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/* Because this code is derived from the 4.3BSD compress source:
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* Copyright (c) 1985, 1986 The Regents of the University of California.
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* This code is derived from software contributed to Berkeley by
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* James A. Woods, derived from original work by Spencer Thomas
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* $Id: bsd-comp.c,v 1.4 2004/01/17 05:47:55 carlsonj Exp $
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#include <sys/types.h>
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* PPP "BSD compress" compression
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* The differences between this compression and the classic BSD LZW
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* source are obvious from the requirement that the classic code worked
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* with files while this handles arbitrarily long streams that
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* are broken into packets. They are:
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* When the code size expands, a block of junk is not emitted by
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* the compressor and not expected by the decompressor.
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* New codes are not necessarily assigned every time an old
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* code is output by the compressor. This is because a packet
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* end forces a code to be emitted, but does not imply that a
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* new sequence has been seen.
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* The compression ratio is checked at the first end of a packet
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* after the appropriate gap. Besides simplifying and speeding
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* things up, this makes it more likely that the transmitter
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* and receiver will agree when the dictionary is cleared when
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* compression is not going well.
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* A dictionary for doing BSD compress.
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int totlen; /* length of this structure */
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u_int hsize; /* size of the hash table */
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u_char hshift; /* used in hash function */
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u_char n_bits; /* current bits/code */
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u_short seqno; /* sequence number of next packet */
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u_int hdrlen; /* header length to preallocate */
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u_int maxmaxcode; /* largest valid code */
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u_int max_ent; /* largest code in use */
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u_int in_count; /* uncompressed bytes, aged */
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u_int bytes_out; /* compressed bytes, aged */
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u_int ratio; /* recent compression ratio */
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u_int checkpoint; /* when to next check the ratio */
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u_int clear_count; /* times dictionary cleared */
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u_int incomp_count; /* incompressible packets */
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u_int incomp_bytes; /* incompressible bytes */
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u_int uncomp_count; /* uncompressed packets */
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u_int uncomp_bytes; /* uncompressed bytes */
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u_int comp_count; /* compressed packets */
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u_int comp_bytes; /* compressed bytes */
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u_short *lens; /* array of lengths of codes */
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union { /* hash value */
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#ifdef BSD_LITTLE_ENDIAN
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u_short prefix; /* preceding code */
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u_char suffix; /* last character of new code */
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u_char suffix; /* last character of new code */
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u_short prefix; /* preceding code */
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u_short codem1; /* output of hash table -1 */
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u_short cptr; /* map code to hash table entry */
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#define BSD_OVHD 2 /* BSD compress overhead/packet */
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#define BSD_INIT_BITS BSD_MIN_BITS
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static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
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static void bsd_free __P((void *state));
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static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
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int unit, int hdrlen, int mru, int debug));
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static void bsd_incomp __P((void *state, u_char *dmsg, int len));
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static int bsd_decompress __P((void *state, u_char *cmp, int inlen,
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u_char *dmp, int *outlen));
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static void bsd_reset __P((void *state));
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static void bsd_comp_stats __P((void *state, struct compstat *stats));
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* Exported procedures.
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struct compressor ppp_bsd_compress = {
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CI_BSD_COMPRESS, /* compress_proto */
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bsd_decomp_alloc, /* decomp_alloc */
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bsd_free, /* decomp_free */
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bsd_decomp_init, /* decomp_init */
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bsd_reset, /* decomp_reset */
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bsd_decompress, /* decompress */
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bsd_incomp, /* incomp */
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bsd_comp_stats, /* decomp_stat */
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* the next two codes should not be changed lightly, as they must not
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* lie within the contiguous general code space.
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#define CLEAR 256 /* table clear output code */
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#define FIRST 257 /* first free entry */
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#define MAXCODE(b) ((1 << (b)) - 1)
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#define BADCODEM1 MAXCODE(BSD_MAX_BITS)
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#define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \
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^ (u_int32_t)(prefix))
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#define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \
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+ (u_int32_t)(prefix))
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#define CHECK_GAP 10000 /* Ratio check interval */
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#define RATIO_SCALE_LOG 8
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#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
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#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
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* clear the dictionary
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db->max_ent = FIRST-1;
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db->n_bits = BSD_INIT_BITS;
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db->checkpoint = CHECK_GAP;
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* If the dictionary is full, then see if it is time to reset it.
