1 /* $Id: bsd-comp.c,v 1.6 1996/08/28 06:31:58 paulus Exp $ */
3 /* Because this code is derived from the 4.3BSD compress source:
6 * Copyright (c) 1985, 1986 The Regents of the University of California.
9 * This code is derived from software contributed to Berkeley by
10 * James A. Woods, derived from original work by Spencer Thomas
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
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.
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
43 * This version is for use with mbufs on BSD-derived systems.
46 #include <sys/param.h>
47 #include <sys/types.h>
48 #include <sys/systm.h>
50 #include <sys/socket.h>
52 #include <net/if_types.h>
53 #include <net/ppp_defs.h>
54 #include <net/if_ppp.h>
56 #define PACKETPTR struct mbuf *
57 #include <net/ppp-comp.h>
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:
67 * When the code size expands, a block of junk is not emitted by
68 * the compressor and not expected by the decompressor.
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.
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.
83 * A dictionary for doing BSD compress.
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 */
93 u_int16_t seqno; /* sequence # of next packet */
94 u_int hdrlen; /* header length to preallocate */
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_int16_t *lens; /* array of lengths of codes */
111 union { /* hash value */
114 #if BYTE_ORDER == LITTLE_ENDIAN
115 u_int16_t prefix; /* preceding code */
116 u_char suffix; /* last character of new code */
120 u_char suffix; /* last character of new code */
121 u_int16_t prefix; /* preceding code */
125 u_int16_t codem1; /* output of hash table -1 */
126 u_int16_t cptr; /* map code to hash table entry */
130 #define BSD_OVHD 2 /* BSD compress overhead/packet */
131 #define BSD_INIT_BITS BSD_MIN_BITS
133 static void *bsd_comp_alloc __P((u_char *options, int opt_len));
134 static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
135 static void bsd_free __P((void *state));
136 static int bsd_comp_init __P((void *state, u_char *options, int opt_len,
137 int unit, int hdrlen, int debug));
138 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
139 int unit, int hdrlen, int mru, int debug));
140 static int bsd_compress __P((void *state, struct mbuf **mret,
141 struct mbuf *mp, int slen, int maxolen));
142 static void bsd_incomp __P((void *state, struct mbuf *dmsg));
143 static int bsd_decompress __P((void *state, struct mbuf *cmp,
144 struct mbuf **dmpp));
145 static void bsd_reset __P((void *state));
146 static void bsd_comp_stats __P((void *state, struct compstat *stats));
149 * Procedures exported to if_ppp.c.
151 struct compressor ppp_bsd_compress = {
152 CI_BSD_COMPRESS, /* compress_proto */
153 bsd_comp_alloc, /* comp_alloc */
154 bsd_free, /* comp_free */
155 bsd_comp_init, /* comp_init */
156 bsd_reset, /* comp_reset */
157 bsd_compress, /* compress */
158 bsd_comp_stats, /* comp_stat */
159 bsd_decomp_alloc, /* decomp_alloc */
160 bsd_free, /* decomp_free */
161 bsd_decomp_init, /* decomp_init */
162 bsd_reset, /* decomp_reset */
163 bsd_decompress, /* decompress */
164 bsd_incomp, /* incomp */
165 bsd_comp_stats, /* decomp_stat */
169 * the next two codes should not be changed lightly, as they must not
170 * lie within the contiguous general code space.
172 #define CLEAR 256 /* table clear output code */
173 #define FIRST 257 /* first free entry */
176 #define MAXCODE(b) ((1 << (b)) - 1)
177 #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
179 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
180 ^ (u_int32_t)(prefix))
181 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
182 + (u_int32_t)(prefix))
184 #define CHECK_GAP 10000 /* Ratio check interval */
186 #define RATIO_SCALE_LOG 8
187 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
188 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
190 static void bsd_clear __P((struct bsd_db *));
191 static int bsd_check __P((struct bsd_db *));
192 static void *bsd_alloc __P((u_char *, int, int));
193 static int bsd_init __P((struct bsd_db *, u_char *, int, int, int, int,
197 * clear the dictionary
204 db->max_ent = FIRST-1;
205 db->n_bits = BSD_INIT_BITS;
209 db->checkpoint = CHECK_GAP;
213 * If the dictionary is full, then see if it is time to reset it.
215 * Compute the compression ratio using fixed-point arithmetic
216 * with 8 fractional bits.
218 * Since we have an infinite stream instead of a single file,
219 * watch only the local compression ratio.
