📄 bsd_comp.c
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//==========================================================================
//
// src/bsd_comp.c
//
//==========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Portions created by Nick Garnett are
// Copyright (C) 2003 eCosCentric Ltd.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License along
// with eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
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// in accordance with section (3) of the GNU General Public License.
//
// This exception does not invalidate any other reasons why a work based on
// this file might be covered by the GNU General Public License.
//
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//####BSDCOPYRIGHTBEGIN####
//
// -------------------------------------------
//
// Portions of this software may have been derived from OpenBSD,
// FreeBSD or other sources, and are covered by the appropriate
// copyright disclaimers included herein.
//
// -------------------------------------------
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//####BSDCOPYRIGHTEND####
//==========================================================================
/* Because this code is derived from the 4.3BSD compress source:
*
*
* Copyright (c) 1985, 1986 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* James A. Woods, derived from original work by Spencer Thomas
* and Joseph Orost.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* This version is for use with mbufs on BSD-derived systems.
*
* $FreeBSD: src/sys/net/bsd_comp.c,v 1.11 1999/08/28 00:48:14 peter Exp $
*/
#define _KERNEL
#include <sys/param.h>
//#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <cyg/ppp/net/ppp_defs.h>
#define PACKETPTR struct mbuf *
#include <cyg/ppp/net/ppp_comp.h>
#if DO_BSD_COMPRESS
/*
* PPP "BSD compress" compression
* The differences between this compression and the classic BSD LZW
* source are obvious from the requirement that the classic code worked
* with files while this handles arbitrarily long streams that
* are broken into packets. They are:
*
* When the code size expands, a block of junk is not emitted by
* the compressor and not expected by the decompressor.
*
* New codes are not necessarily assigned every time an old
* code is output by the compressor. This is because a packet
* end forces a code to be emitted, but does not imply that a
* new sequence has been seen.
*
* The compression ratio is checked at the first end of a packet
* after the appropriate gap. Besides simplifying and speeding
* things up, this makes it more likely that the transmitter
* and receiver will agree when the dictionary is cleared when
* compression is not going well.
*/
/*
* A dictionary for doing BSD compress.
*/
struct bsd_db {
int totlen; /* length of this structure */
u_int hsize; /* size of the hash table */
u_char hshift; /* used in hash function */
u_char n_bits; /* current bits/code */
u_char maxbits;
u_char debug;
u_char unit;
u_int16_t seqno; /* sequence # of next packet */
u_int hdrlen; /* header length to preallocate */
u_int mru;
u_int maxmaxcode; /* largest valid code */
u_int max_ent; /* largest code in use */
u_int in_count; /* uncompressed bytes, aged */
u_int bytes_out; /* compressed bytes, aged */
u_int ratio; /* recent compression ratio */
u_int checkpoint; /* when to next check the ratio */
u_int clear_count; /* times dictionary cleared */
u_int incomp_count; /* incompressible packets */
u_int incomp_bytes; /* incompressible bytes */
u_int uncomp_count; /* uncompressed packets */
u_int uncomp_bytes; /* uncompressed bytes */
u_int comp_count; /* compressed packets */
u_int comp_bytes; /* compressed bytes */
u_int16_t *lens; /* array of lengths of codes */
struct bsd_dict {
union { /* hash value */
u_int32_t fcode;
struct {
#if BYTE_ORDER == LITTLE_ENDIAN
u_int16_t prefix; /* preceding code */
u_char suffix; /* last character of new code */
u_char pad;
#else
u_char pad;
u_char suffix; /* last character of new code */
u_int16_t prefix; /* preceding code */
#endif
} hs;
} f;
u_int16_t codem1; /* output of hash table -1 */
u_int16_t cptr; /* map code to hash table entry */
} dict[1];
};
#define BSD_OVHD 2 /* BSD compress overhead/packet */
#define BSD_INIT_BITS BSD_MIN_BITS
static void bsd_clear __P((struct bsd_db *db));
static int bsd_check __P((struct bsd_db *db));
static void *bsd_alloc __P((u_char *options, int opt_len, int decomp));
static int bsd_init __P((struct bsd_db *db, u_char *options, int opt_len,
int unit, int hdrlen, int mru, int debug,
int decomp));
static void *bsd_comp_alloc __P((u_char *options, int opt_len));
static void *bsd_decomp_alloc __P((u_char *options, int opt_len));
static void bsd_free __P((void *state));
static int bsd_comp_init __P((void *state, u_char *options, int opt_len,
int unit, int hdrlen, int debug));
static int bsd_decomp_init __P((void *state, u_char *options, int opt_len,
int unit, int hdrlen, int mru, int debug));
static int bsd_compress __P((void *state, struct mbuf **mret,
struct mbuf *mp, int slen, int maxolen));
static void bsd_incomp __P((void *state, struct mbuf *dmsg));
static int bsd_decompress __P((void *state, struct mbuf *cmp,
struct mbuf **dmpp));
static void bsd_reset __P((void *state));
static void bsd_comp_stats __P((void *state, struct compstat *stats));
/*
* Procedures exported to if_ppp.c.
