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make aucat(1) stop automatically the audio(1) device if it's idle. This
way, when in server mode, it consumes no CPU if there are no clients.
Later, this will allow to start aucat(1) at session or system startup.

/*	$OpenBSD: abuf.h,v 1.12 2008/11/09 16:26:07 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.
 */
#ifndef ABUF_H
#define ABUF_H

#include <sys/queue.h>

struct abuf;
struct aproc;
struct aparam;

struct abuf {
	/*
	 * Misc aproc-specific per-buffer parameters.
	 * since the buffer can connect any pair of aproc structure,
	 * each aproc must have it's own specific data. Thus we cannot 
	 * use an union. The only exception is the xrun field, because
	 * there can be only one aproc that absorbs xruns in any 
	 * intput->output path.
	 */
	int mixivol;		/* volume of the source stream */
	unsigned mixodone;	/* bytes done on the dest stream */
	unsigned mixitodo;	/* bytes to do on the source stream */
	unsigned subidone;	/* bytes copied from the source stream */
#define XRUN_IGNORE	0	/* on xrun silently insert/discard samples */
#define XRUN_SYNC	1	/* catchup to sync to the mix/sub */
#define XRUN_ERROR	2	/* xruns are errors, eof/hup buffer */
	unsigned xrun;		/* common to mix and sub */
	LIST_ENTRY(abuf) ient;	/* for mix inputs list */
	LIST_ENTRY(abuf) oent;	/* for sub outputs list */
	
	/*
	 * fifo parameters
	 */
	unsigned bpf;		/* bytes per frame */
	unsigned cmin, cmax;	/* channel range of this buf */
	unsigned start;		/* offset where data starts */
	unsigned used;		/* valid data */
	unsigned len;		/* size of the ring */
	unsigned abspos;	/* frame number of the start position */
	unsigned silence;	/* silence to insert on next write */
	unsigned drop;		/* bytes to drop on next read */
	struct aproc *rproc;	/* reader */
	struct aproc *wproc;	/* writer */
	struct abuf *duplex;	/* link to buffer of the other direction */
	unsigned inuse;		/* in abuf_{flush,fill,run}() */
	unsigned char *data;	/* actual data (immediately following) */
};

/*
 * the buffer contains at least one frame. This macro should
 * be used to check if the buffer can be flushed
 */
#define ABUF_ROK(b) ((b)->used >= (b)->bpf)

/*
 * there's room for at least one frame
 */
#define ABUF_WOK(b) ((b)->len - (b)->used >= (b)->bpf)

/*
 * the buffer is empty and has no more writer
 */
#define ABUF_EOF(b) (!ABUF_ROK(b) && (b)->wproc == NULL)

/*
 * the buffer is empty and has no more writer
 */
#define ABUF_HUP(b) (!ABUF_WOK(b) && (b)->rproc == NULL)

/*
 * similar to !ABUF_WOK, but is used for file i/o, where
 * operation may not involve an integer number of frames
 */
#define ABUF_FULL(b) ((b)->used == (b)->len)

/*
 * same as !ABUF_ROK, but used for files, where
 * operations are byte orientated, not frame-oriented
 */
#define ABUF_EMPTY(b) ((b)->used == 0)

struct abuf *abuf_new(unsigned, struct aparams *);
void abuf_del(struct abuf *);
void abuf_clear(struct abuf *);
unsigned char *abuf_rgetblk(struct abuf *, unsigned *, unsigned);
unsigned char *abuf_wgetblk(struct abuf *, unsigned *, unsigned);
void abuf_rdiscard(struct abuf *, unsigned);
void abuf_wcommit(struct abuf *, unsigned);
int abuf_fill(struct abuf *);
int abuf_flush(struct abuf *);
void abuf_eof(struct abuf *);
void abuf_hup(struct abuf *);
void abuf_run(struct abuf *);
void abuf_ipos(struct abuf *, int);
void abuf_opos(struct abuf *, int);

#endif /* !defined(ABUF_H) */