mask_based_range_hashing.hpp
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// -*- C++ -*-
// Copyright (C) 2005-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library 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 3, 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
// General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice
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/**
* @file mask_based_range_hashing.hpp
* Contains a range hashing policy base.
*/
#ifndef PB_DS_MASK_BASED_RANGE_HASHING_HPP
#define PB_DS_MASK_BASED_RANGE_HASHING_HPP
namespace __gnu_pbds
{
namespace detail
{
/// Range hashing policy.
template<typename Size_Type>
class mask_based_range_hashing
{
protected:
typedef Size_Type size_type;
void
swap(mask_based_range_hashing& other)
{ std::swap(m_mask, other.m_mask); }
void
notify_resized(size_type size);
inline size_type
range_hash(size_type hash) const
{ return size_type(hash & m_mask); }
private:
size_type m_mask;
const static size_type s_num_bits_in_size_type;
const static size_type s_highest_bit_1;
};
template<typename Size_Type>
const typename mask_based_range_hashing<Size_Type>::size_type
mask_based_range_hashing<Size_Type>::s_num_bits_in_size_type =
sizeof(typename mask_based_range_hashing<Size_Type>::size_type) << 3;
template<typename Size_Type>
const typename mask_based_range_hashing<Size_Type>::size_type mask_based_range_hashing<Size_Type>::s_highest_bit_1 = static_cast<typename mask_based_range_hashing<Size_Type>::size_type>(1) << (s_num_bits_in_size_type - 1);
template<typename Size_Type>
void
mask_based_range_hashing<Size_Type>::
notify_resized(size_type size)
{
size_type i = 0;
while (size ^ s_highest_bit_1)
{
size <<= 1;
++i;
}
m_mask = 1;
i += 2;
while (i++ < s_num_bits_in_size_type)
m_mask = (m_mask << 1) ^ 1;
}
} // namespace detail
} // namespace __gnu_pbds
#endif