1 // std::__detail definitions -*- C++ -*-
3 // Copyright (C) 2007-2013 Free Software Foundation, Inc.
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)
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.
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.
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/>.
25 #if __cplusplus < 201103L
26 # error "hashtable_c++0x.cc must be compiled with -std=gnu++0x"
29 #include <initializer_list>
31 #include <bits/hashtable_policy.h>
33 namespace std _GLIBCXX_VISIBILITY(default)
35 #include "../shared/hashtable-aux.cc"
39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
41 // Return a prime no smaller than n.
43 _Prime_rehash_policy::_M_next_bkt(std::size_t __n) const
45 // Optimize lookups involving the first elements of __prime_list.
46 // (useful to speed-up, eg, constructors)
47 static const unsigned char __fast_bkt[12]
48 = { 2, 2, 2, 3, 5, 5, 7, 7, 11, 11, 11, 11 };
53 __builtin_ceil(__fast_bkt[__n] * (long double)_M_max_load_factor);
54 return __fast_bkt[__n];
57 const unsigned long* __next_bkt =
58 std::lower_bound(__prime_list + 5, __prime_list + _S_n_primes, __n);
60 __builtin_ceil(*__next_bkt * (long double)_M_max_load_factor);
64 // Finds the smallest prime p such that alpha p > __n_elt + __n_ins.
65 // If p > __n_bkt, return make_pair(true, p); otherwise return
66 // make_pair(false, 0). In principle this isn't very different from
67 // _M_bkt_for_elements.
69 // The only tricky part is that we're caching the element count at
70 // which we need to rehash, so we don't have to do a floating-point
71 // multiply for every insertion.
73 std::pair<bool, std::size_t>
74 _Prime_rehash_policy::
75 _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,
76 std::size_t __n_ins) const
78 if (__n_elt + __n_ins >= _M_next_resize)
80 long double __min_bkts = (__n_elt + __n_ins)
81 / (long double)_M_max_load_factor;
82 if (__min_bkts >= __n_bkt)
83 return std::make_pair(true,
84 _M_next_bkt(std::max<std::size_t>(__builtin_floor(__min_bkts) + 1,
85 __n_bkt * _S_growth_factor)));
88 = __builtin_floor(__n_bkt * (long double)_M_max_load_factor);
89 return std::make_pair(false, 0);
92 return std::make_pair(false, 0);
95 _GLIBCXX_END_NAMESPACE_VERSION
96 } // namespace __detail