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 2007 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 /* 30 * We keep our own copy of this algorithm for 2 main reasons: 31 * 1. If we didn't, anyone modifying common/os/compress.c would 32 * directly break our on disk format 33 * 2. Our version of lzjb does not have a number of checks that the 34 * common/os version needs and uses 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 256 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; 57 uint16_t *hp; 58 uint16_t lempel[LEMPEL_SIZE]; /* uninitialized; see above */ 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 if (d_len != s_len) 64 return (s_len); 65 mlen = s_len; 66 for (src = s_start, dst = d_start; mlen; mlen--) 67 *dst++ = *src++; 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 hp = &lempel[((src[0] + 13) ^ (src[1] - 13) ^ src[2]) & 79 (LEMPEL_SIZE - 1)]; 80 offset = (intptr_t)(src - *hp) & OFFSET_MASK; 81 *hp = (uint16_t)(uintptr_t)src; 82 cpy = src - offset; 83 if (cpy >= (uchar_t *)s_start && cpy != src && 84 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) { 85 *copymap |= copymask; 86 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++) 87 if (src[mlen] != cpy[mlen]) 88 break; 89 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) | 90 (offset >> NBBY); 91 *dst++ = (uchar_t)offset; 92 src += mlen; 93 } else { 94 *dst++ = *src++; 95 } 96 } 97 return (dst - (uchar_t *)d_start); 98 } 99 100 /*ARGSUSED*/ 101 int 102 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 103 { 104 uchar_t *src = s_start; 105 uchar_t *dst = d_start; 106 uchar_t *d_end = (uchar_t *)d_start + d_len; 107 uchar_t *cpy, copymap; 108 int copymask = 1 << (NBBY - 1); 109 110 while (dst < d_end) { 111 if ((copymask <<= 1) == (1 << NBBY)) { 112 copymask = 1; 113 copymap = *src++; 114 } 115 if (copymap & copymask) { 116 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 117 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 118 src += 2; 119 if ((cpy = dst - offset) < (uchar_t *)d_start) 120 return (-1); 121 while (--mlen >= 0 && dst < d_end) 122 *dst++ = *cpy++; 123 } else { 124 *dst++ = *src++; 125 } 126 } 127 return (0); 128 } 129