1 /* Because this code is derived from the 4.3BSD compress source:
2 *
3 *
4 * Copyright (c) 1985, 1986 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * James A. Woods, derived from original work by Spencer Thomas
9 * and Joseph Orost.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by the University of
22 * California, Berkeley and its contributors.
23 * 4. Neither the name of the University nor the names of its contributors
24 * may be used to endorse or promote products derived from this software
25 * without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 */
39
40 /*
41 * $Id: bsd-comp.c,v 1.3 1999/04/16 11:35:59 paulus Exp $
42 */
43
44 #include <sys/types.h>
45 #include <stddef.h>
46 #include <stdlib.h>
47 #ifdef PPP_DEFS_IN_NET
48 #include <net/ppp_defs.h>
49 #else
50 #include "ppp_defs.h"
51 #endif
52 #include "ppp-comp.h"
53
54 #if DO_BSD_COMPRESS
55
56 /*
57 * PPP "BSD compress" compression
58 * The differences between this compression and the classic BSD LZW
59 * source are obvious from the requirement that the classic code worked
60 * with files while this handles arbitrarily long streams that
61 * are broken into packets. They are:
62 *
63 * When the code size expands, a block of junk is not emitted by
64 * the compressor and not expected by the decompressor.
65 *
66 * New codes are not necessarily assigned every time an old
67 * code is output by the compressor. This is because a packet
68 * end forces a code to be emitted, but does not imply that a
69 * new sequence has been seen.
70 *
71 * The compression ratio is checked at the first end of a packet
72 * after the appropriate gap. Besides simplifying and speeding
73 * things up, this makes it more likely that the transmitter
74 * and receiver will agree when the dictionary is cleared when
75 * compression is not going well.
76 */
77
78 /*
79 * A dictionary for doing BSD compress.
80 */
81 struct bsd_db {
82 int totlen; /* length of this structure */
83 u_int hsize; /* size of the hash table */
84 u_char hshift; /* used in hash function */
85 u_char n_bits; /* current bits/code */
86 u_char maxbits;
87 u_char debug;
88 u_char unit;
89 u_short seqno; /* sequence number of next packet */
90 u_int hdrlen; /* header length to preallocate */
91 u_int mru;
92 u_int maxmaxcode; /* largest valid code */
93 u_int max_ent; /* largest code in use */
94 u_int in_count; /* uncompressed bytes, aged */
95 u_int bytes_out; /* compressed bytes, aged */
96 u_int ratio; /* recent compression ratio */
97 u_int checkpoint; /* when to next check the ratio */
98 u_int clear_count; /* times dictionary cleared */
99 u_int incomp_count; /* incompressible packets */
100 u_int incomp_bytes; /* incompressible bytes */
101 u_int uncomp_count; /* uncompressed packets */
102 u_int uncomp_bytes; /* uncompressed bytes */
103 u_int comp_count; /* compressed packets */
104 u_int comp_bytes; /* compressed bytes */
105 u_short *lens; /* array of lengths of codes */
106 struct bsd_dict {
107 union { /* hash value */
108 u_int32_t fcode;
109 struct {
110 #ifdef BSD_LITTLE_ENDIAN
111 u_short prefix; /* preceding code */
112 u_char suffix; /* last character of new code */
113 u_char pad;
114 #else
115 u_char pad;
116 u_char suffix; /* last character of new code */
117 u_short prefix; /* preceding code */
118 #endif
119 } hs;
120 } f;
121 u_short codem1; /* output of hash table -1 */
122 u_short cptr; /* map code to hash table entry */
123 } dict[1];
124 };
125
126 #define BSD_OVHD 2 /* BSD compress overhead/packet */
127 #define BSD_INIT_BITS BSD_MIN_BITS
128
129 static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
130 static void bsd_free __P((void *state));
131 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
132 int unit, int hdrlen, int mru, int debug));
133 static void bsd_incomp __P((void *state, u_char *dmsg, int len));
134 static int bsd_decompress __P((void *state, u_char *cmp, int inlen,
135 u_char *dmp, int *outlen));
136 static void bsd_reset __P((void *state));
137 static void bsd_comp_stats __P((void *state, struct compstat *stats));
138
139 /*
140 * Exported procedures.
