1/* $NetBSD: bsd-comp.c,v 1.2 2013/11/28 22:33:42 christos Exp $ */
2
3/* Because this code is derived from the 4.3BSD compress source:
4 *
5 *
6 * Copyright (c) 1985, 1986 The Regents of the University of California.
7 * All rights reserved.
8 *
9 * This code is derived from software contributed to Berkeley by
10 * James A. Woods, derived from original work by Spencer Thomas
11 * and Joseph Orost.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. All advertising materials mentioning features or use of this software
22 * must display the following acknowledgement:
23 * This product includes software developed by the University of
24 * California, Berkeley and its contributors.
25 * 4. Neither the name of the University nor the names of its contributors
26 * may be used to endorse or promote products derived from this software
27 * without specific prior written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * SUCH DAMAGE.
40 */
41
42#include <sys/cdefs.h>
43__RCSID("$NetBSD: bsd-comp.c,v 1.2 2013/11/28 22:33:42 christos Exp $");
44
45/*
46 * Id: bsd-comp.c,v 1.4 2004/01/17 05:47:55 carlsonj Exp
47 */
48
49#include <sys/types.h>
50#include <stdio.h>
51#include <stddef.h>
52#include <stdlib.h>
53#include <string.h>
54#include "pppdump.h"
55#include "ppp_defs.h"
56#include "ppp-comp.h"
57
58#if DO_BSD_COMPRESS
59
60/*
61 * PPP "BSD compress" compression
62 * The differences between this compression and the classic BSD LZW
63 * source are obvious from the requirement that the classic code worked
64 * with files while this handles arbitrarily long streams that
65 * are broken into packets. They are:
66 *
67 * When the code size expands, a block of junk is not emitted by
68 * the compressor and not expected by the decompressor.
69 *
70 * New codes are not necessarily assigned every time an old
71 * code is output by the compressor. This is because a packet
72 * end forces a code to be emitted, but does not imply that a
73 * new sequence has been seen.
74 *
75 * The compression ratio is checked at the first end of a packet
76 * after the appropriate gap. Besides simplifying and speeding
77 * things up, this makes it more likely that the transmitter
78 * and receiver will agree when the dictionary is cleared when
79 * compression is not going well.
80 */
81
82/*
83 * A dictionary for doing BSD compress.
84 */
85struct bsd_db {
86 int totlen; /* length of this structure */
87 u_int hsize; /* size of the hash table */
88 u_char hshift; /* used in hash function */
89 u_char n_bits; /* current bits/code */
90 u_char maxbits;
91 u_char debug;
92 u_char unit;
93 u_short seqno; /* sequence number of next packet */
94 u_int hdrlen; /* header length to preallocate */
95 u_int mru;
96 u_int maxmaxcode; /* largest valid code */
97 u_int max_ent; /* largest code in use */
98 u_int in_count; /* uncompressed bytes, aged */
99 u_int bytes_out; /* compressed bytes, aged */
100 u_int ratio; /* recent compression ratio */
101 u_int checkpoint; /* when to next check the ratio */
102 u_int clear_count; /* times dictionary cleared */
103 u_int incomp_count; /* incompressible packets */
104 u_int incomp_bytes; /* incompressible bytes */
105 u_int uncomp_count; /* uncompressed packets */
106 u_int uncomp_bytes; /* uncompressed bytes */
107 u_int comp_count; /* compressed packets */
108 u_int comp_bytes; /* compressed bytes */
109 u_short *lens; /* array of lengths of codes */
110 struct bsd_dict {
111 union { /* hash value */
112 u_int32_t fcode;
113 struct {
114#ifdef BSD_LITTLE_ENDIAN
115 u_short prefix; /* preceding code */
116 u_char suffix; /* last character of new code */
117 u_char pad;
118#else
119 u_char pad;
120 u_char suffix; /* last character of new code */
121 u_short prefix; /* preceding code */
122#endif
123 } hs;
124 } f;
125 u_short codem1; /* output of hash table -1 */
126 u_short cptr; /* map code to hash table entry */
127 } dict[1];
128};
129
130#define BSD_OVHD 2 /* BSD compress overhead/packet */
131#define BSD_INIT_BITS BSD_MIN_BITS
132
133static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
134static void bsd_free __P((void *state));
135static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
136 int unit, int hdrlen, int mru, int debug));
137static void bsd_incomp __P((void *state, PACKETPTR in));
138static int bsd_decompress __P((void *state, PACKETPTR in, PACKETPTR *out));
139static void bsd_reset __P((void *state));
140static void bsd_comp_stats __P((void *state, struct compstat *stats));
141
142/*
143 * Exported procedures.
