/*-
* Copyright (c) 2002-2004 Jan Dubiec <jdx@slackware.pl>
* Copyright (c) 2007 Alexander Motin <mav@freebsd.org>
* All rights reserved.
*
* 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 unmodified, 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/
/*
* MPPC decompression library.
* Version 1.0
*
* Note that Hi/Fn (later acquired by Exar Corporation) held US patents
* on some implementation-critical aspects of MPPC compression.
* These patents lapsed due to non-payment of fees in 2007 and by 2015
* expired altogether.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <net/mppc.h>
#define MPPE_HIST_LEN 8192
#define HASH(x) (((40543*(((((x)[0]<<4)^(x)[1])<<4)^(x)[2]))>>4) & 0x1fff)
struct MPPC_comp_state {
uint8_t hist[2*MPPE_HIST_LEN];
uint16_t histptr;
uint16_t hash[MPPE_HIST_LEN];
};
/* Inserts 1 to 8 bits into the output buffer. */
static void __inline
putbits8(uint8_t *buf, uint32_t val, const uint32_t n, uint32_t *i, uint32_t *l)
{
buf += *i;
if (*l >= n) {
*l = (*l) - n;
val <<= *l;
*buf = *buf | (val & 0xff);
if (*l == 0) {
*l = 8;
(*i)++;
*(++buf) = 0;
}
} else {
(*i)++;
*l = 8 - n + (*l);
val <<= *l;
*buf = *buf | ((val >> 8) & 0xff);
*(++buf) = val & 0xff;
}
}
/* Inserts 9 to 16 bits into the output buffer. */
static void __inline
putbits16(uint8_t *buf, uint32_t val, const uint32_t n, uint32_t *i, uint32_t *l)
{
buf += *i;
if (*l >= n - 8) {
(*i)++;
*l = 8 - n + (*l);
val <<= *l;
*buf = *buf | ((val >> 8) & 0xff);
*(++buf) = val & 0xff;
if (*l == 0) {
*l = 8;
(*i)++;
*(++buf) = 0;
}
} else {
(*i)++; (*i)++;
*l = 16 - n + (*l);
val <<= *l;
*buf = *buf | ((val >> 16) & 0xff);
*(++buf) = (val >> 8) & 0xff;
*(++buf) = val & 0xff;
}
}
/* Inserts 17 to 24 bits into the output buffer. */
static void __inline
putbits24(uint8_t *buf, uint32_t val, const uint32_t n, uint32_t *i, uint32_t *l)
{
buf += *i;
if (*l >= n - 16) {
(*i)++; (*i)++;
*l = 16 - n + (*l);
val <<= *l;
*buf = *buf | ((val >> 16) & 0xff);
*(++buf) = (val >> 8) & 0xff;
*(++buf) = val & 0xff;
if (*l == 0) {
*l = 8;
(*i)++;
*(++buf) = 0;
}
} else {
(*i)++; (*i)++; (*i)++;
*l = 24 - n + (*l);
val <<= *l;
*buf = *buf | ((val >> 24) & 0xff);
*(++buf) = (val >> 16) & 0xff;
*(++buf) = (val >> 8) & 0xff;
*(++buf) = val & 0xff;
}
}
size_t MPPC_SizeOfCompressionHistory(void)
{
return (sizeof(struct MPPC_comp_state));
}
void MPPC_InitCompressionHistory(char *history)
{
struct MPPC_comp_state *state = (struct MPPC_comp_state*)history;
bzero(history, sizeof(struct MPPC_comp_state));
state->histptr = MPPE_HIST_LEN;
}
int MPPC_Compress(u_char **src, u_char **dst, u_long *srcCnt, u_long *dstCnt, char *history, int flags, int undef)
{
struct MPPC_comp_state *state = (struct MPPC_comp_state*)history;
uint32_t olen, off, len, idx, i, l;
uint8_t *hist, *sbuf, *p, *q, *r, *s;
int rtn = MPPC_OK;
/*
* At this point, to avoid possible buffer overflow caused by packet
* expansion during/after compression, we should make sure we have
* space for the worst case.
* Maximum MPPC packet expansion is 12.5%. This is the worst case when
* all octets in the input buffer are >= 0x80 and we cannot find any
* repeated tokens.