141 */
142 struct compressor ppp_bsd_compress = {
143 CI_BSD_COMPRESS, /* compress_proto */
144 bsd_decomp_alloc, /* decomp_alloc */
145 bsd_free, /* decomp_free */
146 bsd_decomp_init, /* decomp_init */
147 bsd_reset, /* decomp_reset */
148 bsd_decompress, /* decompress */
149 bsd_incomp, /* incomp */
150 bsd_comp_stats, /* decomp_stat */
151 };
152
153 /*
154 * the next two codes should not be changed lightly, as they must not
155 * lie within the contiguous general code space.
156 */
157 #define CLEAR 256 /* table clear output code */
158 #define FIRST 257 /* first free entry */
159 #define LAST 255
160
161 #define MAXCODE(b) ((1 << (b)) - 1)
162 #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
163
164 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
165 ^ (u_int32_t)(prefix))
166 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
167 + (u_int32_t)(prefix))
168
169 #define CHECK_GAP 10000 /* Ratio check interval */
170
171 #define RATIO_SCALE_LOG 8
172 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
173 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
174
175 /*
176 * clear the dictionary
177 */
178 static void
bsd_clear(db)179 bsd_clear(db)
180 struct bsd_db *db;
181 {
182 db->clear_count++;
183 db->max_ent = FIRST-1;
184 db->n_bits = BSD_INIT_BITS;
185 db->ratio = 0;
186 db->bytes_out = 0;
187 db->in_count = 0;
188 db->checkpoint = CHECK_GAP;
189 }
190
191 /*
192 * If the dictionary is full, then see if it is time to reset it.
193 *
194 * Compute the compression ratio using fixed-point arithmetic
195 * with 8 fractional bits.
196 *
197 * Since we have an infinite stream instead of a single file,
198 * watch only the local compression ratio.
199 *
200 * Since both peers must reset the dictionary at the same time even in
201 * the absence of CLEAR codes (while packets are incompressible), they
202 * must compute the same ratio.
203 */
204 static int /* 1=output CLEAR */
bsd_check(db)205 bsd_check(db)
206 struct bsd_db *db;
207 {
208 u_int new_ratio;
209
210 if (db->in_count >= db->checkpoint) {
211 /* age the ratio by limiting the size of the counts */
212 if (db->in_count >= RATIO_MAX
213 || db->bytes_out >= RATIO_MAX) {
214 db->in_count -= db->in_count/4;
215 db->bytes_out -= db->bytes_out/4;
216 }
217
218 db->checkpoint = db->in_count + CHECK_GAP;
219
220 if (db->max_ent >= db->maxmaxcode) {
221 /* Reset the dictionary only if the ratio is worse,
222 * or if it looks as if it has been poisoned
223 * by incompressible data.
224 *
225 * This does not overflow, because
226 * db->in_count <= RATIO_MAX.
227 */
228 new_ratio = db->in_count << RATIO_SCALE_LOG;
229 if (db->bytes_out != 0)
230 new_ratio /= db->bytes_out;
231
232 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
233 bsd_clear(db);
234 return 1;
235 }
236 db->ratio = new_ratio;
237 }
238 }
239 return 0;
240 }
241
242 /*
243 * Return statistics.