144 */
145struct compressor ppp_bsd_compress = {
146 CI_BSD_COMPRESS, /* compress_proto */
147 NULL, /* comp_alloc */
148 NULL, /* comp_free */
149 NULL, /* comp_init */
150 NULL, /* comp_reset */
151 NULL, /* comp_compress */
152 NULL, /* comp_stat */
153 bsd_decomp_alloc, /* decomp_alloc */
154 bsd_free, /* decomp_free */
155 bsd_decomp_init, /* decomp_init */
156 bsd_reset, /* decomp_reset */
157 bsd_decompress, /* decompress */
158 bsd_incomp, /* incomp */
159 bsd_comp_stats, /* decomp_stat */
160};
161
162/*
163 * the next two codes should not be changed lightly, as they must not
164 * lie within the contiguous general code space.
165 */
166#define CLEAR 256 /* table clear output code */
167#define FIRST 257 /* first free entry */
168#define LAST 255
169
170#define MAXCODE(b) ((1 << (b)) - 1)
171#define BADCODEM1 MAXCODE(BSD_MAX_BITS)
172
173#define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
174 ^ (u_int32_t)(prefix))
175#define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
176 + (u_int32_t)(prefix))
177
178#define CHECK_GAP 10000 /* Ratio check interval */
179
180#define RATIO_SCALE_LOG 8
181#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
182#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
183
184static void bsd_clear __P((struct bsd_db *));
185static int bsd_check __P((struct bsd_db *));
186static void *bsd_alloc __P((u_char *, int, int));
187static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int,
188 int, int));
189
190/*
191 * clear the dictionary
192 */
193static void
194bsd_clear(db)
195 struct bsd_db *db;
196{
197 db->clear_count++;
198 db->max_ent = FIRST-1;
199 db->n_bits = BSD_INIT_BITS;
200 db->ratio = 0;
201 db->bytes_out = 0;
202 db->in_count = 0;
203 db->checkpoint = CHECK_GAP;
204}
205
206/*
207 * If the dictionary is full, then see if it is time to reset it.
208 *
209 * Compute the compression ratio using fixed-point arithmetic
210 * with 8 fractional bits.
211 *
212 * Since we have an infinite stream instead of a single file,
213 * watch only the local compression ratio.
214 *
215 * Since both peers must reset the dictionary at the same time even in
216 * the absence of CLEAR codes (while packets are incompressible), they
217 * must compute the same ratio.
218 */
219static int /* 1=output CLEAR */
220bsd_check(db)
221 struct bsd_db *db;
222{
223 u_int new_ratio;
224
225 if (db->in_count >= db->checkpoint) {
226 /* age the ratio by limiting the size of the counts */
227 if (db->in_count >= RATIO_MAX
228 || db->bytes_out >= RATIO_MAX) {
229 db->in_count -= db->in_count/4;
230 db->bytes_out -= db->bytes_out/4;
231 }
232
233 db->checkpoint = db->in_count + CHECK_GAP;
234
235 if (db->max_ent >= db->maxmaxcode) {
236 /* Reset the dictionary only if the ratio is worse,
237 * or if it looks as if it has been poisoned
238 * by incompressible data.
239 *
240 * This does not overflow, because
241 * db->in_count <= RATIO_MAX.
