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34 #include "telnet_locl.h"
36 RCSID("$Id: ring.c,v 1.11 2000/02/06 05:15:21 assar 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)
51 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
52 (a)-(b): (((a)-(b))+(d)->size))
54 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
55 (a)+(c) : (((a)+(c))-(d)->size))
57 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
58 (a)-(c) : (((a)-(c))-(d)->size))
62 * The following is a clock, used to determine full, empty, etc.
64 * There is some trickiness here. Since the ring buffers are initialized
65 * to ZERO on allocation, we need to make sure, when interpreting the
66 * clock, that when the times are EQUAL, then the buffer is FULL.
68 static u_long ring_clock = 0;
71 #define ring_empty(d) (((d)->consume == (d)->supply) && \
72 ((d)->consumetime >= (d)->supplytime))
73 #define ring_full(d) (((d)->supply == (d)->consume) && \
74 ((d)->supplytime > (d)->consumetime))
80 /* Buffer state transition routines */
83 ring_init(Ring *ring, unsigned char *buffer, int count)
85 memset(ring, 0, sizeof *ring);
89 ring->supply = ring->consume = ring->bottom = buffer;
91 ring->top = ring->bottom+ring->size;
93 #if defined(ENCRYPTION)
103 * Mark the most recently supplied byte.
107 ring_mark(Ring *ring)
109 ring->mark = ring_decrement(ring, ring->supply, 1);
113 * Is the ring pointing to the mark?
117 ring_at_mark(Ring *ring)
119 if (ring->mark == ring->consume) {
127 * Clear any mark set on the ring.
131 ring_clear_mark(Ring *ring)
137 * Add characters from current segment to ring buffer.
140 ring_supplied(Ring *ring, int count)
142 ring->supply = ring_increment(ring, ring->supply, count);
143 ring->supplytime = ++ring_clock;
147 * We have just consumed "c" bytes.
150 ring_consumed(Ring *ring, int count)
152 if (count == 0) /* don't update anything */
156 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
159 #if defined(ENCRYPTION)
160 if (ring->consume < ring->clearto &&
161 ring->clearto <= ring->consume + count)
163 else if (ring->consume + count > ring->top &&
164 ring->bottom <= ring->clearto &&
165 ring->bottom + ((ring->consume + count) - ring->top))
168 ring->consume = ring_increment(ring, ring->consume, count);
169 ring->consumetime = ++ring_clock;
171 * Try to encourage "ring_empty_consecutive()" to be large.
173 if (ring_empty(ring)) {
174 ring->consume = ring->supply = ring->bottom;
180 /* Buffer state query routines */
183 /* Number of bytes that may be supplied */
185 ring_empty_count(Ring *ring)
187 if (ring_empty(ring)) { /* if empty */
190 return ring_subtract(ring, ring->consume, ring->supply);
194 /* number of CONSECUTIVE bytes that may be supplied */
196 ring_empty_consecutive(Ring *ring)
198 if ((ring->consume < ring->supply) || ring_empty(ring)) {
200 * if consume is "below" supply, or empty, then
201 * return distance to the top
203 return ring_subtract(ring, ring->top, ring->supply);
206 * else, return what we may.
208 return ring_subtract(ring, ring->consume, ring->supply);
212 /* Return the number of bytes that are available for consuming
213 * (but don't give more than enough to get to cross over set mark)
217 ring_full_count(Ring *ring)
219 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
220 if (ring_full(ring)) {
221 return ring->size; /* nothing consumed, but full */
223 return ring_subtract(ring, ring->supply, ring->consume);
226 return ring_subtract(ring, ring->mark, ring->consume);
231 * Return the number of CONSECUTIVE bytes available for consuming.
232 * However, don't return more than enough to cross over set mark.
235 ring_full_consecutive(Ring *ring)
237 if ((ring->mark == 0) || (ring->mark == ring->consume)) {
238 if ((ring->supply < ring->consume) || ring_full(ring)) {
239 return ring_subtract(ring, ring->top, ring->consume);
241 return ring_subtract(ring, ring->supply, ring->consume);
244 if (ring->mark < ring->consume) {
245 return ring_subtract(ring, ring->top, ring->consume);
246 } else { /* Else, distance to mark */
247 return ring_subtract(ring, ring->mark, ring->consume);
253 * Move data into the "supply" portion of of the ring buffer.
256 ring_supply_data(Ring *ring, unsigned char *buffer, int count)
261 i = min(count, ring_empty_consecutive(ring));
262 memmove(ring->supply, buffer, i);
263 ring_supplied(ring, i);
272 * Move data from the "consume" portion of the ring buffer
275 ring_consume_data(Ring *ring, unsigned char *buffer, int count)
280 i = min(count, ring_full_consecutive(ring));
281 memmove(buffer, ring->consume, i);
282 ring_consumed(ring, i);
289 #if defined(ENCRYPTION)
291 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
293 unsigned char *s, *c;
295 if (ring_empty(ring) || ring->clearto == ring->supply)
298 if (!(c = ring->clearto))
304 (*encryptor)(c, ring->top - c);
305 (*encryptor)(ring->bottom, s - ring->bottom);
307 (*encryptor)(c, s - c);
309 ring->clearto = ring->supply;
313 ring_clearto(Ring *ring)
315 if (!ring_empty(ring))
316 ring->clearto = ring->supply;