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Currently midi capable programs can control midi hardware, but
cannot cooperate with other programs.  The aim of this change is
to allow any program to send midi data to other programs as they
were midi hardware. For instance, this change should solve the
longstanding problem of using a midi sequencer with software
synthesizers. More precisely:

 - new midicat(1) utility (actually hardlink to aucat(1)).
   it creates software midi thru boxes, allowing programs
   to send midi messages to other programs as they were
   midi(4) hardware.

 - new midi api in libsndio (see mio_open(3)), to access
   midi(4) devices and midicat(1) sockets in a uniform way.

 - new device naming scheme <service>:<unit>[.<option>],
   common to audio and midi.

 - new sndio(7) manual describing concepts and naming

The current audio device naming still works, but people having
scripts or configuration files containing device names could read
the sndio(7) man page and slowly start updating device names.

discussed with jakemsr@ and deraadt@, help form jmc@

/*	$OpenBSD: midi.c,v 1.1 2009/07/25 08:44:27 ratchov Exp $	*/
/*
 * Copyright (c) 2008 Alexandre Ratchov <alex@caoua.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/*
 * TODO
 *
 * use abuf->duplex to implement bidirectionnal sockets
 * that don't receive what they send
 *
 * use shadow variables in the midi merger
 *
 * make output and input identical when only one
 * input is used (fix running status)
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "conf.h"
#include "abuf.h"
#include "aproc.h"
#include "midi.h"

/*
 * input data rate is XFER / TIMO (in bytes per microsecond),
 * it must be slightly larger than the MIDI standard 3125 bytes/s
 */ 
#define MIDITHRU_XFER 340
#define MIDITHRU_TIMO 100000

struct aproc *thrubox = NULL;

unsigned voice_len[] = { 3, 3, 3, 3, 2, 2, 3 };
unsigned common_len[] = { 0, 2, 3, 2, 0, 0, 1, 1 };

void
thru_flush(struct aproc *p, struct abuf *ibuf, struct abuf *obuf)
{
	unsigned ocount, itodo;
	unsigned char *odata, *idata;

	itodo = ibuf->mused;
	idata = ibuf->mdata;
	DPRINTFN(4, "thru_flush: mused = %u\n", itodo);
	while (itodo > 0) {
		if (!ABUF_WOK(obuf)) {
			abuf_rdiscard(obuf, obuf->used);
			DPRINTFN(2, "thru_flush: discarded %u\n", obuf->used);
			if (p->u.thru.owner == ibuf)
				p->u.thru.owner = NULL;
			return;
		}
		odata = abuf_wgetblk(obuf, &ocount, 0);
		if (ocount > itodo)
			ocount = itodo;
		memcpy(odata, idata, ocount);
		abuf_wcommit(obuf, ocount);
		itodo -= ocount;
		idata += ocount;
	}
	ibuf->mused = 0;
	p->u.thru.owner = ibuf;
}

void
thru_rt(struct aproc *p, struct abuf *ibuf, struct abuf *obuf, unsigned c)
{
	unsigned ocount;
	unsigned char *odata;

	DPRINTFN(4, "thru_rt:\n");
	if (!ABUF_WOK(obuf)) {
		DPRINTFN(2, "thru_rt: discarded %u\n", obuf->used);
		abuf_rdiscard(obuf, obuf->used);
		if (p->u.thru.owner == ibuf)
			p->u.thru.owner = NULL;
	}
	odata = abuf_wgetblk(obuf, &ocount, 0);
	odata[0] = c;
	abuf_wcommit(obuf, 1);
}


void
thru_bcopy(struct aproc *p, struct abuf *ibuf, struct abuf *obuf, unsigned todo)
{
	unsigned char *idata;
	unsigned c, icount, ioffs;