242 */
243 new_ratio = db->in_count << RATIO_SCALE_LOG;
244 if (db->bytes_out != 0)
245 new_ratio /= db->bytes_out;
246
247 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
248 bsd_clear(db);
249 return 1;
250 }
251 db->ratio = new_ratio;
252 }
253 }
254 return 0;
255}
256
257/*
258 * Return statistics.
259 */
260static void
261bsd_comp_stats(state, stats)
262 void *state;
263 struct compstat *stats;
264{
265 struct bsd_db *db = (struct bsd_db *) state;
266 u_int out;
267
268 stats->unc_bytes = db->uncomp_bytes;
269 stats->unc_packets = db->uncomp_count;
270 stats->comp_bytes = db->comp_bytes;
271 stats->comp_packets = db->comp_count;
272 stats->inc_bytes = db->incomp_bytes;
273 stats->inc_packets = db->incomp_count;
274 stats->ratio = db->in_count;
275 out = db->bytes_out;
276 if (stats->ratio <= 0x7fffff)
277 stats->ratio <<= 8;
278 else
279 out >>= 8;
280 if (out != 0)
281 stats->ratio /= out;
282}
283
284/*
285 * Reset state, as on a CCP ResetReq.
286 */
287static void
288bsd_reset(state)
289 void *state;
290{
291 struct bsd_db *db = (struct bsd_db *) state;
292
293 db->seqno = 0;
294 bsd_clear(db);
295 db->clear_count = 0;
296}
297
298/*
299 * Allocate space for a (de) compressor.
300 */
301static void *
302bsd_alloc(options, opt_len, decomp)
303 u_char *options;
304 int opt_len, decomp;
305{
306 int bits;
307 u_int newlen, hsize, hshift, maxmaxcode;
308 struct bsd_db *db;
309
310 if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3
311 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
312 return NULL;
313
314 bits = BSD_NBITS(options[2]);
315 switch (bits) {
316 case 9: /* needs 82152 for both directions */
317 case 10: /* needs 84144 */
318 case 11: /* needs 88240 */
319 case 12: /* needs 96432 */
320 hsize = 5003;
321 hshift = 4;
322 break;
323 case 13: /* needs 176784 */
324 hsize = 9001;
325 hshift = 5;
326 break;
327 case 14: /* needs 353744 */
328 hsize = 18013;
329 hshift = 6;
330 break;
331 case 15: /* needs 691440 */
332 hsize = 35023;
333 hshift = 7;
334 break;
335 case 16: /* needs 1366160--far too much, */
336 /* hsize = 69001; */ /* and 69001 is too big for cptr */
337 /* hshift = 8; */ /* in struct bsd_db */
338 /* break; */
339 default:
340 return NULL;
341 }
342
343 maxmaxcode = MAXCODE(bits);
344 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
345 db = (struct bsd_db *) malloc(newlen);
346 if (!db)
347 return NULL;
348 memset(db, 0, sizeof(*db) - sizeof(db->dict));
349
350 if (!decomp) {
351 db->lens = NULL;
352 } else {
353 db->lens = (u_short *) malloc((maxmaxcode+1) * sizeof(db->lens[0]));
354 if (!db->lens) {
355 free(db);
356 return NULL;
357 }
358 }
359
360 db->totlen = newlen;
361 db->hsize = hsize;
362 db->hshift = hshift;
363 db->maxmaxcode = maxmaxcode;
364 db->maxbits = bits;
365
366 return (void *) db;
367}
368
369static void
370bsd_free(state)
371 void *state;
372{
373 struct bsd_db *db = (struct bsd_db *) state;
374
375 if (db->lens)
376 free(db->lens);
377 free(db);
378}
379
380static void *
381bsd_decomp_alloc(options, opt_len)
382 u_char *options;
383 int opt_len;
384{
385 return bsd_alloc(options, opt_len, 1);
386}
387
388/*
389 * Initialize the database.
