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 #include <sys/cdefs.h> 35 36 __FBSDID("$FreeBSD: src/usr.bin/telnet/ring.c,v 1.3.6.1 2002/04/13 11:07:13 markm Exp $"); 37 38 #ifndef lint 39 static const char sccsid[] = "@(#)ring.c 8.2 (Berkeley) 5/30/95"; 40 #endif 41 42 /* 43 * This defines a structure for a ring buffer. 44 * 45 * The circular buffer has two parts: 46 *((( 47 * full: [consume, supply) 48 * empty: [supply, consume) 49 *]]] 50 * 51 */ 52 53 #include <errno.h> 54 #include <stdio.h> 55 #include <string.h> 56 57 #ifdef size_t 58 #undef size_t 59 #endif 60 61 #include <sys/types.h> 62 #ifndef FILIO_H 63 #include <sys/ioctl.h> 64 #endif 65 #include <sys/socket.h> 66 67 #include "ring.h" 68 #include "general.h" 69 70 /* Internal macros */ 71 72 #if !defined(MIN) 73 #define MIN(a,b) (((a)<(b))? (a):(b)) 74 #endif /* !defined(MIN) */ 75 76 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \ 77 (a)-(b): (((a)-(b))+(d)->size)) 78 79 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ 80 (a)+(c) : (((a)+(c))-(d)->size)) 81 82 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ 83 (a)-(c) : (((a)-(c))-(d)->size)) 84 85 86 /* 87 * The following is a clock, used to determine full, empty, etc. 88 * 89 * There is some trickiness here. Since the ring buffers are initialized 90 * to ZERO on allocation, we need to make sure, when interpreting the 91 * clock, that when the times are EQUAL, then the buffer is FULL. 92 */ 93 static u_long ring_clock = 0; 94 95 96 #define ring_empty(d) (((d)->consume == (d)->supply) && \ 97 ((d)->consumetime >= (d)->supplytime)) 98 #define ring_full(d) (((d)->supply == (d)->consume) && \ 99 ((d)->supplytime > (d)->consumetime)) 100 101 /* Buffer state transition routines */ 102 103 int 104 ring_init(Ring *ring, unsigned char *buffer, int count) 105 { 106 memset((char *)ring, 0, sizeof *ring); 107 108 ring->size = count; 109 110 ring->supply = ring->consume = ring->bottom = buffer; 111 112 ring->top = ring->bottom+ring->size; 113 114 115 return 1; 116 } 117 118 /* Mark routines */ 119 120 /* 121 * Mark the most recently supplied byte. 122 */ 123 124 void 125 ring_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 */ 133 134 int 135 ring_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 */ 147 148 void 149 ring_clear_mark(Ring *ring) 150 { 151 ring->mark = 0; 152 } 153 154 /* 155 * Add characters from current segment to ring buffer. 156 */ 157 void 158 ring_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 */ 167 void 168 ring_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 ring->consume = ring_increment(ring, ring->consume, count); 178 ring->consumetime = ++ring_clock; 179 /* 180 * Try to encourage "ring_empty_consecutive()" to be large. 181 */ 182 if (ring_empty(ring)) { 183 ring->consume = ring->supply = ring->bottom; 184 } 185 } 186 187 188 189 /* Buffer state query routines */ 190 191 192 /* Number of bytes that may be supplied */ 193 int 194 ring_empty_count(Ring *ring) 195 { 196 if (ring_empty(ring)) { /* if empty */ 197 return ring->size; 198 } else { 199 return ring_subtract(ring, ring->consume, ring->supply); 200 } 201 } 202 203 /* number of CONSECUTIVE bytes that may be supplied */ 204 int 205 ring_empty_consecutive(Ring *ring) 206 { 207 if ((ring->consume < ring->supply) || ring_empty(ring)) { 208 /* 209 * if consume is "below" supply, or empty, then 210 * return distance to the top 211 */ 212 return ring_subtract(ring, ring->top, ring->supply); 213 } else { 214 /* 215 * else, return what we may. 216 */ 217 return ring_subtract(ring, ring->consume, ring->supply); 218 } 219 } 220 221 /* Return the number of bytes that are available for consuming 222 * (but don't give more than enough to get to cross over set mark) 223 */ 224 225 int 226 ring_full_count(Ring *ring) 227 { 228 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 229 if (ring_full(ring)) { 230 return ring->size; /* nothing consumed, but full */ 231 } else { 232 return ring_subtract(ring, ring->supply, ring->consume); 233 } 234 } else { 235 return ring_subtract(ring, ring->mark, ring->consume); 236 } 237 } 238 239 /* 240 * Return the number of CONSECUTIVE bytes available for consuming. 241 * However, don't return more than enough to cross over set mark. 242 */ 243 int 244 ring_full_consecutive(Ring *ring) 245 { 246 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 247 if ((ring->supply < ring->consume) || ring_full(ring)) { 248 return ring_subtract(ring, ring->top, ring->consume); 249 } else { 250 return ring_subtract(ring, ring->supply, ring->consume); 251 } 252 } else { 253 if (ring->mark < ring->consume) { 254 return ring_subtract(ring, ring->top, ring->consume); 255 } else { /* Else, distance to mark */ 256 return ring_subtract(ring, ring->mark, ring->consume); 257 } 258 } 259 } 260 261 /* 262 * Move data into the "supply" portion of of the ring buffer. 263 */ 264 void 265 ring_supply_data(Ring *ring, unsigned char *buffer, int count) 266 { 267 int i; 268 269 while (count) { 270 i = MIN(count, ring_empty_consecutive(ring)); 271 memcpy(ring->supply, buffer, i); 272 ring_supplied(ring, i); 273 count -= i; 274 buffer += i; 275 } 276 } 277 278