1 // std::__detail definitions -*- C++ -*- 2 3 // Copyright (C) 2007-2014 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 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU 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 #if __cplusplus < 201103L 26 # error "hashtable_c++0x.cc must be compiled with -std=gnu++0x" 27 #endif 28 29 #include <initializer_list> 30 #include <tuple> 31 #include <ext/aligned_buffer.h> 32 #include <ext/alloc_traits.h> 33 #include <bits/hashtable_policy.h> 34 35 namespace std _GLIBCXX_VISIBILITY(default) 36 { 37 #include "../shared/hashtable-aux.cc" 38 39 namespace __detail 40 { 41 _GLIBCXX_BEGIN_NAMESPACE_VERSION 42 43 // Return a prime no smaller than n. 44 std::size_t _M_next_bkt(std::size_t __n) const45 _Prime_rehash_policy::_M_next_bkt(std::size_t __n) const 46 { 47 // Optimize lookups involving the first elements of __prime_list. 48 // (useful to speed-up, eg, constructors) 49 static const unsigned char __fast_bkt[12] 50 = { 2, 2, 2, 3, 5, 5, 7, 7, 11, 11, 11, 11 }; 51 52 if (__n <= 11) 53 { 54 _M_next_resize = 55 __builtin_ceil(__fast_bkt[__n] * (long double)_M_max_load_factor); 56 return __fast_bkt[__n]; 57 } 58 59 const unsigned long* __next_bkt = 60 std::lower_bound(__prime_list + 5, __prime_list + _S_n_primes, __n); 61 _M_next_resize = 62 __builtin_ceil(*__next_bkt * (long double)_M_max_load_factor); 63 return *__next_bkt; 64 } 65 66 // Finds the smallest prime p such that alpha p > __n_elt + __n_ins. 67 // If p > __n_bkt, return make_pair(true, p); otherwise return 68 // make_pair(false, 0). In principle this isn't very different from 69 // _M_bkt_for_elements. 70 71 // The only tricky part is that we're caching the element count at 72 // which we need to rehash, so we don't have to do a floating-point 73 // multiply for every insertion. 74 75 std::pair<bool, std::size_t> 76 _Prime_rehash_policy:: _M_need_rehash(std::size_t __n_bkt,std::size_t __n_elt,std::size_t __n_ins) const77 _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt, 78 std::size_t __n_ins) const 79 { 80 if (__n_elt + __n_ins >= _M_next_resize) 81 { 82 long double __min_bkts = (__n_elt + __n_ins) 83 / (long double)_M_max_load_factor; 84 if (__min_bkts >= __n_bkt) 85 return std::make_pair(true, 86 _M_next_bkt(std::max<std::size_t>(__builtin_floor(__min_bkts) + 1, 87 __n_bkt * _S_growth_factor))); 88 89 _M_next_resize 90 = __builtin_floor(__n_bkt * (long double)_M_max_load_factor); 91 return std::make_pair(false, 0); 92 } 93 else 94 return std::make_pair(false, 0); 95 } 96 97 _GLIBCXX_END_NAMESPACE_VERSION 98 } // namespace __detail 99 } // namespace std 100