244 */
245 static void
bsd_comp_stats(state,stats)246 bsd_comp_stats(state, stats)
247 void *state;
248 struct compstat *stats;
249 {
250 struct bsd_db *db = (struct bsd_db *) state;
251 u_int out;
252
253 stats->unc_bytes = db->uncomp_bytes;
254 stats->unc_packets = db->uncomp_count;
255 stats->comp_bytes = db->comp_bytes;
256 stats->comp_packets = db->comp_count;
257 stats->inc_bytes = db->incomp_bytes;
258 stats->inc_packets = db->incomp_count;
259 stats->ratio = db->in_count;
260 out = db->bytes_out;
261 if (stats->ratio <= 0x7fffff)
262 stats->ratio <<= 8;
263 else
264 out >>= 8;
265 if (out != 0)
266 stats->ratio /= out;
267 }
268
269 /*
270 * Reset state, as on a CCP ResetReq.
271 */
272 static void
bsd_reset(state)273 bsd_reset(state)
274 void *state;
275 {
276 struct bsd_db *db = (struct bsd_db *) state;
277
278 db->seqno = 0;
279 bsd_clear(db);
280 db->clear_count = 0;
281 }
282
283 /*
284 * Allocate space for a (de) compressor.
285 */
286 static void *
bsd_alloc(options,opt_len,decomp)287 bsd_alloc(options, opt_len, decomp)
288 u_char *options;
289 int opt_len, decomp;
290 {
291 int bits;
292 u_int newlen, hsize, hshift, maxmaxcode;
293 struct bsd_db *db;
294
295 if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3
296 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
297 return NULL;
298
299 bits = BSD_NBITS(options[2]);
300 switch (bits) {
301 case 9: /* needs 82152 for both directions */
302 case 10: /* needs 84144 */
303 case 11: /* needs 88240 */
304 case 12: /* needs 96432 */
305 hsize = 5003;
306 hshift = 4;
307 break;
308 case 13: /* needs 176784 */
309 hsize = 9001;
310 hshift = 5;
311 break;
312 case 14: /* needs 353744 */
313 hsize = 18013;
314 hshift = 6;
315 break;
316 case 15: /* needs 691440 */
317 hsize = 35023;
318 hshift = 7;
319 break;
320 case 16: /* needs 1366160--far too much, */
321 /* hsize = 69001; */ /* and 69001 is too big for cptr */
322 /* hshift = 8; */ /* in struct bsd_db */
323 /* break; */
324 default:
325 return NULL;
326 }
327
328 maxmaxcode = MAXCODE(bits);
329 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
330 db = (struct bsd_db *) malloc(newlen);
331 if (!db)
332 return NULL;
333 memset(db, 0, sizeof(*db) - sizeof(db->dict));
334
335 if (!decomp) {
336 db->lens = NULL;
337 } else {
338 db->lens = (u_short *) malloc((maxmaxcode+1) * sizeof(db->lens[0]));
339 if (!db->lens) {
340 free(db);
341 return NULL;
342 }
343 }
344
345 db->totlen = newlen;
346 db->hsize = hsize;
347 db->hshift = hshift;
348 db->maxmaxcode = maxmaxcode;
349 db->maxbits = bits;
350
351 return (void *) db;
352 }
353
354 static void
bsd_free(state)355 bsd_free(state)
356 void *state;
357 {
358 struct bsd_db *db = (struct bsd_db *) state;
359
360 if (db->lens)
361 free(db->lens);
362 free(db);
363 }
364
365 static void *
bsd_decomp_alloc(options,opt_len)366 bsd_decomp_alloc(options, opt_len)
367 u_char *options;
368 int opt_len;
369 {
370 return bsd_alloc(options, opt_len, 1);
371 }
372
373 /*
374 * Initialize the database.
