telnet.tproj/ring.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * "Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.0 (the 'License').  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License."
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*
  25  * Copyright (c) 1988, 1993
  26  *      The Regents of the University of California.  All rights reserved.
  27  *
  28  * Redistribution and use in source and binary forms, with or without
  29  * modification, are permitted provided that the following conditions
  30  * are met:
  31  * 1. Redistributions of source code must retain the above copyright
  32  *    notice, this list of conditions and the following disclaimer.
  33  * 2. Redistributions in binary form must reproduce the above copyright
  34  *    notice, this list of conditions and the following disclaimer in the
  35  *    documentation and/or other materials provided with the distribution.
  36  * 3. All advertising materials mentioning features or use of this software
  37  *    must display the following acknowledgement:
  38  *      This product includes software developed by the University of
  39  *      California, Berkeley and its contributors.
  40  * 4. Neither the name of the University nor the names of its contributors
  41  *    may be used to endorse or promote products derived from this software
  42  *    without specific prior written permission.
  43  *
  44  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  45  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  46  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  47  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  48  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  49  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  50  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  51  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  52  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  53  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  54  * SUCH DAMAGE.
  55  */
  56
  57 #ifndef lint
  58 static char sccsid[] = "@(#)ring.c      8.2 (Berkeley) 5/30/95";
  59 #endif /* not lint */
  60
  61 /*
  62  * This defines a structure for a ring buffer.
  63  *
  64  * The circular buffer has two parts:
  65  *(((
  66  *      full:   [consume, supply)
  67  *      empty:  [supply, consume)
  68  *]]]
  69  *
  70  */
  71
  72 #include        <stdio.h>
  73 #include        <errno.h>
  74
  75 #ifdef  size_t
  76 #undef  size_t
  77 #endif
  78
  79 #include        <sys/types.h>
  80 #ifndef FILIO_H
  81 #include        <sys/ioctl.h>
  82 #endif
  83 #include        <sys/socket.h>
  84
  85 #include        "ring.h"
  86 #include        "general.h"
  87
  88 /* Internal macros */
  89
  90 #if     !defined(MIN)
  91 #define MIN(a,b)        (((a)<(b))? (a):(b))
  92 #endif  /* !defined(MIN) */
  93
  94 #define ring_subtract(d,a,b)    (((a)-(b) >= 0)? \
  95                                         (a)-(b): (((a)-(b))+(d)->size))
  96
  97 #define ring_increment(d,a,c)   (((a)+(c) < (d)->top)? \
  98                                         (a)+(c) : (((a)+(c))-(d)->size))
  99
 100 #define ring_decrement(d,a,c)   (((a)-(c) >= (d)->bottom)? \
 101                                         (a)-(c) : (((a)-(c))-(d)->size))
 102
 103
 104 /*
 105  * The following is a clock, used to determine full, empty, etc.
 106  *
 107  * There is some trickiness here.  Since the ring buffers are initialized
 108  * to ZERO on allocation, we need to make sure, when interpreting the
 109  * clock, that when the times are EQUAL, then the buffer is FULL.
 110  */
 111 static u_long ring_clock = 0;
 112
 113
 114 #define ring_empty(d) (((d)->consume == (d)->supply) && \
 115                                 ((d)->consumetime >= (d)->supplytime))
 116 #define ring_full(d) (((d)->supply == (d)->consume) && \
 117                                 ((d)->supplytime > (d)->consumetime))
 118
 119
 120
 121
 122
 123 /* Buffer state transition routines */
 124
 125     ring_init(ring, buffer, count)
 126 Ring *ring;
 127     unsigned char *buffer;
 128     int count;
 129 {
 130     memset((char *)ring, 0, sizeof *ring);
 131
 132     ring->size = count;
 133
 134     ring->supply = ring->consume = ring->bottom = buffer;
 135
 136     ring->top = ring->bottom+ring->size;
 137
 138 #ifdef  ENCRYPTION
 139     ring->clearto = 0;
 140 #endif  /* ENCRYPTION */
 141
 142     return 1;
 143 }
 144
 145 /* Mark routines */
 146
 147 /*
 148  * Mark the most recently supplied byte.
 149  */
 150
 151     void
 152 ring_mark(ring)
 153     Ring *ring;
 154 {
 155     ring->mark = ring_decrement(ring, ring->supply, 1);
 156 }
 157
 158 /*
 159  * Is the ring pointing to the mark?
 160  */
 161
 162     int
 163 ring_at_mark(ring)
 164     Ring *ring;
 165 {
 166     if (ring->mark == ring->consume) {
 167         return 1;
 168     } else {
 169         return 0;
 170     }
 171 }
 172
 173 /*
 174  * Clear any mark set on the ring.
 175  */
 176
 177     void
 178 ring_clear_mark(ring)
 179     Ring *ring;
 180 {
 181     ring->mark = 0;
 182 }
 183
 184 /*
 185  * Add characters from current segment to ring buffer.
 186  */
 187     void
 188 ring_supplied(ring, count)
 189     Ring *ring;
 190     int count;
 191 {
 192     ring->supply = ring_increment(ring, ring->supply, count);
 193     ring->supplytime = ++ring_clock;
 194 }
 195
 196 /*
 197  * We have just consumed "c" bytes.
