/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License, Version 1.0 only

 * (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 2005 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*

 * This is stolen from common/os/compress.c and will be removed once

 * our changes have made it into the on10 source base.

 *

 * In particular, we are adding the "feature" that compress() can

 * take a destination buffer size and return -1 if the data will not

 * compress to d_len or less.

 */

#include <sys/types.h>

#define	MATCH_BITS	6

#define	MATCH_MIN	3

#define	MATCH_MAX	((1 << MATCH_BITS) + (MATCH_MIN - 1))

#define	OFFSET_MASK	((1 << (16 - MATCH_BITS)) - 1)

#define	LEMPEL_SIZE	256

size_t

lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len)

{

	uchar_t *src = s_start;

	uchar_t *dst = d_start;

	uchar_t *cpy, *copymap;

	int copymask = 1 << (NBBY - 1);

	int mlen, offset;

	uint16_t *hp;

	uint16_t lempel[LEMPEL_SIZE];	/* uninitialized; see above */

	while (src < (uchar_t *)s_start + s_len) {

		if ((copymask <<= 1) == (1 << NBBY)) {

			if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) {

				if (d_len != s_len)

					return (s_len);

				mlen = s_len;

				for (src = s_start, dst = d_start; mlen; mlen--)

					*dst++ = *src++;

				return (s_len);

			}

			copymask = 1;

			copymap = dst;

			*dst++ = 0;

		}

		if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {

			*dst++ = *src++;

			continue;

		}

		hp = &lempel[((src[0] + 13) ^ (src[1] - 13) ^ src[2]) &

		    (LEMPEL_SIZE - 1)];

		offset = (intptr_t)(src - *hp) & OFFSET_MASK;

		*hp = (uint16_t)(uintptr_t)src;

		cpy = src - offset;

		if (cpy >= (uchar_t *)s_start && cpy != src &&

		    src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {

			*copymap |= copymask;

			for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)

				if (src[mlen] != cpy[mlen])

					break;

			*dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |

			    (offset >> NBBY);

			*dst++ = (uchar_t)offset;

			src += mlen;

		} else {

			*dst++ = *src++;

		}

	}

	return (dst - (uchar_t *)d_start);

}

/*ARGSUSED*/

int

lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len)

{

	uchar_t *src = s_start;

	uchar_t *dst = d_start;

	uchar_t *d_end = (uchar_t *)d_start + d_len;

	uchar_t *cpy, copymap;

	int copymask = 1 << (NBBY - 1);

	while (dst < d_end) {

		if ((copymask <<= 1) == (1 << NBBY)) {

			copymask = 1;

			copymap = *src++;

		}

		if (copymap & copymask) {

			int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;

			int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;

			src += 2;

			if ((cpy = dst - offset) < (uchar_t *)d_start)

				return (-1);

			while (--mlen >= 0 && dst < d_end)

				*dst++ = *cpy++;

		} else {

			*dst++ = *src++;

		}

	}

	return (0);

}