| /* Implement simple hashing table with string based keys. |

| Copyright (C) 1994-1997, 2000, 2001, 2002 Free Software Foundation, Inc. |

| This file is part of the GNU C Library. |

| Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, October 1994. |

| |

| The GNU C Library is free software; you can redistribute it and/or |

| modify it under the terms of the GNU Lesser General Public |

| License as published by the Free Software Foundation; either |

| version 2.1 of the License, or (at your option) any later version. |

| |

| The GNU C Library is distributed in the hope that it will be useful, |

| but WITHOUT ANY WARRANTY; without even the implied warranty of |

| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |

| Lesser General Public License for more details. |

| |

| You should have received a copy of the GNU Lesser General Public |

| License along with the GNU C Library; if not, write to the Free |

| Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |

| 02111-1307 USA. */ |

| |

| #ifndef hashval_t |

| # define hashval_t unsigned long int |

| #endif |

| #include <limits.h> /* For CHAR_BIT. */ |

| |

| hashval_t |

| compute_hashval (const void *key, size_t keylen) |

| { |

| size_t cnt; |

| hashval_t hval; |

| |

| /* Compute the hash value for the given string. The algorithm |

| is taken from [Aho,Sethi,Ullman], modified to reduce the number of |

| collisions for short strings with very varied bit patterns. |

| See http://www.clisp.org/haible/hashfunc.html. */ |

| cnt = 0; |

| hval = keylen; |

| while (cnt < keylen) |

| { |

| hval = (hval << 9) | (hval >> (sizeof hval * CHAR_BIT - 9)); |

| hval += (hashval_t) *(((char *) key) + cnt++); |

| } |

| return hval != 0 ? hval : ~((hashval_t) 0); |

| } |