 198  */
 199     void
 200 ring_consumed(ring, count)
 201     Ring *ring;
 202     int count;
 203 {
 204     if (count == 0)     /* don't update anything */
 205         return;
 206
 207     if (ring->mark &&
 208                 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
 209         ring->mark = 0;
 210     }
 211 #ifdef  ENCRYPTION
 212     if (ring->consume < ring->clearto &&
 213                 ring->clearto <= ring->consume + count)
 214         ring->clearto = 0;
 215     else if (ring->consume + count > ring->top &&
 216                 ring->bottom <= ring->clearto &&
 217                 ring->bottom + ((ring->consume + count) - ring->top))
 218         ring->clearto = 0;
 219 #endif  /* ENCRYPTION */
 220     ring->consume = ring_increment(ring, ring->consume, count);
 221     ring->consumetime = ++ring_clock;
 222     /*
 223      * Try to encourage "ring_empty_consecutive()" to be large.
 224      */
 225     if (ring_empty(ring)) {
 226         ring->consume = ring->supply = ring->bottom;
 227     }
 228 }
 229
 230
 231
 232 /* Buffer state query routines */
 233
 234
 235 /* Number of bytes that may be supplied */
 236     int
 237 ring_empty_count(ring)
 238     Ring *ring;
 239 {
 240     if (ring_empty(ring)) {     /* if empty */
 241             return ring->size;
 242     } else {
 243         return ring_subtract(ring, ring->consume, ring->supply);
 244     }
 245 }
 246
 247 /* number of CONSECUTIVE bytes that may be supplied */
 248     int
 249 ring_empty_consecutive(ring)
 250     Ring *ring;
 251 {
 252     if ((ring->consume < ring->supply) || ring_empty(ring)) {
 253                             /*
 254                              * if consume is "below" supply, or empty, then
 255                              * return distance to the top
 256                              */
 257         return ring_subtract(ring, ring->top, ring->supply);
 258     } else {
 259                                     /*
 260                                      * else, return what we may.
 261                                      */
 262         return ring_subtract(ring, ring->consume, ring->supply);
 263     }
 264 }
 265
 266 /* Return the number of bytes that are available for consuming
 267  * (but don't give more than enough to get to cross over set mark)
 268  */
 269
 270     int
 271 ring_full_count(ring)
 272     Ring *ring;
 273 {
 274     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 275         if (ring_full(ring)) {
 276             return ring->size;  /* nothing consumed, but full */
 277         } else {
 278             return ring_subtract(ring, ring->supply, ring->consume);
 279         }
 280     } else {
 281         return ring_subtract(ring, ring->mark, ring->consume);
 282     }
 283 }
 284
 285 /*
 286  * Return the number of CONSECUTIVE bytes available for consuming.
 287  * However, don't return more than enough to cross over set mark.
 288  */
 289     int
 290 ring_full_consecutive(ring)
 291     Ring *ring;
 292 {
 293     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 294         if ((ring->supply < ring->consume) || ring_full(ring)) {
 295             return ring_subtract(ring, ring->top, ring->consume);
 296         } else {
 297             return ring_subtract(ring, ring->supply, ring->consume);
 298         }
 299     } else {
 300         if (ring->mark < ring->consume) {
 301             return ring_subtract(ring, ring->top, ring->consume);
 302         } else {        /* Else, distance to mark */
 303             return ring_subtract(ring, ring->mark, ring->consume);
 304         }
 305     }
 306 }
 307
 308 /*
 309  * Move data into the "supply" portion of of the ring buffer.
 310  */
 311     void
 312 ring_supply_data(ring, buffer, count)
 313     Ring *ring;
 314     unsigned char *buffer;
 315     int count;
 316 {
 317     int i;
 318
 319     while (count) {
 320         i = MIN(count, ring_empty_consecutive(ring));
 321         memmove(ring->supply, buffer, i);
 322         ring_supplied(ring, i);
 323         count -= i;
 324         buffer += i;
 325     }
 326 }
 327
 328 #ifdef notdef
 329
 330 /*
 331  * Move data from the "consume" portion of the ring buffer
 332  */
 333     void
 334 ring_consume_data(ring, buffer, count)
 335     Ring *ring;
 336     unsigned char *buffer;
 337     int count;
 338 {
 339     int i;
 340
 341     while (count) {
 342         i = MIN(count, ring_full_consecutive(ring));
 343         memmove(buffer, ring->consume, i);
 344         ring_consumed(ring, i);
 345         count -= i;
 346         buffer += i;
 347     }
 348 }
 349 #endif
 350
 351 #ifdef  ENCRYPTION
 352     void
 353 ring_encrypt(ring, encryptor)
 354     Ring *ring;
 355     void (*encryptor)();
 356 {
 357     unsigned char *s, *c;
 358
 359     if (ring_empty(ring) || ring->clearto == ring->supply)
 360         return;
 361
 362     if (!(c = ring->clearto))
 363         c = ring->consume;
 364
 365     s = ring->supply;
 366
 367     if (s <= c) {
 368         (*encryptor)(c, ring->top - c);
 369         (*encryptor)(ring->bottom, s - ring->bottom);
 370     } else
 371         (*encryptor)(c, s - c);
 372
 373     ring->clearto = ring->supply;
 374 }
 375
 376     void
 377 ring_clearto(ring)
 378     Ring *ring;
 379 {
 380     if (!ring_empty(ring))
 381         ring->clearto = ring->supply;
 382     else
 383         ring->clearto = 0;
 384 }
 385 #endif  /* ENCRYPTION */