/* This file is part of KDevelop
   Copyright 2012 Olivier de Gaalon <olivier.jg@gmail.com>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License version 2 as published by the Free Software Foundation.

   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., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/

#ifndef KDEVPLATFORM_KDEVHASH_H
#define KDEVPLATFORM_KDEVHASH_H

#include <QHash>

/**
 * A helper class to implement hashing for aggregate types.
 *
 * @code
 * class MyType {
 *     ...
 *     uint hash() const
 *     {
 *         KDevHash hash;
 *         return hash << m_1 << m_2 << ...;
 *     }
 * };
 * @endcode
 */
class KDevHash
{
public:
  enum {
      DEFAULT_SEED = 2166136261u
  };

  explicit KDevHash(uint hash = DEFAULT_SEED)
    : m_hash(hash)
  {}

  KDevHash(const KDevHash&) = delete;
  KDevHash& operator=(const KDevHash&) = delete;

  inline operator uint() const
  {
    return m_hash;
  }

  template<typename T>
  inline KDevHash& operator<<(T value)
  {
    m_hash = hash_combine(m_hash, qHash(value));
    return *this;
  }

  static inline uint hash_combine(uint seed, uint hash)
  {
    // this is copied from boost::hash_combine
    return seed ^ (hash + 0x9e3779b9 + (seed << 6) + (seed >> 2));
  }

private:
  uint m_hash;
};

#endif //KDEVPLATFORM_KDEVHASH_H
