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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* Zero-length encoding. This is a fast and simple algorithm to eliminate
* runs of zeroes. Each chunk of compressed data begins with a length byte, b.
* If b < n (where n is the compression parameter) then the next b + 1 bytes
* are literal values. If b >= n then the next (256 - b + 1) bytes are zero.
*/
#include <sys/types.h>
#include <sys/sysmacros.h>
size_t
zle_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
uchar_t *src = s_start;
uchar_t *dst = d_start;
uchar_t *s_end = src + s_len;
uchar_t *d_end = dst + d_len;
while (src < s_end && dst < d_end - 1) {
uchar_t *first = src;
uchar_t *len = dst++;
if (src[0] == 0) {
uchar_t *last = src + (256 - n);
while (src < MIN(last, s_end) && src[0] == 0)
src++;
*len = src - first - 1 + n;
} else {
uchar_t *last = src + n;
if (d_end - dst < n)
break;
while (src < MIN(last, s_end) - 1 && (src[0] | src[1]))
*dst++ = *src++;
if (src[0])
*dst++ = *src++;
*len = src - first - 1;
}
}
return (src == s_end ? dst - (uchar_t *)d_start : s_len);
}
int
zle_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
{
uchar_t *src = s_start;
uchar_t *dst = d_start;
uchar_t *s_end = src + s_len;
uchar_t *d_end = dst + d_len;
while (src < s_end && dst < d_end) {
int len = 1 + *src++;
if (len <= n) {
while (len-- != 0)
*dst++ = *src++;
} else {
len -= n;
while (len-- != 0)
*dst++ = 0;
}
}
return (dst == d_end ? 0 : -1);
}
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