316 lines
7.2 KiB
C
316 lines
7.2 KiB
C
/*
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* Copyright (c) 1988, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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static char sccsid[] = "@(#)ring.c 8.1 (Berkeley) 6/6/93";
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#endif /* not lint */
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/*
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* This defines a structure for a ring buffer.
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*
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* The circular buffer has two parts:
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*(((
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* full: [consume, supply)
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* empty: [supply, consume)
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*]]]
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*
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*/
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#include <stdio.h>
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#include <errno.h>
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#ifdef size_t
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#undef size_t
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#endif
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#include <sys/types.h>
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#ifndef FILIO_H
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#include <sys/ioctl.h>
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#endif
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#include <sys/socket.h>
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#include "ring.h"
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#include "general.h"
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/* Internal macros */
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#if !defined(MIN)
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#define MIN(a,b) (((a)<(b))? (a):(b))
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#endif /* !defined(MIN) */
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#define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
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(a)-(b): (((a)-(b))+(d)->size))
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#define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
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(a)+(c) : (((a)+(c))-(d)->size))
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#define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
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(a)-(c) : (((a)-(c))-(d)->size))
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/*
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* The following is a clock, used to determine full, empty, etc.
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*
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* There is some trickiness here. Since the ring buffers are initialized
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* to ZERO on allocation, we need to make sure, when interpreting the
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* clock, that when the times are EQUAL, then the buffer is FULL.
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*/
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static u_long ring_clock = 0;
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#define ring_empty(d) (((d)->consume == (d)->supply) && \
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((d)->consumetime >= (d)->supplytime))
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#define ring_full(d) (((d)->supply == (d)->consume) && \
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((d)->supplytime > (d)->consumetime))
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/* Buffer state transition routines */
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ring_init(ring, buffer, count)
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Ring *ring;
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unsigned char *buffer;
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int count;
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{
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memset((char *)ring, 0, sizeof *ring);
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ring->size = count;
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ring->supply = ring->consume = ring->bottom = buffer;
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ring->top = ring->bottom+ring->size;
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return 1;
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}
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/* Mark routines */
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/*
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* Mark the most recently supplied byte.
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*/
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void
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ring_mark(ring)
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Ring *ring;
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{
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ring->mark = ring_decrement(ring, ring->supply, 1);
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}
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/*
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* Is the ring pointing to the mark?
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*/
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int
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ring_at_mark(ring)
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Ring *ring;
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{
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if (ring->mark == ring->consume) {
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return 1;
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} else {
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return 0;
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}
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}
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/*
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* Clear any mark set on the ring.
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*/
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void
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ring_clear_mark(ring)
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Ring *ring;
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{
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ring->mark = 0;
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}
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/*
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* Add characters from current segment to ring buffer.
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*/
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void
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ring_supplied(ring, count)
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Ring *ring;
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int count;
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{
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ring->supply = ring_increment(ring, ring->supply, count);
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ring->supplytime = ++ring_clock;
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}
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/*
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* We have just consumed "c" bytes.
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*/
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void
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ring_consumed(ring, count)
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Ring *ring;
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int count;
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{
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if (count == 0) /* don't update anything */
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return;
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if (ring->mark &&
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(ring_subtract(ring, ring->mark, ring->consume) < count)) {
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ring->mark = 0;
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}
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ring->consume = ring_increment(ring, ring->consume, count);
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ring->consumetime = ++ring_clock;
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/*
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* Try to encourage "ring_empty_consecutive()" to be large.
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*/
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if (ring_empty(ring)) {
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ring->consume = ring->supply = ring->bottom;
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}
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}
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/* Buffer state query routines */
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/* Number of bytes that may be supplied */
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int
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ring_empty_count(ring)
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Ring *ring;
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{
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if (ring_empty(ring)) { /* if empty */
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return ring->size;
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} else {
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return ring_subtract(ring, ring->consume, ring->supply);
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}
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}
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/* number of CONSECUTIVE bytes that may be supplied */
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int
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ring_empty_consecutive(ring)
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Ring *ring;
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{
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if ((ring->consume < ring->supply) || ring_empty(ring)) {
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/*
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* if consume is "below" supply, or empty, then
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* return distance to the top
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*/
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return ring_subtract(ring, ring->top, ring->supply);
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} else {
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/*
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* else, return what we may.
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*/
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return ring_subtract(ring, ring->consume, ring->supply);
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}
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}
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/* Return the number of bytes that are available for consuming
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* (but don't give more than enough to get to cross over set mark)
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*/
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int
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ring_full_count(ring)
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Ring *ring;
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{
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if ((ring->mark == 0) || (ring->mark == ring->consume)) {
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if (ring_full(ring)) {
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return ring->size; /* nothing consumed, but full */
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} else {
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return ring_subtract(ring, ring->supply, ring->consume);
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}
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} else {
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return ring_subtract(ring, ring->mark, ring->consume);
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}
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}
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/*
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* Return the number of CONSECUTIVE bytes available for consuming.
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* However, don't return more than enough to cross over set mark.
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*/
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int
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ring_full_consecutive(ring)
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Ring *ring;
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{
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if ((ring->mark == 0) || (ring->mark == ring->consume)) {
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if ((ring->supply < ring->consume) || ring_full(ring)) {
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return ring_subtract(ring, ring->top, ring->consume);
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} else {
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return ring_subtract(ring, ring->supply, ring->consume);
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}
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} else {
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if (ring->mark < ring->consume) {
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return ring_subtract(ring, ring->top, ring->consume);
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} else { /* Else, distance to mark */
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return ring_subtract(ring, ring->mark, ring->consume);
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}
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}
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}
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/*
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* Move data into the "supply" portion of of the ring buffer.
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*/
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void
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ring_supply_data(ring, buffer, count)
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Ring *ring;
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unsigned char *buffer;
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int count;
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{
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int i;
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while (count) {
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i = MIN(count, ring_empty_consecutive(ring));
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memcpy(ring->supply, buffer, i);
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ring_supplied(ring, i);
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count -= i;
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buffer += i;
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}
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}
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#ifdef notdef
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/*
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* Move data from the "consume" portion of the ring buffer
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*/
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void
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ring_consume_data(ring, buffer, count)
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Ring *ring;
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unsigned char *buffer;
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int count;
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{
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int i;
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while (count) {
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i = MIN(count, ring_full_consecutive(ring));
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memcpy(buffer, ring->consume, i);
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ring_consumed(ring, i);
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count -= i;
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buffer += i;
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}
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}
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#endif
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