usr.bin/telnet/ring.c

   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/crypto/telnet/telnet/ring.c,v 1.2.8.2 2002/04/13 10:59:08 markm Exp $
  35  * $DragonFly: src/crypto/telnet/telnet/ring.c,v 1.2 2003/06/17 04:24:37 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 #ifdef  ENCRYPTION
 111     ring->clearto = 0;
 112 #endif  /* ENCRYPTION */
 113
 114     return 1;
 115 }
 116
 117 /* Mark routines */
 118
 119 /*
 120  * Mark the most recently supplied byte.
 121  */
 122
 123 void
 124 ring_mark(Ring *ring)
 125 {
 126     ring->mark = ring_decrement(ring, ring->supply, 1);
 127 }
 128
 129 /*
 130  * Is the ring pointing to the mark?
 131  */
 132
 133 int
 134 ring_at_mark(Ring *ring)
 135 {
 136     if (ring->mark == ring->consume) {
 137         return 1;
 138     } else {
 139         return 0;
 140     }
 141 }
 142
 143 /*
 144  * Clear any mark set on the ring.
 145  */
 146
 147 void
 148 ring_clear_mark(Ring *ring)
 149 {
 150     ring->mark = 0;
 151 }
 152
 153 /*
 154  * Add characters from current segment to ring buffer.
 155  */
 156 void
 157 ring_supplied(Ring *ring, int count)
 158 {
 159     ring->supply = ring_increment(ring, ring->supply, count);
 160     ring->supplytime = ++ring_clock;
 161 }
 162
 163 /*
 164  * We have just consumed "c" bytes.
 165  */
 166 void
 167 ring_consumed(Ring *ring, int count)
 168 {
 169     if (count == 0)     /* don't update anything */
 170         return;
 171
 172     if (ring->mark &&
 173                 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
 174         ring->mark = 0;
 175     }
 176 #ifdef  ENCRYPTION
 177     if (ring->consume < ring->clearto &&
 178                 ring->clearto <= ring->consume + count)
 179         ring->clearto = 0;
 180     else if (ring->consume + count > ring->top &&
 181                 ring->bottom <= ring->clearto &&
 182                 ring->bottom + ((ring->consume + count) - ring->top))
 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 */
 201 int
 202 ring_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 */
 212 int
 213 ring_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
 233 int
 234 ring_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  */
 251 int
 252 ring_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 of the ring buffer.
 271  */
 272 void
 273 ring_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         memcpy(ring->supply, buffer, i);
 280         ring_supplied(ring, i);
 281         count -= i;
 282         buffer += i;
 283     }
 284 }
 285
 286 #ifdef  ENCRYPTION
 287 void
 288 ring_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
 309     void
 310 ring_clearto(ring)
 311     Ring *ring;
 312 {
 313     if (!ring_empty(ring))
 314         ring->clearto = ring->supply;
 315     else
 316         ring->clearto = 0;
 317 }
 318 #endif  /* ENCRYPTION */