hash_prime_size_policy_imp.hpp
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// -*- C++ -*-
// Copyright (C) 2005-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
// Foundation; either version 3, or (at your option) any later
// version.
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
// Permission to use, copy, modify, sell, and distribute this software
// is hereby granted without fee, provided that the above copyright
// notice appears in all copies, and that both that copyright notice
// and this permission notice appear in supporting documentation. None
// of the above authors, nor IBM Haifa Research Laboratories, make any
// representation about the suitability of this software for any
// purpose. It is provided "as is" without express or implied
// warranty.
/**
* @file hash_prime_size_policy_imp.hpp
* Contains a resize size policy implementation.
*/
#pragma GCC system_header
namespace detail
{
enum
{
num_distinct_sizes_32_bit = 30,
num_distinct_sizes_64_bit = 62,
num_distinct_sizes = sizeof(std::size_t) != 8 ?
num_distinct_sizes_32_bit : num_distinct_sizes_64_bit,
};
// Originally taken from the SGI implementation; acknowledged in the docs.
// Further modified (for 64 bits) from tr1's hashtable.
static const std::size_t g_a_sizes[num_distinct_sizes_64_bit] =
{
/* 0 */ 5ul,
/* 1 */ 11ul,
/* 2 */ 23ul,
/* 3 */ 47ul,
/* 4 */ 97ul,
/* 5 */ 199ul,
/* 6 */ 409ul,
/* 7 */ 823ul,
/* 8 */ 1741ul,
/* 9 */ 3469ul,
/* 10 */ 6949ul,
/* 11 */ 14033ul,
/* 12 */ 28411ul,
/* 13 */ 57557ul,
/* 14 */ 116731ul,
/* 15 */ 236897ul,
/* 16 */ 480881ul,
/* 17 */ 976369ul,
/* 18 */ 1982627ul,
/* 19 */ 4026031ul,
/* 20 */ 8175383ul,
/* 21 */ 16601593ul,
/* 22 */ 33712729ul,
/* 23 */ 68460391ul,
/* 24 */ 139022417ul,
/* 25 */ 282312799ul,
/* 26 */ 573292817ul,
/* 27 */ 1164186217ul,
/* 28 */ 2364114217ul,
/* 29 */ 4294967291ul,
/* 30 */ (std::size_t)8589934583ull,
/* 31 */ (std::size_t)17179869143ull,
/* 32 */ (std::size_t)34359738337ull,
/* 33 */ (std::size_t)68719476731ull,
/* 34 */ (std::size_t)137438953447ull,
/* 35 */ (std::size_t)274877906899ull,
/* 36 */ (std::size_t)549755813881ull,
/* 37 */ (std::size_t)1099511627689ull,
/* 38 */ (std::size_t)2199023255531ull,
/* 39 */ (std::size_t)4398046511093ull,
/* 40 */ (std::size_t)8796093022151ull,
/* 41 */ (std::size_t)17592186044399ull,
/* 42 */ (std::size_t)35184372088777ull,
/* 43 */ (std::size_t)70368744177643ull,
/* 44 */ (std::size_t)140737488355213ull,
/* 45 */ (std::size_t)281474976710597ull,
/* 46 */ (std::size_t)562949953421231ull,
/* 47 */ (std::size_t)1125899906842597ull,
/* 48 */ (std::size_t)2251799813685119ull,
/* 49 */ (std::size_t)4503599627370449ull,
/* 50 */ (std::size_t)9007199254740881ull,
/* 51 */ (std::size_t)18014398509481951ull,
/* 52 */ (std::size_t)36028797018963913ull,
/* 53 */ (std::size_t)72057594037927931ull,
/* 54 */ (std::size_t)144115188075855859ull,
/* 55 */ (std::size_t)288230376151711717ull,
/* 56 */ (std::size_t)576460752303423433ull,
/* 57 */ (std::size_t)1152921504606846883ull,
/* 58 */ (std::size_t)2305843009213693951ull,
/* 59 */ (std::size_t)4611686018427387847ull,
/* 60 */ (std::size_t)9223372036854775783ull,
/* 61 */ (std::size_t)18446744073709551557ull,
};
} // namespace detail
PB_DS_CLASS_T_DEC
inline
PB_DS_CLASS_C_DEC::
hash_prime_size_policy(size_type n) : m_start_size(n)
{ m_start_size = get_nearest_larger_size(n); }
PB_DS_CLASS_T_DEC
inline void
PB_DS_CLASS_C_DEC::
swap(PB_DS_CLASS_C_DEC& other)
{ std::swap(m_start_size, other.m_start_size); }
PB_DS_CLASS_T_DEC
inline PB_DS_CLASS_C_DEC::size_type
PB_DS_CLASS_C_DEC::
get_nearest_larger_size(size_type n) const
{
const std::size_t* const p_upper = std::upper_bound(detail::g_a_sizes,
detail::g_a_sizes + detail::num_distinct_sizes, n);
if (p_upper == detail::g_a_sizes + detail::num_distinct_sizes)
__throw_resize_error();
return *p_upper;
}
PB_DS_CLASS_T_DEC
inline PB_DS_CLASS_C_DEC::size_type
PB_DS_CLASS_C_DEC::
get_nearest_smaller_size(size_type n) const
{
const std::size_t* p_lower = std::lower_bound(detail::g_a_sizes,
detail::g_a_sizes + detail::num_distinct_sizes, n);
if (*p_lower >= n && p_lower != detail::g_a_sizes)
--p_lower;
if (*p_lower < m_start_size)
return m_start_size;
return *p_lower;
}