1 /*
2 * Copyright (c) 1988, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 */
7
8 #ifndef lint
9 static char sccsid[] = "@(#)ring.c 8.2 (Berkeley) 05/30/95";
10 #endif /* not lint */
11
12 /*
13 * This defines a structure for a ring buffer.
14 *
15 * The circular buffer has two parts:
16 *(((
17 * full: [consume, supply)
18 * empty: [supply, consume)
19 *]]]
20 *
21 */
22
23 #include <stdio.h>
24 #include <errno.h>
25
26 #ifdef size_t
27 #undef size_t
28 #endif
29
30 #include <sys/types.h>
31 #ifndef FILIO_H
32 #include <sys/ioctl.h>
33 #endif
34 #include <sys/socket.h>
35
36 #include "ring.h"
37 #include "general.h"
38
39 /* Internal macros */
40
41 #if !defined(MIN)
42 #define MIN(a,b) (((a)<(b))? (a):(b))
43 #endif /* !defined(MIN) */
44
45 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
46 (a)-(b): (((a)-(b))+(d)->size))
47
48 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
49 (a)+(c) : (((a)+(c))-(d)->size))
50
51 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
52 (a)-(c) : (((a)-(c))-(d)->size))
53
54
55 /*
56 * The following is a clock, used to determine full, empty, etc.
57 *
58 * There is some trickiness here. Since the ring buffers are initialized
59 * to ZERO on allocation, we need to make sure, when interpreting the
60 * clock, that when the times are EQUAL, then the buffer is FULL.
61 */
62 static u_long ring_clock = 0;
63
64
65 #define ring_empty(d) (((d)->consume == (d)->supply) && \
66 ((d)->consumetime >= (d)->supplytime))
67 #define ring_full(d) (((d)->supply == (d)->consume) && \
68 ((d)->supplytime > (d)->consumetime))
69
70
71
72
73
74 /* Buffer state transition routines */
75
ring_init(ring,buffer,count)76 ring_init(ring, buffer, count)
77 Ring *ring;
78 unsigned char *buffer;
79 int count;
80 {
81 memset((char *)ring, 0, sizeof *ring);
82
83 ring->size = count;
84
85 ring->supply = ring->consume = ring->bottom = buffer;
86
87 ring->top = ring->bottom+ring->size;
88
89 #ifdef ENCRYPTION
90 ring->clearto = 0;
91 #endif /* ENCRYPTION */
92
93 return 1;
94 }
95
96 /* Mark routines */
97
98 /*
99 * Mark the most recently supplied byte.
100 */
101
102 void
ring_mark(ring)103 ring_mark(ring)
104 Ring *ring;
105 {
106 ring->mark = ring_decrement(ring, ring->supply, 1);
107 }
108
109 /*
110 * Is the ring pointing to the mark?
111 */
112
113 int
ring_at_mark(ring)114 ring_at_mark(ring)
115 Ring *ring;
116 {
117 if (ring->mark == ring->consume) {
118 return 1;
119 } else {
120 return 0;
121 }
122 }
123
124 /*
125 * Clear any mark set on the ring.
126 */
127
128 void
ring_clear_mark(ring)129 ring_clear_mark(ring)
130 Ring *ring;
131 {
132 ring->mark = 0;
133 }
134
135 /*
136 * Add characters from current segment to ring buffer.
137 */
138 void
ring_supplied(ring,count)139 ring_supplied(ring, count)
140 Ring *ring;
141 int count;
142 {
143 ring->supply = ring_increment(ring, ring->supply, count);
144 ring->supplytime = ++ring_clock;
145 }
146
147 /*
148 * We have just consumed "c" bytes.
149 */
150 void
ring_consumed(ring,count)151 ring_consumed(ring, count)
152 Ring *ring;
153 int count;
154 {
155 if (count == 0) /* don't update anything */
156 return;
157
158 if (ring->mark &&
159 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
160 ring->mark = 0;
161 }
162 #ifdef ENCRYPTION
163 if (ring->consume < ring->clearto &&
164 ring->clearto <= ring->consume + count)
165 ring->clearto = 0;
166 else if (ring->consume + count > ring->top &&
167 ring->bottom <= ring->clearto &&
168 ring->bottom + ((ring->consume + count) - ring->top))
169 ring->clearto = 0;
170 #endif /* ENCRYPTION */
171 ring->consume = ring_increment(ring, ring->consume, count);
172 ring->consumetime = ++ring_clock;
173 /*
174 * Try to encourage "ring_empty_consecutive()" to be large.
