usr.bin/telnet/ring.c

   1 /*      $NetBSD: ring.c,v 1.12 2003/07/14 15:56:29 itojun Exp $ */
   2
   3 /*
   4  * Copyright (c) 1988, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #ifndef lint
  34 #if 0
  35 static char sccsid[] = "@(#)ring.c      8.2 (Berkeley) 5/30/95";
  36 #else
  37 __RCSID("$NetBSD: ring.c,v 1.12 2003/07/14 15:56:29 itojun Exp $");
  38 #endif
  39 #endif /* not lint */
  40
  41 /*
  42  * This defines a structure for a ring buffer.
  43  *
  44  * The circular buffer has two parts:
  45  *(((
  46  *      full:   [consume, supply)
  47  *      empty:  [supply, consume)
  48  *]]]
  49  *
  50  */
  51
  52 #include        <stdio.h>
  53 #include        <string.h>
  54 #include        <strings.h>
  55 #include        <errno.h>
  56 #include        <sys/types.h>
  57 #include        <sys/ioctl.h>
  58 #include        <sys/socket.h>
  59
  60 #include        "ring.h"
  61 #include        "general.h"
  62
  63 /* Internal macros */
  64
  65 #if     !defined(MIN)
  66 #define MIN(a,b)        (((a)<(b))? (a):(b))
  67 #endif  /* !defined(MIN) */
  68
  69 #define ring_subtract(d,a,b)    (((a)-(b) >= 0)? \
  70                                         (a)-(b): (((a)-(b))+(d)->size))
  71
  72 #define ring_increment(d,a,c)   (((a)+(c) < (d)->top)? \
  73                                         (a)+(c) : (((a)+(c))-(d)->size))
  74
  75 #define ring_decrement(d,a,c)   (((a)-(c) >= (d)->bottom)? \
  76                                         (a)-(c) : (((a)-(c))-(d)->size))
  77
  78
  79 /*
  80  * The following is a clock, used to determine full, empty, etc.
  81  *
  82  * There is some trickiness here.  Since the ring buffers are initialized
  83  * to ZERO on allocation, we need to make sure, when interpreting the
  84  * clock, that when the times are EQUAL, then the buffer is FULL.
  85  */
  86 static u_long ring_clock = 0;
  87
  88
  89 #define ring_empty(d) (((d)->consume == (d)->supply) && \
  90                                 ((d)->consumetime >= (d)->supplytime))
  91 #define ring_full(d) (((d)->supply == (d)->consume) && \
  92                                 ((d)->supplytime > (d)->consumetime))
  93
  94
  95
  96
  97
  98 /* Buffer state transition routines */
  99
 100 int
 101 ring_init(Ring *ring, unsigned char *buffer, int count)
 102 {
 103     memset((char *)ring, 0, sizeof *ring);
 104
 105     ring->size = count;
 106
 107     ring->supply = ring->consume = ring->bottom = buffer;
 108
 109     ring->top = ring->bottom+ring->size;
 110
 111 #ifdef  ENCRYPTION
 112     ring->clearto = 0;
 113 #endif  /* ENCRYPTION */
 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 #ifdef  ENCRYPTION
 178     if (ring->consume < ring->clearto &&
 179                 ring->clearto <= ring->consume + count)
 180         ring->clearto = 0;
 181     else if (ring->consume + count > ring->top &&
 182                 ring->bottom <= ring->clearto &&
 183                 ring->bottom + ((ring->consume + count) - ring->top))
 184         ring->clearto = 0;
 185 #endif  /* ENCRYPTION */
 186     ring->consume = ring_increment(ring, ring->consume, count);
 187     ring->consumetime = ++ring_clock;
 188     /*
 189      * Try to encourage "ring_empty_consecutive()" to be large.
