1 /* $Id: bsd-comp.c,v 1.1 1995/12/11 05:17:05 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.
45 * $Id: bsd-comp.c,v 1.1 1995/12/11 05:17:05 paulus Exp $
48 #include <sys/param.h>
49 #include <sys/types.h>
51 #include <sys/socket.h>
53 #include <net/if_types.h>
54 #include <net/ppp_defs.h>
55 #include <net/if_ppp.h>
57 #define PACKETPTR struct mbuf *
58 #include <net/ppp-comp.h>
62 * PPP "BSD compress" compression
63 * The differences between this compression and the classic BSD LZW
64 * source are obvious from the requirement that the classic code worked
65 * with files while this handles arbitrarily long streams that
66 * are broken into packets. They are:
68 * When the code size expands, a block of junk is not emitted by
69 * the compressor and not expected by the decompressor.
71 * New codes are not necessarily assigned every time an old
72 * code is output by the compressor. This is because a packet
73 * end forces a code to be emitted, but does not imply that a
74 * new sequence has been seen.
76 * The compression ratio is checked at the first end of a packet
77 * after the appropriate gap. Besides simplifying and speeding
78 * things up, this makes it more likely that the transmitter
79 * and receiver will agree when the dictionary is cleared when
80 * compression is not going well.
84 * A dictionary for doing BSD compress.
87 int totlen; /* length of this structure */
88 u_int hsize; /* size of the hash table */
89 u_char hshift; /* used in hash function */
90 u_char n_bits; /* current bits/code */
94 u_int16_t seqno; /* sequence # of next packet */
95 u_int hdrlen; /* header length to preallocate */
97 u_int maxmaxcode; /* largest valid code */
98 u_int max_ent; /* largest code in use */
99 u_int in_count; /* uncompressed bytes, aged */
100 u_int bytes_out; /* compressed bytes, aged */
101 u_int ratio; /* recent compression ratio */
102 u_int checkpoint; /* when to next check the ratio */
103 u_int clear_count; /* times dictionary cleared */
104 u_int incomp_count; /* incompressible packets */
105 u_int incomp_bytes; /* incompressible bytes */
106 u_int uncomp_count; /* uncompressed packets */
107 u_int uncomp_bytes; /* uncompressed bytes */
108 u_int comp_count; /* compressed packets */
109 u_int comp_bytes; /* compressed bytes */
110 u_int16_t *lens; /* array of lengths of codes */
112 union { /* hash value */
115 #if BYTE_ORDER == LITTLE_ENDIAN
116 u_int16_t prefix; /* preceding code */
117 u_char suffix; /* last character of new code */
121 u_char suffix; /* last character of new code */
122 u_int16_t prefix; /* preceding code */
126 u_int16_t codem1; /* output of hash table -1 */
127 u_int16_t cptr; /* map code to hash table entry */
131 #define BSD_OVHD 2 /* BSD compress overhead/packet */
132 #define BSD_INIT_BITS BSD_MIN_BITS
134 static void *bsd_comp_alloc __P((u_char *options, int opt_len));
135 static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
136 static void bsd_free __P((void *state));
137 static int bsd_comp_init __P((void *state, u_char *options, int opt_len,
138 int unit, int hdrlen, int debug));
139 static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
140 int unit, int hdrlen, int mru, int debug));
141 static int bsd_compress __P((void *state, struct mbuf **mret,
142 struct mbuf *mp, int slen, int maxolen));
143 static void bsd_incomp __P((void *state, struct mbuf *dmsg));
144 static int bsd_decompress __P((void *state, struct mbuf *cmp,
145 struct mbuf **dmpp));
146 static void bsd_reset __P((void *state));
147 static void bsd_comp_stats __P((void *state, struct compstat *stats));
150 * Procedures exported to if_ppp.c.
152 struct compressor ppp_bsd_compress = {
153 CI_BSD_COMPRESS, /* compress_proto */
154 bsd_comp_alloc, /* comp_alloc */
155 bsd_free, /* comp_free */
156 bsd_comp_init, /* comp_init */
157 bsd_reset, /* comp_reset */
158 bsd_compress, /* compress */
159 bsd_comp_stats, /* comp_stat */
160 bsd_decomp_alloc, /* decomp_alloc */
161 bsd_free, /* decomp_free */
162 bsd_decomp_init, /* decomp_init */
163 bsd_reset, /* decomp_reset */
164 bsd_decompress, /* decompress */
165 bsd_incomp, /* incomp */
166 bsd_comp_stats, /* decomp_stat */
170 * the next two codes should not be changed lightly, as they must not
171 * lie within the contiguous general code space.
