1 /* Because this code is derived from the 4.3BSD compress source:
4 * Copyright (c) 1985, 1986 The Regents of the University of California.
7 * This code is derived from software contributed to Berkeley by
8 * James A. Woods, derived from original work by Spencer Thomas
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
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.
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
41 * This version is for use with mbufs on BSD-derived systems.
43 * $Id: bsd-comp.c,v 1.1 1995/10/27 03:35:14 paulus Exp $
46 #include <sys/param.h>
47 #include <sys/systm.h>
48 #include <sys/types.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)
191 * clear the dictionary
198 db->max_ent = FIRST-1;
199 db->n_bits = BSD_INIT_BITS;
203 db->incomp_count = 0;
204 db->checkpoint = CHECK_GAP;
208 * If the dictionary is full, then see if it is time to reset it.
210 * Compute the compression ratio using fixed-point arithmetic
211 * with 8 fractional bits.
213 * Since we have an infinite stream instead of a single file,
214 * watch only the local compression ratio.
216 * Since both peers must reset the dictionary at the same time even in
217 * the absence of CLEAR codes (while packets are incompressible), they
218 * must compute the same ratio.
220 static int /* 1=output CLEAR */
226 if (db->in_count >= db->checkpoint) {
227 /* age the ratio by limiting the size of the counts */
228 if (db->in_count >= RATIO_MAX
229 || db->bytes_out >= RATIO_MAX) {
230 db->in_count -= db->in_count/4;
231 db->bytes_out -= db->bytes_out/4;
234 db->checkpoint = db->in_count + CHECK_GAP;
236 if (db->max_ent >= db->maxmaxcode) {
237 /* Reset the dictionary only if the ratio is worse,
238 * or if it looks as if it has been poisoned
239 * by incompressible data.
241 * This does not overflow, because
242 * db->in_count <= RATIO_MAX.
244 new_ratio = db->in_count << RATIO_SCALE_LOG;
245 if (db->bytes_out != 0)
246 new_ratio /= db->bytes_out;
248 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
252 db->ratio = new_ratio;
262 bsd_comp_stats(state, stats)
264 struct compstat *stats;
266 struct bsd_db *db = (struct bsd_db *) state;
269 stats->unc_bytes = db->uncomp_bytes;
270 stats->unc_packets = db->uncomp_count;
271 stats->comp_bytes = db->comp_bytes;
272 stats->comp_packets = db->comp_count;
273 stats->inc_bytes = db->incomp_bytes;
274 stats->inc_packets = db->incomp_count;
275 stats->ratio = db->in_count;
277 if (stats->ratio <= 0x7fffff)
286 * Reset state, as on a CCP ResetReq.
292 struct bsd_db *db = (struct bsd_db *) state;
300 * Allocate space for a (de) compressor.
303 bsd_alloc(options, opt_len, decomp)
308 u_int newlen, hsize, hshift, maxmaxcode;
311 if (opt_len != CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
312 || options[1] != CILEN_BSD_COMPRESS
313 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
315 bits = BSD_NBITS(options[2]);
317 case 9: /* needs 82152 for both directions */
318 case 10: /* needs 84144 */
319 case 11: /* needs 88240 */
320 case 12: /* needs 96432 */
324 case 13: /* needs 176784 */
328 case 14: /* needs 353744 */
332 case 15: /* needs 691440 */
336 case 16: /* needs 1366160--far too much, */
337 /* hsize = 69001; */ /* and 69001 is too big for cptr */
338 /* hshift = 8; */ /* in struct bsd_db */
344 maxmaxcode = MAXCODE(bits);
345 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
346 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
349 bzero(db, sizeof(*db) - sizeof(db->dict));
354 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
365 db->maxmaxcode = maxmaxcode;
375 struct bsd_db *db = (struct bsd_db *) state;
378 FREE(db->lens, M_DEVBUF);
383 bsd_comp_alloc(options, opt_len)
387 return bsd_alloc(options, opt_len, 0);
391 bsd_decomp_alloc(options, opt_len)
395 return bsd_alloc(options, opt_len, 1);
399 * Initialize the database.
402 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
405 int opt_len, unit, hdrlen, mru, debug, decomp;
409 if (opt_len != CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
410 || options[1] != CILEN_BSD_COMPRESS
411 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
412 || BSD_NBITS(options[2]) != db->maxbits
413 || decomp && db->lens == NULL)
423 db->dict[--i].codem1 = BADCODEM1;
424 db->dict[i].cptr = 0;
441 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
444 int opt_len, unit, hdrlen, debug;
446 return bsd_init((struct bsd_db *) state, options, opt_len,
447 unit, hdrlen, 0, debug, 0);
451 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
454 int opt_len, unit, hdrlen, mru, debug;
456 return bsd_init((struct bsd_db *) state, options, opt_len,
457 unit, hdrlen, mru, debug, 1);
463 * One change from the BSD compress command is that when the
464 * code size expands, we do not output a bunch of padding.
