Annotation of src/usr.bin/telnet/ring.c, Revision 1.1.1.1
1.1 deraadt 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. 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.
20: *
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
31: * SUCH DAMAGE.
32: */
33:
34: #ifndef lint
35: /* from: static char sccsid[] = "@(#)ring.c 8.1 (Berkeley) 6/6/93"; */
36: static char *rcsid = "$Id: ring.c,v 1.4 1994/12/24 17:50:06 cgd Exp $";
37: #endif /* not lint */
38:
39: /*
40: * This defines a structure for a ring buffer.
41: *
42: * The circular buffer has two parts:
43: *(((
44: * full: [consume, supply)
45: * empty: [supply, consume)
46: *]]]
47: *
48: */
49:
50: #include <stdio.h>
51: #ifndef NO_STRING_H
52: #include <string.h>
53: #endif
54: #include <strings.h>
55: #include <errno.h>
56:
57: #ifdef size_t
58: #undef size_t
59: #endif
60:
61: #include <sys/types.h>
62: #ifndef FILIO_H
63: #include <sys/ioctl.h>
64: #endif
65: #include <sys/socket.h>
66:
67: #include "ring.h"
68: #include "general.h"
69:
70: /* Internal macros */
71:
72: #if !defined(MIN)
73: #define MIN(a,b) (((a)<(b))? (a):(b))
74: #endif /* !defined(MIN) */
75:
76: #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \
77: (a)-(b): (((a)-(b))+(d)->size))
78:
79: #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \
80: (a)+(c) : (((a)+(c))-(d)->size))
81:
82: #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \
83: (a)-(c) : (((a)-(c))-(d)->size))
84:
85:
86: /*
87: * The following is a clock, used to determine full, empty, etc.
88: *
89: * There is some trickiness here. Since the ring buffers are initialized
90: * to ZERO on allocation, we need to make sure, when interpreting the
91: * clock, that when the times are EQUAL, then the buffer is FULL.
92: */
93: static u_long ring_clock = 0;
94:
95:
96: #define ring_empty(d) (((d)->consume == (d)->supply) && \
97: ((d)->consumetime >= (d)->supplytime))
98: #define ring_full(d) (((d)->supply == (d)->consume) && \
99: ((d)->supplytime > (d)->consumetime))
100:
101:
102:
103:
104:
105: /* Buffer state transition routines */
106:
107: ring_init(ring, buffer, count)
108: Ring *ring;
109: unsigned char *buffer;
110: int count;
111: {
112: memset((char *)ring, 0, sizeof *ring);
113:
114: ring->size = count;
115:
116: ring->supply = ring->consume = ring->bottom = buffer;
117:
118: ring->top = ring->bottom+ring->size;
119:
120:
121: return 1;
122: }
123:
124: /* Mark routines */
125:
126: /*
127: * Mark the most recently supplied byte.
128: */
129:
130: void
131: ring_mark(ring)
132: Ring *ring;
133: {
134: ring->mark = ring_decrement(ring, ring->supply, 1);
135: }
136:
137: /*
138: * Is the ring pointing to the mark?
139: */
140:
141: int
142: ring_at_mark(ring)
143: Ring *ring;
144: {
145: if (ring->mark == ring->consume) {
146: return 1;
147: } else {
148: return 0;
149: }
150: }
151:
152: /*
153: * Clear any mark set on the ring.
154: */
155:
156: void
157: ring_clear_mark(ring)
158: Ring *ring;
159: {
160: ring->mark = 0;
161: }
162:
163: /*
164: * Add characters from current segment to ring buffer.
165: */
166: void
167: ring_supplied(ring, count)
168: Ring *ring;
169: int count;
170: {
171: ring->supply = ring_increment(ring, ring->supply, count);
172: ring->supplytime = ++ring_clock;
173: }
174:
175: /*
176: * We have just consumed "c" bytes.