173 #define CLEAR 256 /* table clear output code */
174 #define FIRST 257 /* first free entry */
177 #define MAXCODE(b) ((1 << (b)) - 1)
178 #define BADCODEM1 MAXCODE(BSD_MAX_BITS)
180 #define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
181 ^ (u_int32_t)(prefix))
182 #define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
183 + (u_int32_t)(prefix))
185 #define CHECK_GAP 10000 /* Ratio check interval */
187 #define RATIO_SCALE_LOG 8
188 #define RATIO_SCALE (1<<RATIO_SCALE_LOG)
189 #define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
192 * clear the dictionary
199 db->max_ent = FIRST-1;
200 db->n_bits = BSD_INIT_BITS;
204 db->incomp_count = 0;
205 db->checkpoint = CHECK_GAP;
209 * If the dictionary is full, then see if it is time to reset it.
211 * Compute the compression ratio using fixed-point arithmetic
212 * with 8 fractional bits.
214 * Since we have an infinite stream instead of a single file,
215 * watch only the local compression ratio.
217 * Since both peers must reset the dictionary at the same time even in
218 * the absence of CLEAR codes (while packets are incompressible), they
219 * must compute the same ratio.
221 static int /* 1=output CLEAR */
227 if (db->in_count >= db->checkpoint) {
228 /* age the ratio by limiting the size of the counts */
229 if (db->in_count >= RATIO_MAX
230 || db->bytes_out >= RATIO_MAX) {
231 db->in_count -= db->in_count/4;
232 db->bytes_out -= db->bytes_out/4;
235 db->checkpoint = db->in_count + CHECK_GAP;
237 if (db->max_ent >= db->maxmaxcode) {
238 /* Reset the dictionary only if the ratio is worse,
239 * or if it looks as if it has been poisoned
240 * by incompressible data.
242 * This does not overflow, because
243 * db->in_count <= RATIO_MAX.
245 new_ratio = db->in_count << RATIO_SCALE_LOG;
246 if (db->bytes_out != 0)
247 new_ratio /= db->bytes_out;
249 if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
253 db->ratio = new_ratio;
263 bsd_comp_stats(state, stats)
265 struct compstat *stats;
267 struct bsd_db *db = (struct bsd_db *) state;
270 stats->unc_bytes = db->uncomp_bytes;
271 stats->unc_packets = db->uncomp_count;
272 stats->comp_bytes = db->comp_bytes;
273 stats->comp_packets = db->comp_count;
274 stats->inc_bytes = db->incomp_bytes;
275 stats->inc_packets = db->incomp_count;
276 stats->ratio = db->in_count;
278 if (stats->ratio <= 0x7fffff)
287 * Reset state, as on a CCP ResetReq.
293 struct bsd_db *db = (struct bsd_db *) state;
301 * Allocate space for a (de) compressor.
304 bsd_alloc(options, opt_len, decomp)
309 u_int newlen, hsize, hshift, maxmaxcode;
312 if (opt_len != CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
313 || options[1] != CILEN_BSD_COMPRESS
314 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
316 bits = BSD_NBITS(options[2]);
318 case 9: /* needs 82152 for both directions */
319 case 10: /* needs 84144 */
320 case 11: /* needs 88240 */
321 case 12: /* needs 96432 */
325 case 13: /* needs 176784 */
329 case 14: /* needs 353744 */
333 case 15: /* needs 691440 */
337 case 16: /* needs 1366160--far too much, */
338 /* hsize = 69001; */ /* and 69001 is too big for cptr */
339 /* hshift = 8; */ /* in struct bsd_db */
345 maxmaxcode = MAXCODE(bits);
346 newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
347 MALLOC(db, struct bsd_db *, newlen, M_DEVBUF, M_NOWAIT);
350 bzero(db, sizeof(*db) - sizeof(db->dict));
355 MALLOC(db->lens, u_int16_t *, (maxmaxcode+1) * sizeof(db->lens[0]),
366 db->maxmaxcode = maxmaxcode;
376 struct bsd_db *db = (struct bsd_db *) state;
379 FREE(db->lens, M_DEVBUF);
384 bsd_comp_alloc(options, opt_len)
388 return bsd_alloc(options, opt_len, 0);
392 bsd_decomp_alloc(options, opt_len)
396 return bsd_alloc(options, opt_len, 1);
400 * Initialize the database.