375 */
376 static int
bsd_init(db,options,opt_len,unit,hdrlen,mru,debug,decomp)377 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
378 struct bsd_db *db;
379 u_char *options;
380 int opt_len, unit, hdrlen, mru, debug, decomp;
381 {
382 int i;
383
384 if (opt_len < CILEN_BSD_COMPRESS
385 || options[0] != CI_BSD_COMPRESS || options[1] != CILEN_BSD_COMPRESS
386 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
387 || BSD_NBITS(options[2]) != db->maxbits
388 || decomp && db->lens == NULL)
389 return 0;
390
391 if (decomp) {
392 i = LAST+1;
393 while (i != 0)
394 db->lens[--i] = 1;
395 }
396 i = db->hsize;
397 while (i != 0) {
398 db->dict[--i].codem1 = BADCODEM1;
399 db->dict[i].cptr = 0;
400 }
401
402 db->unit = unit;
403 db->hdrlen = hdrlen;
404 db->mru = mru;
405 if (debug)
406 db->debug = 1;
407
408 bsd_reset(db);
409
410 return 1;
411 }
412
413 static int
bsd_decomp_init(state,options,opt_len,unit,hdrlen,mru,debug)414 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
415 void *state;
416 u_char *options;
417 int opt_len, unit, hdrlen, mru, debug;
418 {
419 return bsd_init((struct bsd_db *) state, options, opt_len,
420 unit, hdrlen, mru, debug, 1);
421 }
422
423
424 /*
425 * Update the "BSD Compress" dictionary on the receiver for
426 * incompressible data by pretending to compress the incoming data.
427 */
428 static void
bsd_incomp(state,dmsg,mlen)429 bsd_incomp(state, dmsg, mlen)
430 void *state;
431 u_char *dmsg;
432 int mlen;
433 {
434 struct bsd_db *db = (struct bsd_db *) state;
435 u_int hshift = db->hshift;
436 u_int max_ent = db->max_ent;
437 u_int n_bits = db->n_bits;
438 struct bsd_dict *dictp;
439 u_int32_t fcode;
440 u_char c;
441 long hval, disp;
442 int slen, ilen;
443 u_int bitno = 7;
444 u_char *rptr;
445 u_int ent;
446
447 rptr = dmsg;
448 ent = rptr[0]; /* get the protocol */
449 if (ent == 0) {
450 ++rptr;
451 --mlen;
452 ent = rptr[0];
453 }
454 if ((ent & 1) == 0 || ent < 0x21 || ent > 0xf9)
455 return;
456
457 db->seqno++;
458 ilen = 1; /* count the protocol as 1 byte */
459 ++rptr;
460 slen = dmsg + mlen - rptr;
461 ilen += slen;
462 for (; slen > 0; --slen) {
463 c = *rptr++;
464 fcode = BSD_KEY(ent, c);
465 hval = BSD_HASH(ent, c, hshift);
466 dictp = &db->dict[hval];
467
468 /* validate and then check the entry */
469 if (dictp->codem1 >= max_ent)
470 goto nomatch;
471 if (dictp->f.fcode == fcode) {
472 ent = dictp->codem1+1;
473 continue; /* found (prefix,suffix) */
474 }
475
476 /* continue probing until a match or invalid entry */
477 disp = (hval == 0) ? 1 : hval;
478 do {
479 hval += disp;
480 if (hval >= db->hsize)
481 hval -= db->hsize;
482 dictp = &db->dict[hval];
483 if (dictp->codem1 >= max_ent)
484 goto nomatch;
485 } while (dictp->f.fcode != fcode);
486 ent = dictp->codem1+1;
487 continue; /* finally found (prefix,suffix) */
488
489 nomatch: /* output (count) the prefix */
490 bitno += n_bits;
491
492 /* code -> hashtable */
493 if (max_ent < db->maxmaxcode) {
494 struct bsd_dict *dictp2;
495 /* expand code size if needed */
496 if (max_ent >= MAXCODE(n_bits))
497 db->n_bits = ++n_bits;
498
499 /* Invalidate previous hash table entry
500 * assigned this code, and then take it over.
