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1 // <bit> -*- C++ -*-
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2
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145
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3 // Copyright (C) 2018-2020 Free Software Foundation, Inc.
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131
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4 //
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5 // This file is part of the GNU ISO C++ Library. This library is free
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6 // software; you can redistribute it and/or modify it under the
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7 // terms of the GNU General Public License as published by the
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8 // Free Software Foundation; either version 3, or (at your option)
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9 // any later version.
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10
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11 // This library is distributed in the hope that it will be useful,
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12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 // GNU General Public License for more details.
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15
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16 // Under Section 7 of GPL version 3, you are granted additional
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17 // permissions described in the GCC Runtime Library Exception, version
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18 // 3.1, as published by the Free Software Foundation.
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19
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20 // You should have received a copy of the GNU General Public License and
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21 // a copy of the GCC Runtime Library Exception along with this program;
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 // <http://www.gnu.org/licenses/>.
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24
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25 /** @file include/bit
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26 * This is a Standard C++ Library header.
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27 */
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28
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29 #ifndef _GLIBCXX_BIT
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30 #define _GLIBCXX_BIT 1
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31
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32 #pragma GCC system_header
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33
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34 #if __cplusplus >= 201402L
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35
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36 #include <type_traits>
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37 #include <limits>
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38
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39 namespace std _GLIBCXX_VISIBILITY(default)
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40 {
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41 _GLIBCXX_BEGIN_NAMESPACE_VERSION
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42
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145
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43 /**
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44 * @defgroup bit_manip Bit manipulation
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45 * @ingroup numerics
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46 *
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47 * Utilities for examining and manipulating individual bits.
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48 *
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49 * @{
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50 */
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51
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52 /// @cond undoc
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53
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131
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54 template<typename _Tp>
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55 constexpr _Tp
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56 __rotl(_Tp __x, int __s) noexcept
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131
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57 {
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58 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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59 const int __r = __s % _Nd;
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60 if (__r == 0)
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61 return __x;
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62 else if (__r > 0)
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63 return (__x << __r) | (__x >> ((_Nd - __r) % _Nd));
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64 else
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65 return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r)
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131
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66 }
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67
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68 template<typename _Tp>
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69 constexpr _Tp
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70 __rotr(_Tp __x, int __s) noexcept
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131
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71 {
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72 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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73 const int __r = __s % _Nd;
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74 if (__r == 0)
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75 return __x;
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76 else if (__r > 0)
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77 return (__x >> __r) | (__x << ((_Nd - __r) % _Nd));
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78 else
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79 return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r)
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131
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80 }
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81
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82 template<typename _Tp>
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83 constexpr int
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84 __countl_zero(_Tp __x) noexcept
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85 {
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86 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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87
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88 if (__x == 0)
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89 return _Nd;
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90
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91 constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
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92 constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
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93 constexpr auto _Nd_u = numeric_limits<unsigned>::digits;
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94
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95 if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
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96 {
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97 constexpr int __diff = _Nd_u - _Nd;
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98 return __builtin_clz(__x) - __diff;
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99 }
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100 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
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101 {
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102 constexpr int __diff = _Nd_ul - _Nd;
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103 return __builtin_clzl(__x) - __diff;
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104 }
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105 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
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106 {
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107 constexpr int __diff = _Nd_ull - _Nd;
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108 return __builtin_clzll(__x) - __diff;
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109 }
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110 else // (_Nd > _Nd_ull)
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111 {
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112 static_assert(_Nd <= (2 * _Nd_ull),
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113 "Maximum supported integer size is 128-bit");
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114
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115 unsigned long long __high = __x >> _Nd_ull;
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116 if (__high != 0)
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117 {
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118 constexpr int __diff = (2 * _Nd_ull) - _Nd;
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119 return __builtin_clzll(__high) - __diff;
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120 }
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121 constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
