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October 10, 2015 23:40
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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/zfs_context.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; | |
uchar_t *copymap = NULL; | |
int copymask = 1 << (NBBY - 1); | |
int mlen, offset, hash; | |
uint16_t *hp; | |
uint16_t *lempel; | |
lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP); | |
while (src < (uchar_t *)s_start + s_len) { | |
if ((copymask <<= 1) == (1 << NBBY)) { | |
if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) { | |
kmem_free(lempel, | |
LEMPEL_SIZE*sizeof (uint16_t)); | |
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++; | |
} | |
} | |
kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t)); | |
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; | |
uchar_t 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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