390 */
391static int
392bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
393 struct bsd_db *db;
394 u_char *options;
395 int opt_len, unit, hdrlen, mru, debug, decomp;
396{
397 int i;
398
399 if (opt_len < CILEN_BSD_COMPRESS
400 || options[0] != CI_BSD_COMPRESS || options[1] != CILEN_BSD_COMPRESS
401 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
402 || BSD_NBITS(options[2]) != db->maxbits
403 || (decomp && db->lens == NULL))
404 return 0;
405
406 if (decomp) {
407 i = LAST+1;
408 while (i != 0)
409 db->lens[--i] = 1;
410 }
411 i = db->hsize;
412 while (i != 0) {
413 db->dict[--i].codem1 = BADCODEM1;
414 db->dict[i].cptr = 0;
415 }
416
417 db->unit = unit;
418 db->hdrlen = hdrlen;
419 db->mru = mru;
420 if (debug)
421 db->debug = 1;
422
423 bsd_reset(db);
424
425 return 1;
426}
427
428static int
429bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
430 void *state;
431 u_char *options;
432 int opt_len, unit, hdrlen, mru, debug;
433{
434 return bsd_init((struct bsd_db *) state, options, opt_len,
435 unit, hdrlen, mru, debug, 1);
436}
437
438
439/*
440 * Update the "BSD Compress" dictionary on the receiver for
441 * incompressible data by pretending to compress the incoming data.
442 */
443static void
444bsd_incomp(state, in)
445 void *state;
446 PACKETPTR in;
447{
448 struct bsd_db *db = (struct bsd_db *) state;
449 u_int hshift = db->hshift;
450 u_int max_ent = db->max_ent;
451 u_int n_bits = db->n_bits;
452 struct bsd_dict *dictp;
453 u_int32_t fcode;
454 u_char c;
455 long hval, disp;
456 int slen, ilen;
457 u_int bitno = 7;
458 u_char *rptr;
459 u_int ent;
460
461 rptr = in->buf;
462 ent = rptr[0]; /* get the protocol */
463 if (ent == 0) {
464 ++rptr;
465 in->len--;
466 ent = rptr[0];
467 }
468 if ((ent & 1) == 0 || ent < 0x21 || ent > 0xf9)
469 return;
470
471 db->seqno++;
472 ilen = 1; /* count the protocol as 1 byte */
473 ++rptr;
474 slen = in->buf + in->len - rptr;
475 ilen += slen;
476 for (; slen > 0; --slen) {
477 c = *rptr++;
478 fcode = BSD_KEY(ent, c);
479 hval = BSD_HASH(ent, c, hshift);
480 dictp = &db->dict[hval];
481
482 /* validate and then check the entry */
483 if (dictp->codem1 >= max_ent)
484 goto nomatch;
485 if (dictp->f.fcode == fcode) {
486 ent = dictp->codem1+1;
487 continue; /* found (prefix,suffix) */
488 }
489
490 /* continue probing until a match or invalid entry */
491 disp = (hval == 0) ? 1 : hval;
492 do {
493 hval += disp;
494 if (hval >= db->hsize)
495 hval -= db->hsize;
496 dictp = &db->dict[hval];
497 if (dictp->codem1 >= max_ent)
498 goto nomatch;
499 } while (dictp->f.fcode != fcode);
500 ent = dictp->codem1+1;
501 continue; /* finally found (prefix,suffix) */
502
503 nomatch: /* output (count) the prefix */
504 bitno += n_bits;
505
506 /* code -> hashtable */
507 if (max_ent < db->maxmaxcode) {
508 struct bsd_dict *dictp2;
509 /* expand code size if needed */
510 if (max_ent >= MAXCODE(n_bits))
511 db->n_bits = ++n_bits;
512
513 /* Invalidate previous hash table entry
514 * assigned this code, and then take it over.