221 * Since both peers must reset the dictionary at the same time even in
222 * the absence of CLEAR codes (while packets are incompressible), they
223 * must compute the same ratio.
225 static int /* 1=output CLEAR */
231 if (db->in_count >= db->checkpoint) {
232 /* age the ratio by limiting the size of the counts */
233 if (db->in_count >= RATIO_MAX
234 || db->bytes_out >= RATIO_MAX) {
235 db->in_count -= db->in_count/4;
236 db->bytes_out -= db->bytes_out/4;
239 db->checkpoint = db->in_count + CHECK_GAP;
241 if (db->max_ent >= db->maxmaxcode) {
242 /* Reset the dictionary only if the ratio is worse,
243 * or if it looks as if it has been poisoned
244 * by incompressible data.
246 * This does not overflow, because
247 * db->in_count <= RATIO_MAX.
249 new_ratio = db->in_count << RATIO_SCALE_LOG;
250 if (db->bytes_out != 0)
251 new_ratio /= db->bytes_out;
253 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
257 db->ratio = new_ratio;
267 bsd_comp_stats(state, stats)
269 struct compstat *stats;
271 struct bsd_db *db = (struct bsd_db *) state;
274 stats->unc_bytes = db->uncomp_bytes;
275 stats->unc_packets = db->uncomp_count;
276 stats->comp_bytes = db->comp_bytes;
277 stats->comp_packets = db->comp_count;
278 stats->inc_bytes = db->incomp_bytes;
279 stats->inc_packets = db->incomp_count;
280 stats->ratio = db->in_count;
282 if (stats->ratio <= 0x7fffff)
291 * Reset state, as on a CCP ResetReq.
297 struct bsd_db *db = (struct bsd_db *) state;
305 * Allocate space for a (de) compressor.
308 bsd_alloc(options, opt_len, decomp)
313 u_int newlen, hsize, hshift, maxmaxcode;
316 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
317 || options[1] != CILEN_BSD_COMPRESS
318 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
320 bits = BSD_NBITS(options[2]);
322 case 9: /* needs 82152 for both directions */
323 case 10: /* needs 84144 */
324 case 11: /* needs 88240 */
325 case 12: /* needs 96432 */
329 case 13: /* needs 176784 */
333 case 14: /* needs 353744 */
337 case 15: /* needs 691440 */
341 case 16: /* needs 1366160--far too much, */
342 /* hsize = 69001; */ /* and 69001 is too big for cptr */
343 /* hshift = 8; */ /* in struct bsd_db */
349 maxmaxcode = MAXCODE(bits);
350 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
351 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
354 bzero(db, sizeof(*db) - sizeof(db->dict));
359 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
370 db->maxmaxcode = maxmaxcode;
380 struct bsd_db *db = (struct bsd_db *) state;
383 FREE(db->lens, M_DEVBUF);
388 bsd_comp_alloc(options, opt_len)
392 return bsd_alloc(options, opt_len, 0);
396 bsd_decomp_alloc(options, opt_len)
400 return bsd_alloc(options, opt_len, 1);
404 * Initialize the database.
407 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
410 int opt_len, unit, hdrlen, mru, debug, decomp;
414 if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
415 || options[1] != CILEN_BSD_COMPRESS
416 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
417 || BSD_NBITS(options[2]) != db->maxbits
418 || (decomp && db->lens == NULL))
428 db->dict[--i].codem1 = BADCODEM1;
429 db->dict[i].cptr = 0;
446 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
449 int opt_len, unit, hdrlen, debug;
451 return bsd_init((struct bsd_db *) state, options, opt_len,
452 unit, hdrlen, 0, debug, 0);
456 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
459 int opt_len, unit, hdrlen, mru, debug;
461 return bsd_init((struct bsd_db *) state, options, opt_len,
462 unit, hdrlen, mru, debug, 1);
468 * One change from the BSD compress command is that when the
469 * code size expands, we do not output a bunch of padding.
472 bsd_compress(state, mret, mp, slen, maxolen)
474 struct mbuf **mret; /* return compressed mbuf chain here */
475 struct mbuf *mp; /* from here */
476 int slen; /* uncompressed length */
477 int maxolen; /* max compressed length */
479 struct bsd_db *db = (struct bsd_db *) state;
480 int hshift = db->hshift;
481 u_int max_ent = db->max_ent;
482 u_int n_bits = db->n_bits;
484 u_int32_t accm = 0, fcode;
485 struct bsd_dict *dictp;
487 int hval, disp, ent, ilen;
493 #define PUTBYTE(v) { \
497 if (wptr >= cp_end) { \
498 m->m_len = wptr - mtod(m, u_char *); \
499 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
503 if (maxolen - olen > MLEN) \
504 MCLGET(m, M_DONTWAIT); \
505 wptr = mtod(m, u_char *); \
506 cp_end = wptr + M_TRAILINGSPACE(m); \
513 #define OUTPUT(ent) { \
515 accm |= ((ent) << bitno); \
517 PUTBYTE(accm >> 24); \
520 } while (bitno <= 24); \
524 * If the protocol is not in the range we're interested in,
525 * just return without compressing the packet. If it is,
526 * the protocol becomes the first byte to compress.
