From 4c89419158d9aff46164db5ef49004152fbc9453 Mon Sep 17 00:00:00 2001
From: root <root>
Date: Sun, 27 Mar 2011 23:53:23 +0000
Subject: *** empty log message ***

---
 lzf_c.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

(limited to 'lzf_c.c')

diff --git a/lzf_c.c b/lzf_c.c
index bc07084..99d93cb 100644
--- a/lzf_c.c
+++ b/lzf_c.c
@@ -47,22 +47,22 @@
 #ifndef FRST
 # define FRST(p) (((p[0]) << 8) | p[1])
 # define NEXT(v,p) (((v) << 8) | p[2])
-# if ULTRA_FAST
-#  define IDX(h) ((( h             >> (3*8 - HLOG)) - h  ) & (HSIZE - 1))
-# elif VERY_FAST
-#  define IDX(h) ((( h             >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
+# if MULTIPLICATION_IS_SLOW
+#  if ULTRA_FAST
+#   define IDX(h) ((( h             >> (3*8 - HLOG)) - h  ) & (HSIZE - 1))
+#  elif VERY_FAST
+#   define IDX(h) ((( h             >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
+#  else
+#   define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
+#  endif
 # else
-#  define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
+/* this one was developed with sesse,
+ * and is very similar to the one in snappy.
+ * it does need a modern enough cpu with a fast multiplication.
+ */
+#  define IDX(h) (((h * 0x1e35a7bdU) >> (32 - HLOG - 8)) & (HSIZE - 1))
 # endif
 #endif
-/*
- * IDX works because it is very similar to a multiplicative hash, e.g.
- * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
- * the latter is also quite fast on newer CPUs, and compresses similarly.
- *
- * the next one is also quite good, albeit slow ;)
- * (int)(cos(h & 0xffffff) * 1e6)
- */
 
 #if 0
 /* original lzv-like hash function, much worse and thus slower */
-- 
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