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 #define MATCH_BITS 6 41 #define MATCH_MIN 3 42 #define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1)) 43 #define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1) 44 #define LEMPEL_SIZE 256 45 46 /*ARGSUSED*/ 47 static int 48 lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 49 { 50 unsigned char *src = s_start; 51 unsigned char *dst = d_start; 52 unsigned char *d_end = (unsigned char *)d_start + d_len; 53 unsigned char *cpy, copymap = 0; 54 int copymask = 1 << (NBBY - 1); 55 56 while (dst < d_end) { 57 if ((copymask <<= 1) == (1 << NBBY)) { 58 copymask = 1; 59 copymap = *src++; 60 } 61 if (copymap & copymask) { 62 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 63 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 64 src += 2; 65 if ((cpy = dst - offset) < (unsigned char *)d_start) 66 return (-1); 67 while (--mlen >= 0 && dst < d_end) 68 *dst++ = *cpy++; 69 } else { 70 *dst++ = *src++; 71 } 72 } 73 return (0); 74 } 75