1 // -*- C++ -*- 2 3 // Copyright (C) 2005-2013 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 3, 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 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL. 26 27 // Permission to use, copy, modify, sell, and distribute this software 28 // is hereby granted without fee, provided that the above copyright 29 // notice appears in all copies, and that both that copyright notice 30 // and this permission notice appear in supporting documentation. None 31 // of the above authors, nor IBM Haifa Research Laboratories, make any 32 // representation about the suitability of this software for any 33 // purpose. It is provided "as is" without express or implied 34 // warranty. 35 36 /** 37 * @file mask_based_range_hashing.hpp 38 * Contains a range hashing policy base. 39 */ 40 41 #ifndef PB_DS_MASK_BASED_RANGE_HASHING_HPP 42 #define PB_DS_MASK_BASED_RANGE_HASHING_HPP 43 44 namespace __gnu_pbds 45 { 46 namespace detail 47 { 48 /// Range hashing policy. 49 template<typename Size_Type> 50 class mask_based_range_hashing 51 { 52 protected: 53 typedef Size_Type size_type; 54 55 void 56 swap(mask_based_range_hashing& other) 57 { std::swap(m_mask, other.m_mask); } 58 59 void 60 notify_resized(size_type size); 61 62 inline size_type 63 range_hash(size_type hash) const 64 { return size_type(hash & m_mask); } 65 66 private: 67 size_type m_mask; 68 const static size_type s_num_bits_in_size_type; 69 const static size_type s_highest_bit_1; 70 }; 71 72 template<typename Size_Type> 73 const typename mask_based_range_hashing<Size_Type>::size_type 74 mask_based_range_hashing<Size_Type>::s_num_bits_in_size_type = 75 sizeof(typename mask_based_range_hashing<Size_Type>::size_type) << 3; 76 77 template<typename Size_Type> 78 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); 79 80 81 template<typename Size_Type> 82 void 83 mask_based_range_hashing<Size_Type>:: 84 notify_resized(size_type size) 85 { 86 size_type i = 0; 87 while (size ^ s_highest_bit_1) 88 { 89 size <<= 1; 90 ++i; 91 } 92 93 m_mask = 1; 94 i += 2; 95 while (i++ < s_num_bits_in_size_type) 96 m_mask = (m_mask << 1) ^ 1; 97 } 98 } // namespace detail 99 } // namespace __gnu_pbds 100 101 #endif 102
