JavaScriptCore/kjs/pointer_hash.h

// -*- c-basic-offset: 2 -*-
/*
 *  This file is part of the KDE libraries
 *  Copyright (C) 2005 Apple Computer, Inc.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This 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
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 *  Boston, MA 02111-1307, USA.
 *
 */


#ifndef _KJS_POINTER_HASH_H_
#define _KJS_POINTER_HASH_H_

namespace KJS {

#include <stdint.h>

template <int size> unsigned pointerHash(void *pointer);

// Thomas Wang's 32 bit mix
// http://www.cris.com/~Ttwang/tech/inthash.htm
template <> inline unsigned pointerHash<4>(void *pointer) 
{
  uint32_t key = reinterpret_cast<uint32_t>(pointer);
  key += ~(key << 15);
  key ^= (key >> 10);
  key += (key << 3);
  key ^= (key >> 6);
  key += ~(key << 11);
  key ^= (key >> 16);
  return key;
}

// Thomas Wang's 64 bit mix
// http://www.cris.com/~Ttwang/tech/inthash.htm
template <> inline unsigned pointerHash<8>(void *pointer)
{
  uint64_t key = reinterpret_cast<uint64_t>(pointer);
  key += ~(key << 32);
  key ^= (key >> 22);
  key += ~(key << 13);
  key ^= (key >> 8);
  key += (key << 3);
  key ^= (key >> 15);
  key += ~(key << 27);
  key ^= (key >> 31);
  return key;
}

inline unsigned pointerHash(void *p)
{
    return pointerHash<sizeof(void *)>(p);
}

} // namespace KJS

#endif // _KJS_POINTER_HASH_H_