mingw/lib/gcc/mingw32/4.3.3/include/c++/ext/pb_ds/detail/hash_fn/mask_based_range_hashing.hpp

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 2, or (at your option) any later
   9 // version.
  10
  11 // This library is distributed in the hope that it will be useful, but
  12 // WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 // General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License
  17 // along with this library; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  19 // MA 02111-1307, USA.
  20
  21 // As a special exception, you may use this file as part of a free
  22 // software library without restriction.  Specifically, if other files
  23 // instantiate templates or use macros or inline functions from this
  24 // file, or you compile this file and link it with other files to
  25 // produce an executable, this file does not by itself cause the
  26 // resulting executable to be covered by the GNU General Public
  27 // License.  This exception does not however invalidate any other
  28 // reasons why the executable file might be covered by the GNU General
  29 // Public License.
  30
  31 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  32
  33 // Permission to use, copy, modify, sell, and distribute this software
  34 // is hereby granted without fee, provided that the above copyright
  35 // notice appears in all copies, and that both that copyright notice
  36 // and this permission notice appear in supporting documentation. None
  37 // of the above authors, nor IBM Haifa Research Laboratories, make any
  38 // representation about the suitability of this software for any
  39 // purpose. It is provided "as is" without express or implied
  40 // warranty.
  41
  42 /**
  43  * @file mask_based_range_hashing.hpp
  44  * Contains a range hashing policy base.
  45  */
  46
  47 #ifndef PB_DS_MASK_BASED_RANGE_HASHING_HPP
  48 #define PB_DS_MASK_BASED_RANGE_HASHING_HPP
  49
  50 namespace __gnu_pbds
  51 {
  52   namespace detail
  53   {
  54 #define PB_DS_CLASS_T_DEC template<typename Size_Type>
  55 #define PB_DS_CLASS_C_DEC mask_based_range_hashing<Size_Type>
  56
  57     template<typename Size_Type>
  58     class mask_based_range_hashing
  59     {
  60     protected:
  61       typedef Size_Type size_type;
  62
  63       void
  64       swap(mask_based_range_hashing& other)
  65       { std::swap(m_mask, other.m_mask); }
  66
  67       void
  68       notify_resized(size_type size);
  69
  70       inline size_type
  71       range_hash(size_type hash) const
  72       { return size_type(hash & m_mask); }
  73
  74     private:
  75       size_type                 m_mask;
  76       const static size_type    s_num_bits_in_size_type;
  77       const static size_type    s_highest_bit_1;
  78     };
  79
  80     PB_DS_CLASS_T_DEC
  81     const typename PB_DS_CLASS_C_DEC::size_type
  82     PB_DS_CLASS_C_DEC::s_num_bits_in_size_type =
  83       sizeof(typename PB_DS_CLASS_C_DEC::size_type) << 3;
  84
  85     PB_DS_CLASS_T_DEC
  86     const typename PB_DS_CLASS_C_DEC::size_type PB_DS_CLASS_C_DEC::s_highest_bit_1 = static_cast<typename PB_DS_CLASS_C_DEC::size_type>(1) << (s_num_bits_in_size_type - 1);
  87
  88
  89     PB_DS_CLASS_T_DEC
  90     void
  91     PB_DS_CLASS_C_DEC::
  92     notify_resized(size_type size)
  93     {
  94       size_type i = 0;
  95       while (size ^ s_highest_bit_1)
  96         {
  97           size <<= 1;
  98           ++i;
  99         }
 100
 101       m_mask = 1;
 102       i += 2;
 103       while (i++ < s_num_bits_in_size_type)
 104         m_mask = (m_mask << 1) ^ 1;
 105     }
 106
 107 #undef PB_DS_CLASS_T_DEC
 108 #undef PB_DS_CLASS_C_DEC
 109
 110   } // namespace detail
 111 } // namespace __gnu_pbds
 112
 113 #endif