1/* $NetBSD: ring.c,v 1.17 2024/05/13 00:32:39 msaitoh 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. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32#include <sys/cdefs.h> 33#ifndef lint 34#if 0 35static char sccsid[] = "@(#)ring.c 8.2 (Berkeley) 5/30/95"; 36#else 37__RCSID("$NetBSD: ring.c,v 1.17 2024/05/13 00:32:39 msaitoh Exp $"); 38#endif 39#endif /* not lint */ 40 41/* 42 * This defines a structure for a ring buffer. 43 * 44 * The circular buffer has two parts: 45 *((( 46 * full: [consume, supply) 47 * empty: [supply, consume) 48 *]]] 49 * 50 */ 51 52#include <stdio.h> 53#include <string.h> 54#include <strings.h> 55#include <errno.h> 56#include <sys/types.h> 57#include <sys/ioctl.h> 58#include <sys/socket.h> 59 60#include "ring.h" 61#include "general.h" 62 63/* Internal macros */ 64 65#if !defined(MIN) 66#define MIN(a,b) (((a)<(b))? (a):(b)) 67#endif /* !defined(MIN) */ 68 69#define ring_subtract(d,a,b) (((a)-(b) >= 0)? \ 70 (a)-(b): (((a)-(b))+(d)->size)) 71 72#define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ 73 (a)+(c) : (((a)+(c))-(d)->size)) 74 75#define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ 76 (a)-(c) : (((a)-(c))-(d)->size)) 77 78 79/* 80 * The following is a clock, used to determine full, empty, etc. 81 * 82 * There is some trickiness here. Since the ring buffers are initialized 83 * to ZERO on allocation, we need to make sure, when interpreting the 84 * clock, that when the times are EQUAL, then the buffer is FULL. 85 */ 86static u_long ring_clock = 0; 87 88 89#define ring_empty(d) (((d)->consume == (d)->supply) && \ 90 ((d)->consumetime >= (d)->supplytime)) 91#define ring_full(d) (((d)->supply == (d)->consume) && \ 92 ((d)->supplytime > (d)->consumetime)) 93 94 95 96 97 98/* Buffer state transition routines */ 99 100int 101ring_init(Ring *ring, unsigned char *buffer, int count) 102{ 103 memset(ring, 0, sizeof *ring); 104 105 ring->size = count; 106 107 ring->supply = ring->consume = ring->bottom = buffer; 108 109 ring->top = ring->bottom+ring->size; 110 111#ifdef ENCRYPTION 112 ring->clearto = 0; 113#endif /* ENCRYPTION */ 114 115 return 1; 116} 117 118/* Mark routines */ 119 120/* 121 * Mark the most recently supplied byte. 122 */ 123 124void 125ring_mark(Ring *ring) 126{ 127 ring->mark = ring_decrement(ring, ring->supply, 1); 128} 129 130/* 131 * Is the ring pointing to the mark? 132 */ 133 134int 135ring_at_mark(Ring *ring) 136{ 137 if (ring->mark == ring->consume) { 138 return 1; 139 } else { 140 return 0; 141 } 142} 143 144/* 145 * Clear any mark set on the ring. 146 */ 147 148void 149ring_clear_mark(Ring *ring) 150{ 151 ring->mark = 0; 152} 153 154/* 155 * Add characters from current segment to ring buffer. 156 */ 157void 158ring_supplied(Ring *ring, int count) 159{ 160 ring->supply = ring_increment(ring, ring->supply, count); 161 ring->supplytime = ++ring_clock; 162} 163 164/* 165 * We have just consumed "c" bytes. 166 */ 167void 168ring_consumed(Ring *ring, int count) 169{ 170 if (count == 0) /* don't update anything */ 171 return; 172 173 if (ring->mark && 174 (ring_subtract(ring, ring->mark, ring->consume) < count)) { 175 ring->mark = 0; 176 } 177#ifdef ENCRYPTION 178 if (ring->consume < ring->clearto && 179 ring->clearto <= ring->consume + count) 180 ring->clearto = 0; 181 else if (ring->consume + count > ring->top && 182 ring->bottom <= ring->clearto) 183 ring->clearto = 0; 184#endif /* ENCRYPTION */ 185 ring->consume = ring_increment(ring, ring->consume, count); 186 ring->consumetime = ++ring_clock; 187 /* 188 * Try to encourage "ring_empty_consecutive()" to be large. 