528 rptr = mtod(mp, u_char *);
529 ent = PPP_PROTOCOL(rptr);
530 if (ent < 0x21 || ent > 0xf9) {
535 /* Don't generate compressed packets which are larger than
536 the uncompressed packet. */
540 /* Allocate one mbuf to start with. */
541 MGET(m, M_DONTWAIT, MT_DATA);
545 if (maxolen + db->hdrlen > MLEN)
546 MCLGET(m, M_DONTWAIT);
547 m->m_data += db->hdrlen;
548 wptr = mtod(m, u_char *);
549 cp_end = wptr + M_TRAILINGSPACE(m);
551 wptr = cp_end = NULL;
554 * Copy the PPP header over, changing the protocol,
555 * and install the 2-byte packet sequence number.
558 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
559 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
560 *wptr++ = 0; /* change the protocol */
562 *wptr++ = db->seqno >> 8;
569 slen = mp->m_len - PPP_HDRLEN;
576 rptr = mtod(mp, u_char *);
579 continue; /* handle 0-length buffers */
585 fcode = BSD_KEY(ent, c);
586 hval = BSD_HASH(ent, c, hshift);
587 dictp = &db->dict[hval];
589 /* Validate and then check the entry. */
590 if (dictp->codem1 >= max_ent)
592 if (dictp->f.fcode == fcode) {
593 ent = dictp->codem1+1;
594 continue; /* found (prefix,suffix) */
597 /* continue probing until a match or invalid entry */
598 disp = (hval == 0) ? 1 : hval;
601 if (hval >= db->hsize)
603 dictp = &db->dict[hval];
604 if (dictp->codem1 >= max_ent)
606 } while (dictp->f.fcode != fcode);
607 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
611 OUTPUT(ent); /* output the prefix */
613 /* code -> hashtable */
614 if (max_ent < db->maxmaxcode) {
615 struct bsd_dict *dictp2;
616 /* expand code size if needed */
617 if (max_ent >= MAXCODE(n_bits))
618 db->n_bits = ++n_bits;
620 /* Invalidate old hash table entry using
621 * this code, and then take it over.
623 dictp2 = &db->dict[max_ent+1];
624 if (db->dict[dictp2->cptr].codem1 == max_ent)
625 db->dict[dictp2->cptr].codem1 = BADCODEM1;
627 dictp->codem1 = max_ent;
628 dictp->f.fcode = fcode;
630 db->max_ent = ++max_ent;
635 OUTPUT(ent); /* output the last code */
636 db->bytes_out += olen;
637 db->in_count += ilen;
639 ++db->bytes_out; /* count complete bytes */
642 OUTPUT(CLEAR); /* do not count the CLEAR */
645 * Pad dribble bits of last code with ones.
646 * Do not emit a completely useless byte of ones.
649 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
652 m->m_len = wptr - mtod(m, u_char *);
657 * Increase code size if we would have without the packet
658 * boundary and as the decompressor will.
660 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
663 db->uncomp_bytes += ilen;
665 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
666 /* throw away the compressed stuff if it is longer than uncompressed */
672 db->incomp_bytes += ilen;
675 db->comp_bytes += olen + BSD_OVHD;
678 return olen + PPP_HDRLEN + BSD_OVHD;
685 * Update the "BSD Compress" dictionary on the receiver for
686 * incompressible data by pretending to compress the incoming data.
689 bsd_incomp(state, dmsg)
693 struct bsd_db *db = (struct bsd_db *) state;
694 u_int hshift = db->hshift;
695 u_int max_ent = db->max_ent;
696 u_int n_bits = db->n_bits;
697 struct bsd_dict *dictp;
700 u_int32_t hval, disp;
707 * If the protocol is not in the range we're interested in,
708 * just return without looking at the packet. If it is,
709 * the protocol becomes the first byte to "compress".