403 bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
406 int opt_len, unit, hdrlen, mru, debug, decomp;
410 if (opt_len != CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
411 || options[1] != CILEN_BSD_COMPRESS
412 || BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
413 || BSD_NBITS(options[2]) != db->maxbits
414 || decomp && db->lens == NULL)
424 db->dict[--i].codem1 = BADCODEM1;
425 db->dict[i].cptr = 0;
442 bsd_comp_init(state, options, opt_len, unit, hdrlen, debug)
445 int opt_len, unit, hdrlen, debug;
447 return bsd_init((struct bsd_db *) state, options, opt_len,
448 unit, hdrlen, 0, debug, 0);
452 bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
455 int opt_len, unit, hdrlen, mru, debug;
457 return bsd_init((struct bsd_db *) state, options, opt_len,
458 unit, hdrlen, mru, debug, 1);
464 * One change from the BSD compress command is that when the
465 * code size expands, we do not output a bunch of padding.
468 bsd_compress(state, mret, mp, slen, maxolen)
470 struct mbuf **mret; /* return compressed mbuf chain here */
471 struct mbuf *mp; /* from here */
472 int slen; /* uncompressed length */
473 int maxolen; /* max compressed length */
475 struct bsd_db *db = (struct bsd_db *) state;
476 int hshift = db->hshift;
477 u_int max_ent = db->max_ent;
478 u_int n_bits = db->n_bits;
480 u_int32_t accm = 0, fcode;
481 struct bsd_dict *dictp;
483 int hval, disp, ent, ilen;
488 struct mbuf *m, **mnp;
490 #define PUTBYTE(v) { \
494 if (wptr >= cp_end) { \
495 m->m_len = wptr - mtod(m, u_char *); \
496 MGET(m->m_next, M_DONTWAIT, MT_DATA); \
500 if (maxolen - olen > MLEN) \
501 MCLGET(m, M_DONTWAIT); \
502 wptr = mtod(m, u_char *); \
503 cp_end = wptr + M_TRAILINGSPACE(m); \
510 #define OUTPUT(ent) { \
512 accm |= ((ent) << bitno); \
514 PUTBYTE(accm >> 24); \
517 } while (bitno <= 24); \
521 * If the protocol is not in the range we're interested in,
522 * just return without compressing the packet. If it is,
523 * the protocol becomes the first byte to compress.
525 rptr = mtod(mp, u_char *);
526 ent = PPP_PROTOCOL(rptr);
527 if (ent < 0x21 || ent > 0xf9) {
532 /* Don't generate compressed packets which are larger than
533 the uncompressed packet. */
537 /* Allocate one mbuf to start with. */
538 MGET(m, M_DONTWAIT, MT_DATA);
542 if (maxolen + db->hdrlen > MLEN)
543 MCLGET(m, M_DONTWAIT);
544 m->m_data += db->hdrlen;
545 wptr = mtod(m, u_char *);
546 cp_end = wptr + M_TRAILINGSPACE(m);
548 wptr = cp_end = NULL;
551 * Copy the PPP header over, changing the protocol,
552 * and install the 2-byte packet sequence number.
