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ng_mppc(4): Bring netgraph(3) MPPC compression support.

Browse Source 
Support for compression has been available from July 2007 but it
was never imported due to concerns with patents once held by
STAC/HiFn. The issues have clearly been resolved so bring it
in now.

Special thanks to Brett Glass for preserving the code and
pointing documentation for the expiration case.

Obtained from:	mav (through Brett Glass)
Relnotes:	yes
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D6739
This commit is contained in:
Pedro F. Giffuni 2016-06-07 15:07:00 +00:00
parent 43ce40e891
commit c3fb425204
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=301549
4 changed files with 646 additions and 2 deletions
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3
sys/modules/netgraph/mppc/Makefile
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@ -4,11 +4,10 @@
KMOD= ng_mppc
SRCS= ng_mppc.c opt_netgraph.h
NETGRAPH_MPPC_COMPRESSION?= 0
NETGRAPH_MPPC_COMPRESSION?= 1
NETGRAPH_MPPC_ENCRYPTION?= 1
.if ${NETGRAPH_MPPC_COMPRESSION} > 0
# XXX These files don't exist yet, but hopefully someday they will...
.PATH: ${.CURDIR}/../../../net
SRCS+= mppcc.c mppcd.c
.endif

62
sys/net/mppc.h Normal file
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@ -0,0 +1,62 @@
/*-
* 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.
*
* $FreeBSD$
*/
/*
* 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.
*/
#ifndef _NET_MPPC_H_
#define _NET_MPPC_H_
#define MPPC_MANDATORY_COMPRESS_FLAGS 0
#define MPPC_MANDATORY_DECOMPRESS_FLAGS 0
#define MPPC_SAVE_HISTORY 1
#define MPPC_OK 5
#define MPPC_EXPANDED 8
#define MPPC_RESTART_HISTORY 16
#define MPPC_DEST_EXHAUSTED 32
extern size_t MPPC_SizeOfCompressionHistory(void);
extern size_t MPPC_SizeOfDecompressionHistory(void);
extern void MPPC_InitCompressionHistory(char *history);
extern void MPPC_InitDecompressionHistory(char *history);
extern int MPPC_Compress(u_char **src, u_char **dst, u_long *srcCnt, u_long *dstCnt, char *history, int flags, int undef);
extern int MPPC_Decompress(u_char **src, u_char **dst, u_long *srcCnt, u_long *dstCnt, char *history, int flags);
#endif

299
sys/net/mppcc.c Normal file
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@ -0,0 +1,299 @@
/*-
* 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.
*
* $FreeBSD$
*/
/*
* 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 */
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);
}

