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 * @(#)ring.c 8.2 (Berkeley) 5/30/95 34 * $FreeBSD: src/usr.bin/telnet/ring.c,v 1.3.6.1 2002/04/13 11:07:13 markm Exp $ 35 * $DragonFly: src/usr.bin/telnet/ring.c,v 1.2 2003/06/17 04:29:32 dillon Exp $ 36 */ 37 38 /* 39 * This defines a structure for a ring buffer. 40 * 41 * The circular buffer has two parts: 42 *((( 43 * full: [consume, supply) 44 * empty: [supply, consume) 45 *]]] 46 * 47 */ 48 49 #include <errno.h> 50 #include <stdio.h> 51 #include <string.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 /* Buffer state transition routines */ 98 99 int 100 ring_init(Ring *ring, unsigned char *buffer, int count) 101 { 102 memset((char *)ring, 0, sizeof *ring); 103 104 ring->size = count; 105 106 ring->supply = ring->consume = ring->bottom = buffer; 107 108 ring->top = ring->bottom+ring->size; 109 110 111 return 1; 112 } 113 114 /* Mark routines */ 115 116 /* 117 * Mark the most recently supplied byte. 118 */ 119 120 void 121 ring_mark(Ring *ring) 122 { 123 ring->mark = ring_decrement(ring, ring->supply, 1); 124 } 125 126 /* 127 * Is the ring pointing to the mark? 128 */ 129 130 int 131 ring_at_mark(Ring *ring) 132 { 133 if (ring->mark == ring->consume) { 134 return 1; 135 } else { 136 return 0; 137 } 138 } 139 140 /* 141 * Clear any mark set on the ring. 142 */ 143 144 void 145 ring_clear_mark(Ring *ring) 146 { 147 ring->mark = 0; 148 } 149 150 /* 151 * Add characters from current segment to ring buffer. 152 */ 153 void 154 ring_supplied(Ring *ring, int count) 155 { 156 ring->supply = ring_increment(ring, ring->supply, count); 157 ring->supplytime = ++ring_clock; 158 } 159 160 /* 161 * We have just consumed "c" bytes. 162 */ 163 void 164 ring_consumed(Ring *ring, int count) 165 { 166 if (count == 0) /* don't update anything */ 167 return; 168 169 if (ring->mark && 170 (ring_subtract(ring, ring->mark, ring->consume) < count)) { 171 ring->mark = 0; 172 } 173 ring->consume = ring_increment(ring, ring->consume, count); 174 ring->consumetime = ++ring_clock; 175 /* 176 * Try to encourage "ring_empty_consecutive()" to be large. 177 */ 178 if (ring_empty(ring)) { 179 ring->consume = ring->supply = ring->bottom; 180 } 181 } 182 183 184 185 /* Buffer state query routines */ 186 187 188 /* Number of bytes that may be supplied */ 189 int 190 ring_empty_count(Ring *ring) 191 { 192 if (ring_empty(ring)) { /* if empty */ 193 return ring->size; 194 } else { 195 return ring_subtract(ring, ring->consume, ring->supply); 196 } 197 } 198 199 /* number of CONSECUTIVE bytes that may be supplied */ 200 int 201 ring_empty_consecutive(Ring *ring) 202 { 203 if ((ring->consume < ring->supply) || ring_empty(ring)) { 204 /* 205 * if consume is "below" supply, or empty, then 206 * return distance to the top 207 */ 208 return ring_subtract(ring, ring->top, ring->supply); 209 } else { 210 /* 211 * else, return what we may. 212 */ 213 return ring_subtract(ring, ring->consume, ring->supply); 214 } 215 } 216 217 /* Return the number of bytes that are available for consuming 218 * (but don't give more than enough to get to cross over set mark) 219 */ 220 221 int 222 ring_full_count(Ring *ring) 223 { 224 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 225 if (ring_full(ring)) { 226 return ring->size; /* nothing consumed, but full */ 227 } else { 228 return ring_subtract(ring, ring->supply, ring->consume); 229 } 230 } else { 231 return ring_subtract(ring, ring->mark, ring->consume); 232 } 233 } 234 235 /* 236 * Return the number of CONSECUTIVE bytes available for consuming. 237 * However, don't return more than enough to cross over set mark. 238 */ 239 int 240 ring_full_consecutive(Ring *ring) 241 { 242 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 243 if ((ring->supply < ring->consume) || ring_full(ring)) { 244 return ring_subtract(ring, ring->top, ring->consume); 245 } else { 246 return ring_subtract(ring, ring->supply, ring->consume); 247 } 248 } else { 249 if (ring->mark < ring->consume) { 250 return ring_subtract(ring, ring->top, ring->consume); 251 } else { /* Else, distance to mark */ 252 return ring_subtract(ring, ring->mark, ring->consume); 253 } 254 } 255 } 256 257 /* 258 * Move data into the "supply" portion of of the ring buffer. 259 */ 260 void 261 ring_supply_data(Ring *ring, unsigned char *buffer, int count) 262 { 263 int i; 264 265 while (count) { 266 i = MIN(count, ring_empty_consecutive(ring)); 267 memcpy(ring->supply, buffer, i); 268 ring_supplied(ring, i); 269 count -= i; 270 buffer += i; 271 } 272 } 273 274