555 *wptr++ = PPP_ADDRESS(rptr); /* assumes the ppp header is */
556 *wptr++ = PPP_CONTROL(rptr); /* all in one mbuf */
557 *wptr++ = 0; /* change the protocol */
559 *wptr++ = db->seqno >> 8;
566 slen = mp->m_len - PPP_HDRLEN;
573 rptr = mtod(mp, u_char *);
576 continue; /* handle 0-length buffers */
582 fcode = BSD_KEY(ent, c);
583 hval = BSD_HASH(ent, c, hshift);
584 dictp = &db->dict[hval];
586 /* Validate and then check the entry. */
587 if (dictp->codem1 >= max_ent)
589 if (dictp->f.fcode == fcode) {
590 ent = dictp->codem1+1;
591 continue; /* found (prefix,suffix) */
594 /* continue probing until a match or invalid entry */
595 disp = (hval == 0) ? 1 : hval;
598 if (hval >= db->hsize)
600 dictp = &db->dict[hval];
601 if (dictp->codem1 >= max_ent)
603 } while (dictp->f.fcode != fcode);
604 ent = dictp->codem1 + 1; /* finally found (prefix,suffix) */
608 OUTPUT(ent); /* output the prefix */
610 /* code -> hashtable */
611 if (max_ent < db->maxmaxcode) {
612 struct bsd_dict *dictp2;
613 /* expand code size if needed */
614 if (max_ent >= MAXCODE(n_bits))
615 db->n_bits = ++n_bits;
617 /* Invalidate old hash table entry using
618 * this code, and then take it over.
620 dictp2 = &db->dict[max_ent+1];
621 if (db->dict[dictp2->cptr].codem1 == max_ent)
622 db->dict[dictp2->cptr].codem1 = BADCODEM1;
624 dictp->codem1 = max_ent;
625 dictp->f.fcode = fcode;
627 db->max_ent = ++max_ent;
632 OUTPUT(ent); /* output the last code */
633 db->bytes_out += olen;
634 db->in_count += ilen;
636 ++db->bytes_out; /* count complete bytes */
639 OUTPUT(CLEAR); /* do not count the CLEAR */
642 * Pad dribble bits of last code with ones.
643 * Do not emit a completely useless byte of ones.
646 PUTBYTE((accm | (0xff << (bitno-8))) >> 24);
649 m->m_len = wptr - mtod(m, u_char *);
654 * Increase code size if we would have without the packet
655 * boundary and as the decompressor will.
657 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
660 db->uncomp_bytes += ilen;
662 if (olen + PPP_HDRLEN + BSD_OVHD > maxolen) {
663 /* throw away the compressed stuff if it is longer than uncompressed */
669 db->incomp_bytes += ilen;
672 db->comp_bytes += olen + BSD_OVHD;
675 return olen + PPP_HDRLEN + BSD_OVHD;
682 * Update the "BSD Compress" dictionary on the receiver for
683 * incompressible data by pretending to compress the incoming data.
686 bsd_incomp(state, dmsg)
690 struct bsd_db *db = (struct bsd_db *) state;
691 u_int hshift = db->hshift;
692 u_int max_ent = db->max_ent;
693 u_int n_bits = db->n_bits;
694 struct bsd_dict *dictp;
697 u_int32_t hval, disp;
704 * If the protocol is not in the range we're interested in,
705 * just return without looking at the packet. If it is,
706 * the protocol becomes the first byte to "compress".
708 rptr = mtod(dmsg, u_char *);
709 ent = PPP_PROTOCOL(rptr);
710 if (ent < 0x21 || ent > 0xf9)
715 ilen = 1; /* count the protocol as 1 byte */
717 slen = dmsg->m_len - PPP_HDRLEN;
723 rptr = mtod(dmsg, u_char *);
731 fcode = BSD_KEY(ent, c);
732 hval = BSD_HASH(ent, c, hshift);
733 dictp = &db->dict[hval];
735 /* validate and then check the entry */
736 if (dictp->codem1 >= max_ent)
738 if (dictp->f.fcode == fcode) {
739 ent = dictp->codem1+1;
740 continue; /* found (prefix,suffix) */
743 /* continue probing until a match or invalid entry */
744 disp = (hval == 0) ? 1 : hval;
747 if (hval >= db->hsize)
749 dictp = &db->dict[hval];
750 if (dictp->codem1 >= max_ent)
752 } while (dictp->f.fcode != fcode);
753 ent = dictp->codem1+1;
754 continue; /* finally found (prefix,suffix) */
756 nomatch: /* output (count) the prefix */
759 /* code -> hashtable */
760 if (max_ent < db->maxmaxcode) {
761 struct bsd_dict *dictp2;
762 /* expand code size if needed */
763 if (max_ent >= MAXCODE(n_bits))
764 db->n_bits = ++n_bits;
766 /* Invalidate previous hash table entry
767 * assigned this code, and then take it over.
