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 /* 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 * In particular, we are adding the "feature" that compress() can 34 * take a destination buffer size and return -1 if the data will not 35 * compress to d_len or less. 36 */ 37 38 #define MATCH_BITS 6 39 #define MATCH_MIN 3 40 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1)) 41 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1) 42 #define LEMPEL_SIZE 256 43 44 /*ARGSUSED*/ 45 static int 46 lzjb_decompress(void *s_start, void *d_start, size_t s_len __unused, 47 size_t d_len, int n __unused) 48 { 49 unsigned char *src = s_start; 50 unsigned char *dst = d_start; 51 unsigned char *d_end = (unsigned char *)d_start + d_len; 52 unsigned char *cpy, copymap = 0; 53 int copymask = 1 << (NBBY - 1); 54 55 while (dst < d_end) { 56 if ((copymask <<= 1) == (1 << NBBY)) { 57 copymask = 1; 58 copymap = *src++; 59 } 60 if (copymap & copymask) { 61 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 62 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 63 src += 2; 64 if ((cpy = dst - offset) < (unsigned char *)d_start) 65 return (-1); 66 while (--mlen >= 0 && dst < d_end) 67 *dst++ = *cpy++; 68 } else { 69 *dst++ = *src++; 70 } 71 } 72 return (0); 73 } 74