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 2009 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 /* 28 * We keep our own copy of this algorithm for 2 main reasons: 29 * 1. If we didn't, anyone modifying common/os/compress.c would 30 * directly break our on disk format 31 * 2. Our version of lzjb does not have a number of checks that the 32 * common/os version needs and uses 33 * 3. We initialize the lempel to ensure deterministic results, 34 * so that identical blocks can always be deduplicated. 35 * In particular, we are adding the "feature" that compress() can 36 * take a destination buffer size and return -1 if the data will not 37 * compress to d_len or less. 38 */ 39 40 #include <sys/types.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, *copymap; 55 int copymask = 1 << (NBBY - 1); 56 int mlen, offset, hash; 57 uint16_t *hp; 58 uint16_t lempel[LEMPEL_SIZE] = { 0 }; 59 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 return (s_len); 64 copymask = 1; 65 copymap = dst; 66 *dst++ = 0; 67 } 68 if (src > (uchar_t *)s_start + s_len - MATCH_MAX) { 69 *dst++ = *src++; 70 continue; 71 } 72 hash = (src[0] << 16) + (src[1] << 8) + src[2]; 73 hash += hash >> 9; 74 hash += hash >> 5; 75 hp = &lempel[hash & (LEMPEL_SIZE - 1)]; 76 offset = (intptr_t)(src - *hp) & OFFSET_MASK; 77 *hp = (uint16_t)(uintptr_t)src; 78 cpy = src - offset; 79 if (cpy >= (uchar_t *)s_start && cpy != src && 80 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) { 81 *copymap |= copymask; 82 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++) 83 if (src[mlen] != cpy[mlen]) 84 break; 85 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) | 86 (offset >> NBBY); 87 *dst++ = (uchar_t)offset; 88 src += mlen; 89 } else { 90 *dst++ = *src++; 91 } 92 } 93 return (dst - (uchar_t *)d_start); 94 } 95 96 /*ARGSUSED*/ 97 int 98 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 99 { 100 uchar_t *src = s_start; 101 uchar_t *dst = d_start; 102 uchar_t *d_end = (uchar_t *)d_start + d_len; 103 uchar_t *cpy, copymap; 104 int copymask = 1 << (NBBY - 1); 105 106 while (dst < d_end) { 107 if ((copymask <<= 1) == (1 << NBBY)) { 108 copymask = 1; 109 copymap = *src++; 110 } 111 if (copymap & copymask) { 112 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 113 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 114 src += 2; 115 if ((cpy = dst - offset) < (uchar_t *)d_start) 116 return (-1); 117 while (--mlen >= 0 && dst < d_end) 118 *dst++ = *cpy++; 119 } else { 120 *dst++ = *src++; 121 } 122 } 123 return (0); 124 } 125