/*

 * 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);

}