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/crypto/telnet/telnet/ring.c,v 1.2.8.2 2002/04/13 10:59:08 markm Exp $
38 * This defines a structure for a ring buffer.
40 * The circular buffer has two parts:
42 * full: [consume, supply)
43 * empty: [supply, consume)
56 #include <sys/types.h>
58 #include <sys/ioctl.h>
60 #include <sys/socket.h>
68 #define MIN(a,b) (((a)<(b))? (a):(b))
69 #endif /* !defined(MIN) */
71 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
72 (a)-(b): (((a)-(b))+(d)->size))
74 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
75 (a)+(c) : (((a)+(c))-(d)->size))
77 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
78 (a)-(c) : (((a)-(c))-(d)->size))
82 * The following is a clock, used to determine full, empty, etc.
84 * There is some trickiness here. Since the ring buffers are initialized
85 * to ZERO on allocation, we need to make sure, when interpreting the
86 * clock, that when the times are EQUAL, then the buffer is FULL.
88 static u_long ring_clock = 0;
91 #define ring_empty(d) (((d)->consume == (d)->supply) && \
92 ((d)->consumetime >= (d)->supplytime))
93 #define ring_full(d) (((d)->supply == (d)->consume) && \
94 ((d)->supplytime > (d)->consumetime))
96 /* Buffer state transition routines */
99 ring_init(Ring *ring, unsigned char *buffer, int count)
101 memset((char *)ring, 0, sizeof *ring);
105 ring->supply = ring->consume = ring->bottom = buffer;
107 ring->top = ring->bottom+ring->size;
111 #endif /* ENCRYPTION */
119 * Mark the most recently supplied byte.
123 ring_mark(Ring *ring)
125 ring->mark = ring_decrement(ring, ring->supply, 1);
129 * Is the ring pointing to the mark?
133 ring_at_mark(Ring *ring)
135 if (ring->mark == ring->consume) {
143 * Clear any mark set on the ring.
147 ring_clear_mark(Ring *ring)
153 * Add characters from current segment to ring buffer.
156 ring_supplied(Ring *ring, int count)
158 ring->supply = ring_increment(ring, ring->supply, count);
159 ring->supplytime = ++ring_clock;
163 * We have just consumed "c" bytes.
166 ring_consumed(Ring *ring, int count)
168 if (count == 0) /* don't update anything */
172 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
176 if (ring->consume < ring->clearto &&
177 ring->clearto <= ring->consume + count)
179 else if (ring->consume + count > ring->top &&
180 ring->bottom <= ring->clearto &&
181 ring->bottom + ((ring->consume + count) - ring->top))
183 #endif /* ENCRYPTION */
184 ring->consume = ring_increment(ring, ring->consume, count);
185 ring->consumetime = ++ring_clock;
187 * Try to encourage "ring_empty_consecutive()" to be large.
189 if (ring_empty(ring)) {
190 ring->consume = ring->supply = ring->bottom;
196 /* Buffer state query routines */
199 /* Number of bytes that may be supplied */
201 ring_empty_count(Ring *ring)
203 if (ring_empty(ring)) { /* if empty */
206 return ring_subtract(ring, ring->consume, ring->supply);
210 /* number of CONSECUTIVE bytes that may be supplied */
212 ring_empty_consecutive(Ring *ring)
214 if ((ring->consume < ring->supply) || ring_empty(ring)) {
216 * if consume is "below" supply, or empty, then
217 * return distance to the top
219 return ring_subtract(ring, ring->top, ring->supply);
222 * else, return what we may.
224 return ring_subtract(ring, ring->consume, ring->supply);
228 /* Return the number of bytes that are available for consuming
229 * (but don't give more than enough to get to cross over set mark)
233 ring_full_count(Ring *ring)
235 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
236 if (ring_full(ring)) {
237 return ring->size; /* nothing consumed, but full */
239 return ring_subtract(ring, ring->supply, ring->consume);
242 return ring_subtract(ring, ring->mark, ring->consume);
247 * Return the number of CONSECUTIVE bytes available for consuming.
248 * However, don't return more than enough to cross over set mark.
251 ring_full_consecutive(Ring *ring)
253 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
254 if ((ring->supply < ring->consume) || ring_full(ring)) {
255 return ring_subtract(ring, ring->top, ring->consume);
257 return ring_subtract(ring, ring->supply, ring->consume);
260 if (ring->mark < ring->consume) {
261 return ring_subtract(ring, ring->top, ring->consume);
262 } else { /* Else, distance to mark */
263 return ring_subtract(ring, ring->mark, ring->consume);
269 * Move data into the "supply" portion of of the ring buffer.
272 ring_supply_data(Ring *ring, unsigned char *buffer, int count)
277 i = MIN(count, ring_empty_consecutive(ring));
278 memcpy(ring->supply, buffer, i);
279 ring_supplied(ring, i);
287 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
289 unsigned char *s, *c;
291 if (ring_empty(ring) || ring->clearto == ring->supply)
294 if (!(c = ring->clearto))
300 (*encryptor)(c, ring->top - c);
301 (*encryptor)(ring->bottom, s - ring->bottom);
303 (*encryptor)(c, s - c);
305 ring->clearto = ring->supply;
309 ring_clearto(Ring *ring)
311 if (!ring_empty(ring))
312 ring->clearto = ring->supply;
316 #endif /* ENCRYPTION */