4.3BSD-Reno/src/usr.bin/telnet/ring.c
/*
* Copyright (c) 1988 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted provided
* that: (1) source distributions retain this entire copyright notice and
* comment, and (2) distributions including binaries display the following
* acknowledgement: ``This product includes software developed by the
* University of California, Berkeley and its contributors'' in the
* documentation or other materials provided with the distribution and in
* all advertising materials mentioning features or use of this software.
* 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static char sccsid[] = "@(#)ring.c 1.13 (Berkeley) 6/28/90";
#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>
#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;
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;
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;
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