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 pb_ds 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 swap(mask_based_range_hashing & other)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 range_hash(size_type hash) const71 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:: notify_resized(size_type size)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 pb_ds 112 113 #endif 114