467 bsd_compress(state, mret, mp, slen, maxolen)
469 struct mbuf **mret; /* return compressed mbuf chain here */
470 struct mbuf *mp; /* from here */
471 int slen; /* uncompressed length */
472 int maxolen; /* max compressed length */
474 struct bsd_db *db = (struct bsd_db *) state;
475 int hshift = db->hshift;
476 u_int max_ent = db->max_ent;
477 u_int n_bits = db->n_bits;
479 u_int32_t accm = 0, fcode;
480 struct bsd_dict *dictp;
482 int hval, disp, ent, ilen;
487 struct mbuf *m, **mnp;
489 #define PUTBYTE(v) { \
493 if (wptr >= cp_end) { \
494 m->m_len = wptr - mtod(m, u_char *); \
495 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
499 if (maxolen - olen > MLEN) \
500 MCLGET(m, M_DONTWAIT); \
501 wptr = mtod(m, u_char *); \
502 cp_end = wptr + M_TRAILINGSPACE(m); \
509 #define OUTPUT(ent) { \
511 accm |= ((ent) << bitno); \
513 PUTBYTE(accm >> 24); \
516 } while (bitno <= 24); \
520 * If the protocol is not in the range we're interested in,
521 * just return without compressing the packet. If it is,
522 * the protocol becomes the first byte to compress.
524 rptr = mtod(mp, u_char *);
525 ent = PPP_PROTOCOL(rptr);
526 if (ent < 0x21 || ent > 0xf9) {
531 /* Don't generate compressed packets which are larger than
532 the uncompressed packet. */
536 /* Allocate one mbuf to start with. */
537 MGET(m, M_DONTWAIT, MT_DATA);
541 if (maxolen + db->hdrlen > MLEN)
542 MCLGET(m, M_DONTWAIT);
543 m->m_data += db->hdrlen;
544 wptr = mtod(m, u_char *);
545 cp_end = wptr + M_TRAILINGSPACE(m);
547 wptr = cp_end = NULL;
550 * Copy the PPP header over, changing the protocol,
551 * and install the 2-byte packet sequence number.
554 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
555 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
556 *wptr++ = 0; /* change the protocol */
558 *wptr++ = db->seqno >> 8;
565 slen = mp->m_len - PPP_HDRLEN;
572 rptr = mtod(mp, u_char *);
575 continue; /* handle 0-length buffers */
581 fcode = BSD_KEY(ent, c);
582 hval = BSD_HASH(ent, c, hshift);
583 dictp = &db->dict[hval];
585 /* Validate and then check the entry. */
586 if (dictp->codem1 >= max_ent)
588 if (dictp->f.fcode == fcode) {
589 ent = dictp->codem1+1;
590 continue; /* found (prefix,suffix) */
593 /* continue probing until a match or invalid entry */
594 disp = (hval == 0) ? 1 : hval;
597 if (hval >= db->hsize)
599 dictp = &db->dict[hval];
600 if (dictp->codem1 >= max_ent)
602 } while (dictp->f.fcode != fcode);
603 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
607 OUTPUT(ent); /* output the prefix */
609 /* code -> hashtable */
610 if (max_ent < db->maxmaxcode) {
611 struct bsd_dict *dictp2;
612 /* expand code size if needed */
613 if (max_ent >= MAXCODE(n_bits))
614 db->n_bits = ++n_bits;
616 /* Invalidate old hash table entry using
617 * this code, and then take it over.
619 dictp2 = &db->dict[max_ent+1];
620 if (db->dict[dictp2->cptr].codem1 == max_ent)
621 db->dict[dictp2->cptr].codem1 = BADCODEM1;
623 dictp->codem1 = max_ent;
624 dictp->f.fcode = fcode;
626 db->max_ent = ++max_ent;
631 OUTPUT(ent); /* output the last code */
632 db->bytes_out += olen;
633 db->in_count += ilen;
635 ++db->bytes_out; /* count complete bytes */
638 OUTPUT(CLEAR); /* do not count the CLEAR */
641 * Pad dribble bits of last code with ones.
642 * Do not emit a completely useless byte of ones.
645 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
648 m->m_len = wptr - mtod(m, u_char *);
653 * Increase code size if we would have without the packet
654 * boundary and as the decompressor will.
656 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
659 db->uncomp_bytes += ilen;
661 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
662 /* throw away the compressed stuff if it is longer than uncompressed */
668 db->incomp_bytes += ilen;
671 db->comp_bytes += olen + BSD_OVHD;
674 return olen + PPP_HDRLEN + BSD_OVHD;
681 * Update the "BSD Compress" dictionary on the receiver for
682 * incompressible data by pretending to compress the incoming data.
