move to the FNV1 hash alghorithm seem good

the test revealed 15 collision with 1 Million long file names :-)

Simo.
(This used to be commit 77dc498b6f0c435f082eb2d934920d3f3bef0b65)

diff --git a/source3/smbd/mangle.c b/source3/smbd/mangle.c
index 20b2b419cf1eb921e24634422ae4583ff0eb13fe..66dd2c00b7a98b328230e43f9eaf4ac7ffa89ebd 100644 (file)
--- a/source3/smbd/mangle.c
+++ b/source3/smbd/mangle.c
@@ -29,6 +29,7 @@ static struct {
 } mangle_backends[] = {
        { "hash", mangle_hash_init },
        { "hash2", mangle_hash2_init },
+       /*{ "tdb", mangle_tdb_init }, */
        { NULL, NULL }
 };
 

diff --git a/source3/smbd/mangle_hash2.c b/source3/smbd/mangle_hash2.c
index a473de38d606e77310761a268991a7dea40fc916..1c8b0689a179c0e9008ab1d3c67746ba5bb08038 100644 (file)
--- a/source3/smbd/mangle_hash2.c
+++ b/source3/smbd/mangle_hash2.c
@@ -2,6 +2,7 @@
    Unix SMB/CIFS implementation.
    new hash based name mangling implementation
    Copyright (C) Andrew Tridgell 2002
+   Copyright (C) Simo Sorce 2002
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -30,6 +31,10 @@
   for simplicity, we only allow ascii characters in 8.3 names
  */
 
+ /* hash alghorithm changed to FNV1 by idra@samba.org (Simo Sorce).
+  * see http://www.isthe.com/chongo/tech/comp/fnv/index.html for a
+  * discussion on Fowler / Noll / Vo (FNV) Hash by one of it's authors
+  */
 
 /*
   ===============================================================================
@@ -73,6 +78,10 @@
 #define MANGLE_CACHE_SIZE 4096
 #endif
 
+#define FNV1_PRIME 0x01000193
+/*the following number is a fnv1 of the string: idra@samba.org 2002 */
+#define FNV1_INIT  0xa6b93095
+
 /* these tables are used to provide fast tests for characters */
 static unsigned char char_flags[256];
 
@@ -121,13 +130,14 @@ static u32 mangle_hash(const char *key, unsigned length)
        length = strlen(str);
 
        /* Set the initial value from the key size. */
-       for (value = 0x238F13AF * length, i=0; i < length; i++) {
-               value = (value + (((unsigned char)str[i]) << (i*5 % 24)));
-       }
+       for (value = FNV1_INIT, i=0; i < length; i++) {
+                value *= (u32)FNV1_PRIME;
+                value ^= (u32)(str[i]);
+        }
 
        /* note that we force it to a 31 bit hash, to keep within the limits
           of the 36^6 mangle space */
-       return (1103515243 * value + 12345) & ~0x80000000;  
+       return value & ~0x80000000;  
 }
 
 /*