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 1.3 1994/02/25 03:00:34 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 #include <errno.h> 52 53 #ifdef size_t 54 #undef size_t 55 #endif 56 57 #include <sys/types.h> 58 #ifndef FILIO_H 59 #include <sys/ioctl.h> 60 #endif 61 #include <sys/socket.h> 62 63 #include "ring.h" 64 #include "general.h" 65 66 /* Internal macros */ 67 68 #if !defined(MIN) 69 #define MIN(a,b) (((a)<(b))? (a):(b)) 70 #endif /* !defined(MIN) */ 71 72 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \ 73 (a)-(b): (((a)-(b))+(d)->size)) 74 75 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ 76 (a)+(c) : (((a)+(c))-(d)->size)) 77 78 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ 79 (a)-(c) : (((a)-(c))-(d)->size)) 80 81 82 /* 83 * The following is a clock, used to determine full, empty, etc. 84 * 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. 88 */ 89 static u_long ring_clock = 0; 90 91 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)) 96 97 98 99 100 101 /* Buffer state transition routines */ 102 103 ring_init(ring, buffer, count) 104 Ring *ring; 105 unsigned char *buffer; 106 int count; 107 { 108 memset((char *)ring, 0, sizeof *ring); 109 110 ring->size = count; 111 112 ring->supply = ring->consume = ring->bottom = buffer; 113 114 ring->top = ring->bottom+ring->size; 115 116 117 return 1; 118 } 119 120 /* Mark routines */ 121 122 /* 123 * Mark the most recently supplied byte. 124 */ 125 126 void 127 ring_mark(ring) 128 Ring *ring; 129 { 130 ring->mark = ring_decrement(ring, ring->supply, 1); 131 } 132 133 /* 134 * Is the ring pointing to the mark? 135 */ 136 137 int 138 ring_at_mark(ring) 139 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) 154 Ring *ring; 155 { 156 ring->mark = 0; 157 } 158 159 /* 160 * Add characters from current segment to ring buffer. 161 */ 162 void 163 ring_supplied(ring, count) 164 Ring *ring; 165 int count; 166 { 167 ring->supply = ring_increment(ring, ring->supply, count); 168 ring->supplytime = ++ring_clock; 169 } 170 171 /* 172 * We have just consumed "c" bytes. 173 */ 174 void 175 ring_consumed(ring, count) 176 Ring *ring; 177 int count; 178 { 179 if (count == 0) /* don't update anything */ 180 return; 181 182 if (ring->mark && 183 (ring_subtract(ring, ring->mark, ring->consume) < count)) { 184 ring->mark = 0; 185 } 186 ring->consume = ring_increment(ring, ring->consume, count); 187 ring->consumetime = ++ring_clock; 188 /* 189 * Try to encourage "ring_empty_consecutive()" to be large. 190 */ 191 if (ring_empty(ring)) { 192 ring->consume = ring->supply = ring->bottom; 193 } 194 } 195 196 197 198 /* Buffer state query routines */ 199 200 201 /* Number of bytes that may be supplied */ 202 int 203 ring_empty_count(ring) 204 Ring *ring; 205 { 206 if (ring_empty(ring)) { /* if empty */ 207 return ring->size; 208 } else { 209 return ring_subtract(ring, ring->consume, ring->supply); 210 } 211 } 212 213 /* number of CONSECUTIVE bytes that may be supplied */ 214 int 215 ring_empty_consecutive(ring) 216 Ring *ring; 217 { 218 if ((ring->consume < ring->supply) || ring_empty(ring)) { 219 /* 220 * if consume is "below" supply, or empty, then 221 * return distance to the top 222 */ 223 return ring_subtract(ring, ring->top, ring->supply); 224 } else { 225 /* 226 * else, return what we may. 227 */ 228 return ring_subtract(ring, ring->consume, ring->supply); 229 } 230 } 231 232 /* Return the number of bytes that are available for consuming 233 * (but don't give more than enough to get to cross over set mark) 234 */ 235 236 int 237 ring_full_count(ring) 238 Ring *ring; 239 { 240 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 241 if (ring_full(ring)) { 242 return ring->size; /* nothing consumed, but full */ 243 } else { 244 return ring_subtract(ring, ring->supply, ring->consume); 245 } 246 } else { 247 return ring_subtract(ring, ring->mark, ring->consume); 248 } 249 } 250 251 /* 252 * Return the number of CONSECUTIVE bytes available for consuming. 253 * However, don't return more than enough to cross over set mark. 254 */ 255 int 256 ring_full_consecutive(ring) 257 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, buffer, count) 279 Ring *ring; 280 unsigned char *buffer; 281 int count; 282 { 283 int i; 284 285 while (count) { 286 i = MIN(count, ring_empty_consecutive(ring)); 287 memcpy(ring->supply, buffer, i); 288 ring_supplied(ring, i); 289 count -= i; 290 buffer += i; 291 } 292 } 293 294 #ifdef notdef 295 296 /* 297 * Move data from the "consume" portion of the ring buffer 298 */ 299 void 300 ring_consume_data(ring, buffer, count) 301 Ring *ring; 302 unsigned char *buffer; 303 int count; 304 { 305 int i; 306 307 while (count) { 308 i = MIN(count, ring_full_consecutive(ring)); 309 memcpy(buffer, ring->consume, i); 310 ring_consumed(ring, i); 311 count -= i; 312 buffer += i; 313 } 314 } 315 #endif 316 317