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* Compute the compression ratio using fixed-point arithmetic
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* with 8 fractional bits.
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* Since we have an infinite stream instead of a single file,
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* watch only the local compression ratio.
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* Since both peers must reset the dictionary at the same time even in
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* the absence of CLEAR codes (while packets are incompressible), they
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* must compute the same ratio.
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static int /* 1=output CLEAR */
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if (db->in_count >= db->checkpoint) {
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/* age the ratio by limiting the size of the counts */
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if (db->in_count >= RATIO_MAX
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|| db->bytes_out >= RATIO_MAX) {
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db->in_count -= db->in_count/4;
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db->bytes_out -= db->bytes_out/4;
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db->checkpoint = db->in_count + CHECK_GAP;
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if (db->max_ent >= db->maxmaxcode) {
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/* Reset the dictionary only if the ratio is worse,
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* or if it looks as if it has been poisoned
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* by incompressible data.
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* This does not overflow, because
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* db->in_count <= RATIO_MAX.
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new_ratio = db->in_count << RATIO_SCALE_LOG;
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if (db->bytes_out != 0)
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new_ratio /= db->bytes_out;
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if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
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db->ratio = new_ratio;
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bsd_comp_stats(state, stats)
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struct compstat *stats;
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struct bsd_db *db = (struct bsd_db *) state;
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stats->unc_bytes = db->uncomp_bytes;
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stats->unc_packets = db->uncomp_count;
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stats->comp_bytes = db->comp_bytes;
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stats->comp_packets = db->comp_count;
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stats->inc_bytes = db->incomp_bytes;
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stats->inc_packets = db->incomp_count;
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stats->ratio = db->in_count;
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if (stats->ratio <= 0x7fffff)
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* Reset state, as on a CCP ResetReq.
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struct bsd_db *db = (struct bsd_db *) state;
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* Allocate space for a (de) compressor.
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bsd_alloc(options, opt_len, decomp)
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u_int newlen, hsize, hshift, maxmaxcode;
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if (opt_len != 3 || options[0] != CI_BSD_COMPRESS || options[1] != 3
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|| BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
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bits = BSD_NBITS(options[2]);
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case 9: /* needs 82152 for both directions */
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case 10: /* needs 84144 */
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case 11: /* needs 88240 */
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case 12: /* needs 96432 */
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case 13: /* needs 176784 */
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case 14: /* needs 353744 */
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case 15: /* needs 691440 */
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case 16: /* needs 1366160--far too much, */
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/* hsize = 69001; */ /* and 69001 is too big for cptr */
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/* hshift = 8; */ /* in struct bsd_db */
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maxmaxcode = MAXCODE(bits);
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newlen = sizeof(*db) + (hsize-1) * (sizeof(db->dict[0]));
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db = (struct bsd_db *) malloc(newlen);
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memset(db, 0, sizeof(*db) - sizeof(db->dict));
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db->lens = (u_short *) malloc((maxmaxcode+1) * sizeof(db->lens[0]));
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db->maxmaxcode = maxmaxcode;
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struct bsd_db *db = (struct bsd_db *) state;
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bsd_decomp_alloc(options, opt_len)
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return bsd_alloc(options, opt_len, 1);
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* Initialize the database.
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bsd_init(db, options, opt_len, unit, hdrlen, mru, debug, decomp)
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int opt_len, unit, hdrlen, mru, debug, decomp;
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if (opt_len < CILEN_BSD_COMPRESS
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|| options[0] != CI_BSD_COMPRESS || options[1] != CILEN_BSD_COMPRESS
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|| BSD_VERSION(options[2]) != BSD_CURRENT_VERSION
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|| BSD_NBITS(options[2]) != db->maxbits
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|| decomp && db->lens == NULL)
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db->dict[--i].codem1 = BADCODEM1;
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db->dict[i].cptr = 0;
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bsd_decomp_init(state, options, opt_len, unit, hdrlen, mru, debug)
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int opt_len, unit, hdrlen, mru, debug;
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return bsd_init((struct bsd_db *) state, options, opt_len,
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unit, hdrlen, mru, debug, 1);
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* Update the "BSD Compress" dictionary on the receiver for
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* incompressible data by pretending to compress the incoming data.
