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 "telnet_locl.h" 35 36 RCSID("$Id$"); 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 /* Internal macros */ 50 51 #define ring_subtract(d,a,b) (((a)-(b) >= 0)? \ 52 (a)-(b): (((a)-(b))+(d)->size)) 53 54 #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ 55 (a)+(c) : (((a)+(c))-(d)->size)) 56 57 #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ 58 (a)-(c) : (((a)-(c))-(d)->size)) 59 60 61 /* 62 * The following is a clock, used to determine full, empty, etc. 63 * 64 * There is some trickiness here. Since the ring buffers are initialized 65 * to ZERO on allocation, we need to make sure, when interpreting the 66 * clock, that when the times are EQUAL, then the buffer is FULL. 67 */ 68 static u_long ring_clock = 0; 69 70 71 #define ring_empty(d) (((d)->consume == (d)->supply) && \ 72 ((d)->consumetime >= (d)->supplytime)) 73 #define ring_full(d) (((d)->supply == (d)->consume) && \ 74 ((d)->supplytime > (d)->consumetime)) 75 76 77 78 79 80 /* Buffer state transition routines */ 81 82 int 83 ring_init(Ring *ring, unsigned char *buffer, int count) 84 { 85 memset(ring, 0, sizeof *ring); 86 87 ring->size = count; 88 89 ring->supply = ring->consume = ring->bottom = buffer; 90 91 ring->top = ring->bottom+ring->size; 92 93 #if defined(ENCRYPTION) 94 ring->clearto = 0; 95 #endif 96 97 return 1; 98 } 99 100 /* Mark routines */ 101 102 /* 103 * Mark the most recently supplied byte. 104 */ 105 106 void 107 ring_mark(Ring *ring) 108 { 109 ring->mark = ring_decrement(ring, ring->supply, 1); 110 } 111 112 /* 113 * Is the ring pointing to the mark? 114 */ 115 116 int 117 ring_at_mark(Ring *ring) 118 { 119 if (ring->mark == ring->consume) { 120 return 1; 121 } else { 122 return 0; 123 } 124 } 125 126 /* 127 * Clear any mark set on the ring. 128 */ 129 130 void 131 ring_clear_mark(Ring *ring) 132 { 133 ring->mark = 0; 134 } 135 136 /* 137 * Add characters from current segment to ring buffer. 138 */ 139 void 140 ring_supplied(Ring *ring, int count) 141 { 142 ring->supply = ring_increment(ring, ring->supply, count); 143 ring->supplytime = ++ring_clock; 144 } 145 146 /* 147 * We have just consumed "c" bytes. 148 */ 149 void 150 ring_consumed(Ring *ring, int count) 151 { 152 if (count == 0) /* don't update anything */ 153 return; 154 155 if (ring->mark && 156 (ring_subtract(ring, ring->mark, ring->consume) < count)) { 157 ring->mark = 0; 158 } 159 #if defined(ENCRYPTION) 160 if (ring->consume < ring->clearto && 161 ring->clearto <= ring->consume + count) 162 ring->clearto = 0; 163 else if (ring->consume + count > ring->top && 164 ring->bottom <= ring->clearto && 165 ring->bottom + ((ring->consume + count) - ring->top)) 166 ring->clearto = 0; 167 #endif 168 ring->consume = ring_increment(ring, ring->consume, count); 169 ring->consumetime = ++ring_clock; 170 /* 171 * Try to encourage "ring_empty_consecutive()" to be large. 172 */ 173 if (ring_empty(ring)) { 174 ring->consume = ring->supply = ring->bottom; 175 } 176 } 177 178 179 180 /* Buffer state query routines */ 181 182 183 /* Number of bytes that may be supplied */ 184 int 185 ring_empty_count(Ring *ring) 186 { 187 if (ring_empty(ring)) { /* if empty */ 188 return ring->size; 189 } else { 190 return ring_subtract(ring, ring->consume, ring->supply); 191 } 192 } 193 194 /* number of CONSECUTIVE bytes that may be supplied */ 195 int 196 ring_empty_consecutive(Ring *ring) 197 { 198 if ((ring->consume < ring->supply) || ring_empty(ring)) { 199 /* 200 * if consume is "below" supply, or empty, then 201 * return distance to the top 202 */ 203 return ring_subtract(ring, ring->top, ring->supply); 204 } else { 205 /* 206 * else, return what we may. 207 */ 208 return ring_subtract(ring, ring->consume, ring->supply); 209 } 210 } 211 212 /* Return the number of bytes that are available for consuming 213 * (but don't give more than enough to get to cross over set mark) 214 */ 215 216 int 217 ring_full_count(Ring *ring) 218 { 219 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 220 if (ring_full(ring)) { 221 return ring->size; /* nothing consumed, but full */ 222 } else { 223 return ring_subtract(ring, ring->supply, ring->consume); 224 } 225 } else { 226 return ring_subtract(ring, ring->mark, ring->consume); 227 } 228 } 229 230 /* 231 * Return the number of CONSECUTIVE bytes available for consuming. 232 * However, don't return more than enough to cross over set mark. 233 */ 234 int 235 ring_full_consecutive(Ring *ring) 236 { 237 if ((ring->mark == 0) || (ring->mark == ring->consume)) { 238 if ((ring->supply < ring->consume) || ring_full(ring)) { 239 return ring_subtract(ring, ring->top, ring->consume); 240 } else { 241 return ring_subtract(ring, ring->supply, ring->consume); 242 } 243 } else { 244 if (ring->mark < ring->consume) { 245 return ring_subtract(ring, ring->top, ring->consume); 246 } else { /* Else, distance to mark */ 247 return ring_subtract(ring, ring->mark, ring->consume); 248 } 249 } 250 } 251 252 /* 253 * Move data into the "supply" portion of of the ring buffer. 254 */ 255 void 256 ring_supply_data(Ring *ring, unsigned char *buffer, int count) 257 { 258 int i; 259 260 while (count) { 261 i = min(count, ring_empty_consecutive(ring)); 262 memmove(ring->supply, buffer, i); 263 ring_supplied(ring, i); 264 count -= i; 265 buffer += i; 266 } 267 } 268 269 #ifdef notdef 270 271 /* 272 * Move data from the "consume" portion of the ring buffer 273 */ 274 void 275 ring_consume_data(Ring *ring, unsigned char *buffer, int count) 276 { 277 int i; 278 279 while (count) { 280 i = min(count, ring_full_consecutive(ring)); 281 memmove(buffer, ring->consume, i); 282 ring_consumed(ring, i); 283 count -= i; 284 buffer += i; 285 } 286 } 287 #endif 288 289 #if defined(ENCRYPTION) 290 void 291 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int)) 292 { 293 unsigned char *s, *c; 294 295 if (ring_empty(ring) || ring->clearto == ring->supply) 296 return; 297 298 if (!(c = ring->clearto)) 299 c = ring->consume; 300 301 s = ring->supply; 302 303 if (s <= c) { 304 (*encryptor)(c, ring->top - c); 305 (*encryptor)(ring->bottom, s - ring->bottom); 306 } else 307 (*encryptor)(c, s - c); 308 309 ring->clearto = ring->supply; 310 } 311 312 void 313 ring_clearto(Ring *ring) 314 { 315 if (!ring_empty(ring)) 316 ring->clearto = ring->supply; 317 else 318 ring->clearto = 0; 319 } 320 #endif 321 322