515 */
516 dictp2 = &db->dict[max_ent+1];
517 if (db->dict[dictp2->cptr].codem1 == max_ent)
518 db->dict[dictp2->cptr].codem1 = BADCODEM1;
519 dictp2->cptr = hval;
520 dictp->codem1 = max_ent;
521 dictp->f.fcode = fcode;
522
523 db->max_ent = ++max_ent;
524 db->lens[max_ent] = db->lens[ent]+1;
525 }
526 ent = c;
527 }
528 bitno += n_bits; /* output (count) the last code */
529 db->bytes_out += bitno/8;
530 db->in_count += ilen;
531 (void)bsd_check(db);
532
533 ++db->incomp_count;
534 db->incomp_bytes += ilen;
535 ++db->uncomp_count;
536 db->uncomp_bytes += ilen;
537
538 /* Increase code size if we would have without the packet
539 * boundary and as the decompressor will.
540 */
541 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
542 db->n_bits++;
543}
544
545
546/*
547 * Decompress "BSD Compress"
548 *
549 * Because of patent problems, we return DECOMP_ERROR for errors
550 * found by inspecting the input data and for system problems, but
551 * DECOMP_FATALERROR for any errors which could possibly be said to
552 * be being detected "after" decompression. For DECOMP_ERROR,
553 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
554 * infringing a patent of Motorola's if we do, so we take CCP down
555 * instead.
556 *
557 * Given that the frame has the correct sequence number and a good FCS,
558 * errors such as invalid codes in the input most likely indicate a
559 * bug, so we return DECOMP_FATALERROR for them in order to turn off
560 * compression, even though they are detected by inspecting the input.
561 */
562static int
563bsd_decompress(state, in, out)
564 void *state;
565 PACKETPTR in;
566 PACKETPTR *out;
567{
568 struct bsd_db *db = (struct bsd_db *) state;
569 u_int max_ent = db->max_ent;
570 u_int32_t accm = 0;
571 u_int bitno = 32; /* 1st valid bit in accm */
572 u_int n_bits = db->n_bits;
573 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
574 struct bsd_dict *dictp;
575 int explen, seq, len;
576 u_int incode, oldcode, finchar;
577 u_char *p, *rptr, *wptr;
578 int ilen;
579 int codelen, extra;
580
581 rptr = in->buf;
582 if (*rptr == 0)
583 ++rptr;
584 ++rptr; /* skip protocol (assumed 0xfd) */
585 seq = (rptr[0] << 8) + rptr[1];
586 rptr += BSD_OVHD;
587 ilen = len = in->buf + in->len - rptr;
588
589 /*
590 * Check the sequence number and give up if it is not what we expect.
591 */
592 if (seq != db->seqno++) {
593 if (db->debug)
594 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
595 db->unit, seq, db->seqno - 1);
596 return DECOMP_ERROR;
597 }
598
599 wptr = (*out)->buf + db->hdrlen;
600
601 oldcode = CLEAR;
602 explen = 0;
603 while (len > 0) {
604 /*
605 * Accumulate bytes until we have a complete code.
606 * Then get the next code, relying on the 32-bit,
607 * unsigned accm to mask the result.
608 */
609 bitno -= 8;
610 accm |= *rptr++ << bitno;
611 --len;
612 if (tgtbitno < bitno)
613 continue;
614 incode = accm >> tgtbitno;
615 accm <<= n_bits;
616 bitno += n_bits;
617
618 if (incode == CLEAR) {
619 /*
620 * The dictionary must only be cleared at
621 * the end of a packet. But there could be an
622 * empty message block at the end.
