4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
23 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
27 * We keep our own copy of this algorithm for 3 main reasons:
28 * 1. If we didn't, anyone modifying common/os/compress.c would
29 * directly break our on disk format
30 * 2. Our version of lzjb does not have a number of checks that the
31 * common/os version needs and uses
32 * 3. We initialize the lempel to ensure deterministic results,
33 * so that identical blocks can always be deduplicated.
34 * In particular, we are adding the "feature" that compress() can
35 * take a destination buffer size and returns the compressed length, or the
36 * source length if compression would overflow the destination buffer.
39 #include <sys/zfs_context.h>
43 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
44 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
45 #define LEMPEL_SIZE 1024
49 lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
51 uchar_t *src = s_start;
52 uchar_t *dst = d_start;
53 uchar_t *cpy, *copymap = NULL;
54 int copymask = 1 << (NBBY - 1);
55 int mlen, offset, hash;
59 lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP);
60 while (src < (uchar_t *)s_start + s_len) {
61 if ((copymask <<= 1) == (1 << NBBY)) {
62 if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) {
63 kmem_free(lempel, LEMPEL_SIZE*sizeof(uint16_t));
70 if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {
74 hash = (src[0] << 16) + (src[1] << 8) + src[2];
77 hp = &lempel[hash & (LEMPEL_SIZE - 1)];
78 offset = (intptr_t)(src - *hp) & OFFSET_MASK;
79 *hp = (uint16_t)(uintptr_t)src;
81 if (cpy >= (uchar_t *)s_start && cpy != src &&
82 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {
84 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)
85 if (src[mlen] != cpy[mlen])
87 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |
89 *dst++ = (uchar_t)offset;
96 kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t));
97 return (dst - (uchar_t *)d_start);
102 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
104 uchar_t *src = s_start;
105 uchar_t *dst = d_start;
106 uchar_t *d_end = (uchar_t *)d_start + d_len;
107 uchar_t *cpy, copymap = 0;
108 int copymask = 1 << (NBBY - 1);
110 while (dst < d_end) {
111 if ((copymask <<= 1) == (1 << NBBY)) {
115 if (copymap & copymask) {
116 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
117 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
119 if ((cpy = dst - offset) < (uchar_t *)d_start)
121 while (--mlen >= 0 && dst < d_end)