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122 unsigned long long __low = __x & __max_ull;
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123 return (_Nd - _Nd_ull) + __builtin_clzll(__low);
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124 }
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125 }
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126
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127 template<typename _Tp>
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128 constexpr int
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129 __countl_one(_Tp __x) noexcept
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130 {
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131 if (__x == numeric_limits<_Tp>::max())
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132 return numeric_limits<_Tp>::digits;
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133 return std::__countl_zero<_Tp>((_Tp)~__x);
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134 }
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135
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136 template<typename _Tp>
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137 constexpr int
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138 __countr_zero(_Tp __x) noexcept
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139 {
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140 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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141
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142 if (__x == 0)
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143 return _Nd;
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144
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145 constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
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146 constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
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147 constexpr auto _Nd_u = numeric_limits<unsigned>::digits;
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148
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149 if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
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150 return __builtin_ctz(__x);
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151 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
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152 return __builtin_ctzl(__x);
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153 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
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154 return __builtin_ctzll(__x);
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155 else // (_Nd > _Nd_ull)
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156 {
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157 static_assert(_Nd <= (2 * _Nd_ull),
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158 "Maximum supported integer size is 128-bit");
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159
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160 constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
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161 unsigned long long __low = __x & __max_ull;
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162 if (__low != 0)
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163 return __builtin_ctzll(__low);
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164 unsigned long long __high = __x >> _Nd_ull;
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165 return __builtin_ctzll(__high) + _Nd_ull;
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166 }
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167 }
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168
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169 template<typename _Tp>
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170 constexpr int
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171 __countr_one(_Tp __x) noexcept
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172 {
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173 if (__x == numeric_limits<_Tp>::max())
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174 return numeric_limits<_Tp>::digits;
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175 return std::__countr_zero((_Tp)~__x);
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176 }
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177
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178 template<typename _Tp>
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179 constexpr int
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180 __popcount(_Tp __x) noexcept
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181 {
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182 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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183
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184 if (__x == 0)
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185 return 0;
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186
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187 constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
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188 constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
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189 constexpr auto _Nd_u = numeric_limits<unsigned>::digits;
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190
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191 if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
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192 return __builtin_popcount(__x);
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193 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
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194 return __builtin_popcountl(__x);
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195 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
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196 return __builtin_popcountll(__x);
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197 else // (_Nd > _Nd_ull)
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198 {
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199 static_assert(_Nd <= (2 * _Nd_ull),
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200 "Maximum supported integer size is 128-bit");
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201
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202 constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
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203 unsigned long long __low = __x & __max_ull;
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204 unsigned long long __high = __x >> _Nd_ull;
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205 return __builtin_popcountll(__low) + __builtin_popcountll(__high);
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206 }
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207 }
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208
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209 template<typename _Tp>
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210 constexpr bool
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211 __ispow2(_Tp __x) noexcept
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212 { return std::__popcount(__x) == 1; }
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213
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214 template<typename _Tp>
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215 constexpr _Tp
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216 __ceil2(_Tp __x) noexcept
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217 {
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218 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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219 if (__x == 0 || __x == 1)
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220 return 1;
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221 auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u));
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222 // If the shift exponent equals _Nd then the correct result is not
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223 // representable as a value of _Tp, and so the result is undefined.
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224 // Want that undefined behaviour to be detected in constant expressions,
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225 // by UBSan, and by debug assertions.
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226 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
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227 if (!__builtin_is_constant_evaluated())
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228 {
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229 __glibcxx_assert( __shift_exponent != numeric_limits<_Tp>::digits );
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230 }
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231 #endif
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232 using __promoted_type = decltype(__x << 1);
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233 if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value)
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234 {
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235 // If __x undergoes integral promotion then shifting by _Nd is
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236 // not undefined. In order to make the shift undefined, so that
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237 // it is diagnosed in constant expressions and by UBsan, we also
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238 // need to "promote" the shift exponent to be too large for the
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239 // promoted type.
