1 /*
2 * CDDL HEADER START
3 *
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.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or https://opensource.org/licenses/CDDL-1.0.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
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]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
24 */
25
26 /*
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.
37 */
38
39 #include <sys/zfs_context.h>
40 #include <sys/zio_compress.h>
41
42 #define MATCH_BITS 6
43 #define MATCH_MIN 3
44 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
45 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
46 #define LEMPEL_SIZE 1024
47
48 static size_t
zfs_lzjb_compress_buf(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)49 zfs_lzjb_compress_buf(void *s_start, void *d_start, size_t s_len,
50 size_t d_len, int n)
51 {
52 (void) n;
53 uchar_t *src = s_start;
54 uchar_t *dst = d_start;
55 uchar_t *cpy;
56 uchar_t *copymap = NULL;
57 int copymask = 1 << (NBBY - 1);
58 int mlen, offset, hash;
59 uint16_t *hp;
60 uint16_t *lempel;
61
62 lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP);
63 while (src < (uchar_t *)s_start + s_len) {
64 if ((copymask <<= 1) == (1 << NBBY)) {
65 if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) {
66 kmem_free(lempel,
67 LEMPEL_SIZE*sizeof (uint16_t));
68 return (s_len);
69 }
70 copymask = 1;
71 copymap = dst;
72 *dst++ = 0;
73 }
74 if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {
75 *dst++ = *src++;
76 continue;
77 }
78 hash = (src[0] << 16) + (src[1] << 8) + src[2];
79 hash += hash >> 9;
80 hash += hash >> 5;
81 hp = &lempel[hash & (LEMPEL_SIZE - 1)];
82 offset = (intptr_t)(src - *hp) & OFFSET_MASK;
83 *hp = (uint16_t)(uintptr_t)src;
84 cpy = src - offset;
85 if (cpy >= (uchar_t *)s_start && cpy != src &&
86 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {
87 *copymap |= copymask;
88 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)
89 if (src[mlen] != cpy[mlen])
90 break;
91 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |
92 (offset >> NBBY);
93 *dst++ = (uchar_t)offset;
94 src += mlen;
95 } else {
96 *dst++ = *src++;
97 }
98 }
99
100 kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t));
101 return (dst - (uchar_t *)d_start);
102 }
103
104 static int
zfs_lzjb_decompress_buf(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)105 zfs_lzjb_decompress_buf(void *s_start, void *d_start,
106 size_t s_len, size_t d_len, int n)
107 {
108 (void) s_len, (void) n;
109 uchar_t *src = s_start;
110 uchar_t *dst = d_start;
111 uchar_t *d_end = (uchar_t *)d_start + d_len;
112 uchar_t *cpy;
113 uchar_t copymap = 0;
114 int copymask = 1 << (NBBY - 1);
115
116 while (dst < d_end) {
117 if ((copymask <<= 1) == (1 << NBBY)) {
118 copymask = 1;
119 copymap = *src++;
120 }
121 if (copymap & copymask) {
122 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
123 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
124 src += 2;
125 if ((cpy = dst - offset) < (uchar_t *)d_start)
126 return (-1);
127 while (--mlen >= 0 && dst < d_end)
128 *dst++ = *cpy++;
129 } else {
130 *dst++ = *src++;
131 }
132 }
133 return (0);
134 }
135
136 ZFS_COMPRESS_WRAP_DECL(zfs_lzjb_compress)
137 ZFS_DECOMPRESS_WRAP_DECL(zfs_lzjb_decompress)
138