90 lines
2.5 KiB
C
90 lines
2.5 KiB
C
/*
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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 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* Zero-length encoding. This is a fast and simple algorithm to eliminate
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* runs of zeroes. Each chunk of compressed data begins with a length byte, b.
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* If b < n (where n is the compression parameter) then the next b + 1 bytes
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* are literal values. If b >= n then the next (256 - b + 1) bytes are zero.
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*/
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#include <sys/types.h>
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#include <sys/sysmacros.h>
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size_t
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zle_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
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{
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uchar_t *src = s_start;
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uchar_t *dst = d_start;
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uchar_t *s_end = src + s_len;
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uchar_t *d_end = dst + d_len;
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while (src < s_end && dst < d_end - 1) {
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uchar_t *first = src;
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uchar_t *len = dst++;
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if (src[0] == 0) {
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uchar_t *last = src + (256 - n);
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while (src < MIN(last, s_end) && src[0] == 0)
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src++;
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*len = src - first - 1 + n;
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} else {
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uchar_t *last = src + n;
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if (d_end - dst < n)
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break;
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while (src < MIN(last, s_end) - 1 && (src[0] | src[1]))
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*dst++ = *src++;
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if (src[0])
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*dst++ = *src++;
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*len = src - first - 1;
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}
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}
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return (src == s_end ? dst - (uchar_t *)d_start : s_len);
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}
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int
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zle_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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uchar_t *src = s_start;
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uchar_t *dst = d_start;
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uchar_t *s_end = src + s_len;
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uchar_t *d_end = dst + d_len;
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while (src < s_end && dst < d_end) {
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int len = 1 + *src++;
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if (len <= n) {
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if (src + len > s_end || dst + len > d_end)
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return (-1);
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while (len-- != 0)
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*dst++ = *src++;
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} else {
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len -= n;
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if (dst + len > d_end)
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return (-1);
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while (len-- != 0)
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*dst++ = 0;
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}
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}
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return (dst == d_end ? 0 : -1);
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}
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