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240 const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2;
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241 __shift_exponent |= (__shift_exponent & _Nd) << __extra_exp;
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242 }
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243 return (_Tp)1u << __shift_exponent;
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131
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244 }
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245
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246 template<typename _Tp>
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247 constexpr _Tp
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248 __floor2(_Tp __x) noexcept
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249 {
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250 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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251 if (__x == 0)
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252 return 0;
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253 return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1)));
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254 }
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255
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256 template<typename _Tp>
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257 constexpr _Tp
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258 __log2p1(_Tp __x) noexcept
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259 {
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260 constexpr auto _Nd = numeric_limits<_Tp>::digits;
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261 return _Nd - std::__countl_zero(__x);
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262 }
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263
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145
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264 /// @endcond
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265
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131
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266 #if __cplusplus > 201703L
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267
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145
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268 #define __cpp_lib_bitops 201907L
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131
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269
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270 /// @cond undoc
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271 template<typename _Tp, typename _Up = _Tp>
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272 using _If_is_unsigned_integer
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273 = enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>;
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274 /// @endcond
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275
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276 // [bit.rot], rotating
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277
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278 /// Rotate `x` to the left by `s` bits.
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131
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279 template<typename _Tp>
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280 [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
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281 rotl(_Tp __x, int __s) noexcept
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131
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282 { return std::__rotl(__x, __s); }
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283
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284 /// Rotate `x` to the right by `s` bits.
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131
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285 template<typename _Tp>
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286 [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
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287 rotr(_Tp __x, int __s) noexcept
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131
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288 { return std::__rotr(__x, __s); }
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289
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290 // [bit.count], counting
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291
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292 /// The number of contiguous zero bits, starting from the highest bit.
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293 template<typename _Tp>
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294 constexpr _If_is_unsigned_integer<_Tp, int>
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295 countl_zero(_Tp __x) noexcept
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296 { return std::__countl_zero(__x); }
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297
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298 /// The number of contiguous one bits, starting from the highest bit.
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299 template<typename _Tp>
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300 constexpr _If_is_unsigned_integer<_Tp, int>
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301 countl_one(_Tp __x) noexcept
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302 { return std::__countl_one(__x); }
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303
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304 /// The number of contiguous zero bits, starting from the lowest bit.
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131
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305 template<typename _Tp>
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306 constexpr _If_is_unsigned_integer<_Tp, int>
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307 countr_zero(_Tp __x) noexcept
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308 { return std::__countr_zero(__x); }
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309
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310 /// The number of contiguous one bits, starting from the lowest bit.
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131
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311 template<typename _Tp>
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312 constexpr _If_is_unsigned_integer<_Tp, int>
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313 countr_one(_Tp __x) noexcept
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314 { return std::__countr_one(__x); }
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315
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316 /// The number of bits set in `x`.
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131
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317 template<typename _Tp>
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318 constexpr _If_is_unsigned_integer<_Tp, int>
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319 popcount(_Tp __x) noexcept
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320 { return std::__popcount(__x); }
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321
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322 // [bit.pow.two], integral powers of 2
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323
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324 /// True if `x` is a power of two, false otherwise.
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131
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325 template<typename _Tp>
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326 constexpr _If_is_unsigned_integer<_Tp, bool>
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327 ispow2(_Tp __x) noexcept
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328 { return std::__ispow2(__x); }
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329
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330 /// The smallest power-of-two not less than `x`.
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131
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331 template<typename _Tp>
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332 constexpr _If_is_unsigned_integer<_Tp>
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333 ceil2(_Tp __x) noexcept
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334 { return std::__ceil2(__x); }
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335
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336 /// The largest power-of-two not greater than `x`.
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131
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337 template<typename _Tp>
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338 constexpr _If_is_unsigned_integer<_Tp>
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339 floor2(_Tp __x) noexcept
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340 { return std::__floor2(__x); }
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341
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342 /// The smallest integer greater than the base-2 logarithm of `x`.
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131
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343 template<typename _Tp>
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344 constexpr _If_is_unsigned_integer<_Tp>
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345 log2p1(_Tp __x) noexcept
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346 { return std::__log2p1(__x); }
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347
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145
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348 #define __cpp_lib_endian 201907L
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131
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349
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145
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350 /// Byte order
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351 enum class endian
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352 {
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353 little = __ORDER_LITTLE_ENDIAN__,
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354 big = __ORDER_BIG_ENDIAN__,
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355 native = __BYTE_ORDER__
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356 };
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357 #endif // C++2a
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131
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358
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145
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359 /// @}
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131
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360
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361 _GLIBCXX_END_NAMESPACE_VERSION
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362 } // namespace std
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363
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364 #endif // C++14
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365 #endif // _GLIBCXX_BIT
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