1 // SPDX-License-Identifier: CDDL-1.0
2 /*
3 * CDDL HEADER START
4 *
5 * The contents of this file are subject to the terms of the
6 * Common Development and Distribution License (the "License").
7 * You may not use this file except in compliance with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or https://opensource.org/licenses/CDDL-1.0.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22
23 /*
24 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
25 * Use is subject to license terms.
26 */
27
28 /*
29 * Zero-length encoding. This is a fast and simple algorithm to eliminate
30 * runs of zeroes. Each chunk of compressed data begins with a length byte, b.
31 * If b < n (where n is the compression parameter) then the next b + 1 bytes
32 * are literal values. If b >= n then the next (256 - b + 1) bytes are zero.
33 */
34 #include <sys/types.h>
35 #include <sys/sysmacros.h>
36 #include <sys/zio_compress.h>
37
38 static size_t
zfs_zle_compress_buf(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)39 zfs_zle_compress_buf(void *s_start, void *d_start, size_t s_len,
40 size_t d_len, int n)
41 {
42 uchar_t *src = s_start;
43 uchar_t *dst = d_start;
44 uchar_t *s_end = src + s_len;
45 uchar_t *d_end = dst + d_len;
46
47 while (src < s_end && dst < d_end - 1) {
48 uchar_t *first = src;
49 uchar_t *len = dst++;
50 if (src[0] == 0) {
51 uchar_t *last = src + (256 - n);
52 while (src < MIN(last, s_end) && src[0] == 0)
53 src++;
54 *len = src - first - 1 + n;
55 } else {
56 uchar_t *last = src + n;
57 if (d_end - dst < n)
58 break;
59 while (src < MIN(last, s_end) - 1 && (src[0] | src[1]))
60 *dst++ = *src++;
61 if (src[0])
62 *dst++ = *src++;
63 *len = src - first - 1;
64 }
65 }
66 return (src == s_end ? dst - (uchar_t *)d_start : s_len);
67 }
68
69 static int
zfs_zle_decompress_buf(void * s_start,void * d_start,size_t s_len,size_t d_len,int n)70 zfs_zle_decompress_buf(void *s_start, void *d_start, size_t s_len,
71 size_t d_len, int n)
72 {
73 uchar_t *src = s_start;
74 uchar_t *dst = d_start;
75 uchar_t *s_end = src + s_len;
76 uchar_t *d_end = dst + d_len;
77
78 while (src < s_end && dst < d_end) {
79 int len = 1 + *src++;
80 if (len <= n) {
81 if (src + len > s_end || dst + len > d_end)
82 return (-1);
83 while (len-- != 0)
84 *dst++ = *src++;
85 } else {
86 len -= n;
87 if (dst + len > d_end)
88 return (-1);
89 while (len-- != 0)
90 *dst++ = 0;
91 }
92 }
93 return (dst == d_end ? 0 : -1);
94 }
95
96 ZFS_COMPRESS_WRAP_DECL(zfs_zle_compress)
97 ZFS_DECOMPRESS_WRAP_DECL(zfs_zle_decompress)
98