spot  0.9.1
hashfunc.hh
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00001 // Copyright (C) 2004, 2005  Laboratoire d'Informatique de Paris 6 (LIP6),
00002 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
00003 // et Marie Curie.
00004 //
00005 // This file is part of Spot, a model checking library.
00006 //
00007 // Spot is free software; you can redistribute it and/or modify it
00008 // under the terms of the GNU General Public License as published by
00009 // the Free Software Foundation; either version 2 of the License, or
00010 // (at your option) any later version.
00011 //
00012 // Spot is distributed in the hope that it will be useful, but WITHOUT
00013 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
00014 // or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
00015 // License for more details.
00016 //
00017 // You should have received a copy of the GNU General Public License
00018 // along with Spot; see the file COPYING.  If not, write to the Free
00019 // Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
00020 // 02111-1307, USA.
00021 
00022 #ifndef SPOT_MISC_HASHFUNC_HH
00023 # define SPOT_MISC_HASHFUNC_HH
00024 # include <cstddef>
00025 
00026 namespace spot
00027 {
00031 
00036   inline size_t
00037   wang32_hash(size_t key)
00038   {
00039     // We assume that size_t has at least 32bits.
00040     key += ~(key << 15);
00041     key ^=  (key >> 10);
00042     key +=  (key << 3);
00043     key ^=  (key >> 6);
00044     key += ~(key << 11);
00045     key ^=  (key >> 16);
00046     return key;
00047   }
00048 
00055   inline size_t
00056   knuth32_hash(size_t key)
00057   {
00058     // 2654435761 is the golden ratio of 2^32.  The right shift of 3
00059     // bits assumes that all objects are aligned on a 8 byte boundary.
00060     return (key >> 3) * 2654435761U;
00061   }
00063 }
00064 
00065 #endif // SPOT_MISC_HASHFUNC_HH

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