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