sfhashfcn.c

   1 /****************************************************************************
   2  *
   3  * Copyright (C) 2003-2009 Sourcefire, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License Version 2 as
   7  * published by the Free Software Foundation.  You may not use, modify or
   8  * distribute this program under any other version of the GNU General
   9  * Public License.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  *
  20  ****************************************************************************/
  21
  22 /*
  23      sfhashfcn.c
  24
  25      Each hash table must allocate it's own SFGHASH struct, this is because
  26      sfghash_new uses the number of rows in the hash table to modulo the random
  27      values.
  28
  29      Updates:
  30
  31      8/31/2006 - man - changed to use sfprimetable.c
  32 */
  33
  34 #include "sfhashfcn.h"
  35 #include "sfprimetable.h"
  36
  37
  38 SFHASHFCN * sfhashfcn_new( int m )
  39 {
  40     SFHASHFCN * p;
  41     static int one=1;
  42
  43     if( one ) /* one time init */
  44     {
  45         srand( (unsigned) time(0) );
  46         one = 0;
  47     }
  48
  49     // This can make all of the hashing static for testing.
  50     //#define rand() 0
  51
  52     p = (SFHASHFCN*) calloc( 1,sizeof(SFHASHFCN) );
  53     if( !p )
  54         return 0;
  55
  56     {
  57         p->seed     = sf_nearest_prime( (rand()%m)+3191 );
  58         p->scale    = sf_nearest_prime( (rand()%m)+709 );
  59         p->hardener = (rand()*rand()) + 133824503;
  60     }
  61
  62     p->hash_fcn   = &sfhashfcn_hash;
  63     p->keycmp_fcn = &memcmp;
  64
  65     return p;
  66 }
  67
  68 void sfhashfcn_free( SFHASHFCN * p )
  69 {
  70    if( p )
  71    {
  72        free( p);
  73    }
  74 }
  75
  76 void sfhashfcn_static( SFHASHFCN * p )
  77 {
  78     p->seed     = 3193;
  79     p->scale    = 719;
  80     p->hardener = 133824503;
  81 }
  82
  83 unsigned sfhashfcn_hash( SFHASHFCN * p, unsigned char *d, int n )
  84 {
  85 #if 1
  86     unsigned hash = p->seed;
  87     while( n )
  88     {
  89         hash *=  p->scale;
  90         hash += *d++;
  91         n--;
  92     }
  93     return hash ^ p->hardener;
  94 #else
  95     unsigned int hash = 5381;
  96     while(n){
  97             hash += (hash << 5) + (*d++);
  98             n--;
  99     }
 100     return hash;
 101 #endif
 102 }
 103
 104 /**
 105  * Make sfhashfcn use a separate set of operators for the backend.
 106  *
 107  * @param h sfhashfcn ptr
 108  * @param hash_fcn user specified hash function
 109  * @param keycmp_fcn user specified key comparisoin function
 110  */
 111 int sfhashfcn_set_keyops( SFHASHFCN *h,
 112                           unsigned (*hash_fcn)( SFHASHFCN * p,
 113                                                 unsigned char *d,
 114                                                 int n),
 115                           int (*keycmp_fcn)( const void *s1,
 116                                              const void *s2,
 117                                              size_t n))
 118 {
 119     if(h && hash_fcn && keycmp_fcn)
 120     {
 121         h->hash_fcn   = hash_fcn;
 122         h->keycmp_fcn = keycmp_fcn;
 123
 124         return 0;
 125     }
 126
 127     return -1;
 128 }
 129