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
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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
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23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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35 static const char sccsid[] = "@(#)ring.c 8.2 (Berkeley) 5/30/95";
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))
101 /* Buffer state transition routines */
104 ring_init(ring, buffer, count)
106 unsigned char *buffer;
109 memset((char *)ring, 0, sizeof *ring);
113 ring->supply = ring->consume = ring->bottom = buffer;
115 ring->top = ring->bottom+ring->size;
119 #endif /* ENCRYPTION */
127 * Mark the most recently supplied byte.
134 ring->mark = ring_decrement(ring, ring->supply, 1);
138 * Is the ring pointing to the mark?
145 if (ring->mark == ring->consume) {
153 * Clear any mark set on the ring.
157 ring_clear_mark(ring)
164 * Add characters from current segment to ring buffer.
167 ring_supplied(ring, count)
171 ring->supply = ring_increment(ring, ring->supply, count);
172 ring->supplytime = ++ring_clock;
176 * We have just consumed "c" bytes.
179 ring_consumed(ring, count)
183 if (count == 0) /* don't update anything */
187 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
191 if (ring->consume < ring->clearto &&
192 ring->clearto <= ring->consume + count)
194 else if (ring->consume + count > ring->top &&
195 ring->bottom <= ring->clearto &&
196 ring->bottom + ((ring->consume + count) - ring->top))
198 #endif /* ENCRYPTION */
199 ring->consume = ring_increment(ring, ring->consume, count);
200 ring->consumetime = ++ring_clock;
202 * Try to encourage "ring_empty_consecutive()" to be large.
204 if (ring_empty(ring)) {
205 ring->consume = ring->supply = ring->bottom;
211 /* Buffer state query routines */
214 /* Number of bytes that may be supplied */
216 ring_empty_count(ring)
219 if (ring_empty(ring)) { /* if empty */
222 return ring_subtract(ring, ring->consume, ring->supply);
226 /* number of CONSECUTIVE bytes that may be supplied */
228 ring_empty_consecutive(ring)
231 if ((ring->consume < ring->supply) || ring_empty(ring)) {
233 * if consume is "below" supply, or empty, then
234 * return distance to the top
236 return ring_subtract(ring, ring->top, ring->supply);
239 * else, return what we may.
241 return ring_subtract(ring, ring->consume, ring->supply);
245 /* Return the number of bytes that are available for consuming
246 * (but don't give more than enough to get to cross over set mark)
250 ring_full_count(ring)
253 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
254 if (ring_full(ring)) {
255 return ring->size; /* nothing consumed, but full */
257 return ring_subtract(ring, ring->supply, ring->consume);
260 return ring_subtract(ring, ring->mark, ring->consume);
265 * Return the number of CONSECUTIVE bytes available for consuming.
266 * However, don't return more than enough to cross over set mark.
269 ring_full_consecutive(ring)
272 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
273 if ((ring->supply < ring->consume) || ring_full(ring)) {
274 return ring_subtract(ring, ring->top, ring->consume);
276 return ring_subtract(ring, ring->supply, ring->consume);
279 if (ring->mark < ring->consume) {
280 return ring_subtract(ring, ring->top, ring->consume);
281 } else { /* Else, distance to mark */
282 return ring_subtract(ring, ring->mark, ring->consume);
288 * Move data into the "supply" portion of of the ring buffer.
291 ring_supply_data(ring, buffer, count)
293 unsigned char *buffer;
299 i = MIN(count, ring_empty_consecutive(ring));
300 memmove(ring->supply, buffer, i);
301 ring_supplied(ring, i);
310 * Move data from the "consume" portion of the ring buffer
313 ring_consume_data(ring, buffer, count)
315 unsigned char *buffer;
321 i = MIN(count, ring_full_consecutive(ring));
322 memmove(buffer, ring->consume, i);
323 ring_consumed(ring, i);
332 ring_encrypt(ring, encryptor)
336 unsigned char *s, *c;
338 if (ring_empty(ring) || ring->clearto == ring->supply)
341 if (!(c = ring->clearto))
347 (*encryptor)(c, ring->top - c);
348 (*encryptor)(ring->bottom, s - ring->bottom);
350 (*encryptor)(c, s - c);
352 ring->clearto = ring->supply;
359 if (!ring_empty(ring))
360 ring->clearto = ring->supply;
364 #endif /* ENCRYPTION */