1 /*
2 * Copyright (c) 1988, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #if 0
31 #ifndef lint
32 static const char sccsid[] = "@(#)ring.c 8.2 (Berkeley) 5/30/95";
33 #endif
34 #endif
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
37
38 /*
39 * This defines a structure for a ring buffer.
40 *
41 * The circular buffer has two parts:
42 *(((
43 * full: [consume, supply)
44 * empty: [supply, consume)
45 *]]]
46 *
47 */
48
49 #include <errno.h>
50 #include <stdio.h>
51 #include <string.h>
52
53 #ifdef size_t
54 #undef size_t
55 #endif
56
57 #include <sys/types.h>
58 #ifndef FILIO_H
59 #include <sys/ioctl.h>
60 #endif
61 #include <sys/socket.h>
62
63 #include "ring.h"
64 #include "general.h"
65
66 /* Internal macros */
67
68 #if !defined(MIN)
69 #define MIN(a,b) (((a)<(b))? (a):(b))
70 #endif /* !defined(MIN) */
71
72 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
73 (a)-(b): (((a)-(b))+(d)->size))
74
75 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
76 (a)+(c) : (((a)+(c))-(d)->size))
77
78 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
79 (a)-(c) : (((a)-(c))-(d)->size))
80
81
82 /*
83 * The following is a clock, used to determine full, empty, etc.
84 *
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.
88 */
89 static u_long ring_clock = 0;
90
91
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))
96
97 /* Buffer state transition routines */
98
99 int
ring_init(Ring * ring,unsigned char * buffer,int count)100 ring_init(Ring *ring, unsigned char *buffer, int count)
101 {
102 memset((char *)ring, 0, sizeof *ring);
103
104 ring->size = count;
105
106 ring->supply = ring->consume = ring->bottom = buffer;
107
108 ring->top = ring->bottom+ring->size;
109
110 #ifdef ENCRYPTION
111 ring->clearto = 0;
112 #endif /* ENCRYPTION */
113
114 return 1;
115 }
116
117 /* Mark routines */
118
119 /*
120 * Mark the most recently supplied byte.
121 */
122
123 void
ring_mark(Ring * ring)124 ring_mark(Ring *ring)
125 {
126 ring->mark = ring_decrement(ring, ring->supply, 1);
127 }
128
129 /*
130 * Is the ring pointing to the mark?
131 */
132
133 int
ring_at_mark(Ring * ring)134 ring_at_mark(Ring *ring)
135 {
136 if (ring->mark == ring->consume) {
137 return 1;
138 } else {
139 return 0;
140 }
141 }
142
143 /*
144 * Clear any mark set on the ring.
145 */
146
147 void
ring_clear_mark(Ring * ring)148 ring_clear_mark(Ring *ring)
149 {
150 ring->mark = 0;
151 }
152
153 /*
154 * Add characters from current segment to ring buffer.
155 */
156 void
ring_supplied(Ring * ring,int count)157 ring_supplied(Ring *ring, int count)
158 {
159 ring->supply = ring_increment(ring, ring->supply, count);
160 ring->supplytime = ++ring_clock;
161 }
162
163 /*
164 * We have just consumed "c" bytes.
165 */
166 void
ring_consumed(Ring * ring,int count)167 ring_consumed(Ring *ring, int count)
168 {
169 if (count == 0) /* don't update anything */
170 return;
171
172 if (ring->mark &&
173 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
174 ring->mark = 0;
175 }
176 #ifdef ENCRYPTION
177 if (ring->consume < ring->clearto &&
178 ring->clearto <= ring->consume + count)
179 ring->clearto = 0;
180 else if (ring->consume + count > ring->top &&
181 ring->bottom <= ring->clearto &&
182 ring->bottom + ((ring->consume + count) - ring->top))
183 ring->clearto = 0;
184 #endif /* ENCRYPTION */
185 ring->consume = ring_increment(ring, ring->consume, count);
186 ring->consumetime = ++ring_clock;
187 /*
188 * Try to encourage "ring_empty_consecutive()" to be large.
