| /* |
| * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. |
| */ |
| |
| /* |
| * We keep our own copy of this algorithm for 3 main reasons: |
| * 1. If we didn't, anyone modifying common/os/compress.c would |
| * directly break our on disk format |
| * 2. Our version of lzjb does not have a number of checks that the |
| * common/os version needs and uses |
| * 3. We initialize the lempel to ensure deterministic results, |
| * so that identical blocks can always be deduplicated. |
| * In particular, we are adding the "feature" that compress() can |
| * take a destination buffer size and returns the compressed length, or the |
| * source length if compression would overflow the destination buffer. |
| */ |
| |
| #include <sys/zfs_context.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 1024 |
| |
| /*ARGSUSED*/ |
| size_t |
| lzjb_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 *cpy; |
| uchar_t *copymap = NULL; |
| int copymask = 1 << (NBBY - 1); |
| int mlen, offset, hash; |
| uint16_t *hp; |
| uint16_t *lempel; |
| |
| lempel = kmem_zalloc(LEMPEL_SIZE * sizeof (uint16_t), KM_SLEEP); |
| while (src < (uchar_t *)s_start + s_len) { |
| if ((copymask <<= 1) == (1 << NBBY)) { |
| if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) { |
| kmem_free(lempel, |
| LEMPEL_SIZE*sizeof (uint16_t)); |
| return (s_len); |
| } |
| copymask = 1; |
| copymap = dst; |
| *dst++ = 0; |
| } |
| if (src > (uchar_t *)s_start + s_len - MATCH_MAX) { |
| *dst++ = *src++; |
| continue; |
| } |
| 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++; |
| } |
| } |
| |
| kmem_free(lempel, LEMPEL_SIZE * sizeof (uint16_t)); |
| 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); |
| } |