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Diffstat (limited to 'lib/hash-pjw.c')
-rw-r--r-- | lib/hash-pjw.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/lib/hash-pjw.c b/lib/hash-pjw.c new file mode 100644 index 0000000..bd94036 --- /dev/null +++ b/lib/hash-pjw.c @@ -0,0 +1,41 @@ +/* hash-pjw.c -- compute a hash value from a NUL-terminated string. + + Copyright (C) 2001, 2003, 2006 Free Software Foundation, Inc. + + 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 + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +#include <config.h> + +#include "hash-pjw.h" + +#include <limits.h> + +#define SIZE_BITS (sizeof (size_t) * CHAR_BIT) + +/* A hash function for NUL-terminated char* strings using + the method described by Bruno Haible. + See http://www.haible.de/bruno/hashfunc.html. */ + +size_t +hash_pjw (const void *x, size_t tablesize) +{ + const char *s; + size_t h = 0; + + for (s = x; *s; s++) + h = *s + ((h << 9) | (h >> (SIZE_BITS - 9))); + + return h % tablesize; +} |