1 /* $NetBSD: ring.c,v 1.12 2003/07/14 15:56:29 itojun Exp $ */ 2 3 /* 4 * Copyright (c) 1988, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <sys/cdefs.h> 37 #ifndef lint 38 #if 0 39 static char sccsid[] = "@(#)ring.c 8.2 (Berkeley) 5/30/95"; 40 #else 41 __RCSID("$NetBSD: ring.c,v 1.12 2003/07/14 15:56:29 itojun Exp $"); 42 #endif 43 #endif /* not lint */ 44 45 /* 46 * This defines a structure for a ring buffer. 47 * 48 * The circular buffer has two parts: 49 *((( 50 * full: [consume, supply) 51 * empty: [supply, consume) 52 *]]] 53 * 54 */ 55 56 #include <stdio.h> 57 #include <string.h> 58 #include <strings.h> 59 #include <errno.h> 60 #include <sys/types.h> 61 #include <sys/ioctl.h> 62 #include <sys/socket.h> 63 64 #include "ring.h" 65 #include "general.h" 66 67 /* Internal macros */ 68 69 #if !defined(MIN) 70 #define MIN(a,b) (((a)<(b))? (a):(b)) 71 #endif /* !defined(MIN) */ 72 73 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \ 74 (a)-(b): (((a)-(b))+(d)->size)) 75 76 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ 77 (a)+(c) : (((a)+(c))-(d)->size)) 78 79 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ 80 (a)-(c) : (((a)-(c))-(d)->size)) 81 82 83 /* 84 * The following is a clock, used to determine full, empty, etc. 85 * 86 * There is some trickiness here. Since the ring buffers are initialized 87 * to ZERO on allocation, we need to make sure, when interpreting the 88 * clock, that when the times are EQUAL, then the buffer is FULL. 89 */ 90 static u_long ring_clock = 0; 91 92 93 #define ring_empty(d) (((d)->consume == (d)->supply) && \ 94 ((d)->consumetime >= (d)->supplytime)) 95 #define ring_full(d) (((d)->supply == (d)->consume) && \ 96 ((d)->supplytime > (d)->consumetime)) 97 98 99 100 101 102 /* Buffer state transition routines */ 103 104 int 105 ring_init(Ring *ring, unsigned char *buffer, int count) 106 { 107 memset((char *)ring, 0, sizeof *ring); 108 109 ring->size = count; 110 111 ring->supply = ring->consume = ring->bottom = buffer; 112 113 ring->top = ring->bottom+ring->size; 114 115 #ifdef ENCRYPTION 116 ring->clearto = 0; 117 #endif /* ENCRYPTION */ 118 119 return 1; 120 } 121 122 /* Mark routines */ 123 124 /* 125 * Mark the most recently supplied byte. 126 */ 127 128 void 129 ring_mark(Ring *ring) 130 { 131 ring->mark = ring_decrement(ring, ring->supply, 1); 132 } 133 134 /* 135 * Is the ring pointing to the mark? 136 */ 137 138 int 139 ring_at_mark(Ring *ring) 140 { 141 if (ring->mark == ring->consume) { 142 return 1; 143 } else { 144 return 0; 145 } 146 } 147 148 /* 149 * Clear any mark set on the ring. 150 */ 151 152 void 153 ring_clear_mark(Ring *ring) 154 { 155 ring->mark = 0; 156 } 157 158 /* 159 * Add characters from current segment to ring buffer. 160 */ 161 void 162 ring_supplied(Ring *ring, int count) 163 { 164 ring->supply = ring_increment(ring, ring->supply, count); 165 ring->supplytime = ++ring_clock; 166 } 167 168 /* 169 * We have just consumed "c" bytes. 