685 bsd_incomp(state, dmsg)
689 struct bsd_db *db = (struct bsd_db *) state;
690 u_int hshift = db->hshift;
691 u_int max_ent = db->max_ent;
692 u_int n_bits = db->n_bits;
693 struct bsd_dict *dictp;
696 u_int32_t hval, disp;
703 * If the protocol is not in the range we're interested in,
704 * just return without looking at the packet. If it is,
705 * the protocol becomes the first byte to "compress".
707 rptr = mtod(dmsg, u_char *);
708 ent = PPP_PROTOCOL(rptr);
709 if (ent < 0x21 || ent > 0xf9)
714 ilen = 1; /* count the protocol as 1 byte */
716 slen = dmsg->m_len - PPP_HDRLEN;
722 rptr = mtod(dmsg, u_char *);
730 fcode = BSD_KEY(ent, c);
731 hval = BSD_HASH(ent, c, hshift);
732 dictp = &db->dict[hval];
734 /* validate and then check the entry */
735 if (dictp->codem1 >= max_ent)
737 if (dictp->f.fcode == fcode) {
738 ent = dictp->codem1+1;
739 continue; /* found (prefix,suffix) */
742 /* continue probing until a match or invalid entry */
743 disp = (hval == 0) ? 1 : hval;
746 if (hval >= db->hsize)
748 dictp = &db->dict[hval];
749 if (dictp->codem1 >= max_ent)
751 } while (dictp->f.fcode != fcode);
752 ent = dictp->codem1+1;
753 continue; /* finally found (prefix,suffix) */
755 nomatch: /* output (count) the prefix */
758 /* code -> hashtable */
759 if (max_ent < db->maxmaxcode) {
760 struct bsd_dict *dictp2;
761 /* expand code size if needed */
762 if (max_ent >= MAXCODE(n_bits))
763 db->n_bits = ++n_bits;
765 /* Invalidate previous hash table entry
766 * assigned this code, and then take it over.
768 dictp2 = &db->dict[max_ent+1];
769 if (db->dict[dictp2->cptr].codem1 == max_ent)
770 db->dict[dictp2->cptr].codem1 = BADCODEM1;
772 dictp->codem1 = max_ent;
773 dictp->f.fcode = fcode;
775 db->max_ent = ++max_ent;
776 db->lens[max_ent] = db->lens[ent]+1;
779 } while (--slen != 0);
781 bitno += n_bits; /* output (count) the last code */
782 db->bytes_out += bitno/8;
783 db->in_count += ilen;
787 db->incomp_bytes += ilen;
789 db->uncomp_bytes += ilen;
791 /* Increase code size if we would have without the packet
792 * boundary and as the decompressor will.
794 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
800 * Decompress "BSD Compress".
802 * Because of patent problems, we return DECOMP_ERROR for errors
803 * found by inspecting the input data and for system problems, but
804 * DECOMP_FATALERROR for any errors which could possibly be said to
805 * be being detected "after" decompression. For DECOMP_ERROR,
806 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
807 * infringing a patent of Motorola's if we do, so we take CCP down
810 * Given that the frame has the correct sequence number and a good FCS,
811 * errors such as invalid codes in the input most likely indicate a
812 * bug, so we return DECOMP_FATALERROR for them in order to turn off
813 * compression, even though they are detected by inspecting the input.
816 bsd_decompress(state, cmp, dmpp)
818 struct mbuf *cmp, **dmpp;
820 struct bsd_db *db = (struct bsd_db *) state;
821 u_int max_ent = db->max_ent;
823 u_int bitno = 32; /* 1st valid bit in accm */
824 u_int n_bits = db->n_bits;
825 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
826 struct bsd_dict *dictp;
827 int explen, i, seq, len;
828 u_int incode, oldcode, finchar;
829 u_char *p, *rptr, *wptr;
830 struct mbuf *m, *dmp, *mret;
831 int adrs, ctrl, ilen;
832 int space, codelen, extra;
836 * Save the address/control from the PPP header
837 * and then get the sequence number.
840 rptr = mtod(cmp, u_char *);
841 adrs = PPP_ADDRESS(rptr);
842 ctrl = PPP_CONTROL(rptr);
844 len = cmp->m_len - PPP_HDRLEN;
846 for (i = 0; i < 2; ++i) {
851 rptr = mtod(cmp, u_char *);
854 seq = (seq << 8) + *rptr++;
859 * Check the sequence number and give up if it differs from
860 * the value we're expecting.
862 if (seq != db->seqno) {
864 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
865 db->unit, seq, db->seqno - 1);
871 * Allocate one mbuf to start with.
