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/*

 * 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        <string.h>

#include        <errno.h>

#ifdef  size_t

#undef  size_t

#endif

#include        <sys/types.h>

#ifndef FILIO_H

#include        <sys/ioctl.h>

#endif

#include        <sys/socket.h>

#include        "ring.h"

#include        "general.h"

/* Internal macros */

#if     !defined(MIN)

#define MIN(a,b)        (((a)<(b))? (a):(b))

#endif  /* !defined(MIN) */

#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.

 */

static u_long 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 */

    ring_init(ring, buffer, count)

Ring *ring;

    unsigned char *buffer;

    int count;

{

    memset((char *)ring, 0, sizeof *ring);

    ring->size = count;

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

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

    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;

    }

    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));

        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