diff options
Diffstat (limited to 'module/zfs/lzjb.c')
| -rw-r--r-- | module/zfs/lzjb.c | 30 |
1 files changed, 13 insertions, 17 deletions
diff --git a/module/zfs/lzjb.c b/module/zfs/lzjb.c index 7fcde8475..10952f472 100644 --- a/module/zfs/lzjb.c +++ b/module/zfs/lzjb.c @@ -20,18 +20,18 @@ */ /* - * Copyright 2007 Sun Microsystems, Inc. All rights reserved. + * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ -#pragma ident "%Z%%M% %I% %E% SMI" - /* * We keep our own copy of this algorithm for 2 main reasons: - * 1. If we didn't, anyone modifying common/os/compress.c would + * 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 + * 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 return -1 if the data will not * compress to d_len or less. @@ -43,7 +43,7 @@ #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 +#define LEMPEL_SIZE 1024 /*ARGSUSED*/ size_t @@ -53,20 +53,14 @@ lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) uchar_t *dst = d_start; uchar_t *cpy, *copymap; int copymask = 1 << (NBBY - 1); - int mlen, offset; + int mlen, offset, hash; uint16_t *hp; - uint16_t lempel[LEMPEL_SIZE]; /* uninitialized; see above */ + 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) { - if (d_len != s_len) - return (s_len); - mlen = s_len; - for (src = s_start, dst = d_start; mlen; mlen--) - *dst++ = *src++; + if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) return (s_len); - } copymask = 1; copymap = dst; *dst++ = 0; @@ -75,8 +69,10 @@ lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) *dst++ = *src++; continue; } - hp = &lempel[((src[0] + 13) ^ (src[1] - 13) ^ src[2]) & - (LEMPEL_SIZE - 1)]; + 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; |