1 /* $NetBSD: ring.c,v 1.8 1998/02/27 10:44:13 christos 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 1.8 1998/02/27 10:44:13 christos 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 #ifndef NO_STRING_H 58 #include <string.h> 59 #endif 60 #include <strings.h> 61 #include <errno.h> 62 63 #ifdef size_t 64 #undef size_t 65 #endif 66 67 #include <sys/types.h> 68 #ifndef FILIO_H 69 #include <sys/ioctl.h> 70 #endif 71 #include <sys/socket.h> 72 73 #include "ring.h" 74 #include "general.h" 75 76 /* Internal macros */ 77 78 #if !defined(MIN) 79 #define MIN(a,b) (((a)<(b))? (a):(b)) 80 #endif /* !defined(MIN) */ 81 82 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \ 83 (a)-(b): (((a)-(b))+(d)->size)) 84 85 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ 86 (a)+(c) : (((a)+(c))-(d)->size)) 87 88 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ 89 (a)-(c) : (((a)-(c))-(d)->size)) 90 91 92 /* 93 * The following is a clock, used to determine full, empty, etc. 94 * 95 * There is some trickiness here. Since the ring buffers are initialized 96 * to ZERO on allocation, we need to make sure, when interpreting the 97 * clock, that when the times are EQUAL, then the buffer is FULL. 98 */ 99 static u_long ring_clock = 0; 100 101 102 #define ring_empty(d) (((d)->consume == (d)->supply) && \ 103 ((d)->consumetime >= (d)->supplytime)) 104 #define ring_full(d) (((d)->supply == (d)->consume) && \ 105 ((d)->supplytime > (d)->consumetime)) 106 107 108 109 110 111 /* Buffer state transition routines */ 112 113 int 114 ring_init(ring, buffer, count) 115 Ring *ring; 116 unsigned char *buffer; 117 int count; 118 { 119 memset((char *)ring, 0, sizeof *ring); 120 121 ring->size = count; 122 123 ring->supply = ring->consume = ring->bottom = buffer; 124 125 ring->top = ring->bottom+ring->size; 126 127 128 return 1; 129 } 130 131 /* Mark routines */ 132 133 /* 134 * Mark the most recently supplied byte. 135 */ 136 137 void 138 ring_mark(ring) 139 Ring *ring; 140 { 141 ring->mark = ring_decrement(ring, ring->supply, 1); 142 } 143 144 /* 145 * Is the ring pointing to the mark? 146 */ 147 148 int 149 ring_at_mark(ring) 150 Ring *ring; 151 { 152 if (ring->mark == ring->consume) { 153 return 1; 154 } else { 155 return 0; 156 } 157 } 158 159 /* 160 * Clear any mark set on the ring. 161 */ 162 163 void 164 ring_clear_mark(ring) 165 Ring *ring; 166 { 167 ring->mark = 0; 168 } 169 170 /* 171 * Add characters from current segment to ring buffer. 172 */ 173 void 174 ring_supplied(ring, count) 175 Ring *ring; 176 int count; 177 { 178 ring->supply = ring_increment(ring, ring->supply, count); 179 ring->supplytime = ++ring_clock; 180 } 181 182 /* 183 * We have just consumed "c" bytes. 184 */ 185 void 186 ring_consumed(ring, count) 187 Ring *ring; 188 int count; 189 { 190 if (count == 0) /* don't update anything */ 191 return; 192 193 if (ring->mark && 194 (ring_subtract(ring, ring->mark, ring->consume) < count)) { 195 ring->mark = 0; 196 } 197 ring->consume = ring_increment(ring, ring->consume, count); 198 ring->consumetime = ++ring_clock; 199 /* 200 * Try to encourage "ring_empty_consecutive()" to be large. 201 */ 202 if (ring_empty(ring)) { 203 ring->consume = ring->supply = ring->bottom; 204 } 205 } 206 207 208 209 /* Buffer state query routines */ 210 211 212 /* Number of bytes that may be supplied */ 213 int 214 ring_empty_count(ring) 215 Ring *ring; 216 { 217 if (ring_empty(ring)) { /* if empty */ 218 return ring->size; 219 } else { 220 return ring_subtract(ring, ring->consume, ring->supply); 221 } 222 } 223 224 /* number of CONSECUTIVE bytes that may be supplied */ 225 int 226 ring_empty_consecutive(ring) 227 Ring *ring; 228 { 229 if ((ring->consume < ring->supply) || ring_empty(ring)) { 230 /* 231 * if consume is "below" supply, or empty, then 232 * return distance to the top 233 */ 234 return ring_subtract(ring, ring->top, ring->supply); 235 } else { 236 /* 237 * else, return what we may. 238 */ 239 return ring_subtract(ring, ring->consume, ring->supply); 240 } 241 } 242 243 /* Return the number of bytes that are available for consuming 244 * (but don't give more than enough to get to cross over set mark) 245 */ 246 247 int 248 ring_full_count(ring) 249 Ring *ring; 250 { 251 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 252 if (ring_full(ring)) { 253 return ring->size; /* nothing consumed, but full */ 254 } else { 255 return ring_subtract(ring, ring->supply, ring->consume); 256 } 257 } else { 258 return ring_subtract(ring, ring->mark, ring->consume); 259 } 260 } 261 262 /* 263 * Return the number of CONSECUTIVE bytes available for consuming. 264 * However, don't return more than enough to cross over set mark. 265 */ 266 int 267 ring_full_consecutive(ring) 268 Ring *ring; 269 { 270 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 271 if ((ring->supply < ring->consume) || ring_full(ring)) { 272 return ring_subtract(ring, ring->top, ring->consume); 273 } else { 274 return ring_subtract(ring, ring->supply, ring->consume); 275 } 276 } else { 277 if (ring->mark < ring->consume) { 278 return ring_subtract(ring, ring->top, ring->consume); 279 } else { /* Else, distance to mark */ 280 return ring_subtract(ring, ring->mark, ring->consume); 281 } 282 } 283 } 284 285 /* 286 * Move data into the "supply" portion of of the ring buffer. 287 */ 288 void 289 ring_supply_data(ring, buffer, count) 290 Ring *ring; 291 unsigned char *buffer; 292 int count; 293 { 294 int i; 295 296 while (count) { 297 i = MIN(count, ring_empty_consecutive(ring)); 298 memmove(ring->supply, buffer, i); 299 ring_supplied(ring, i); 300 count -= i; 301 buffer += i; 302 } 303 } 304 305 #ifdef notdef 306 307 /* 308 * Move data from the "consume" portion of the ring buffer 309 */ 310 void 311 ring_consume_data(ring, buffer, count) 312 Ring *ring; 313 unsigned char *buffer; 314 int count; 315 { 316 int i; 317 318 while (count) { 319 i = MIN(count, ring_full_consecutive(ring)); 320 memmove(buffer, ring->consume, i); 321 ring_consumed(ring, i); 322 count -= i; 323 buffer += i; 324 } 325 } 326 #endif 327 328