623 */
624 if (len > 0) {
625 if (db->debug)
626 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
627 return DECOMP_FATALERROR;
628 }
629 bsd_clear(db);
630 explen = ilen = 0;
631 break;
632 }
633
634 if (incode > max_ent + 2 || incode > db->maxmaxcode
635 || (incode > max_ent && oldcode == CLEAR)) {
636 if (db->debug) {
637 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
638 db->unit, incode, oldcode);
639 printf("max_ent=0x%x seqno=%d\n",
640 max_ent, db->seqno);
641 }
642 return DECOMP_FATALERROR; /* probably a bug */
643 }
644
645 /* Special case for KwKwK string. */
646 if (incode > max_ent) {
647 finchar = oldcode;
648 extra = 1;
649 } else {
650 finchar = incode;
651 extra = 0;
652 }
653
654 codelen = db->lens[finchar];
655 explen += codelen + extra;
656 if (explen > db->mru + 1) {
657 if (db->debug)
658 printf("bsd_decomp%d: ran out of mru\n", db->unit);
659 return DECOMP_FATALERROR;
660 }
661
662 /*
663 * Decode this code and install it in the decompressed buffer.
664 */
665 p = (wptr += codelen);
666 while (finchar > LAST) {
667 dictp = &db->dict[db->dict[finchar].cptr];
668#ifdef DEBUG
669 --codelen;
670 if (codelen <= 0) {
671 printf("bsd_decomp%d: fell off end of chain ", db->unit);
672 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
673 incode, finchar, db->dict[finchar].cptr, max_ent);
674 return DECOMP_FATALERROR;
675 }
676 if (dictp->codem1 != finchar-1) {
677 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
678 db->unit, incode, finchar);
679 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
680 db->dict[finchar].cptr, dictp->codem1);
681 return DECOMP_FATALERROR;
682 }
683#endif
684 *--p = dictp->f.hs.suffix;
685 finchar = dictp->f.hs.prefix;
686 }
687 *--p = finchar;
688
689#ifdef DEBUG
690 if (--codelen != 0)
691 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
692 db->unit, codelen, incode, max_ent);
693#endif
694
695 if (extra) /* the KwKwK case again */
696 *wptr++ = finchar;
697
698 /*
699 * If not first code in a packet, and
700 * if not out of code space, then allocate a new code.
701 *
702 * Keep the hash table correct so it can be used
703 * with uncompressed packets.
704 */
705 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
706 struct bsd_dict *dictp2;
707 u_int32_t fcode;
708 int hval, disp;
709
710 fcode = BSD_KEY(oldcode,finchar);
711 hval = BSD_HASH(oldcode,finchar,db->hshift);
712 dictp = &db->dict[hval];
713
714 /* look for a free hash table entry */
715 if (dictp->codem1 < max_ent) {
716 disp = (hval == 0) ? 1 : hval;
717 do {
718 hval += disp;
719 if (hval >= db->hsize)
720 hval -= db->hsize;
721 dictp = &db->dict[hval];
722 } while (dictp->codem1 < max_ent);
723 }
724
725 /*
726 * Invalidate previous hash table entry
727 * assigned this code, and then take it over
728 */
729 dictp2 = &db->dict[max_ent+1];
730 if (db->dict[dictp2->cptr].codem1 == max_ent) {
731 db->dict[dictp2->cptr].codem1 = BADCODEM1;
732 }
733 dictp2->cptr = hval;
734 dictp->codem1 = max_ent;
735 dictp->f.fcode = fcode;
736
737 db->max_ent = ++max_ent;
738 db->lens[max_ent] = db->lens[oldcode]+1;
739
740 /* Expand code size if needed. */
741 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
742 db->n_bits = ++n_bits;
743 tgtbitno = 32-n_bits;
744 }
745 }
746 oldcode = incode;
747 }
748 (*out)->len = wptr - ((*out)->buf + db->hdrlen);
749
750 /*
751 * Keep the checkpoint right so that incompressible packets
752 * clear the dictionary at the right times.
753 */
754 db->bytes_out += ilen;
755 db->in_count += explen;
756 if (bsd_check(db) && db->debug) {
757 printf("bsd_decomp%d: peer should have cleared dictionary\n",
758 db->unit);
759 }
760
761 ++db->comp_count;
762 db->comp_bytes += ilen + BSD_OVHD;
763 ++db->uncomp_count;
764 db->uncomp_bytes += explen;
765
766 return DECOMP_OK;
767}
768#endif /* DO_BSD_COMPRESS */
769