177: */
178: void
179: ring_consumed(ring, count)
180: Ring *ring;
181: int count;
182: {
183: if (count == 0) /* don't update anything */
184: return;
185:
186: if (ring->mark &&
187: (ring_subtract(ring, ring->mark, ring->consume) < count)) {
188: ring->mark = 0;
189: }
190: ring->consume = ring_increment(ring, ring->consume, count);
191: ring->consumetime = ++ring_clock;
192: /*
193: * Try to encourage "ring_empty_consecutive()" to be large.
194: */
195: if (ring_empty(ring)) {
196: ring->consume = ring->supply = ring->bottom;
197: }
198: }
199:
200:
201:
202: /* Buffer state query routines */
203:
204:
205: /* Number of bytes that may be supplied */
206: int
207: ring_empty_count(ring)
208: Ring *ring;
209: {
210: if (ring_empty(ring)) { /* if empty */
211: return ring->size;
212: } else {
213: return ring_subtract(ring, ring->consume, ring->supply);
214: }
215: }
216:
217: /* number of CONSECUTIVE bytes that may be supplied */
218: int
219: ring_empty_consecutive(ring)
220: Ring *ring;
221: {
222: if ((ring->consume < ring->supply) || ring_empty(ring)) {
223: /*
224: * if consume is "below" supply, or empty, then
225: * return distance to the top
226: */
227: return ring_subtract(ring, ring->top, ring->supply);
228: } else {
229: /*
230: * else, return what we may.
231: */
232: return ring_subtract(ring, ring->consume, ring->supply);
233: }
234: }
235:
236: /* Return the number of bytes that are available for consuming
237: * (but don't give more than enough to get to cross over set mark)
238: */
239:
240: int
241: ring_full_count(ring)
242: Ring *ring;
243: {
244: if ((ring->mark == 0) || (ring->mark == ring->consume)) {
245: if (ring_full(ring)) {
246: return ring->size; /* nothing consumed, but full */
247: } else {
248: return ring_subtract(ring, ring->supply, ring->consume);
249: }
250: } else {
251: return ring_subtract(ring, ring->mark, ring->consume);
252: }
253: }
254:
255: /*
256: * Return the number of CONSECUTIVE bytes available for consuming.
257: * However, don't return more than enough to cross over set mark.
258: */
259: int
260: ring_full_consecutive(ring)
261: Ring *ring;
262: {
263: if ((ring->mark == 0) || (ring->mark == ring->consume)) {
264: if ((ring->supply < ring->consume) || ring_full(ring)) {
265: return ring_subtract(ring, ring->top, ring->consume);
266: } else {
267: return ring_subtract(ring, ring->supply, ring->consume);
268: }
269: } else {
270: if (ring->mark < ring->consume) {
271: return ring_subtract(ring, ring->top, ring->consume);
272: } else { /* Else, distance to mark */
273: return ring_subtract(ring, ring->mark, ring->consume);
274: }
275: }
276: }
277:
278: /*
279: * Move data into the "supply" portion of of the ring buffer.
280: */
281: void
282: ring_supply_data(ring, buffer, count)
283: Ring *ring;
284: unsigned char *buffer;
285: int count;
286: {
287: int i;
288:
289: while (count) {
290: i = MIN(count, ring_empty_consecutive(ring));
291: memcpy(ring->supply, buffer, i);
292: ring_supplied(ring, i);
293: count -= i;
294: buffer += i;
295: }
296: }
297:
298: #ifdef notdef
299:
300: /*
301: * Move data from the "consume" portion of the ring buffer
302: */
303: void
304: ring_consume_data(ring, buffer, count)
305: Ring *ring;
306: unsigned char *buffer;
307: int count;
308: {
309: int i;
310:
311: while (count) {
312: i = MIN(count, ring_full_consecutive(ring));
313: memcpy(buffer, ring->consume, i);
314: ring_consumed(ring, i);
315: count -= i;
316: buffer += i;
317: }
318: }
319: #endif
320:
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