501 */
502 dictp2 = &db->dict[max_ent+1];
503 if (db->dict[dictp2->cptr].codem1 == max_ent)
504 db->dict[dictp2->cptr].codem1 = BADCODEM1;
505 dictp2->cptr = hval;
506 dictp->codem1 = max_ent;
507 dictp->f.fcode = fcode;
508
509 db->max_ent = ++max_ent;
510 db->lens[max_ent] = db->lens[ent]+1;
511 }
512 ent = c;
513 }
514 bitno += n_bits; /* output (count) the last code */
515 db->bytes_out += bitno/8;
516 db->in_count += ilen;
517 (void)bsd_check(db);
518
519 ++db->incomp_count;
520 db->incomp_bytes += ilen;
521 ++db->uncomp_count;
522 db->uncomp_bytes += ilen;
523
524 /* Increase code size if we would have without the packet
525 * boundary and as the decompressor will.
526 */
527 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
528 db->n_bits++;
529 }
530
531
532 /*
533 * Decompress "BSD Compress"
534 *
535 * Because of patent problems, we return DECOMP_ERROR for errors
536 * found by inspecting the input data and for system problems, but
537 * DECOMP_FATALERROR for any errors which could possibly be said to
538 * be being detected "after" decompression. For DECOMP_ERROR,
539 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
540 * infringing a patent of Motorola's if we do, so we take CCP down
541 * instead.
542 *
543 * Given that the frame has the correct sequence number and a good FCS,
544 * errors such as invalid codes in the input most likely indicate a
545 * bug, so we return DECOMP_FATALERROR for them in order to turn off
546 * compression, even though they are detected by inspecting the input.
547 */
548 static int
bsd_decompress(state,cmsg,inlen,dmp,outlenp)549 bsd_decompress(state, cmsg, inlen, dmp, outlenp)
550 void *state;
551 u_char *cmsg, *dmp;
552 int inlen, *outlenp;
553 {
554 struct bsd_db *db = (struct bsd_db *) state;
555 u_int max_ent = db->max_ent;
556 u_int32_t accm = 0;
557 u_int bitno = 32; /* 1st valid bit in accm */
558 u_int n_bits = db->n_bits;
559 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
560 struct bsd_dict *dictp;
561 int explen, i, seq, len;
562 u_int incode, oldcode, finchar;
563 u_char *p, *rptr, *wptr;
564 int ilen;
565 int dlen, space, codelen, extra;
566
567 rptr = cmsg;
568 if (*rptr == 0)
569 ++rptr;
570 ++rptr; /* skip protocol (assumed 0xfd) */
571 seq = (rptr[0] << 8) + rptr[1];
572 rptr += BSD_OVHD;
573 ilen = len = cmsg + inlen - rptr;
574
575 /*
576 * Check the sequence number and give up if it is not what we expect.
577 */
578 if (seq != db->seqno++) {
579 if (db->debug)
580 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
581 db->unit, seq, db->seqno - 1);
582 return DECOMP_ERROR;
583 }
584
585 wptr = dmp + db->hdrlen;
586
587 oldcode = CLEAR;
588 explen = 0;
589 while (len > 0) {
590 /*
591 * Accumulate bytes until we have a complete code.
592 * Then get the next code, relying on the 32-bit,
593 * unsigned accm to mask the result.
594 */
595 bitno -= 8;
596 accm |= *rptr++ << bitno;
597 --len;
598 if (tgtbitno < bitno)
599 continue;
600 incode = accm >> tgtbitno;
601 accm <<= n_bits;
602 bitno += n_bits;
603
604 if (incode == CLEAR) {
605 /*
606 * The dictionary must only be cleared at
607 * the end of a packet. But there could be an
608 * empty message block at the end.
609 */
610 if (len > 0) {
611 if (db->debug)
612 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
613 return DECOMP_FATALERROR;
614 }
615 bsd_clear(db);
616 explen = ilen = 0;
617 break;
618 }
619
620 if (incode > max_ent + 2 || incode > db->maxmaxcode
621 || incode > max_ent && oldcode == CLEAR) {
622 if (db->debug) {
623 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
624 db->unit, incode, oldcode);
625 printf("max_ent=0x%x dlen=%d seqno=%d\n",
626 max_ent, dlen, db->seqno);
627 }
628 return DECOMP_FATALERROR; /* probably a bug */
629 }
630
631 /* Special case for KwKwK string. */
632 if (incode > max_ent) {
633 finchar = oldcode;
634 extra = 1;
635 } else {
636 finchar = incode;
637 extra = 0;
638 }
639
640 codelen = db->lens[finchar];
641 explen += codelen + extra;
642 if (explen > db->mru + 1) {
643 if (db->debug)
644 printf("bsd_decomp%d: ran out of mru\n", db->unit);
645 return DECOMP_FATALERROR;
646 }
647
648 /*
649 * Decode this code and install it in the decompressed buffer.