189 */ 190 if (ring_empty(ring)) { 191 ring->consume = ring->supply = ring->bottom; 192 } 193} 194 195 196 197/* Buffer state query routines */ 198 199 200/* Number of bytes that may be supplied */ 201int 202ring_empty_count(Ring *ring) 203{ 204 if (ring_empty(ring)) { /* if empty */ 205 return ring->size; 206 } else { 207 return ring_subtract(ring, ring->consume, ring->supply); 208 } 209} 210 211/* number of CONSECUTIVE bytes that may be supplied */ 212int 213ring_empty_consecutive(Ring *ring) 214{ 215 if ((ring->consume < ring->supply) || ring_empty(ring)) { 216 /* 217 * if consume is "below" supply, or empty, then 218 * return distance to the top 219 */ 220 return ring_subtract(ring, ring->top, ring->supply); 221 } else { 222 /* 223 * else, return what we may. 224 */ 225 return ring_subtract(ring, ring->consume, ring->supply); 226 } 227} 228 229/* Return the number of bytes that are available for consuming 230 * (but don't give more than enough to get to cross over set mark) 231 */ 232 233int 234ring_full_count(Ring *ring) 235{ 236 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 237 if (ring_full(ring)) { 238 return ring->size; /* nothing consumed, but full */ 239 } else { 240 return ring_subtract(ring, ring->supply, ring->consume); 241 } 242 } else { 243 return ring_subtract(ring, ring->mark, ring->consume); 244 } 245} 246 247/* 248 * Return the number of CONSECUTIVE bytes available for consuming. 249 * However, don't return more than enough to cross over set mark. 250 */ 251int 252ring_full_consecutive(Ring *ring) 253{ 254 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 255 if ((ring->supply < ring->consume) || ring_full(ring)) { 256 return ring_subtract(ring, ring->top, ring->consume); 257 } else { 258 return ring_subtract(ring, ring->supply, ring->consume); 259 } 260 } else { 261 if (ring->mark < ring->consume) { 262 return ring_subtract(ring, ring->top, ring->consume); 263 } else { /* Else, distance to mark */ 264 return ring_subtract(ring, ring->mark, ring->consume); 265 } 266 } 267} 268 269/* 270 * Move data into the "supply" portion of the ring buffer. 271 */ 272void 273ring_supply_data(Ring *ring, unsigned char *buffer, int count) 274{ 275 int i; 276 277 while (count) { 278 i = MIN(count, ring_empty_consecutive(ring)); 279 memmove(ring->supply, buffer, i); 280 ring_supplied(ring, i); 281 count -= i; 282 buffer += i; 283 } 284} 285 286#ifdef ENCRYPTION 287void 288ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int)) 289{ 290 unsigned char *s, *c; 291 292 if (ring_empty(ring) || ring->clearto == ring->supply) 293 return; 294 295 if (!(c = ring->clearto)) 296 c = ring->consume; 297 298 s = ring->supply; 299 300 if (s <= c) { 301 (*encryptor)(c, ring->top - c); 302 (*encryptor)(ring->bottom, s - ring->bottom); 303 } else 304 (*encryptor)(c, s - c); 305 306 ring->clearto = ring->supply; 307} 308 309void 310ring_clearto(Ring *ring) 311{ 312 313 if (!ring_empty(ring)) 314 ring->clearto = ring->supply; 315 else 316 ring->clearto = 0; 317} 318#endif /* ENCRYPTION */ 319