175 */
176 if (ring_empty(ring)) {
177 ring->consume = ring->supply = ring->bottom;
178 }
179 }
180
181
182
183 /* Buffer state query routines */
184
185
186 /* Number of bytes that may be supplied */
187 int
ring_empty_count(ring)188 ring_empty_count(ring)
189 Ring *ring;
190 {
191 if (ring_empty(ring)) { /* if empty */
192 return ring->size;
193 } else {
194 return ring_subtract(ring, ring->consume, ring->supply);
195 }
196 }
197
198 /* number of CONSECUTIVE bytes that may be supplied */
199 int
ring_empty_consecutive(ring)200 ring_empty_consecutive(ring)
201 Ring *ring;
202 {
203 if ((ring->consume < ring->supply) || ring_empty(ring)) {
204 /*
205 * if consume is "below" supply, or empty, then
206 * return distance to the top
207 */
208 return ring_subtract(ring, ring->top, ring->supply);
209 } else {
210 /*
211 * else, return what we may.
212 */
213 return ring_subtract(ring, ring->consume, ring->supply);
214 }
215 }
216
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)
219 */
220
221 int
ring_full_count(ring)222 ring_full_count(ring)
223 Ring *ring;
224 {
225 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
226 if (ring_full(ring)) {
227 return ring->size; /* nothing consumed, but full */
228 } else {
229 return ring_subtract(ring, ring->supply, ring->consume);
230 }
231 } else {
232 return ring_subtract(ring, ring->mark, ring->consume);
233 }
234 }
235
236 /*
237 * Return the number of CONSECUTIVE bytes available for consuming.
238 * However, don't return more than enough to cross over set mark.
239 */
240 int
ring_full_consecutive(ring)241 ring_full_consecutive(ring)
242 Ring *ring;
243 {
244 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
245 if ((ring->supply < ring->consume) || ring_full(ring)) {
246 return ring_subtract(ring, ring->top, ring->consume);
247 } else {
248 return ring_subtract(ring, ring->supply, ring->consume);
249 }
250 } else {
251 if (ring->mark < ring->consume) {
252 return ring_subtract(ring, ring->top, ring->consume);
253 } else { /* Else, distance to mark */
254 return ring_subtract(ring, ring->mark, ring->consume);
255 }
256 }
257 }
258
259 /*
260 * Move data into the "supply" portion of of the ring buffer.
261 */
262 void
ring_supply_data(ring,buffer,count)263 ring_supply_data(ring, buffer, count)
264 Ring *ring;
265 unsigned char *buffer;
266 int count;
267 {
268 int i;
269
270 while (count) {
271 i = MIN(count, ring_empty_consecutive(ring));
272 memmove(ring->supply, buffer, i);
273 ring_supplied(ring, i);
274 count -= i;
275 buffer += i;
276 }
277 }
278
279 #ifdef notdef
280
281 /*
282 * Move data from the "consume" portion of the ring buffer
283 */
284 void
ring_consume_data(ring,buffer,count)285 ring_consume_data(ring, buffer, count)
286 Ring *ring;
287 unsigned char *buffer;
288 int count;
289 {
290 int i;
291
292 while (count) {
293 i = MIN(count, ring_full_consecutive(ring));
294 memmove(buffer, ring->consume, i);
295 ring_consumed(ring, i);
296 count -= i;
297 buffer += i;
298 }
299 }
300 #endif
301
302 #ifdef ENCRYPTION
303 void
ring_encrypt(ring,encryptor)304 ring_encrypt(ring, encryptor)
305 Ring *ring;
306 void (*encryptor)();
307 {
308 unsigned char *s, *c;
309
310 if (ring_empty(ring) || ring->clearto == ring->supply)
311 return;
312
313 if (!(c = ring->clearto))
314 c = ring->consume;
315
316 s = ring->supply;
317
318 if (s <= c) {
319 (*encryptor)(c, ring->top - c);
320 (*encryptor)(ring->bottom, s - ring->bottom);
321 } else
322 (*encryptor)(c, s - c);
323
324 ring->clearto = ring->supply;
325 }
326
327 void
ring_clearto(ring)328 ring_clearto(ring)
329 Ring *ring;
330 {
331 if (!ring_empty(ring))
332 ring->clearto = ring->supply;
333 else
334 ring->clearto = 0;
335 }
336 #endif /* ENCRYPTION */
337