fs/zfs/lzjb.c

4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync/*
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * CDDL HEADER START
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * The contents of this file are subject to the terms of the
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Common Development and Distribution License (the "License").
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * You may not use this file except in compliance with the License.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * or http://www.opensolaris.org/os/licensing.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * See the License for the specific language governing permissions
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * and limitations under the License.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * When distributing Covered Code, include this CDDL HEADER in each
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * If applicable, add the following below this CDDL HEADER, with the
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4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * information: Portions Copyright [yyyy] [name of copyright owner]
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4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * CDDL HEADER END
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync/*
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync/*
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * We keep our own copy of this algorithm for 3 main reasons:
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *  1. If we didn't, anyone modifying common/os/compress.c would
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *         directly break our on disk format
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *  2. Our version of lzjb does not have a number of checks that the
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *         common/os version needs and uses
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *  3. We initialize the lempel to ensure deterministic results,
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync *     so that identical blocks can always be deduplicated.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * In particular, we are adding the "feature" that compress() can
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * take a destination buffer size and returns the compressed length, or the
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync * source length if compression would overflow the destination buffer.
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync */
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#include <sys/types.h>
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#include <sys/param.h>
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#define MATCH_BITS  6
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#define MATCH_MIN   3
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#define MATCH_MAX   ((1 << MATCH_BITS) + (MATCH_MIN - 1))
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync#define LEMPEL_SIZE 1024
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync/*ARGSUSED*/
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsyncsize_t
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsynclzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync{
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    uchar_t *src = s_start;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    uchar_t *dst = d_start;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    uchar_t *cpy;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    uchar_t *copymap = NULL;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    int copymask = 1 << (NBBY - 1);
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    int mlen, offset, hash;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    uint16_t *hp;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    uint16_t lempel[LEMPEL_SIZE] = { 0 };
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync    while (src < (uchar_t *)s_start + s_len) {
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync        if ((copymask <<= 1) == (1 << NBBY)) {
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync            if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY)
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync                return (s_len);
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync            copymask = 1;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync            copymap = dst;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync            *dst++ = 0;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync        }
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync        if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync            *dst++ = *src++;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync            continue;
4fd606d1f5abe38e1f42c38de1d2e895166bd0f4vboxsync        }
        hash = (src[0] << 16) + (src[1] << 8) + src[2];
        hash += hash >> 9;
        hash += hash >> 5;
        hp = &lempel[hash & (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, int n)
{
    uchar_t *src = s_start;
    uchar_t *dst = d_start;
    uchar_t *d_end = (uchar_t *)d_start + d_len;
    uchar_t *cpy;
    uchar_t copymap = 0;
    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);
}