873 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
879 MCLGET(dmp, M_DONTWAIT);
880 dmp->m_data += db->hdrlen;
881 wptr = mtod(dmp, u_char *);
882 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
885 * Fill in the ppp header, but not the last byte of the protocol
886 * (that comes from the decompressed data).
891 wptr += PPP_HDRLEN - 1;
899 if (!cmp) /* quit at end of message */
901 rptr = mtod(cmp, u_char *);
904 continue; /* handle 0-length buffers */
908 * Accumulate bytes until we have a complete code.
909 * Then get the next code, relying on the 32-bit,
910 * unsigned accm to mask the result.
913 accm |= *rptr++ << bitno;
915 if (tgtbitno < bitno)
917 incode = accm >> tgtbitno;
921 if (incode == CLEAR) {
923 * The dictionary must only be cleared at
924 * the end of a packet. But there could be an
925 * empty mbuf at the end.
927 if (len > 0 || cmp->m_next != NULL) {
928 while ((cmp = cmp->m_next) != NULL)
933 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
934 return DECOMP_FATALERROR; /* probably a bug */
942 if (incode > max_ent + 2 || incode > db->maxmaxcode
943 || incode > max_ent && oldcode == CLEAR) {
946 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
947 db->unit, incode, oldcode);
948 printf("max_ent=0x%x explen=%d seqno=%d\n",
949 max_ent, explen, db->seqno);
951 return DECOMP_FATALERROR; /* probably a bug */
954 /* Special case for KwKwK string. */
955 if (incode > max_ent) {
963 codelen = db->lens[finchar];
964 explen += codelen + extra;
965 if (explen > db->mru + 1) {
968 printf("bsd_decomp%d: ran out of mru\n", db->unit);
970 while ((cmp = cmp->m_next) != NULL)
972 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
973 len, finchar, codelen, explen);
976 return DECOMP_FATALERROR;
980 * For simplicity, the decoded characters go in a single mbuf,
981 * so we allocate a single extra cluster mbuf if necessary.
983 if ((space -= codelen + extra) < 0) {
984 dmp->m_len = wptr - mtod(dmp, u_char *);
985 MGET(m, M_DONTWAIT, MT_DATA);
993 MCLGET(m, M_DONTWAIT);
994 space = M_TRAILINGSPACE(m) - (codelen + extra);
996 /* now that's what I call *compression*. */
1001 wptr = mtod(dmp, u_char *);
1005 * Decode this code and install it in the decompressed buffer.
1007 p = (wptr += codelen);
1008 while (finchar > LAST) {
1009 dictp = &db->dict[db->dict[finchar].cptr];
1011 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1014 *--p = dictp->f.hs.suffix;
1015 finchar = dictp->f.hs.prefix;
1021 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1022 db->unit, codelen, incode, max_ent);
1025 if (extra) /* the KwKwK case again */
1029 * If not first code in a packet, and
1030 * if not out of code space, then allocate a new code.
1032 * Keep the hash table correct so it can be used
1033 * with uncompressed packets.
1035 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1036 struct bsd_dict *dictp2;
1038 u_int32_t hval, disp;
1040 fcode = BSD_KEY(oldcode,finchar);
1041 hval = BSD_HASH(oldcode,finchar,db->hshift);
1042 dictp = &db->dict[hval];
1044 /* look for a free hash table entry */
1045 if (dictp->codem1 < max_ent) {
1046 disp = (hval == 0) ? 1 : hval;
1049 if (hval >= db->hsize)
1051 dictp = &db->dict[hval];
1052 } while (dictp->codem1 < max_ent);
1056 * Invalidate previous hash table entry
1057 * assigned this code, and then take it over
1059 dictp2 = &db->dict[max_ent+1];
1060 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1061 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1063 dictp2->cptr = hval;
1064 dictp->codem1 = max_ent;
1065 dictp->f.fcode = fcode;
1067 db->max_ent = ++max_ent;
1068 db->lens[max_ent] = db->lens[oldcode]+1;
1070 /* Expand code size if needed. */
1071 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1072 db->n_bits = ++n_bits;
1073 tgtbitno = 32-n_bits;
1078 dmp->m_len = wptr - mtod(dmp, u_char *);
1081 * Keep the checkpoint right so that incompressible packets
1082 * clear the dictionary at the right times.
1084 db->bytes_out += ilen;
1085 db->in_count += explen;
1086 if (bsd_check(db) && db->debug) {
1087 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1092 db->comp_bytes += ilen + BSD_OVHD;
1094 db->uncomp_bytes += explen;
1102 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1103 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1104 incode, finchar, db->dict[finchar].cptr, max_ent);
1105 } else if (dictp->codem1 != finchar-1) {
1106 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1107 db->unit, incode, finchar);
1108 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1109 db->dict[finchar].cptr, dictp->codem1);
1112 return DECOMP_FATALERROR;
1115 #endif /* DO_BSD_COMPRESS */