd(c);
			}
			if ( c==0xf7 || Mf_nomerge==0 )
				sysex();
			else
				sysexcontinue = 1;  /* merge into next msg */
			break;

		case 0xf7:      /* sysex continuation or arbitrary stuff */

			/* watch out - Don't combine the next 2 statements */
			lng = readvarinum();
			if (midifile_error) return;
			lookfor = Mf_toberead - lng;

			if ( ! sysexcontinue )
				msginit();

			while ( Mf_toberead > lookfor ) {
				c = egetc();
				if (midifile_error) return;
				msgadd(c);
			}
			if ( ! sysexcontinue ) {
					Mf_arbitrary(msgleng(), msg());
			}
			else if ( c == 0xf7 ) {
				sysex();
				sysexcontinue = 0;
			}
			break;
		default:

			badbyte(c);

			break;
		}
	}
		Mf_endtrack();
	return;
}

void Midifile_reader::badbyte(int c)
{
	char buff[32];

	(void) sprintf(buff,"unexpected byte: 0x%02x",c);
	mferror(buff);
}

void Midifile_reader::metaevent(int type)
{
	int leng = msgleng();
	char *m = msg();

	switch  ( type ) {
	case 0x00:
			Mf_seqnum(to16bit(m[0],m[1]));
		break;
	case 0x01:      /* Text event */
	case 0x02:      /* Copyright notice */
	case 0x03:      /* Sequence/Track name */
	case 0x04:      /* Instrument name */
	case 0x05:      /* Lyric */
	case 0x06:      /* Marker */
	case 0x07:      /* Cue point */
	case 0x08:
	case 0x09:
	case 0x0a:
	case 0x0b:
	case 0x0c:
	case 0x0d:
	case 0x0e:
	case 0x0f:
		/* These are all text events */
			Mf_text(type,leng,m);
		break;
	case 0x2f:      /* End of Track */
			Mf_eot();
		break;
	case 0x51:      /* Set tempo */
			Mf_tempo(to32bit(0,m[0],m[1],m[2]));
		break;
	case 0x54:
			Mf_smpte(m[0],m[1],m[2],m[3],m[4]);
		break;
	case 0x58:
			Mf_timesig(m[0],m[1],m[2],m[3]);
		break;
	case 0x59:
			Mf_keysig(m[0],m[1]);
		break;
	case 0x7f:
			Mf_sqspecific(leng,m);
		break;
	default:
			Mf_metamisc(type,leng,m);
	}
}


void Midifile_reader::sysex()
{
	Mf_sysex(msgleng(), msg());
}


void Midifile_reader::chanmessage(int status, int c1, int c2)
{
	int chan = status & 0xf;

	switch ( status & 0xf0 ) {
	case NOTEOFF:
		Mf_off(chan,c1,c2);
		break;
	case NOTEON:
		Mf_on(chan,c1,c2);
		break;
	case PRESSURE:
		Mf_pressure(chan,c1,c2);
		break;
	case CONTROLLER:
		Mf_controller(chan,c1,c2);
		break;
	case PITCHBEND:
		Mf_pitchbend(chan,c1,c2);
		break;
	case PROGRAM:
		Mf_program(chan,c1);
		break;
	case CHANPRESSURE:
		Mf_chanpressure(chan,c1);
		break;
	}
}

/* readvarinum - read a varying-length number, and return the */
/* number of characters it took. */

long Midifile_reader::readvarinum()
{
	long value;
	int c;

	c = egetc();
	if (midifile_error) return 0;

	value = (long) c;
	if ( c & 0x80 ) {
		value &= 0x7f;
		do {
			c = egetc();
			if (midifile_error) return 0;
			value = (value << 7) + (c & 0x7f);
		} while (c & 0x80);
	}
	return (value);
}

long Midifile_reader::to32bit(int c1, int c2, int c3, int c4)
{
	long value = 0L;

	value = (c1 & 0xff);
	value = (value<<8) + (c2 & 0xff);
	value = (value<<8) + (c3 & 0xff);
	value = (value<<8) + (c4 & 0xff);
	return (value);
}

int Midifile_reader::to16bit(int c1, int c2)
{
	return ((c1 & 0xff ) << 8) + (c2 & 0xff);
}

long Midifile_reader::read32bit()
{
	int c1, c2, c3, c4;

	c1 = egetc(); if (midifile_error) return 0;
	c2 = egetc(); if (midifile_error) return 0;
	c3 = egetc(); if (midifile_error) return 0;
	c4 = egetc(); if (midifile_error) return 0;
	return to32bit(c1,c2,c3,c4);
}

int Midifile_reader::read16bit()
{
	int c1, c2;
	c1 = egetc(); if (midifile_error) return 0;
	c2 = egetc(); if (midifile_error) return 0;
	return to16bit(c1,c2);
}

void Midifile_reader::mferror(char *s)
{
	Mf_error(s);
	midifile_error = 1;
}

/* The code below allows collection of a system exclusive message of */
/* arbitrary length.  The Msgbuff is expanded as necessary.  The only */
/* visible data/routines are msginit(), msgadd(), msg(), msgleng(). */

#define MSGINCREMENT 128

Midifile_reader::Midifile_reader()
{
    Mf_nomerge = 0;
    Mf_currtime = 0L;
    Mf_skipinit = 0;
    Mf_toberead = 0;

    Msgbuff = 0;       /* message buffer */
    Msgsize = 0;         /* Size of currently allocated Msg */
    Msgindex = 0;        /* index of next available location in Msg */
}

void Midifile_reader::msginit()
{
	Msgindex = 0;
}

char *Midifile_reader::msg()
{
	return(Msgbuff);
}

int Midifile_reader::msgleng()
{
	return(Msgindex);
}

void Midifile_reader::msgadd(int c)
{
	/* If necessary, allocate larger message buffer. */
	if ( Msgindex >= Msgsize )
		msgenlarge();
	Msgbuff[Msgindex++] = c;
}

void Midifile_reader::msgenlarge()
{
	char *newmess;
	char *oldmess = Msgbuff;
	int oldleng = Msgsize;

	Msgsize += MSGINCREMENT;
	newmess = (char *) Mf_malloc((sizeof(char) * Msgsize) );

	/* copy old message into larger new one */
	if ( oldmess != 0 ) {
		register char *p = newmess;
		register char *q = oldmess;
		register char *endq = &oldmess[oldleng];

		for ( ; q!=endq ; p++,q++ )
			*p = *q;
		Mf_free(oldmess, oldleng);
	}
	Msgbuff = newmess;
}