usr.bin/telnet/ring.c

/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*
 * usr/src/cmd/cmd-inet/usr.bin/telnet/ring.c
 */

/*
 * Copyright (c) 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)ring.c	8.1 (Berkeley) 6/6/93";
#endif /* not lint */

/*
 * This defines a structure for a ring buffer.
 *
 * The circular buffer has two parts:
 * (((
 *	full:	[consume, supply)
 *	empty:	[supply, consume)
 * ]]]
 *
 */

#include	<stdio.h>
#include	<errno.h>
#include	<string.h>

#include	<sys/types.h>
#include	<sys/socket.h>
#include	<sys/sysmacros.h>

#include	"ring.h"
#include	"general.h"


#define	ring_subtract(d, a, b)	(((a)-(b) >= 0)? \
					(a)-(b): (((a)-(b))+(d)->size))

#define	ring_increment(d, a, c)	(((a)+(c) < (d)->top)? \
					(a)+(c) : (((a)+(c))-(d)->size))

#define	ring_decrement(d, a, c)	(((a)-(c) >= (d)->bottom)? \
					(a)-(c) : (((a)-(c))-(d)->size))


/*
 * The following is a clock, used to determine full, empty, etc.
 *
 * There is some trickiness here.  Since the ring buffers are initialized
 * to ZERO on allocation, we need to make sure, when interpreting the
 * clock, that when the times are EQUAL, then the buffer is FULL.
 */
ulong_t ring_clock = 0;


#define	ring_empty(d) (((d)->consume == (d)->supply) && \
				((d)->consumetime >= (d)->supplytime))
#define	ring_full(d) (((d)->supply == (d)->consume) && \
				((d)->supplytime > (d)->consumetime))


/* Buffer state transition routines */

int
    ring_init(ring, buffer, count)
Ring *ring;
    unsigned char *buffer;
    int count;
{
	(void) memset(ring, 0, sizeof (*ring));

	ring->size = count;

	ring->supply = ring->consume = ring->bottom = buffer;

	ring->top = ring->bottom+ring->size;

	ring->clearto = 0;

	return (1);
}

/* Mark routines */

/*
 * Mark the most recently supplied byte.
 */

void
ring_mark(ring)
	Ring *ring;
{
	ring->mark = ring_decrement(ring, ring->supply, 1);
}

/*
 * Is the ring pointing to the mark?
 */

int
ring_at_mark(ring)
	Ring *ring;
{
	if (ring->mark == ring->consume) {
		return (1);
	} else {
		return (0);
	}
}

/*
 * Clear any mark set on the ring.
 */

void
ring_clear_mark(ring)
	Ring *ring;
{
	ring->mark = 0;
}

/*
 * Add characters from current segment to ring buffer.
 */
    void
ring_supplied(ring, count)
    Ring *ring;
    int count;
{
    ring->supply = ring_increment(ring, ring->supply, count);
    ring->supplytime = ++ring_clock;
}

/*
 * We have just consumed "c" bytes.
 */
void
ring_consumed(ring, count)
	Ring *ring;
	int count;
{
	if (count == 0)	/* don't update anything */
		return;

	if (ring->mark &&
	    (ring_subtract(ring, ring->mark, ring->consume) < count)) {
		ring->mark = 0;
	}

	if (ring->consume < ring->clearto &&
	    ring->clearto <= ring->consume + count)
		ring->clearto = 0;
	else if (ring->consume + count > ring->top &&
	    ring->bottom <= ring->clearto &&
	    ring->bottom + ((ring->consume + count) - ring->top))
		ring->clearto = 0;

	ring->consume = ring_increment(ring, ring->consume, count);
	ring->consumetime = ++ring_clock;
	/*
	 * Try to encourage "ring_empty_consecutive()" to be large.
	 */
	if (ring_empty(ring)) {
		ring->consume = ring->supply = ring->bottom;
	}
}


/* Buffer state query routines */


/* Number of bytes that may be supplied */
int
ring_empty_count(ring)
	Ring *ring;
{
	if (ring_empty(ring)) {	/* if empty */
		return (ring->size);
	} else {
		return (ring_subtract(ring, ring->consume, ring->supply));
	}
}

/* number of CONSECUTIVE bytes that may be supplied */
int
ring_empty_consecutive(ring)
	Ring *ring;
{
	if ((ring->consume < ring->supply) || ring_empty(ring)) {
		/*
		 * if consume is "below" supply, or empty, then
		 * return distance to the top
		 */
		return (ring_subtract(ring, ring->top, ring->supply));
	} else {
		/*
		 * else, return what we may.
		 */
		return (ring_subtract(ring, ring->consume, ring->supply));
	}
}

/*
 * Return the number of bytes that are available for consuming
 * (but don't give more than enough to get to cross over set mark)
 */

int
ring_full_count(ring)
	Ring *ring;
{
	if ((ring->mark == 0) || (ring->mark == ring->consume)) {
		if (ring_full(ring)) {
			return (ring->size);	/* nothing consumed, but full */
		} else {
			return (ring_subtract(ring, ring->supply,
			    ring->consume));
		}
	} else {
		return (ring_subtract(ring, ring->mark, ring->consume));
	}
}

/*
 * Return the number of CONSECUTIVE bytes available for consuming.
 * However, don't return more than enough to cross over set mark.
 */
int
ring_full_consecutive(ring)
	Ring *ring;
{
	if ((ring->mark == 0) || (ring->mark == ring->consume)) {
		if ((ring->supply < ring->consume) || ring_full(ring)) {
			return (ring_subtract(ring, ring->top, ring->consume));
		} else {
			return (ring_subtract(ring, ring->supply,
			    ring->consume));
		}
	} else {
		if (ring->mark < ring->consume) {
			return (ring_subtract(ring, ring->top, ring->consume));
		} else {	/* Else, distance to mark */
			return (ring_subtract(ring, ring->mark, ring->consume));
		}
	}
}

/*
 * Move data into the "supply" portion of of the ring buffer.
 */
void
ring_supply_data(ring, buffer, count)
	Ring *ring;
	unsigned char *buffer;
	int count;
{
	int i;

	while (count) {
		i = MIN(count, ring_empty_consecutive(ring));
		(void) memcpy(ring->supply, buffer, i);
		ring_supplied(ring, i);
		count -= i;
		buffer += i;
	}
}

#ifdef notdef

/*
 * Move data from the "consume" portion of the ring buffer
 */
void
ring_consume_data(ring, buffer, count)
	Ring *ring;
	unsigned char *buffer;
	int count;
{
	int i;

	while (count) {
		i = MIN(count, ring_full_consecutive(ring));
		memcpy(buffer, ring->consume, i);
		ring_consumed(ring, i);
		count -= i;
		buffer += i;
	}
}
#endif

void
ring_encrypt(ring, encryptor)
	Ring *ring;
	void (*encryptor)();
{
	unsigned char *s, *c;

	if (ring_empty(ring) || ring->clearto == ring->supply)
		return;

	if ((c = ring->clearto) == NULL)
		c = ring->consume;

	s = ring->supply;

	if (s <= c) {
		(*encryptor)(c, ring->top - c);
		(*encryptor)(ring->bottom, s - ring->bottom);
	} else
		(*encryptor)(c, s - c);

	ring->clearto = ring->supply;
}

    void
ring_clearto(ring)
    Ring *ring;
{
    if (!ring_empty(ring))
	ring->clearto = ring->supply;
    else
	ring->clearto = 0;
}