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 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26 #pragma ident "%Z%%M% %I% %E% SMI" 27 28 /* 29 * We keep our own copy of this algorithm for 2 main reasons: 30 * 1. If we didn't, anyone modifying common/os/compress.c would 31 * directly break our on disk format 32 * 2. Our version of lzjb does not have a number of checks that the 33 * common/os version needs and uses 34 * In particular, we are adding the "feature" that compress() can 35 * take a destination buffer size and return -1 if the data will not 36 * compress to d_len or less. 37 */ 38 39 #include <sys/types.h> 40 41 #define MATCH_BITS 6 42 #define MATCH_MIN 3 43 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1)) 44 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1) 45 #define LEMPEL_SIZE 256 46 47 size_t 48 lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len) 49 { 50 uchar_t *src = s_start; 51 uchar_t *dst = d_start; 52 uchar_t *cpy, *copymap; 53 int copymask = 1 << (NBBY - 1); 54 int mlen, offset; 55 uint16_t *hp; 56 uint16_t lempel[LEMPEL_SIZE]; /* uninitialized; see above */ 57 58 while (src < (uchar_t *)s_start + s_len) { 59 if ((copymask <<= 1) == (1 << NBBY)) { 60 if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) { 61 if (d_len != s_len) 62 return (s_len); 63 mlen = s_len; 64 for (src = s_start, dst = d_start; mlen; mlen--) 65 *dst++ = *src++; 66 return (s_len); 67 } 68 copymask = 1; 69 copymap = dst; 70 *dst++ = 0; 71 } 72 if (src > (uchar_t *)s_start + s_len - MATCH_MAX) { 73 *dst++ = *src++; 74 continue; 75 } 76 hp = &lempel[((src[0] + 13) ^ (src[1] - 13) ^ src[2]) & 77 (LEMPEL_SIZE - 1)]; 78 offset = (intptr_t)(src - *hp) & OFFSET_MASK; 79 *hp = (uint16_t)(uintptr_t)src; 80 cpy = src - offset; 81 if (cpy >= (uchar_t *)s_start && cpy != src && 82 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) { 83 *copymap |= copymask; 84 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++) 85 if (src[mlen] != cpy[mlen]) 86 break; 87 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) | 88 (offset >> NBBY); 89 *dst++ = (uchar_t)offset; 90 src += mlen; 91 } else { 92 *dst++ = *src++; 93 } 94 } 95 return (dst - (uchar_t *)d_start); 96 } 97 98 /*ARGSUSED*/ 99 int 100 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len) 101 { 102 uchar_t *src = s_start; 103 uchar_t *dst = d_start; 104 uchar_t *d_end = (uchar_t *)d_start + d_len; 105 uchar_t *cpy, copymap; 106 int copymask = 1 << (NBBY - 1); 107 108 while (dst < d_end) { 109 if ((copymask <<= 1) == (1 << NBBY)) { 110 copymask = 1; 111 copymap = *src++; 112 } 113 if (copymap & copymask) { 114 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 115 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 116 src += 2; 117 if ((cpy = dst - offset) < (uchar_t *)d_start) 118 return (-1); 119 while (--mlen >= 0 && dst < d_end) 120 *dst++ = *cpy++; 121 } else { 122 *dst++ = *src++; 123 } 124 } 125 return (0); 126 } 127