711 rptr = mtod(dmsg, u_char *);
712 ent = PPP_PROTOCOL(rptr);
713 if (ent < 0x21 || ent > 0xf9)
717 ilen = 1; /* count the protocol as 1 byte */
719 slen = dmsg->m_len - PPP_HDRLEN;
725 rptr = mtod(dmsg, u_char *);
733 fcode = BSD_KEY(ent, c);
734 hval = BSD_HASH(ent, c, hshift);
735 dictp = &db->dict[hval];
737 /* validate and then check the entry */
738 if (dictp->codem1 >= max_ent)
740 if (dictp->f.fcode == fcode) {
741 ent = dictp->codem1+1;
742 continue; /* found (prefix,suffix) */
745 /* continue probing until a match or invalid entry */
746 disp = (hval == 0) ? 1 : hval;
749 if (hval >= db->hsize)
751 dictp = &db->dict[hval];
752 if (dictp->codem1 >= max_ent)
754 } while (dictp->f.fcode != fcode);
755 ent = dictp->codem1+1;
756 continue; /* finally found (prefix,suffix) */
758 nomatch: /* output (count) the prefix */
761 /* code -> hashtable */
762 if (max_ent < db->maxmaxcode) {
763 struct bsd_dict *dictp2;
764 /* expand code size if needed */
765 if (max_ent >= MAXCODE(n_bits))
766 db->n_bits = ++n_bits;
768 /* Invalidate previous hash table entry
769 * assigned this code, and then take it over.
771 dictp2 = &db->dict[max_ent+1];
772 if (db->dict[dictp2->cptr].codem1 == max_ent)
773 db->dict[dictp2->cptr].codem1 = BADCODEM1;
775 dictp->codem1 = max_ent;
776 dictp->f.fcode = fcode;
778 db->max_ent = ++max_ent;
779 db->lens[max_ent] = db->lens[ent]+1;
782 } while (--slen != 0);
784 bitno += n_bits; /* output (count) the last code */
785 db->bytes_out += bitno/8;
786 db->in_count += ilen;
790 db->incomp_bytes += ilen;
792 db->uncomp_bytes += ilen;
794 /* Increase code size if we would have without the packet
795 * boundary and as the decompressor will.
797 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
803 * Decompress "BSD Compress".
805 * Because of patent problems, we return DECOMP_ERROR for errors
806 * found by inspecting the input data and for system problems, but
807 * DECOMP_FATALERROR for any errors which could possibly be said to
808 * be being detected "after" decompression. For DECOMP_ERROR,
809 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
810 * infringing a patent of Motorola's if we do, so we take CCP down
813 * Given that the frame has the correct sequence number and a good FCS,
814 * errors such as invalid codes in the input most likely indicate a
815 * bug, so we return DECOMP_FATALERROR for them in order to turn off
816 * compression, even though they are detected by inspecting the input.
819 bsd_decompress(state, cmp, dmpp)
821 struct mbuf *cmp, **dmpp;
823 struct bsd_db *db = (struct bsd_db *) state;
824 u_int max_ent = db->max_ent;
826 u_int bitno = 32; /* 1st valid bit in accm */
827 u_int n_bits = db->n_bits;
828 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
829 struct bsd_dict *dictp;
830 int explen, i, seq, len;
831 u_int incode, oldcode, finchar;
832 u_char *p, *rptr, *wptr;
833 struct mbuf *m, *dmp, *mret;
834 int adrs, ctrl, ilen;
835 int space, codelen, extra;
838 * Save the address/control from the PPP header
839 * and then get the sequence number.
842 rptr = mtod(cmp, u_char *);
843 adrs = PPP_ADDRESS(rptr);
844 ctrl = PPP_CONTROL(rptr);
846 len = cmp->m_len - PPP_HDRLEN;
848 for (i = 0; i < 2; ++i) {
853 rptr = mtod(cmp, u_char *);
856 seq = (seq << 8) + *rptr++;
861 * Check the sequence number and give up if it differs from
862 * the value we're expecting.
864 if (seq != db->seqno) {
866 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
867 db->unit, seq, db->seqno - 1);
873 * Allocate one mbuf to start with.
875 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
881 MCLGET(dmp, M_DONTWAIT);
882 dmp->m_data += db->hdrlen;
883 wptr = mtod(dmp, u_char *);
884 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
887 * Fill in the ppp header, but not the last byte of the protocol
888 * (that comes from the decompressed data).
893 wptr += PPP_HDRLEN - 1;
901 if (!cmp) /* quit at end of message */
903 rptr = mtod(cmp, u_char *);
906 continue; /* handle 0-length buffers */
910 * Accumulate bytes until we have a complete code.
