libstdc++
|
00001 // -*- C++ -*- 00002 00003 // Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the terms 00007 // of the GNU General Public License as published by the Free Software 00008 // Foundation; either version 3, or (at your option) any later 00009 // version. 00010 00011 // This library is distributed in the hope that it will be useful, but 00012 // WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00014 // General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL. 00026 00027 // Permission to use, copy, modify, sell, and distribute this software 00028 // is hereby granted without fee, provided that the above copyright 00029 // notice appears in all copies, and that both that copyright notice 00030 // and this permission notice appear in supporting documentation. None 00031 // of the above authors, nor IBM Haifa Research Laboratories, make any 00032 // representation about the suitability of this software for any 00033 // purpose. It is provided "as is" without express or implied 00034 // warranty. 00035 00036 /** 00037 * @file mask_based_range_hashing.hpp 00038 * Contains a range hashing policy base. 00039 */ 00040 00041 #ifndef PB_DS_MASK_BASED_RANGE_HASHING_HPP 00042 #define PB_DS_MASK_BASED_RANGE_HASHING_HPP 00043 00044 namespace __gnu_pbds 00045 { 00046 namespace detail 00047 { 00048 /// Range hashing policy. 00049 template<typename Size_Type> 00050 class mask_based_range_hashing 00051 { 00052 protected: 00053 typedef Size_Type size_type; 00054 00055 void 00056 swap(mask_based_range_hashing& other) 00057 { std::swap(m_mask, other.m_mask); } 00058 00059 void 00060 notify_resized(size_type size); 00061 00062 inline size_type 00063 range_hash(size_type hash) const 00064 { return size_type(hash & m_mask); } 00065 00066 private: 00067 size_type m_mask; 00068 const static size_type s_num_bits_in_size_type; 00069 const static size_type s_highest_bit_1; 00070 }; 00071 00072 template<typename Size_Type> 00073 const typename mask_based_range_hashing<Size_Type>::size_type 00074 mask_based_range_hashing<Size_Type>::s_num_bits_in_size_type = 00075 sizeof(typename mask_based_range_hashing<Size_Type>::size_type) << 3; 00076 00077 template<typename Size_Type> 00078 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); 00079 00080 00081 template<typename Size_Type> 00082 void 00083 mask_based_range_hashing<Size_Type>:: 00084 notify_resized(size_type size) 00085 { 00086 size_type i = 0; 00087 while (size ^ s_highest_bit_1) 00088 { 00089 size <<= 1; 00090 ++i; 00091 } 00092 00093 m_mask = 1; 00094 i += 2; 00095 while (i++ < s_num_bits_in_size_type) 00096 m_mask = (m_mask << 1) ^ 1; 00097 } 00098 } // namespace detail 00099 } // namespace __gnu_pbds 00100 00101 #endif