src/bin/network/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
  34 #if 0
  35 #ifndef lint
  36 static const char sccsid[] = "@(#)ring.c        8.2 (Berkeley) 5/30/95";
  37 #endif
  38 #endif
  39 #include <sys/cdefs.h>
  40 __FBSDID("$FreeBSD: src/contrib/telnet/telnet/ring.c,v 1.7 2003/05/04 02:54:48 obrien Exp $");
  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 #ifdef  ENCRYPTION
 115     ring->clearto = 0;
 116 #endif  /* ENCRYPTION */
 117
 118     return 1;
 119 }
 120
 121 /* Mark routines */
 122
 123 /*
 124  * Mark the most recently supplied byte.
 125  */
 126
 127 void
 128 ring_mark(Ring *ring)
 129 {
 130     ring->mark = ring_decrement(ring, ring->supply, 1);
 131 }
 132
 133 /*
 134  * Is the ring pointing to the mark?
 135  */
 136
 137 int
 138 ring_at_mark(Ring *ring)
 139 {
 140     if (ring->mark == ring->consume) {
 141         return 1;
 142     } else {
 143         return 0;
 144     }
 145 }
 146
 147 /*
 148  * Clear any mark set on the ring.
 149  */
 150
 151 void
 152 ring_clear_mark(Ring *ring)
 153 {
 154     ring->mark = 0;
 155 }
 156
 157 /*
 158  * Add characters from current segment to ring buffer.
 159  */
 160 void
 161 ring_supplied(Ring *ring, int count)
 162 {
 163     ring->supply = ring_increment(ring, ring->supply, count);
 164     ring->supplytime = ++ring_clock;
 165 }
 166
 167 /*
 168  * We have just consumed "c" bytes.
 169  */
 170 void
 171 ring_consumed(Ring *ring, int count)
 172 {
 173     if (count == 0)     /* don't update anything */
 174         return;
 175
 176     if (ring->mark &&
 177                 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
 178         ring->mark = 0;
 179     }
 180 #ifdef  ENCRYPTION
 181     if (ring->consume < ring->clearto &&
 182                 ring->clearto <= ring->consume + count)
 183         ring->clearto = 0;
 184     else if (ring->consume + count > ring->top &&
 185                 ring->bottom <= ring->clearto &&
 186                 ring->bottom + ((ring->consume + count) - ring->top))
 187         ring->clearto = 0;
 188 #endif  /* ENCRYPTION */
 189     ring->consume = ring_increment(ring, ring->consume, count);
 190     ring->consumetime = ++ring_clock;
 191     /*
 192      * Try to encourage "ring_empty_consecutive()" to be large.
 193      */
 194     if (ring_empty(ring)) {
 195         ring->consume = ring->supply = ring->bottom;
 196     }
 197 }
 198
 199
 200
 201 /* Buffer state query routines */
 202
 203
 204 /* Number of bytes that may be supplied */
 205 int
 206 ring_empty_count(Ring *ring)
 207 {
 208     if (ring_empty(ring)) {     /* if empty */
 209             return ring->size;
 210     } else {
 211         return ring_subtract(ring, ring->consume, ring->supply);
 212     }
 213 }
 214
 215 /* number of CONSECUTIVE bytes that may be supplied */
 216 int
 217 ring_empty_consecutive(Ring *ring)
 218 {
 219     if ((ring->consume < ring->supply) || ring_empty(ring)) {
 220                             /*
 221                              * if consume is "below" supply, or empty, then
 222                              * return distance to the top
 223                              */
 224         return ring_subtract(ring, ring->top, ring->supply);
 225     } else {
 226                                     /*
 227                                      * else, return what we may.
 228                                      */
 229         return ring_subtract(ring, ring->consume, ring->supply);
 230     }
 231 }
 232
 233 /* Return the number of bytes that are available for consuming
 234  * (but don't give more than enough to get to cross over set mark)
 235  */
 236
 237 int
 238 ring_full_count(Ring *ring)
 239 {
 240     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 241         if (ring_full(ring)) {
 242             return ring->size;  /* nothing consumed, but full */
 243         } else {
 244             return ring_subtract(ring, ring->supply, ring->consume);
 245         }
 246     } else {
 247         return ring_subtract(ring, ring->mark, ring->consume);
 248     }
 249 }
 250
 251 /*
 252  * Return the number of CONSECUTIVE bytes available for consuming.
 253  * However, don't return more than enough to cross over set mark.
 254  */
 255 int
 256 ring_full_consecutive(Ring *ring)
 257 {
 258     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 259         if ((ring->supply < ring->consume) || ring_full(ring)) {
 260             return ring_subtract(ring, ring->top, ring->consume);
 261         } else {
 262             return ring_subtract(ring, ring->supply, ring->consume);
 263         }
 264     } else {
 265         if (ring->mark < ring->consume) {
 266             return ring_subtract(ring, ring->top, ring->consume);
 267         } else {        /* Else, distance to mark */
 268             return ring_subtract(ring, ring->mark, ring->consume);
 269         }
 270     }
 271 }
 272
 273 /*
 274  * Move data into the "supply" portion of of the ring buffer.
 275  */
 276 void
 277 ring_supply_data(Ring *ring, unsigned char *buffer, int count)
 278 {
 279     int i;
 280
 281     while (count) {
 282         i = MIN(count, ring_empty_consecutive(ring));
 283         memcpy(ring->supply, buffer, i);
 284         ring_supplied(ring, i);
 285         count -= i;
 286         buffer += i;
 287     }
 288 }
 289
 290 #ifdef  ENCRYPTION
 291 void
 292 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
 293 {
 294     unsigned char *s, *c;
 295
 296     if (ring_empty(ring) || ring->clearto == ring->supply)
 297         return;
 298
 299     if (!(c = ring->clearto))
 300         c = ring->consume;
 301
 302     s = ring->supply;
 303
 304     if (s <= c) {
 305         (*encryptor)(c, ring->top - c);
 306         (*encryptor)(ring->bottom, s - ring->bottom);
 307     } else
 308         (*encryptor)(c, s - c);
 309
 310     ring->clearto = ring->supply;
 311 }
 312
 313     void
 314 ring_clearto(ring)
 315     Ring *ring;
 316 {
 317     if (!ring_empty(ring))
 318         ring->clearto = ring->supply;
 319     else
 320         ring->clearto = 0;
 321 }
 322 #endif  /* ENCRYPTION */