911 * Then get the next code, relying on the 32-bit,
912 * unsigned accm to mask the result.
915 accm |= *rptr++ << bitno;
917 if (tgtbitno < bitno)
919 incode = accm >> tgtbitno;
923 if (incode == CLEAR) {
925 * The dictionary must only be cleared at
926 * the end of a packet. But there could be an
927 * empty mbuf at the end.
929 if (len > 0 || cmp->m_next != NULL) {
930 while ((cmp = cmp->m_next) != NULL)
935 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
936 return DECOMP_FATALERROR; /* probably a bug */
944 if (incode > max_ent + 2 || incode > db->maxmaxcode
945 || (incode > max_ent && oldcode == CLEAR)) {
948 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
949 db->unit, incode, oldcode);
950 printf("max_ent=0x%x explen=%d seqno=%d\n",
951 max_ent, explen, db->seqno);
953 return DECOMP_FATALERROR; /* probably a bug */
956 /* Special case for KwKwK string. */
957 if (incode > max_ent) {
965 codelen = db->lens[finchar];
966 explen += codelen + extra;
967 if (explen > db->mru + 1) {
970 printf("bsd_decomp%d: ran out of mru\n", db->unit);
972 while ((cmp = cmp->m_next) != NULL)
974 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
975 len, finchar, codelen, explen);
978 return DECOMP_FATALERROR;
982 * For simplicity, the decoded characters go in a single mbuf,
983 * so we allocate a single extra cluster mbuf if necessary.
985 if ((space -= codelen + extra) < 0) {
986 dmp->m_len = wptr - mtod(dmp, u_char *);
987 MGET(m, M_DONTWAIT, MT_DATA);
995 MCLGET(m, M_DONTWAIT);
996 space = M_TRAILINGSPACE(m) - (codelen + extra);
998 /* now that's what I call *compression*. */
1000 return DECOMP_ERROR;
1003 wptr = mtod(dmp, u_char *);
1007 * Decode this code and install it in the decompressed buffer.
1009 p = (wptr += codelen);
1010 while (finchar > LAST) {
1011 dictp = &db->dict[db->dict[finchar].cptr];
1013 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1016 *--p = dictp->f.hs.suffix;
1017 finchar = dictp->f.hs.prefix;
1023 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1024 db->unit, codelen, incode, max_ent);
1027 if (extra) /* the KwKwK case again */
1031 * If not first code in a packet, and
1032 * if not out of code space, then allocate a new code.
1034 * Keep the hash table correct so it can be used
1035 * with uncompressed packets.
1037 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1038 struct bsd_dict *dictp2;
1040 u_int32_t hval, disp;
1042 fcode = BSD_KEY(oldcode,finchar);
1043 hval = BSD_HASH(oldcode,finchar,db->hshift);
1044 dictp = &db->dict[hval];
1046 /* look for a free hash table entry */
1047 if (dictp->codem1 < max_ent) {
1048 disp = (hval == 0) ? 1 : hval;
1051 if (hval >= db->hsize)
1053 dictp = &db->dict[hval];
1054 } while (dictp->codem1 < max_ent);
1058 * Invalidate previous hash table entry
1059 * assigned this code, and then take it over
1061 dictp2 = &db->dict[max_ent+1];
1062 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1063 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1065 dictp2->cptr = hval;
1066 dictp->codem1 = max_ent;
1067 dictp->f.fcode = fcode;
1069 db->max_ent = ++max_ent;
1070 db->lens[max_ent] = db->lens[oldcode]+1;
1072 /* Expand code size if needed. */
1073 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1074 db->n_bits = ++n_bits;
1075 tgtbitno = 32-n_bits;
1080 dmp->m_len = wptr - mtod(dmp, u_char *);
1083 * Keep the checkpoint right so that incompressible packets
1084 * clear the dictionary at the right times.
1086 db->bytes_out += ilen;
1087 db->in_count += explen;
1088 if (bsd_check(db) && db->debug) {
1089 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1094 db->comp_bytes += ilen + BSD_OVHD;
1096 db->uncomp_bytes += explen;
1104 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1105 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1106 incode, finchar, db->dict[finchar].cptr, max_ent);
1107 } else if (dictp->codem1 != finchar-1) {
1108 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1109 db->unit, incode, finchar);
1110 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1111 db->dict[finchar].cptr, dictp->codem1);
1114 return DECOMP_FATALERROR;
1117 #endif /* DO_BSD_COMPRESS */