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 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 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