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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
*/
/*
* We keep our own copy of this algorithm for 3 main reasons:
* 1. If we didn't, anyone modifying common/os/compress.c would
* directly break our on disk format
* 2. Our version of lzjb does not have a number of checks that the
* common/os version needs and uses
* 3. We initialize the lempel to ensure deterministic results,
* so that identical blocks can always be deduplicated.
* In particular, we are adding the "feature" that compress() can
* take a destination buffer size and returns the compressed length, or the
* source length if compression would overflow the destination buffer.
*/
#include <sys/types.h>
#define MATCH_BITS 6
#define MATCH_MIN 3
#define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
#define LEMPEL_SIZE 1024
/*ARGSUSED*/
size_t
lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
uchar_t *src = s_start;
uchar_t *dst = d_start;
uchar_t *cpy, *copymap = NULL;
int copymask = 1 << (NBBY - 1);
int mlen, offset, hash;
uint16_t *hp;
uint16_t lempel[LEMPEL_SIZE] = { 0 };
while (src < (uchar_t *)s_start + s_len) {
if ((copymask <<= 1) == (1 << NBBY)) {
if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY)
return (s_len);
copymask = 1;
copymap = dst;
*dst++ = 0;
}
if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {
*dst++ = *src++;
continue;
}
hash = (src[0] << 16) + (src[1] << 8) + src[2];
hash += hash >> 9;
hash += hash >> 5;
hp = &lempel[hash & (LEMPEL_SIZE - 1)];
offset = (intptr_t)(src - *hp) & OFFSET_MASK;
*hp = (uint16_t)(uintptr_t)src;
cpy = src - offset;
if (cpy >= (uchar_t *)s_start && cpy != src &&
src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {
*copymap |= copymask;
for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)
if (src[mlen] != cpy[mlen])
break;
*dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |
(offset >> NBBY);
*dst++ = (uchar_t)offset;
src += mlen;
} else {
*dst++ = *src++;
}
}
return (dst - (uchar_t *)d_start);
}
/*ARGSUSED*/
int
lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
uchar_t *src = s_start;
uchar_t *dst = d_start;
uchar_t *d_end = (uchar_t *)d_start + d_len;
uchar_t *cpy, copymap = 0;
int copymask = 1 << (NBBY - 1);
while (dst < d_end) {
if ((copymask <<= 1) == (1 << NBBY)) {
copymask = 1;
copymap = *src++;
}
if (copymap & copymask) {
int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
src += 2;
if ((cpy = dst - offset) < (uchar_t *)d_start)
return (-1);
while (--mlen >= 0 && dst < d_end)
*dst++ = *cpy++;
} else {
*dst++ = *src++;
}
}
return (0);
}
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