769 dictp2 = &db->dict[max_ent+1];
770 if (db->dict[dictp2->cptr].codem1 == max_ent)
771 db->dict[dictp2->cptr].codem1 = BADCODEM1;
773 dictp->codem1 = max_ent;
774 dictp->f.fcode = fcode;
776 db->max_ent = ++max_ent;
777 db->lens[max_ent] = db->lens[ent]+1;
780 } while (--slen != 0);
782 bitno += n_bits; /* output (count) the last code */
783 db->bytes_out += bitno/8;
784 db->in_count += ilen;
788 db->incomp_bytes += ilen;
790 db->uncomp_bytes += ilen;
792 /* Increase code size if we would have without the packet
793 * boundary and as the decompressor will.
795 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
801 * Decompress "BSD Compress".
803 * Because of patent problems, we return DECOMP_ERROR for errors
804 * found by inspecting the input data and for system problems, but
805 * DECOMP_FATALERROR for any errors which could possibly be said to
806 * be being detected "after" decompression. For DECOMP_ERROR,
807 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
808 * infringing a patent of Motorola's if we do, so we take CCP down
811 * Given that the frame has the correct sequence number and a good FCS,
812 * errors such as invalid codes in the input most likely indicate a
813 * bug, so we return DECOMP_FATALERROR for them in order to turn off
814 * compression, even though they are detected by inspecting the input.
817 bsd_decompress(state, cmp, dmpp)
819 struct mbuf *cmp, **dmpp;
821 struct bsd_db *db = (struct bsd_db *) state;
822 u_int max_ent = db->max_ent;
824 u_int bitno = 32; /* 1st valid bit in accm */
825 u_int n_bits = db->n_bits;
826 u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
827 struct bsd_dict *dictp;
828 int explen, i, seq, len;
829 u_int incode, oldcode, finchar;
830 u_char *p, *rptr, *wptr;
831 struct mbuf *m, *dmp, *mret;
832 int adrs, ctrl, ilen;
833 int space, codelen, extra;
837 * Save the address/control from the PPP header
838 * and then get the sequence number.
841 rptr = mtod(cmp, u_char *);
842 adrs = PPP_ADDRESS(rptr);
843 ctrl = PPP_CONTROL(rptr);
845 len = cmp->m_len - PPP_HDRLEN;
847 for (i = 0; i < 2; ++i) {
852 rptr = mtod(cmp, u_char *);
855 seq = (seq << 8) + *rptr++;
860 * Check the sequence number and give up if it differs from
861 * the value we're expecting.
863 if (seq != db->seqno) {
865 printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
866 db->unit, seq, db->seqno - 1);
872 * Allocate one mbuf to start with.
874 MGETHDR(dmp, M_DONTWAIT, MT_DATA);
880 MCLGET(dmp, M_DONTWAIT);
881 dmp->m_data += db->hdrlen;
882 wptr = mtod(dmp, u_char *);
883 space = M_TRAILINGSPACE(dmp) - PPP_HDRLEN + 1;
886 * Fill in the ppp header, but not the last byte of the protocol
887 * (that comes from the decompressed data).
892 wptr += PPP_HDRLEN - 1;
900 if (!cmp) /* quit at end of message */
902 rptr = mtod(cmp, u_char *);
905 continue; /* handle 0-length buffers */
909 * Accumulate bytes until we have a complete code.
910 * Then get the next code, relying on the 32-bit,
911 * unsigned accm to mask the result.
914 accm |= *rptr++ << bitno;
916 if (tgtbitno < bitno)
918 incode = accm >> tgtbitno;
922 if (incode == CLEAR) {
924 * The dictionary must only be cleared at
925 * the end of a packet. But there could be an
926 * empty mbuf at the end.
