src/hash.c

   1 /* hash.c */
   2 /* String hashing function */
   3 /* Copyright (C) 1995-2002 Olly Betts
   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 as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18  */
  19
  20 #include <ctype.h>
  21
  22 #include "debug.h"
  23 #include "hash.h"
  24
  25 /* some (preferably prime) number for the hashing function */
  26 #define HASH_PRIME 29363
  27
  28 int
  29 hash_string(const char *p)
  30 {
  31    int hash;
  32    SVX_ASSERT(p);
  33    for (hash = 0; *p; p++)
  34       hash = (hash * HASH_PRIME + *(const unsigned char*)p) & 0x7fff;
  35    return hash;
  36 }
  37
  38 int
  39 hash_lc_string(const char *p)
  40 {
  41    int hash;
  42    SVX_ASSERT(p);
  43    for (hash = 0; *p; p++)
  44       hash = (hash * HASH_PRIME + tolower(*(const unsigned char*)p)) & 0x7fff;
  45    return hash;
  46 }
  47
  48 int
  49 hash_data(const char *p, size_t len)
  50 {
  51    int hash;
  52    SVX_ASSERT(p);
  53    for (hash = 0; len--; p++)
  54       hash = (hash * HASH_PRIME + *(const unsigned char*)p) & 0x7fff;
  55    return hash;
  56 }