2 * Copyright (c) 1988, 1993
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * @(#)ring.c 8.2 (Berkeley) 5/30/95
34 * $FreeBSD: src/usr.bin/telnet/ring.c,v 1.3.6.1 2002/04/13 11:07:13 markm Exp $
35 * $DragonFly: src/usr.bin/telnet/ring.c,v 1.2 2003/06/17 04:29:32 dillon Exp $
39 * This defines a structure for a ring buffer.
41 * The circular buffer has two parts:
43 * full: [consume, supply)
44 * empty: [supply, consume)
57 #include <sys/types.h>
59 #include <sys/ioctl.h>
61 #include <sys/socket.h>
69 #define MIN(a,b) (((a)<(b))? (a):(b))
70 #endif /* !defined(MIN) */
72 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
73 (a)-(b): (((a)-(b))+(d)->size))
75 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
76 (a)+(c) : (((a)+(c))-(d)->size))
78 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
79 (a)-(c) : (((a)-(c))-(d)->size))
83 * The following is a clock, used to determine full, empty, etc.
85 * There is some trickiness here. Since the ring buffers are initialized
86 * to ZERO on allocation, we need to make sure, when interpreting the
87 * clock, that when the times are EQUAL, then the buffer is FULL.
89 static u_long ring_clock
= 0;
92 #define ring_empty(d) (((d)->consume == (d)->supply) && \
93 ((d)->consumetime >= (d)->supplytime))
94 #define ring_full(d) (((d)->supply == (d)->consume) && \
95 ((d)->supplytime > (d)->consumetime))
97 /* Buffer state transition routines */
100 ring_init(Ring
*ring
, unsigned char *buffer
, int count
)
102 memset((char *)ring
, 0, sizeof *ring
);
106 ring
->supply
= ring
->consume
= ring
->bottom
= buffer
;
108 ring
->top
= ring
->bottom
+ring
->size
;
117 * Mark the most recently supplied byte.
121 ring_mark(Ring
*ring
)
123 ring
->mark
= ring_decrement(ring
, ring
->supply
, 1);
127 * Is the ring pointing to the mark?
131 ring_at_mark(Ring
*ring
)
133 if (ring
->mark
== ring
->consume
) {
141 * Clear any mark set on the ring.
145 ring_clear_mark(Ring
*ring
)
151 * Add characters from current segment to ring buffer.
154 ring_supplied(Ring
*ring
, int count
)
156 ring
->supply
= ring_increment(ring
, ring
->supply
, count
);
157 ring
->supplytime
= ++ring_clock
;
161 * We have just consumed "c" bytes.
164 ring_consumed(Ring
*ring
, int count
)
166 if (count
== 0) /* don't update anything */
170 (ring_subtract(ring
, ring
->mark
, ring
->consume
) < count
)) {
173 ring
->consume
= ring_increment(ring
, ring
->consume
, count
);
174 ring
->consumetime
= ++ring_clock
;
176 * Try to encourage "ring_empty_consecutive()" to be large.
178 if (ring_empty(ring
)) {
179 ring
->consume
= ring
->supply
= ring
->bottom
;
185 /* Buffer state query routines */
188 /* Number of bytes that may be supplied */
190 ring_empty_count(Ring
*ring
)
192 if (ring_empty(ring
)) { /* if empty */
195 return ring_subtract(ring
, ring
->consume
, ring
->supply
);
199 /* number of CONSECUTIVE bytes that may be supplied */
201 ring_empty_consecutive(Ring
*ring
)
203 if ((ring
->consume
< ring
->supply
) || ring_empty(ring
)) {
205 * if consume is "below" supply, or empty, then
206 * return distance to the top
208 return ring_subtract(ring
, ring
->top
, ring
->supply
);
211 * else, return what we may.
213 return ring_subtract(ring
, ring
->consume
, ring
->supply
);
217 /* Return the number of bytes that are available for consuming
218 * (but don't give more than enough to get to cross over set mark)
222 ring_full_count(Ring
*ring
)
224 if ((ring
->mark
== 0) || (ring
->mark
== ring
->consume
)) {
225 if (ring_full(ring
)) {
226 return ring
->size
; /* nothing consumed, but full */
228 return ring_subtract(ring
, ring
->supply
, ring
->consume
);
231 return ring_subtract(ring
, ring
->mark
, ring
->consume
);
236 * Return the number of CONSECUTIVE bytes available for consuming.
237 * However, don't return more than enough to cross over set mark.
240 ring_full_consecutive(Ring
*ring
)
242 if ((ring
->mark
== 0) || (ring
->mark
== ring
->consume
)) {
243 if ((ring
->supply
< ring
->consume
) || ring_full(ring
)) {
244 return ring_subtract(ring
, ring
->top
, ring
->consume
);
246 return ring_subtract(ring
, ring
->supply
, ring
->consume
);
249 if (ring
->mark
< ring
->consume
) {
250 return ring_subtract(ring
, ring
->top
, ring
->consume
);
251 } else { /* Else, distance to mark */
252 return ring_subtract(ring
, ring
->mark
, ring
->consume
);
258 * Move data into the "supply" portion of of the ring buffer.
261 ring_supply_data(Ring
*ring
, unsigned char *buffer
, int count
)
266 i
= MIN(count
, ring_empty_consecutive(ring
));
267 memcpy(ring
->supply
, buffer
, i
);
268 ring_supplied(ring
, i
);