928 if (len > 0 || cmp->m_next != NULL) {
929 while ((cmp = cmp->m_next) != NULL)
934 printf("bsd_decomp%d: bad CLEAR\n", db->unit);
935 return DECOMP_FATALERROR; /* probably a bug */
943 if (incode > max_ent + 2 || incode > db->maxmaxcode
944 || incode > max_ent && oldcode == CLEAR) {
947 printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
948 db->unit, incode, oldcode);
949 printf("max_ent=0x%x explen=%d seqno=%d\n",
950 max_ent, explen, db->seqno);
952 return DECOMP_FATALERROR; /* probably a bug */
955 /* Special case for KwKwK string. */
956 if (incode > max_ent) {
964 codelen = db->lens[finchar];
965 explen += codelen + extra;
966 if (explen > db->mru + 1) {
969 printf("bsd_decomp%d: ran out of mru\n", db->unit);
971 while ((cmp = cmp->m_next) != NULL)
973 printf(" len=%d, finchar=0x%x, codelen=%d, explen=%d\n",
974 len, finchar, codelen, explen);
977 return DECOMP_FATALERROR;
981 * For simplicity, the decoded characters go in a single mbuf,
982 * so we allocate a single extra cluster mbuf if necessary.
984 if ((space -= codelen + extra) < 0) {
985 dmp->m_len = wptr - mtod(dmp, u_char *);
986 MGET(m, M_DONTWAIT, MT_DATA);
994 MCLGET(m, M_DONTWAIT);
995 space = M_TRAILINGSPACE(m) - (codelen + extra);
997 /* now that's what I call *compression*. */
1002 wptr = mtod(dmp, u_char *);
1006 * Decode this code and install it in the decompressed buffer.
1008 p = (wptr += codelen);
1009 while (finchar > LAST) {
1010 dictp = &db->dict[db->dict[finchar].cptr];
1012 if (--codelen <= 0 || dictp->codem1 != finchar-1)
1015 *--p = dictp->f.hs.suffix;
1016 finchar = dictp->f.hs.prefix;
1022 printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
1023 db->unit, codelen, incode, max_ent);
1026 if (extra) /* the KwKwK case again */
1030 * If not first code in a packet, and
1031 * if not out of code space, then allocate a new code.
1033 * Keep the hash table correct so it can be used
1034 * with uncompressed packets.
1036 if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
1037 struct bsd_dict *dictp2;
1039 u_int32_t hval, disp;
1041 fcode = BSD_KEY(oldcode,finchar);
1042 hval = BSD_HASH(oldcode,finchar,db->hshift);
1043 dictp = &db->dict[hval];
1045 /* look for a free hash table entry */
1046 if (dictp->codem1 < max_ent) {
1047 disp = (hval == 0) ? 1 : hval;
1050 if (hval >= db->hsize)
1052 dictp = &db->dict[hval];
1053 } while (dictp->codem1 < max_ent);
1057 * Invalidate previous hash table entry
1058 * assigned this code, and then take it over
1060 dictp2 = &db->dict[max_ent+1];
1061 if (db->dict[dictp2->cptr].codem1 == max_ent) {
1062 db->dict[dictp2->cptr].codem1 = BADCODEM1;
1064 dictp2->cptr = hval;
1065 dictp->codem1 = max_ent;
1066 dictp->f.fcode = fcode;
1068 db->max_ent = ++max_ent;
1069 db->lens[max_ent] = db->lens[oldcode]+1;
1071 /* Expand code size if needed. */
1072 if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
1073 db->n_bits = ++n_bits;
1074 tgtbitno = 32-n_bits;
1079 dmp->m_len = wptr - mtod(dmp, u_char *);
1082 * Keep the checkpoint right so that incompressible packets
1083 * clear the dictionary at the right times.
1085 db->bytes_out += ilen;
1086 db->in_count += explen;
1087 if (bsd_check(db) && db->debug) {
1088 printf("bsd_decomp%d: peer should have cleared dictionary\n",
1093 db->comp_bytes += ilen + BSD_OVHD;
1095 db->uncomp_bytes += explen;
1103 printf("bsd_decomp%d: fell off end of chain ", db->unit);
1104 printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
1105 incode, finchar, db->dict[finchar].cptr, max_ent);
1106 } else if (dictp->codem1 != finchar-1) {
1107 printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
1108 db->unit, incode, finchar);
1109 printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
1110 db->dict[finchar].cptr, dictp->codem1);
1113 return DECOMP_FATALERROR;
1116 #endif /* DO_BSD_COMPRESS */