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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@

#include <sys/time.h>
#include <sys/types.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "conf.h"
#include "pipe.h"

struct fileops pipe_ops = {
	"pipe",
	sizeof(struct pipe),
	pipe_close,
	pipe_read,
	pipe_write,
	NULL, /* start */
	NULL, /* stop */
	pipe_nfds,
	pipe_pollfd,
	pipe_revents
};

struct pipe *
pipe_new(struct fileops *ops, int fd, char *name)
{
	struct pipe *f;

	f = (struct pipe *)file_new(ops, name, 1);
	if (f == NULL)
		return NULL;
	f->fd = fd;
	return f;
}

unsigned
pipe_read(struct file *file, unsigned char *data, unsigned count)
{
	struct pipe *f = (struct pipe *)file;
	int n;
#ifdef DEBUG
	struct timeval tv0, tv1, dtv;
	unsigned us;

	if (!(f->file.state & FILE_ROK)) {
		DPRINTF("pipe_read: %s: bad state\n", f->file.name);
		abort();
	}
	gettimeofday(&tv0, NULL);
#endif
	while ((n = read(f->fd, data, count)) < 0) {
		f->file.state &= ~FILE_ROK;
		if (errno == EAGAIN) {
			DPRINTFN(3, "pipe_read: %s: blocking...\n",
			    f->file.name);
		} else {
			warn("%s", f->file.name);
			file_eof(&f->file);
		}
		return 0;
	}
	if (n == 0) {
		DPRINTFN(2, "pipe_read: %s: eof\n", f->file.name);
		f->file.state &= ~FILE_ROK;
		file_eof(&f->file);
		return 0;
	}
#ifdef DEBUG
	gettimeofday(&tv1, NULL);
	timersub(&tv1, &tv0, &dtv);
	us = dtv.tv_sec * 1000000 + dtv.tv_usec;
	DPRINTFN(us < 5000 ? 4 : 2,
	    "pipe_read: %s: got %d bytes in %uus\n",
	    f->file.name, n, us);
#endif
	return n;
}


unsigned
pipe_write(struct file *file, unsigned char *data, unsigned count)
{
	struct pipe *f = (struct pipe *)file;
	int n;
#ifdef DEBUG
	struct timeval tv0, tv1, dtv;
	unsigned us;

	if (!(f->file.state & FILE_WOK)) {
		DPRINTF("pipe_write: %s: bad state\n", f->file.name);
		abort();
	}
	gettimeofday(&tv0, NULL);
#endif
	while ((n = write(f->fd, data, count)) < 0) {
		f->file.state &= ~FILE_WOK;
		if (errno == EAGAIN) {
			DPRINTFN(3, "pipe_write: %s: blocking...\n",
			    f->file.name);
		} else {
			if (errno != EPIPE)
				warn("%s", f->file.name);
			file_hup(&f->file);
		}
		return 0;
	}
#ifdef DEBUG
	gettimeofday(&tv1, NULL);
	timersub(&tv1, &tv0, &dtv);
	us = dtv.tv_sec * 1000000 + dtv.tv_usec;
	DPRINTFN(us < 5000 ? 4 : 2,
	    "pipe_write: %s: wrote %d bytes in %uus\n",
	    f->file.name, n, us);
#endif
	return n;
}

int
pipe_nfds(struct file *file) {
	return 1;
}

int
pipe_pollfd(struct file *file, struct pollfd *pfd, int events)
{
	struct pipe *f = (struct pipe *)file;

	pfd->fd = f->fd;
	pfd->events = events;
	return (events != 0) ? 1 : 0;
}

int
pipe_revents(struct file *f, struct pollfd *pfd)
{
	return pfd->revents;
}

void
pipe_close(struct file *file)
{
	struct pipe *f = (struct pipe *)file;

	close(f->fd);
}