diff options
Diffstat (limited to 'uts/common/fs/zfs/lzjb.c')
| -rw-r--r-- | uts/common/fs/zfs/lzjb.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/uts/common/fs/zfs/lzjb.c b/uts/common/fs/zfs/lzjb.c new file mode 100644 index 000000000000..ab3de51b7259 --- /dev/null +++ b/uts/common/fs/zfs/lzjb.c @@ -0,0 +1,123 @@ +/* + * 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/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 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, *copymap; + int copymask = 1 << (NBBY - 1); + int mlen, offset, hash; + uint16_t *hp; + uint16_t lempel[LEMPEL_SIZE] = { 0 }; + + while (src < (uchar_t *)s_start + s_len) { + if ((copymask <<= 1) == (1 << NBBY)) { + if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) + 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++; + } + } + 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, 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); +} |