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bsd_incomp(state, dmsg, mlen)
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struct bsd_db *db = (struct bsd_db *) state;
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u_int hshift = db->hshift;
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u_int max_ent = db->max_ent;
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u_int n_bits = db->n_bits;
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struct bsd_dict *dictp;
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ent = rptr[0]; /* get the protocol */
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if ((ent & 1) == 0 || ent < 0x21 || ent > 0xf9)
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ilen = 1; /* count the protocol as 1 byte */
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slen = dmsg + mlen - rptr;
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for (; slen > 0; --slen) {
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fcode = BSD_KEY(ent, c);
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hval = BSD_HASH(ent, c, hshift);
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dictp = &db->dict[hval];
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/* validate and then check the entry */
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if (dictp->codem1 >= max_ent)
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if (dictp->f.fcode == fcode) {
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ent = dictp->codem1+1;
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continue; /* found (prefix,suffix) */
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/* continue probing until a match or invalid entry */
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disp = (hval == 0) ? 1 : hval;
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if (hval >= db->hsize)
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dictp = &db->dict[hval];
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if (dictp->codem1 >= max_ent)
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} while (dictp->f.fcode != fcode);
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ent = dictp->codem1+1;
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continue; /* finally found (prefix,suffix) */
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nomatch: /* output (count) the prefix */
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/* code -> hashtable */
491
if (max_ent < db->maxmaxcode) {
492
struct bsd_dict *dictp2;
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/* expand code size if needed */
494
if (max_ent >= MAXCODE(n_bits))
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db->n_bits = ++n_bits;
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/* Invalidate previous hash table entry
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* assigned this code, and then take it over.
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dictp2 = &db->dict[max_ent+1];
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if (db->dict[dictp2->cptr].codem1 == max_ent)
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db->dict[dictp2->cptr].codem1 = BADCODEM1;
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dictp->codem1 = max_ent;
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dictp->f.fcode = fcode;
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db->max_ent = ++max_ent;
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db->lens[max_ent] = db->lens[ent]+1;
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bitno += n_bits; /* output (count) the last code */
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db->bytes_out += bitno/8;
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db->in_count += ilen;
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db->incomp_bytes += ilen;
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db->uncomp_bytes += ilen;
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/* Increase code size if we would have without the packet
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* boundary and as the decompressor will.
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if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode)
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* Decompress "BSD Compress"
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* Because of patent problems, we return DECOMP_ERROR for errors
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* found by inspecting the input data and for system problems, but
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* DECOMP_FATALERROR for any errors which could possibly be said to
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* be being detected "after" decompression. For DECOMP_ERROR,
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* we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
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* infringing a patent of Motorola's if we do, so we take CCP down
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* Given that the frame has the correct sequence number and a good FCS,
542
* errors such as invalid codes in the input most likely indicate a
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* bug, so we return DECOMP_FATALERROR for them in order to turn off
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* compression, even though they are detected by inspecting the input.
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bsd_decompress(state, cmsg, inlen, dmp, outlenp)
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struct bsd_db *db = (struct bsd_db *) state;
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u_int max_ent = db->max_ent;
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u_int bitno = 32; /* 1st valid bit in accm */
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u_int n_bits = db->n_bits;
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u_int tgtbitno = 32-n_bits; /* bitno when we have a code */
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struct bsd_dict *dictp;
559
int explen, i, seq, len;
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u_int incode, oldcode, finchar;
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u_char *p, *rptr, *wptr;
563
int dlen, space, codelen, extra;
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++rptr; /* skip protocol (assumed 0xfd) */
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seq = (rptr[0] << 8) + rptr[1];
571
ilen = len = cmsg + inlen - rptr;
574
* Check the sequence number and give up if it is not what we expect.
576
if (seq != db->seqno++) {
578
printf("bsd_decomp%d: bad sequence # %d, expected %d\n",
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db->unit, seq, db->seqno - 1);
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wptr = dmp + db->hdrlen;
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* Accumulate bytes until we have a complete code.
590
* Then get the next code, relying on the 32-bit,
591
* unsigned accm to mask the result.