189 */
190 if (ring_empty(ring)) {
191 ring->consume = ring->supply = ring->bottom;
192 }
193 }
194
195
196
197 /* Buffer state query routines */
198
199
200 /* Number of bytes that may be supplied */
201 int
ring_empty_count(Ring * ring)202 ring_empty_count(Ring *ring)
203 {
204 if (ring_empty(ring)) { /* if empty */
205 return ring->size;
206 } else {
207 return ring_subtract(ring, ring->consume, ring->supply);
208 }
209 }
210
211 /* number of CONSECUTIVE bytes that may be supplied */
212 int
ring_empty_consecutive(Ring * ring)213 ring_empty_consecutive(Ring *ring)
214 {
215 if ((ring->consume < ring->supply) || ring_empty(ring)) {
216 /*
217 * if consume is "below" supply, or empty, then
218 * return distance to the top
219 */
220 return ring_subtract(ring, ring->top, ring->supply);
221 } else {
222 /*
223 * else, return what we may.
224 */
225 return ring_subtract(ring, ring->consume, ring->supply);
226 }
227 }
228
229 /* Return the number of bytes that are available for consuming
230 * (but don't give more than enough to get to cross over set mark)
231 */
232
233 int
ring_full_count(Ring * ring)234 ring_full_count(Ring *ring)
235 {
236 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
237 if (ring_full(ring)) {
238 return ring->size; /* nothing consumed, but full */
239 } else {
240 return ring_subtract(ring, ring->supply, ring->consume);
241 }
242 } else {
243 return ring_subtract(ring, ring->mark, ring->consume);
244 }
245 }
246
247 /*
248 * Return the number of CONSECUTIVE bytes available for consuming.
249 * However, don't return more than enough to cross over set mark.
250 */
251 int
ring_full_consecutive(Ring * ring)252 ring_full_consecutive(Ring *ring)
253 {
254 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
255 if ((ring->supply < ring->consume) || ring_full(ring)) {
256 return ring_subtract(ring, ring->top, ring->consume);
257 } else {
258 return ring_subtract(ring, ring->supply, ring->consume);
259 }
260 } else {
261 if (ring->mark < ring->consume) {
262 return ring_subtract(ring, ring->top, ring->consume);
263 } else { /* Else, distance to mark */
264 return ring_subtract(ring, ring->mark, ring->consume);
265 }
266 }
267 }
268
269 /*
270 * Move data into the "supply" portion of of the ring buffer.
271 */
272 void
ring_supply_data(Ring * ring,unsigned char * buffer,int count)273 ring_supply_data(Ring *ring, unsigned char *buffer, int count)
274 {
275 int i;
276
277 while (count) {
278 i = MIN(count, ring_empty_consecutive(ring));
279 memcpy(ring->supply, buffer, i);
280 ring_supplied(ring, i);
281 count -= i;
282 buffer += i;
283 }
284 }
285
286 #ifdef ENCRYPTION
287 void
ring_encrypt(Ring * ring,void (* encryptor)(unsigned char *,int))288 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
289 {
290 unsigned char *s, *c;
291
292 if (ring_empty(ring) || ring->clearto == ring->supply)
293 return;
294
295 if (!(c = ring->clearto))
296 c = ring->consume;
297
298 s = ring->supply;
299
300 if (s <= c) {
301 (*encryptor)(c, ring->top - c);
302 (*encryptor)(ring->bottom, s - ring->bottom);
303 } else
304 (*encryptor)(c, s - c);
305
306 ring->clearto = ring->supply;
307 }
308
309 void
ring_clearto(ring)310 ring_clearto(ring)
311 Ring *ring;
312 {
313 if (!ring_empty(ring))
314 ring->clearto = ring->supply;
315 else
316 ring->clearto = 0;
317 }
318 #endif /* ENCRYPTION */
319