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36fed23c | 1 | // -*- C++ -*- |
2 | ||
f1717362 | 3 | // Copyright (C) 2005-2016 Free Software Foundation, Inc. |
36fed23c | 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 | |
6bc9506f | 8 | // Foundation; either version 3, or (at your option) any later |
36fed23c | 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 | ||
6bc9506f | 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. | |
36fed23c | 19 | |
6bc9506f | 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/>. | |
36fed23c | 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 | ||
b34535d7 | 44 | namespace __gnu_pbds |
36fed23c | 45 | { |
36fed23c | 46 | namespace detail |
47 | { | |
3f2eba6f | 48 | /// Range hashing policy. |
36fed23c | 49 | template<typename Size_Type> |
50 | class mask_based_range_hashing | |
51 | { | |
52 | protected: | |
3f2eba6f | 53 | typedef Size_Type size_type; |
36fed23c | 54 | |
36fed23c | 55 | void |
ce8b0a77 | 56 | swap(mask_based_range_hashing& other) |
57 | { std::swap(m_mask, other.m_mask); } | |
36fed23c | 58 | |
59 | void | |
60 | notify_resized(size_type size); | |
61 | ||
62 | inline size_type | |
ce8b0a77 | 63 | range_hash(size_type hash) const |
64 | { return size_type(hash & m_mask); } | |
36fed23c | 65 | |
66 | private: | |
ce8b0a77 | 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; | |
36fed23c | 70 | }; |
71 | ||
3f2eba6f | 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; | |
36fed23c | 76 | |
3f2eba6f | 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); | |
36fed23c | 79 | |
ce8b0a77 | 80 | |
3f2eba6f | 81 | template<typename Size_Type> |
36fed23c | 82 | void |
3f2eba6f | 83 | mask_based_range_hashing<Size_Type>:: |
36fed23c | 84 | notify_resized(size_type size) |
85 | { | |
86 | size_type i = 0; | |
36fed23c | 87 | while (size ^ s_highest_bit_1) |
88 | { | |
89 | size <<= 1; | |
36fed23c | 90 | ++i; |
91 | } | |
92 | ||
93 | m_mask = 1; | |
36fed23c | 94 | i += 2; |
36fed23c | 95 | while (i++ < s_num_bits_in_size_type) |
96 | m_mask = (m_mask << 1) ^ 1; | |
97 | } | |
36fed23c | 98 | } // namespace detail |
b34535d7 | 99 | } // namespace __gnu_pbds |
36fed23c | 100 | |
ce8b0a77 | 101 | #endif |