650 */
651 p = (wptr += codelen);
652 while (finchar > LAST) {
653 dictp = &db->dict[db->dict[finchar].cptr];
654 #ifdef DEBUG
655 --codelen;
656 if (codelen <= 0) {
657 printf("bsd_decomp%d: fell off end of chain ", db->unit);
658 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
659 incode, finchar, db->dict[finchar].cptr, max_ent);
660 return DECOMP_FATALERROR;
661 }
662 if (dictp->codem1 != finchar-1) {
663 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
664 db->unit, incode, finchar);
665 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
666 db->dict[finchar].cptr, dictp->codem1);
667 return DECOMP_FATALERROR;
668 }
669 #endif
670 *--p = dictp->f.hs.suffix;
671 finchar = dictp->f.hs.prefix;
672 }
673 *--p = finchar;
674
675 #ifdef DEBUG
676 if (--codelen != 0)
677 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
678 db->unit, codelen, incode, max_ent);
679 #endif
680
681 if (extra) /* the KwKwK case again */
682 *wptr++ = finchar;
683
684 /*
685 * If not first code in a packet, and
686 * if not out of code space, then allocate a new code.
687 *
688 * Keep the hash table correct so it can be used
689 * with uncompressed packets.
690 */
691 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
692 struct bsd_dict *dictp2;
693 u_int32_t fcode;
694 int hval, disp;
695
696 fcode = BSD_KEY(oldcode,finchar);
697 hval = BSD_HASH(oldcode,finchar,db->hshift);
698 dictp = &db->dict[hval];
699
700 /* look for a free hash table entry */
701 if (dictp->codem1 < max_ent) {
702 disp = (hval == 0) ? 1 : hval;
703 do {
704 hval += disp;
705 if (hval >= db->hsize)
706 hval -= db->hsize;
707 dictp = &db->dict[hval];
708 } while (dictp->codem1 < max_ent);
709 }
710
711 /*
712 * Invalidate previous hash table entry
713 * assigned this code, and then take it over
714 */
715 dictp2 = &db->dict[max_ent+1];
716 if (db->dict[dictp2->cptr].codem1 == max_ent) {
717 db->dict[dictp2->cptr].codem1 = BADCODEM1;
718 }
719 dictp2->cptr = hval;
720 dictp->codem1 = max_ent;
721 dictp->f.fcode = fcode;
722
723 db->max_ent = ++max_ent;
724 db->lens[max_ent] = db->lens[oldcode]+1;
725
726 /* Expand code size if needed. */
727 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
728 db->n_bits = ++n_bits;
729 tgtbitno = 32-n_bits;
730 }
731 }
732 oldcode = incode;
733 }
734 *outlenp = wptr - (dmp + db->hdrlen);
735
736 /*
737 * Keep the checkpoint right so that incompressible packets
738 * clear the dictionary at the right times.
739 */
740 db->bytes_out += ilen;
741 db->in_count += explen;
742 if (bsd_check(db) && db->debug) {
743 printf("bsd_decomp%d: peer should have cleared dictionary\n",
744 db->unit);
745 }
746
747 ++db->comp_count;
748 db->comp_bytes += ilen + BSD_OVHD;
749 ++db->uncomp_count;
750 db->uncomp_bytes += explen;
751
752 return DECOMP_OK;
753 }
754 #endif /* DO_BSD_COMPRESS */
755