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 http://www.opensolaris.org/os/licensing. 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 /*ARGSUSED*/ 49 size_t 50 lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 51 { 52 uchar_t *src = s_start; 53 uchar_t *dst = d_start; 54 uchar_t *cpy; 55 uchar_t *copymap = NULL; 56 int copymask = 1 << (NBBY - 1); 57 int mlen, offset, hash; 58 uint16_t *hp; 59 uint16_t *lempel; 60 61 lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP); 62 while (src < (uchar_t *)s_start + s_len) { 63 if ((copymask <<= 1) == (1 << NBBY)) { 64 if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) { 65 kmem_free(lempel, 66 LEMPEL_SIZE*sizeof (uint16_t)); 67 return (s_len); 68 } 69 copymask = 1; 70 copymap = dst; 71 *dst++ = 0; 72 } 73 if (src > (uchar_t *)s_start + s_len - MATCH_MAX) { 74 *dst++ = *src++; 75 continue; 76 } 77 hash = (src[0] << 16) + (src[1] << 8) + src[2]; 78 hash += hash >> 9; 79 hash += hash >> 5; 80 hp = &lempel[hash & (LEMPEL_SIZE - 1)]; 81 offset = (intptr_t)(src - *hp) & OFFSET_MASK; 82 *hp = (uint16_t)(uintptr_t)src; 83 cpy = src - offset; 84 if (cpy >= (uchar_t *)s_start && cpy != src && 85 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) { 86 *copymap |= copymask; 87 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++) 88 if (src[mlen] != cpy[mlen]) 89 break; 90 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) | 91 (offset >> NBBY); 92 *dst++ = (uchar_t)offset; 93 src += mlen; 94 } else { 95 *dst++ = *src++; 96 } 97 } 98 99 kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t)); 100 return (dst - (uchar_t *)d_start); 101 } 102 103 /*ARGSUSED*/ 104 int 105 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 106 { 107 uchar_t *src = s_start; 108 uchar_t *dst = d_start; 109 uchar_t *d_end = (uchar_t *)d_start + d_len; 110 uchar_t *cpy; 111 uchar_t copymap = 0; 112 int copymask = 1 << (NBBY - 1); 113 114 while (dst < d_end) { 115 if ((copymask <<= 1) == (1 << NBBY)) { 116 copymask = 1; 117 copymap = *src++; 118 } 119 if (copymap & copymask) { 120 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 121 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 122 src += 2; 123 if ((cpy = dst - offset) < (uchar_t *)d_start) 124 return (-1); 125 while (--mlen >= 0 && dst < d_end) 126 *dst++ = *cpy++; 127 } else { 128 *dst++ = *src++; 129 } 130 } 131 return (0); 132 } 133