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75 lines
2.3 KiB
C
75 lines
2.3 KiB
C
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/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*#pragma ident "%Z%%M% %I% %E% SMI"*/
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/*
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* We keep our own copy of this algorithm for 2 main reasons:
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* 1. If we didn't, anyone modifying common/os/compress.c would
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* directly break our on disk format
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* 2. Our version of lzjb does not have a number of checks that the
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* common/os version needs and uses
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* In particular, we are adding the "feature" that compress() can
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* take a destination buffer size and return -1 if the data will not
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* compress to d_len or less.
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*/
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#define MATCH_BITS 6
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#define MATCH_MIN 3
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#define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
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#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
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#define LEMPEL_SIZE 256
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/*ARGSUSED*/
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static int
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lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
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{
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unsigned char *src = s_start;
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unsigned char *dst = d_start;
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unsigned char *d_end = (unsigned char *)d_start + d_len;
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unsigned char *cpy, copymap = 0;
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int copymask = 1 << (NBBY - 1);
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while (dst < d_end) {
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if ((copymask <<= 1) == (1 << NBBY)) {
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copymask = 1;
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copymap = *src++;
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}
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if (copymap & copymask) {
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int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
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int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
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src += 2;
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if ((cpy = dst - offset) < (unsigned char *)d_start)
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return (-1);
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while (--mlen >= 0 && dst < d_end)
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*dst++ = *cpy++;
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} else {
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*dst++ = *src++;
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}
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}
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return (0);
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}
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