* 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
* 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
static char sccsid
[] = "@(#)ring.c 8.2 (Berkeley) 5/30/95";
* This defines a structure for a ring buffer.
* The circular buffer has two parts:
* full: [consume, supply)
* empty: [supply, consume)
#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
)
memset((char *)ring
, 0, sizeof *ring
);
ring
->supply
= ring
->consume
= ring
->bottom
= buffer
;
ring
->top
= ring
->bottom
+ring
->size
;
* Mark the most recently supplied byte.
ring
->mark
= ring_decrement(ring
, ring
->supply
, 1);
* Is the ring pointing to the mark?
if (ring
->mark
== ring
->consume
) {
* Clear any mark set on the ring.
* Add characters from current segment to ring buffer.
ring_supplied(ring
, count
)
ring
->supply
= ring_increment(ring
, ring
->supply
, count
);
ring
->supplytime
= ++ring_clock
;
* We have just consumed "c" bytes.
ring_consumed(ring
, count
)
if (count
== 0) /* don't update anything */
(ring_subtract(ring
, ring
->mark
, ring
->consume
) < count
)) {
if (ring
->consume
< ring
->clearto
&&
ring
->clearto
<= ring
->consume
+ count
)
else if (ring
->consume
+ count
> ring
->top
&&
ring
->bottom
<= ring
->clearto
&&
ring
->bottom
+ ((ring
->consume
+ count
) - ring
->top
))
ring
->consume
= ring_increment(ring
, ring
->consume
, count
);
ring
->consumetime
= ++ring_clock
;
* Try to encourage "ring_empty_consecutive()" to be large.
ring
->consume
= ring
->supply
= ring
->bottom
;
/* Buffer state query routines */
/* Number of bytes that may be supplied */
if (ring_empty(ring
)) { /* if empty */
return ring_subtract(ring
, ring
->consume
, ring
->supply
);
/* number of CONSECUTIVE bytes that may be supplied */
ring_empty_consecutive(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, 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)
if ((ring
->mark
== 0) || (ring
->mark
== ring
->consume
)) {
return ring
->size
; /* nothing consumed, but full */
return ring_subtract(ring
, ring
->supply
, ring
->consume
);
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.
ring_full_consecutive(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
);
return ring_subtract(ring
, ring
->supply
, ring
->consume
);
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.
ring_supply_data(ring
, buffer
, count
)
i
= MIN(count
, ring_empty_consecutive(ring
));
memmove(ring
->supply
, buffer
, i
);
* Move data from the "consume" portion of the ring buffer
ring_consume_data(ring
, buffer
, count
)
i
= MIN(count
, ring_full_consecutive(ring
));
memmove(buffer
, ring
->consume
, i
);
ring_encrypt(ring
, encryptor
)
if (ring_empty(ring
) || ring
->clearto
== ring
->supply
)
if (!(c
= ring
->clearto
))
(*encryptor
)(c
, ring
->top
- c
);
(*encryptor
)(ring
->bottom
, s
- ring
->bottom
);
ring
->clearto
= ring
->supply
;
ring
->clearto
= ring
->supply
;