Update core ZFS code from build 121 to build 141.

[zfs.git] / module / zfs / lzjb.c

diff --git a/module/zfs/lzjb.c b/module/zfs/lzjb.c
index 7fcde84..10952f4 100644 (file)
--- 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;