170 */ 171 void 172 ring_consumed(Ring *ring, int count) 173 { 174 if (count == 0) /* don't update anything */ 175 return; 176 177 if (ring->mark && 178 (ring_subtract(ring, ring->mark, ring->consume) < count)) { 179 ring->mark = 0; 180 } 181 #ifdef ENCRYPTION 182 if (ring->consume < ring->clearto && 183 ring->clearto <= ring->consume + count) 184 ring->clearto = 0; 185 else if (ring->consume + count > ring->top && 186 ring->bottom <= ring->clearto && 187 ring->bottom + ((ring->consume + count) - ring->top)) 188 ring->clearto = 0; 189 #endif /* ENCRYPTION */ 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 *ring) 208 { 209 if (ring_empty(ring)) { /* if empty */ 210 return ring->size; 211 } else { 212 return ring_subtract(ring, ring->consume, ring->supply); 213 } 214 } 215 216 /* number of CONSECUTIVE bytes that may be supplied */ 217 int 218 ring_empty_consecutive(Ring *ring) 219 { 220 if ((ring->consume < ring->supply) || ring_empty(ring)) { 221 /* 222 * if consume is "below" supply, or empty, then 223 * return distance to the top 224 */ 225 return ring_subtract(ring, ring->top, ring->supply); 226 } else { 227 /* 228 * else, return what we may. 229 */ 230 return ring_subtract(ring, ring->consume, ring->supply); 231 } 232 } 233 234 /* Return the number of bytes that are available for consuming 235 * (but don't give more than enough to get to cross over set mark) 236 */ 237 238 int 239 ring_full_count(Ring *ring) 240 { 241 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 242 if (ring_full(ring)) { 243 return ring->size; /* nothing consumed, but full */ 244 } else { 245 return ring_subtract(ring, ring->supply, ring->consume); 246 } 247 } else { 248 return ring_subtract(ring, ring->mark, ring->consume); 249 } 250 } 251 252 /* 253 * Return the number of CONSECUTIVE bytes available for consuming. 254 * However, don't return more than enough to cross over set mark. 255 */ 256 int 257 ring_full_consecutive(Ring *ring) 258 { 259 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 260 if ((ring->supply < ring->consume) || ring_full(ring)) { 261 return ring_subtract(ring, ring->top, ring->consume); 262 } else { 263 return ring_subtract(ring, ring->supply, ring->consume); 264 } 265 } else { 266 if (ring->mark < ring->consume) { 267 return ring_subtract(ring, ring->top, ring->consume); 268 } else { /* Else, distance to mark */ 269 return ring_subtract(ring, ring->mark, ring->consume); 270 } 271 } 272 } 273 274 /* 275 * Move data into the "supply" portion of of the ring buffer. 276 */ 277 void 278 ring_supply_data(Ring *ring, unsigned char *buffer, int count) 279 { 280 int i; 281 282 while (count) { 283 i = MIN(count, ring_empty_consecutive(ring)); 284 memmove(ring->supply, buffer, i); 285 ring_supplied(ring, i); 286 count -= i; 287 buffer += i; 288 } 289 } 290 291 #ifdef notdef 292 293 /* 294 * Move data from the "consume" portion of the ring buffer 295 */ 296 void 297 ring_consume_data(Ring *ring, unsigned char *buffer, int count) 298 { 299 int i; 300 301 while (count) { 302 i = MIN(count, ring_full_consecutive(ring)); 303 memmove(buffer, ring->consume, i); 304 ring_consumed(ring, i); 305 count -= i; 306 buffer += i; 307 } 308 } 309 #endif 310 311 #ifdef ENCRYPTION 312 void 313 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int)) 314 { 315 unsigned char *s, *c; 316 317 if (ring_empty(ring) || ring->clearto == ring->supply) 318 return; 319 320 if (!(c = ring->clearto)) 321 c = ring->consume; 322 323 s = ring->supply; 324 325 if (s <= c) { 326 (*encryptor)(c, ring->top - c); 327 (*encryptor)(ring->bottom, s - ring->bottom); 328 } else 329 (*encryptor)(c, s - c); 330 331 ring->clearto = ring->supply; 332 } 333 334 void 335 ring_clearto(Ring *ring) 336 { 337 338 if (!ring_empty(ring)) 339 ring->clearto = ring->supply; 340 else 341 ring->clearto = 0; 342 } 343 #endif /* ENCRYPTION */ 344