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Diffstat (limited to 'REORG.TODO/locale/hashval.h')
-rw-r--r-- | REORG.TODO/locale/hashval.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/REORG.TODO/locale/hashval.h b/REORG.TODO/locale/hashval.h new file mode 100644 index 0000000000..13dabcd692 --- /dev/null +++ b/REORG.TODO/locale/hashval.h @@ -0,0 +1,43 @@ +/* Implement simple hashing table with string based keys. + Copyright (C) 1994-2017 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, see + <http://www.gnu.org/licenses/>. */ + +#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) ((const unsigned char *) key)[cnt++]; + } + return hval != 0 ? hval : ~((hashval_t) 0); +} |