*/
if (*dstCnt < (*srcCnt * 9 / 8 + 2)) {
rtn &= ~MPPC_OK;
return (rtn);
}
/* We can't compress more then MPPE_HIST_LEN bytes in a call. */
if (*srcCnt > MPPE_HIST_LEN) {
rtn &= ~MPPC_OK;
return (rtn);
}
hist = state->hist + MPPE_HIST_LEN;
/* check if there is enough room at the end of the history */
if (state->histptr + *srcCnt >= 2*MPPE_HIST_LEN) {
rtn |= MPPC_RESTART_HISTORY;
state->histptr = MPPE_HIST_LEN;
memcpy(state->hist, hist, MPPE_HIST_LEN);
}
/* Add packet to the history. */
sbuf = state->hist + state->histptr;
memcpy(sbuf, *src, *srcCnt);
state->histptr += *srcCnt;
/* compress data */
r = sbuf + *srcCnt;
**dst = olen = i = 0;
l = 8;
while (i < *srcCnt - 2) {
s = q = sbuf + i;
/* Prognose matching position using hash function. */
idx = HASH(s);
p = hist + state->hash[idx];
state->hash[idx] = (uint16_t) (s - hist);
if (p > s) /* It was before MPPC_RESTART_HISTORY. */
p -= MPPE_HIST_LEN; /* Try previous history buffer. */
off = s - p;
/* Check our prognosis. */
if (off > MPPE_HIST_LEN - 1 || off < 1 || *p++ != *s++ ||
*p++ != *s++ || *p++ != *s++) {
/* No match found; encode literal byte. */
if ((*src)[i] < 0x80) { /* literal byte < 0x80 */
putbits8(*dst, (uint32_t) (*src)[i], 8, &olen, &l);
} else { /* literal byte >= 0x80 */
putbits16(*dst, (uint32_t) (0x100|((*src)[i]&0x7f)), 9,
&olen, &l);
}
++i;
continue;
}
/* Find length of the matching fragment */
#if defined(__amd64__) || defined(__i386__)
/* Optimization for CPUs without strict data aligning requirements */
while ((*((uint32_t*)p) == *((uint32_t*)s)) && (s < (r - 3))) {
p+=4;
s+=4;
}
#endif
while((*p++ == *s++) && (s <= r));
len = s - q - 1;
i += len;
/* At least 3 character match found; code data. */
/* Encode offset. */
if (off < 64) { /* 10-bit offset; 0 <= offset < 64 */
putbits16(*dst, 0x3c0|off, 10, &olen, &l);
} else if (off < 320) { /* 12-bit offset; 64 <= offset < 320 */
putbits16(*dst, 0xe00|(off-64), 12, &olen, &l);
} else if (off < 8192) { /* 16-bit offset; 320 <= offset < 8192 */
putbits16(*dst, 0xc000|(off-320), 16, &olen, &l);
} else { /* NOTREACHED */
__assert_unreachable();
rtn &= ~MPPC_OK;
return (rtn);
}
/* Encode length of match. */
if (len < 4) { /* length = 3 */
putbits8(*dst, 0, 1, &olen, &l);
} else if (len < 8) { /* 4 <= length < 8 */
putbits8(*dst, 0x08|(len&0x03), 4, &olen, &l);
} else if (len < 16) { /* 8 <= length < 16 */
putbits8(*dst, 0x30|(len&0x07), 6, &olen, &l);
} else if (len < 32) { /* 16 <= length < 32 */
putbits8(*dst, 0xe0|(len&0x0f), 8, &olen, &l);
} else if (len < 64) { /* 32 <= length < 64 */
putbits16(*dst, 0x3c0|(len&0x1f), 10, &olen, &l);
} else if (len < 128) { /* 64 <= length < 128 */
putbits16(*dst, 0xf80|(len&0x3f), 12, &olen, &l);
} else if (len < 256) { /* 128 <= length < 256 */
putbits16(*dst, 0x3f00|(len&0x7f), 14, &olen, &l);
} else if (len < 512) { /* 256 <= length < 512 */
putbits16(*dst, 0xfe00|(len&0xff), 16, &olen, &l);
} else if (len < 1024) { /* 512 <= length < 1024 */
putbits24(*dst, 0x3fc00|(len&0x1ff), 18, &olen, &l);
} else if (len < 2048) { /* 1024 <= length < 2048 */
putbits24(*dst, 0xff800|(len&0x3ff), 20, &olen, &l);
} else if (len < 4096) { /* 2048 <= length < 4096 */
putbits24(*dst, 0x3ff000|(len&0x7ff), 22, &olen, &l);
} else if (len < 8192) { /* 4096 <= length < 8192 */
putbits24(*dst, 0xffe000|(len&0xfff), 24, &olen, &l);
} else { /* NOTREACHED */
rtn &= ~MPPC_OK;
return (rtn);
}
}
/* Add remaining octets to the output. */
while(*srcCnt - i > 0) {
if ((*src)[i] < 0x80) { /* literal byte < 0x80 */
putbits8(*dst, (uint32_t) (*src)[i++], 8, &olen, &l);
} else { /* literal byte >= 0x80 */
putbits16(*dst, (uint32_t) (0x100|((*src)[i++]&0x7f)), 9, &olen,
&l);
}
}
/* Reset unused bits of the last output octet. */
if ((l != 0) && (l != 8)) {
putbits8(*dst, 0, l, &olen, &l);
}
/* If result is bigger then original, set flag and flush history. */
if ((*srcCnt < olen) || ((flags & MPPC_SAVE_HISTORY) == 0)) {
if (*srcCnt < olen)
rtn |= MPPC_EXPANDED;
bzero(history, sizeof(struct MPPC_comp_state));
state->histptr = MPPE_HIST_LEN;
}
*src += *srcCnt;
*srcCnt = 0;
*dst += olen;
*dstCnt -= olen;
return (rtn);
}
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