594
accm |= *rptr++ << bitno;
596
if (tgtbitno < bitno)
598
incode = accm >> tgtbitno;
602
if (incode == CLEAR) {
604
* The dictionary must only be cleared at
605
* the end of a packet. But there could be an
606
* empty message block at the end.
610
printf("bsd_decomp%d: bad CLEAR\n", db->unit);
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return DECOMP_FATALERROR;
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if (incode > max_ent + 2 || incode > db->maxmaxcode
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|| incode > max_ent && oldcode == CLEAR) {
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printf("bsd_decomp%d: bad code 0x%x oldcode=0x%x ",
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db->unit, incode, oldcode);
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printf("max_ent=0x%x dlen=%d seqno=%d\n",
624
max_ent, dlen, db->seqno);
626
return DECOMP_FATALERROR; /* probably a bug */
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/* Special case for KwKwK string. */
630
if (incode > max_ent) {
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codelen = db->lens[finchar];
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explen += codelen + extra;
640
if (explen > db->mru + 1) {
642
printf("bsd_decomp%d: ran out of mru\n", db->unit);
643
return DECOMP_FATALERROR;
647
* Decode this code and install it in the decompressed buffer.
649
p = (wptr += codelen);
650
while (finchar > LAST) {
651
dictp = &db->dict[db->dict[finchar].cptr];
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printf("bsd_decomp%d: fell off end of chain ", db->unit);
656
printf("0x%x at 0x%x by 0x%x, max_ent=0x%x\n",
657
incode, finchar, db->dict[finchar].cptr, max_ent);
658
return DECOMP_FATALERROR;
660
if (dictp->codem1 != finchar-1) {
661
printf("bsd_decomp%d: bad code chain 0x%x finchar=0x%x ",
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db->unit, incode, finchar);
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printf("oldcode=0x%x cptr=0x%x codem1=0x%x\n", oldcode,
664
db->dict[finchar].cptr, dictp->codem1);
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return DECOMP_FATALERROR;
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*--p = dictp->f.hs.suffix;
669
finchar = dictp->f.hs.prefix;
675
printf("bsd_decomp%d: short by %d after code 0x%x, max_ent=0x%x\n",
676
db->unit, codelen, incode, max_ent);
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if (extra) /* the KwKwK case again */
683
* If not first code in a packet, and
684
* if not out of code space, then allocate a new code.
686
* Keep the hash table correct so it can be used
687
* with uncompressed packets.
689
if (oldcode != CLEAR && max_ent < db->maxmaxcode) {
690
struct bsd_dict *dictp2;
694
fcode = BSD_KEY(oldcode,finchar);
695
hval = BSD_HASH(oldcode,finchar,db->hshift);
696
dictp = &db->dict[hval];
698
/* look for a free hash table entry */
699
if (dictp->codem1 < max_ent) {
700
disp = (hval == 0) ? 1 : hval;
703
if (hval >= db->hsize)
705
dictp = &db->dict[hval];
706
} while (dictp->codem1 < max_ent);
710
* Invalidate previous hash table entry
711
* assigned this code, and then take it over
713
dictp2 = &db->dict[max_ent+1];
714
if (db->dict[dictp2->cptr].codem1 == max_ent) {
715
db->dict[dictp2->cptr].codem1 = BADCODEM1;
718
dictp->codem1 = max_ent;
719
dictp->f.fcode = fcode;
721
db->max_ent = ++max_ent;
722
db->lens[max_ent] = db->lens[oldcode]+1;
724
/* Expand code size if needed. */
725
if (max_ent >= MAXCODE(n_bits) && max_ent < db->maxmaxcode) {
726
db->n_bits = ++n_bits;
727
tgtbitno = 32-n_bits;
732
*outlenp = wptr - (dmp + db->hdrlen);
735
* Keep the checkpoint right so that incompressible packets
736
* clear the dictionary at the right times.
738
db->bytes_out += ilen;
739
db->in_count += explen;
740
if (bsd_check(db) && db->debug) {
741
printf("bsd_decomp%d: peer should have cleared dictionary\n",
746
db->comp_bytes += ilen + BSD_OVHD;
748
db->uncomp_bytes += explen;
752
#endif /* DO_BSD_COMPRESS */
added
removed
pppdump/bsd-comp.c