	idata = NULL;
	icount = ioffs = 0;
	for (;;) {
		if (icount == 0) {
			if (todo == 0)
				break;
			idata = abuf_rgetblk(ibuf, &icount, ioffs);
			if (icount > todo)
				icount = todo;
			if (icount == 0)
				break;
			todo -= icount;
			ioffs += icount;
		}
		c = *idata++;
		icount--;
		if (c < 0x80) {
			if (ibuf->mindex == 0 && ibuf->mstatus) {
				ibuf->mdata[ibuf->mused++] = ibuf->mstatus;
				ibuf->mindex++;
			}
			ibuf->mdata[ibuf->mused++] = c;
			ibuf->mindex++;
			if (ibuf->mindex == ibuf->mlen) {
				thru_flush(p, ibuf, obuf);
				if (ibuf->mstatus >= 0xf0)
					ibuf->mstatus = 0;
				ibuf->mindex = 0;
			}
			if (ibuf->mused == MDATA_NMAX) {
				if (ibuf->mused == ibuf->mindex ||
				    p->u.thru.owner == ibuf)
					thru_flush(p, ibuf, obuf);
				else
					ibuf->mused = 0;
			}
		} else if (c < 0xf8) {
			if (ibuf->mused == ibuf->mindex ||
			    p->u.thru.owner == ibuf) {
				thru_flush(p, ibuf, obuf);
			} else
				ibuf->mused = 0;
			ibuf->mdata[0] = c;
			ibuf->mused = 1;
			ibuf->mlen = (c >= 0xf0) ? 
			    common_len[c & 7] :
			    voice_len[(c >> 4) & 7];
			if (ibuf->mlen == 1) {
				thru_flush(p, ibuf, obuf);
				ibuf->mindex = 0;
				ibuf->mstatus = 0;
				ibuf->mlen = 0;
			} else { 
				ibuf->mstatus = c;
				ibuf->mindex = 1;
			}
		} else {
			thru_rt(p, ibuf, obuf, c);
		}
	}
}

int
thru_in(struct aproc *p, struct abuf *ibuf)
{
	struct abuf *i, *inext;
	unsigned todo;

	DPRINTFN(3, "thru_in: %s\n", p->name);

	if (!ABUF_ROK(ibuf))
		return 0;
	if (ibuf->mtickets == 0) {
		DPRINTFN(2, "thru_in: out of tickets\n");
		return 0;
	}
	todo = ibuf->used;
	if (todo > ibuf->mtickets)
		todo = ibuf->mtickets;
	ibuf->mtickets -= todo;
	for (i = LIST_FIRST(&p->obuflist); i != NULL; i = inext) {
		inext = LIST_NEXT(i, oent);
		if (ibuf->duplex == i)
			continue;
		thru_bcopy(p, ibuf, i, todo);
		(void)abuf_flush(i);
	}
	abuf_rdiscard(ibuf, todo);
	return 1;
}

int
thru_out(struct aproc *p, struct abuf *obuf)
{
	return 0;
}

void
thru_eof(struct aproc *p, struct abuf *ibuf)
{
	DPRINTF("thru_eof: %s: eof\n", p->name);
}

void
thru_hup(struct aproc *p, struct abuf *obuf)
{
	DPRINTF("thru_hup: %s: detached\n", p->name);
}

void
thru_newin(struct aproc *p, struct abuf *ibuf)
{
	ibuf->mused = 0;
	ibuf->mlen = 0;
	ibuf->mindex = 0;
	ibuf->mstatus = 0;
	ibuf->mtickets = MIDITHRU_XFER;
}

void
thru_done(struct aproc *p)
{
	timo_del(&p->u.thru.timo);
}

struct aproc_ops thru_ops = {
	"thru",
	thru_in,
	thru_out,
	thru_eof,
	thru_hup,
	thru_newin,
	NULL, /* newout */
	NULL, /* ipos */
	NULL, /* opos */
	thru_done
};

void
thru_cb(void *addr)
{
	struct aproc *p = (struct aproc *)addr;
	struct abuf *i, *inext;
	unsigned tickets;

	timo_add(&p->u.thru.timo, MIDITHRU_TIMO);
	
	for (i = LIST_FIRST(&p->ibuflist); i != NULL; i = inext) {
		inext = LIST_NEXT(i, ient);
		tickets = i->mtickets;
		i->mtickets = MIDITHRU_XFER;
		if (tickets == 0)
			abuf_run(i);
	}
}

struct aproc *
thru_new(char *name)
{
	struct aproc *p;

	p = aproc_new(&thru_ops, name);
	p->u.thru.owner = NULL;
	timo_set(&p->u.thru.timo, thru_cb, p);
	timo_add(&p->u.thru.timo, MIDITHRU_TIMO);
	return p;
}