fs/zfs/zle.c

b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick/*
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * CDDL HEADER START
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick *
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * The contents of this file are subject to the terms of the
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * Common Development and Distribution License (the "License").
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * You may not use this file except in compliance with the License.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick *
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * or http://www.opensolaris.org/os/licensing.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * See the License for the specific language governing permissions
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * and limitations under the License.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick *
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * When distributing Covered Code, include this CDDL HEADER in each
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * If applicable, add the following below this CDDL HEADER, with the
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * fields enclosed by brackets "[]" replaced with your own identifying
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * information: Portions Copyright [yyyy] [name of copyright owner]
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick *
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * CDDL HEADER END
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick */
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick/*
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * Use is subject to license terms.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick */
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick/*
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * Zero-length encoding.  This is a fast and simple algorithm to eliminate
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * runs of zeroes.  Each chunk of compressed data begins with a length byte, b.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * If b < n (where n is the compression parameter) then the next b + 1 bytes
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick * are literal values.  If b >= n then the next (256 - b + 1) bytes are zero.
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick */
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick#include <sys/types.h>
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick#include <sys/sysmacros.h>
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwicksize_t
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwickzle_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick{
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *src = s_start;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *dst = d_start;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *s_end = src + s_len;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *d_end = dst + d_len;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    while (src < s_end && dst < d_end - 1) {
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        uchar_t *first = src;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        uchar_t *len = dst++;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        if (src[0] == 0) {
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            uchar_t *last = src + (256 - n);
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            while (src < MIN(last, s_end) && src[0] == 0)
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick                src++;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            *len = src - first - 1 + n;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        } else {
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            uchar_t *last = src + n;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            if (d_end - dst < n)
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick                break;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            while (src < MIN(last, s_end) - 1 && (src[0] | src[1]))
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick                *dst++ = *src++;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            if (src[0])
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick                *dst++ = *src++;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            *len = src - first - 1;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        }
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    }
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    return (src == s_end ? dst - (uchar_t *)d_start : s_len);
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick}
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwickint
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwickzle_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick{
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *src = s_start;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *dst = d_start;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *s_end = src + s_len;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    uchar_t *d_end = dst + d_len;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    while (src < s_end && dst < d_end) {
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        int len = 1 + *src++;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        if (len <= n) {
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            while (len-- != 0)
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick                *dst++ = *src++;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        } else {
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            len -= n;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick            while (len-- != 0)
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick                *dst++ = 0;
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick        }
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    }
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick    return (dst == d_end ? 0 : -1);
b24ab6762772a3f6a89393947930c7fa61306783Jeff Bonwick}