131 lines
3.8 KiB
C
131 lines
3.8 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
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*/
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/*
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* We keep our own copy of this algorithm for 3 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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* 3. We initialize the lempel to ensure deterministic results,
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* so that identical blocks can always be deduplicated.
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* In particular, we are adding the "feature" that compress() can
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* take a destination buffer size and returns the compressed length, or the
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* source length if compression would overflow the destination buffer.
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*/
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#include <sys/zfs_context.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 1024
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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;
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uchar_t *copymap = NULL;
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int copymask = 1 << (NBBY - 1);
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int mlen, offset, hash;
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uint16_t *hp;
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uint16_t *lempel;
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lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP);
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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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kmem_free(lempel,
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LEMPEL_SIZE*sizeof (uint16_t));
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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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hash = (src[0] << 16) + (src[1] << 8) + src[2];
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hash += hash >> 9;
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hash += hash >> 5;
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hp = &lempel[hash & (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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kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t));
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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;
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uchar_t copymap = 0;
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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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