284
sys/net/mppcd.c Normal file
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@ -0,0 +1,284 @@
/*-
* 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.
*
* $FreeBSD$
*/
/*
* 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
struct MPPC_decomp_state {
uint8_t hist[2*MPPE_HIST_LEN];
uint16_t histptr;
};
static uint32_t __inline
getbits(const uint8_t *buf, const uint32_t n, uint32_t *i, uint32_t *l)
{
static const uint32_t m[] = {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
uint32_t res, ol;
ol = *l;
if (*l >= n) {
*l = (*l) - n;
res = (buf[*i] & m[ol]) >> (*l);
if (*l == 0) {
*l = 8;
(*i)++;
}
} else {
*l = 8 - n + (*l);
res = (buf[(*i)++] & m[ol]) << 8;
res = (res | buf[*i]) >> (*l);
}
return (res);
}
static uint32_t __inline
getbyte(const uint8_t *buf, const uint32_t i, const uint32_t l)
{
if (l == 8) {
return (buf[i]);
} else {
return ((((buf[i] << 8) | buf[i+1]) >> l) & 0xff);
}
}
static void __inline
lamecopy(uint8_t *dst, uint8_t *src, uint32_t len)
{
while (len--)
*dst++ = *src++;
}
size_t MPPC_SizeOfDecompressionHistory(void)
{
return (sizeof(struct MPPC_decomp_state));
}
void MPPC_InitDecompressionHistory(char *history)
{
struct MPPC_decomp_state *state = (struct MPPC_decomp_state*)history;
bzero(history, sizeof(struct MPPC_decomp_state));
state->histptr = MPPE_HIST_LEN;
}
int MPPC_Decompress(u_char **src, u_char **dst, u_long *srcCnt, u_long *dstCnt, char *history, int flags)
{
struct MPPC_decomp_state *state = (struct MPPC_decomp_state*)history;
uint32_t olen, off, len, bits, val, sig, i, l;
uint8_t *hist, *s;
u_char *isrc = *src;
int rtn = MPPC_OK;
if ((flags & MPPC_RESTART_HISTORY) != 0) {
memcpy(state->hist, state->hist + MPPE_HIST_LEN, MPPE_HIST_LEN);
state->histptr = MPPE_HIST_LEN;
}
hist = state->hist + state->histptr;
olen = len = i = 0;
l = 8;
bits = *srcCnt * 8;
while (bits >= 8) {
val = getbyte(isrc, i++, l);
if (val < 0x80) { /* literal byte < 0x80 */
if (state->histptr < 2*MPPE_HIST_LEN) {
/* Copy uncompressed byte to the history. */
(state->hist)[(state->histptr)++] = (uint8_t) val;
} else {
/* Buffer overflow; drop packet. */
rtn &= ~MPPC_OK;
return rtn;
}
olen++;
bits -= 8;
continue;
}
sig = val & 0xc0;
if (sig == 0x80) { /* literal byte >= 0x80 */
if (state->histptr < 2*MPPE_HIST_LEN) {
/* Copy uncompressed byte to the history. */
(state->hist)[(state->histptr)++] =
(uint8_t) (0x80|((val&0x3f)<<1)|getbits(isrc, 1 , &i ,&l));
} else {
/* buffer overflow; drop packet */
rtn &= ~MPPC_OK;
return (rtn);
}
olen++;
bits -= 9;
continue;
}
/* Not a literal byte so it must be an (offset,length) pair */
/* decode offset */
sig = val & 0xf0;
if (sig == 0xf0) { /* 10-bit offset; 0 <= offset < 64 */
off = (((val&0x0f)<<2)|getbits(isrc, 2 , &i ,&l));
bits -= 10;
} else {
if (sig == 0xe0) { /* 12-bit offset; 64 <= offset < 320 */
off = ((((val&0x0f)<<4)|getbits(isrc, 4 , &i ,&l))+64);
bits -= 12;
} else {
if ((sig&0xe0) == 0xc0) {/* 16-bit offset; 320 <= offset < 8192 */
off = ((((val&0x1f)<<8)|getbyte(isrc, i++, l))+320);
bits -= 16;
if (off > MPPE_HIST_LEN - 1) {
rtn &= ~MPPC_OK;
return (rtn);
}
} else { /* NOTREACHED */
rtn &= ~MPPC_OK;
return (rtn);
}
}
}
/* Decode length of match. */
val = getbyte(isrc, i, l);
if ((val & 0x80) == 0x00) { /* len = 3 */
len = 3;
bits--;
getbits(isrc, 1 , &i ,&l);
} else if ((val & 0xc0) == 0x80) { /* 4 <= len < 8 */
len = 0x04 | ((val>>4) & 0x03);
bits -= 4;
getbits(isrc, 4 , &i ,&l);
} else if ((val & 0xe0) == 0xc0) { /* 8 <= len < 16 */
len = 0x08 | ((val>>2) & 0x07);
bits -= 6;
getbits(isrc, 6 , &i ,&l);
} else if ((val & 0xf0) == 0xe0) { /* 16 <= len < 32 */
len = 0x10 | (val & 0x0f);
bits -= 8;
i++;
} else {
bits -= 8;
val = (val << 8) | getbyte(isrc, ++i, l);
if ((val & 0xf800) == 0xf000) { /* 32 <= len < 64 */
len = 0x0020 | ((val >> 6) & 0x001f);
bits -= 2;
getbits(isrc, 2 , &i ,&l);
} else if ((val & 0xfc00) == 0xf800) { /* 64 <= len < 128 */
len = 0x0040 | ((val >> 4) & 0x003f);
bits -= 4;
getbits(isrc, 4 , &i ,&l);
} else if ((val & 0xfe00) == 0xfc00) { /* 128 <= len < 256 */
len = 0x0080 | ((val >> 2) & 0x007f);
bits -= 6;
getbits(isrc, 6 , &i ,&l);
} else if ((val & 0xff00) == 0xfe00) { /* 256 <= len < 512 */
len = 0x0100 | (val & 0x00ff);
bits -= 8;
i++;
} else {
bits -= 8;
val = (val << 8) | getbyte(isrc, ++i, l);
if ((val & 0xff8000) == 0xff0000) { /* 512 <= len < 1024 */
len = 0x000200 | ((val >> 6) & 0x0001ff);
bits -= 2;
getbits(isrc, 2 , &i ,&l);
} else if ((val & 0xffc000) == 0xff8000) {/* 1024 <= len < 2048 */
len = 0x000400 | ((val >> 4) & 0x0003ff);
bits -= 4;
getbits(isrc, 4 , &i ,&l);
} else if ((val & 0xffe000) == 0xffc000) {/* 2048 <= len < 4096 */
len = 0x000800 | ((val >> 2) & 0x0007ff);
bits -= 6;
getbits(isrc, 6 , &i ,&l);
} else if ((val & 0xfff000) == 0xffe000) {/* 4096 <= len < 8192 */
len = 0x001000 | (val & 0x000fff);
bits -= 8;
i++;
} else { /* NOTREACHED */
rtn &= ~MPPC_OK;
return (rtn);
}
}
}
s = state->hist + state->histptr;
state->histptr += len;
olen += len;
if (state->histptr < 2*MPPE_HIST_LEN) {
/* Copy uncompressed bytes to the history. */
/*
* In some cases len may be greater than off. It means that memory
* areas pointed by s and s-off overlap. To decode that strange case
* data should be copied exactly by address increasing to make
* some data repeated.
*/
lamecopy(s, s - off, len);
} else {
/* Buffer overflow; drop packet. */
rtn &= ~MPPC_OK;
return (rtn);
}
}
/* Do PFC decompression. */
len = olen;
if ((hist[0] & 0x01) != 0) {
(*dst)[0] = 0;
(*dst)++;
len++;
}
if (len <= *dstCnt) {
/* Copy uncompressed packet to the output buffer. */
memcpy(*dst, hist, olen);
} else {
/* Buffer overflow; drop packet. */
rtn |= MPPC_DEST_EXHAUSTED;
}
*src += *srcCnt;
*srcCnt = 0;
*dst += len;
*dstCnt -= len;
return (rtn);
}