libstdc++-v3/src/c++11/hashtable_c++0x.cc

   1 // std::__detail definitions -*- C++ -*-
   2
   3 // Copyright (C) 2007-2013 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
   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
  45   _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::
  77   _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