*/
struct compressor ppp_bsd_compress = {
CI_BSD_COMPRESS, /* compress_proto */
bsd_comp_alloc, /* comp_alloc */
bsd_free, /* comp_free */
bsd_comp_init, /* comp_init */
bsd_reset, /* comp_reset */
bsd_compress, /* compress */
bsd_comp_stats, /* comp_stat */
bsd_decomp_alloc, /* decomp_alloc */
bsd_free, /* decomp_free */
bsd_decomp_init, /* decomp_init */
bsd_reset, /* decomp_reset */
bsd_decompress, /* decompress */
bsd_incomp, /* incomp */
bsd_comp_stats, /* decomp_stat */
};
/*
* the next two codes should not be changed lightly, as they must not
* lie within the contiguous general code space.
*/
#define CLEAR 256 /* table clear output code */
#define FIRST 257 /* first free entry */
#define LAST 255
#define MAXCODE(b) ((1 << (b)) - 1)
#define BADCODEM1 MAXCODE(BSD_MAX_BITS)
#define BSD_HASH(prefix,suffix,hshift) ((((u_int32_t)(suffix)) << (hshift)) \ ^ (u_int32_t)(prefix))
#define BSD_KEY(prefix,suffix) ((((u_int32_t)(suffix)) << 16) \ + (u_int32_t)(prefix))
#define CHECK_GAP 10000 /* Ratio check interval */
#define RATIO_SCALE_LOG 8
#define RATIO_SCALE (1<<RATIO_SCALE_LOG)
#define RATIO_MAX (0x7fffffff>>RATIO_SCALE_LOG)
/*
* clear the dictionary
*/
static void
bsd_clear(db)
struct bsd_db *db;
{
db->clear_count++;
db->max_ent = FIRST-1;
db->n_bits = BSD_INIT_BITS;
db->ratio = 0;
db->bytes_out = 0;
db->in_count = 0;
db->checkpoint = CHECK_GAP;
}
/*
* If the dictionary is full, then see if it is time to reset it.
*
* Compute the compression ratio using fixed-point arithmetic
* with 8 fractional bits.
*
* Since we have an infinite stream instead of a single file,
* watch only the local compression ratio.
*
* Since both peers must reset the dictionary at the same time even in
* the absence of CLEAR codes (while packets are incompressible), they
* must compute the same ratio.
*/
static int /* 1=output CLEAR */
bsd_check(db)
struct bsd_db *db;
{
u_int new_ratio;
if (db->in_count >= db->checkpoint) {
/* age the ratio by limiting the size of the counts */
if (db->in_count >= RATIO_MAX
|| db->bytes_out >= RATIO_MAX) {
db->in_count -= db->in_count/4;
db->bytes_out -= db->bytes_out/4;
}
db->checkpoint = db->in_count + CHECK_GAP;
if (db->max_ent >= db->maxmaxcode) {
/* Reset the dictionary only if the ratio is worse,
* or if it looks as if it has been poisoned
* by incompressible data.
*
* This does not overflow, because
* db->in_count <= RATIO_MAX.
*/
new_ratio = db->in_count << RATIO_SCALE_LOG;
if (db->bytes_out != 0)
new_ratio /= db->bytes_out;
if (new_ratio < db->ratio || new_ratio < 1 * RATIO_SCALE) {
bsd_clear(db);
return 1;
}
db->ratio = new_ratio;
}
}
return 0;
}
/*
* Return statistics.
*/
static void
bsd_comp_stats(state, stats)
void *state;
struct compstat *stats;
{
struct bsd_db *db = (struct bsd_db *) state;
u_int out;
stats->unc_bytes = db->uncomp_bytes;
stats->unc_packets = db->uncomp_count;
stats->comp_bytes = db->comp_bytes;
stats->comp_packets = db->comp_count;
stats->inc_bytes = db->incomp_bytes;
stats->inc_packets = db->incomp_count;
stats->ratio = db->in_count;
out = db->bytes_out;
if (stats->ratio <= 0x7fffff)
stats->ratio <<= 8;
else
out >>= 8;
if (out != 0)
stats->ratio /= out;
}
/*
* Reset state, as on a CCP ResetReq.
*/
static void
bsd_reset(state)
void *state;
{
struct bsd_db *db = (struct bsd_db *) state;
db->seqno = 0;
bsd_clear(db);
db->clear_count = 0;
}
/*
* Allocate space for a (de) compressor.
*/
static void *
bsd_alloc(options, opt_len, decomp)
u_char *options;
int opt_len, decomp;
{
int bits;
u_int newlen, hsize, hshift, maxmaxcode;
struct bsd_db *db;
if (opt_len < CILEN_BSD_COMPRESS || options[0] != CI_BSD_COMPRESS
|| options[1] != CILEN_BSD_COMPRESS
|| BSD_VERSION(options[2]) != BSD_CURRENT_VERSION)
return NULL;
bits = BSD_NBITS(options[2]);
switch (bits) {
case 9: /* needs 82152 for both directions */
case 10: /* needs 84144 */
case 11: /* needs 88240 */
case 12: /* needs 96432 */
hsize = 5003;
hshift = 4;
break;
case 13: /* needs 176784 */
hsize = 9001;
hshift = 5;
break;
case 14: /* needs 353744 */
hsize = 18013;
hshift = 6;
break;
case 15: /* needs 691440 */
hsize = 35023;
hshift = 7;
break;
case 16: /* needs 1366160--far too much, */
/* hsize = 69001; */ /* and 69001 is too big for cptr */
/* hshift = 8; */ /* in struct bsd_db */
/* break; */
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