f0a75d274a
ZFS file system was ported from OpenSolaris operating system. The code in under CDDL license. I'd like to thank all SUN developers that created this great piece of software. Supported by: Wheel LTD (http://www.wheel.pl/) Supported by: The FreeBSD Foundation (http://www.freebsdfoundation.org/) Supported by: Sentex (http://www.sentex.net/)
130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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#pragma ident "%Z%%M% %I% %E% SMI"
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/*
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* We keep our own copy of this algorithm for 2 main reasons:
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* 1. If we didn't, anyone modifying common/os/compress.c would
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* directly break our on disk format
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* 2. Our version of lzjb does not have a number of checks that the
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* common/os version needs and uses
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* In particular, we are adding the "feature" that compress() can
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* take a destination buffer size and return -1 if the data will not
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* compress to d_len or less.
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*/
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#include <sys/zfs_context.h>
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#include <sys/types.h>
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#define MATCH_BITS 6
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#define MATCH_MIN 3
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#define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
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#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
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#define LEMPEL_SIZE 256
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/*ARGSUSED*/
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size_t
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lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
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{
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uchar_t *src = s_start;
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uchar_t *dst = d_start;
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uchar_t *cpy, *copymap;
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int copymask = 1 << (NBBY - 1);
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int mlen, offset;
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uint16_t *hp;
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uint16_t lempel[LEMPEL_SIZE]; /* uninitialized; see above */
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while (src < (uchar_t *)s_start + s_len) {
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if ((copymask <<= 1) == (1 << NBBY)) {
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if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) {
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if (d_len != s_len)
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return (s_len);
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mlen = s_len;
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for (src = s_start, dst = d_start; mlen; mlen--)
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*dst++ = *src++;
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return (s_len);
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}
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copymask = 1;
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copymap = dst;
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*dst++ = 0;
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}
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if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {
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*dst++ = *src++;
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continue;
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}
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hp = &lempel[((src[0] + 13) ^ (src[1] - 13) ^ src[2]) &
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(LEMPEL_SIZE - 1)];
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offset = (intptr_t)(src - *hp) & OFFSET_MASK;
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*hp = (uint16_t)(uintptr_t)src;
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cpy = src - offset;
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if (cpy >= (uchar_t *)s_start && cpy != src &&
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src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {
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*copymap |= copymask;
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for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)
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if (src[mlen] != cpy[mlen])
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break;
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*dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |
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(offset >> NBBY);
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*dst++ = (uchar_t)offset;
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src += mlen;
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} else {
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*dst++ = *src++;
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}
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}
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return (dst - (uchar_t *)d_start);
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}
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/*ARGSUSED*/
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int
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lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
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{
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uchar_t *src = s_start;
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uchar_t *dst = d_start;
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uchar_t *d_end = (uchar_t *)d_start + d_len;
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uchar_t *cpy, copymap;
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int copymask = 1 << (NBBY - 1);
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while (dst < d_end) {
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if ((copymask <<= 1) == (1 << NBBY)) {
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copymask = 1;
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copymap = *src++;
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}
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if (copymap & copymask) {
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int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
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int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
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src += 2;
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if ((cpy = dst - offset) < (uchar_t *)d_start)
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return (-1);
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while (--mlen >= 0 && dst < d_end)
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*dst++ = *cpy++;
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} else {
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*dst++ = *src++;
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}
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}
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return (0);
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}
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