 190      */
 191     if (ring_empty(ring)) {
 192         ring->consume = ring->supply = ring->bottom;
 193     }
 194 }
 195
 196
 197
 198 /* Buffer state query routines */
 199
 200
 201 /* Number of bytes that may be supplied */
 202 int
 203 ring_empty_count(Ring *ring)
 204 {
 205     if (ring_empty(ring)) {     /* if empty */
 206             return ring->size;
 207     } else {
 208         return ring_subtract(ring, ring->consume, ring->supply);
 209     }
 210 }
 211
 212 /* number of CONSECUTIVE bytes that may be supplied */
 213 int
 214 ring_empty_consecutive(Ring *ring)
 215 {
 216     if ((ring->consume < ring->supply) || ring_empty(ring)) {
 217                             /*
 218                              * if consume is "below" supply, or empty, then
 219                              * return distance to the top
 220                              */
 221         return ring_subtract(ring, ring->top, ring->supply);
 222     } else {
 223                                     /*
 224                                      * else, return what we may.
 225                                      */
 226         return ring_subtract(ring, ring->consume, ring->supply);
 227     }
 228 }
 229
 230 /* Return the number of bytes that are available for consuming
 231  * (but don't give more than enough to get to cross over set mark)
 232  */
 233
 234 int
 235 ring_full_count(Ring *ring)
 236 {
 237     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 238         if (ring_full(ring)) {
 239             return ring->size;  /* nothing consumed, but full */
 240         } else {
 241             return ring_subtract(ring, ring->supply, ring->consume);
 242         }
 243     } else {
 244         return ring_subtract(ring, ring->mark, ring->consume);
 245     }
 246 }
 247
 248 /*
 249  * Return the number of CONSECUTIVE bytes available for consuming.
 250  * However, don't return more than enough to cross over set mark.
 251  */
 252 int
 253 ring_full_consecutive(Ring *ring)
 254 {
 255     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 256         if ((ring->supply < ring->consume) || ring_full(ring)) {
 257             return ring_subtract(ring, ring->top, ring->consume);
 258         } else {
 259             return ring_subtract(ring, ring->supply, ring->consume);
 260         }
 261     } else {
 262         if (ring->mark < ring->consume) {
 263             return ring_subtract(ring, ring->top, ring->consume);
 264         } else {        /* Else, distance to mark */
 265             return ring_subtract(ring, ring->mark, ring->consume);
 266         }
 267     }
 268 }
 269
 270 /*
 271  * Move data into the "supply" portion of of the ring buffer.
 272  */
 273 void
 274 ring_supply_data(Ring *ring, unsigned char *buffer, int count)
 275 {
 276     int i;
 277
 278     while (count) {
 279         i = MIN(count, ring_empty_consecutive(ring));
 280         memmove(ring->supply, buffer, i);
 281         ring_supplied(ring, i);
 282         count -= i;
 283         buffer += i;
 284     }
 285 }
 286
 287 #ifdef notdef
 288
 289 /*
 290  * Move data from the "consume" portion of the ring buffer
 291  */
 292 void
 293 ring_consume_data(Ring *ring, unsigned char *buffer, int count)
 294 {
 295     int i;
 296
 297     while (count) {
 298         i = MIN(count, ring_full_consecutive(ring));
 299         memmove(buffer, ring->consume, i);
 300         ring_consumed(ring, i);
 301         count -= i;
 302         buffer += i;
 303     }
 304 }
 305 #endif
 306
 307 #ifdef  ENCRYPTION
 308 void
 309 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
 310 {
 311         unsigned char *s, *c;
 312
 313         if (ring_empty(ring) || ring->clearto == ring->supply)
 314                 return;
 315
 316         if (!(c = ring->clearto))
 317                 c = ring->consume;
 318
 319         s = ring->supply;
 320
 321         if (s <= c) {
 322                 (*encryptor)(c, ring->top - c);
 323                 (*encryptor)(ring->bottom, s - ring->bottom);
 324         } else
 325                 (*encryptor)(c, s - c);
 326
 327         ring->clearto = ring->supply;
 328 }
 329
 330 void
 331 ring_clearto(Ring *ring)
 332 {
 333
 334         if (!ring_empty(ring))
 335                 ring->clearto = ring->supply;
 336         else
 337                 ring->clearto = 0;
 338 }
 339 #endif  /* ENCRYPTION */