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1 //===----------------------------------------------------------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #ifndef _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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10 #define _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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11
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12 #include <__config>
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13 #include <__algorithm/rotate.h>
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14 #include <__iterator/iterator_traits.h>
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223
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15 #include <__utility/swap.h>
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221
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16 #include <memory>
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17
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18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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19 #pragma GCC system_header
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20 #endif
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21
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22 _LIBCPP_PUSH_MACROS
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23 #include <__undef_macros>
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24
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25 _LIBCPP_BEGIN_NAMESPACE_STD
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26
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27 template <class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
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28 _ForwardIterator
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29 __stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
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30 _Distance __len, _Pair __p, forward_iterator_tag __fit)
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31 {
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32 // *__first is known to be false
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33 // __len >= 1
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34 if (__len == 1)
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35 return __first;
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36 if (__len == 2)
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37 {
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38 _ForwardIterator __m = __first;
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39 if (__pred(*++__m))
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40 {
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41 swap(*__first, *__m);
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42 return __m;
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43 }
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44 return __first;
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45 }
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46 if (__len <= __p.second)
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47 { // The buffer is big enough to use
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48 typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
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49 __destruct_n __d(0);
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50 unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
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51 // Move the falses into the temporary buffer, and the trues to the front of the line
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52 // Update __first to always point to the end of the trues
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53 value_type* __t = __p.first;
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54 ::new ((void*)__t) value_type(_VSTD::move(*__first));
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55 __d.template __incr<value_type>();
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56 ++__t;
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57 _ForwardIterator __i = __first;
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58 while (++__i != __last)
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59 {
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60 if (__pred(*__i))
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61 {
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62 *__first = _VSTD::move(*__i);
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63 ++__first;
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64 }
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65 else
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66 {
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67 ::new ((void*)__t) value_type(_VSTD::move(*__i));
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68 __d.template __incr<value_type>();
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69 ++__t;
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70 }
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71 }
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72 // All trues now at start of range, all falses in buffer
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73 // Move falses back into range, but don't mess up __first which points to first false
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74 __i = __first;
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75 for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
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76 *__i = _VSTD::move(*__t2);
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77 // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
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78 return __first;
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79 }
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80 // Else not enough buffer, do in place
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81 // __len >= 3
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82 _ForwardIterator __m = __first;
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83 _Distance __len2 = __len / 2; // __len2 >= 2
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84 _VSTD::advance(__m, __len2);
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85 // recurse on [__first, __m), *__first know to be false
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86 // F?????????????????
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87 // f m l
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88 typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
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89 _ForwardIterator __first_false = _VSTD::__stable_partition<_PredRef>(__first, __m, __pred, __len2, __p, __fit);
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90 // TTTFFFFF??????????
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91 // f ff m l
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92 // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
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93 _ForwardIterator __m1 = __m;
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94 _ForwardIterator __second_false = __last;
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95 _Distance __len_half = __len - __len2;
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96 while (__pred(*__m1))
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97 {
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98 if (++__m1 == __last)
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99 goto __second_half_done;
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100 --__len_half;
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101 }
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102 // TTTFFFFFTTTF??????
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103 // f ff m m1 l
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104 __second_false = _VSTD::__stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __fit);
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105 __second_half_done:
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106 // TTTFFFFFTTTTTFFFFF
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107 // f ff m sf l
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108 return _VSTD::rotate(__first_false, __m, __second_false);
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109 // TTTTTTTTFFFFFFFFFF
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110 // |
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111 }
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112
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113 template <class _Predicate, class _ForwardIterator>
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114 _ForwardIterator
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115 __stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
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116 forward_iterator_tag)
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117 {
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118 const unsigned __alloc_limit = 3; // might want to make this a function of trivial assignment
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119 // Either prove all true and return __first or point to first false
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120 while (true)
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121 {
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122 if (__first == __last)
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123 return __first;
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124 if (!__pred(*__first))
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125 break;
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126 ++__first;
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127 }
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128 // We now have a reduced range [__first, __last)
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129 // *__first is known to be false
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130 typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
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131 typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
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132 difference_type __len = _VSTD::distance(__first, __last);
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133 pair<value_type*, ptrdiff_t> __p(0, 0);
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134 unique_ptr<value_type, __return_temporary_buffer> __h;
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135 if (__len >= __alloc_limit)
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136 {
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137 __p = _VSTD::get_temporary_buffer<value_type>(__len);
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138 __h.reset(__p.first);
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139 }
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140 return _VSTD::__stable_partition<typename add_lvalue_reference<_Predicate>::type>
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141 (__first, __last, __pred, __len, __p, forward_iterator_tag());
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142 }
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143
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144 template <class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
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145 _BidirectionalIterator
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146 __stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
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147 _Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
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148 {
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149 // *__first is known to be false
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150 // *__last is known to be true
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151 // __len >= 2
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152 if (__len == 2)
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153 {
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154 swap(*__first, *__last);
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155 return __last;
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156 }
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157 if (__len == 3)
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158 {
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159 _BidirectionalIterator __m = __first;
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160 if (__pred(*++__m))
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161 {
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162 swap(*__first, *__m);
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163 swap(*__m, *__last);
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164 return __last;
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165 }
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166 swap(*__m, *__last);
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167 swap(*__first, *__m);
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168 return __m;
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169 }
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170 if (__len <= __p.second)
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171 { // The buffer is big enough to use
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172 typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
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173 __destruct_n __d(0);
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174 unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
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175 // Move the falses into the temporary buffer, and the trues to the front of the line
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176 // Update __first to always point to the end of the trues
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177 value_type* __t = __p.first;
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178 ::new ((void*)__t) value_type(_VSTD::move(*__first));
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179 __d.template __incr<value_type>();
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180 ++__t;
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181 _BidirectionalIterator __i = __first;
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182 while (++__i != __last)
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183 {
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184 if (__pred(*__i))
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185 {
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186 *__first = _VSTD::move(*__i);
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187 ++__first;
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188 }
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189 else
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190 {
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191 ::new ((void*)__t) value_type(_VSTD::move(*__i));
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192 __d.template __incr<value_type>();
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193 ++__t;
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194 }
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195 }
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196 // move *__last, known to be true
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197 *__first = _VSTD::move(*__i);
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198 __i = ++__first;
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199 // All trues now at start of range, all falses in buffer
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200 // Move falses back into range, but don't mess up __first which points to first false
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201 for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
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202 *__i = _VSTD::move(*__t2);
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203 // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
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204 return __first;
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205 }
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206 // Else not enough buffer, do in place
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207 // __len >= 4
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208 _BidirectionalIterator __m = __first;
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209 _Distance __len2 = __len / 2; // __len2 >= 2
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210 _VSTD::advance(__m, __len2);
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211 // recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
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212 // F????????????????T
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213 // f m l
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214 _BidirectionalIterator __m1 = __m;
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215 _BidirectionalIterator __first_false = __first;
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216 _Distance __len_half = __len2;
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217 while (!__pred(*--__m1))
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218 {
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219 if (__m1 == __first)
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220 goto __first_half_done;
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221 --__len_half;
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222 }
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223 // F???TFFF?????????T
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224 // f m1 m l
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225 typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
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226 __first_false = _VSTD::__stable_partition<_PredRef>(__first, __m1, __pred, __len_half, __p, __bit);
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227 __first_half_done:
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228 // TTTFFFFF?????????T
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229 // f ff m l
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230 // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
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231 __m1 = __m;
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232 _BidirectionalIterator __second_false = __last;
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233 ++__second_false;
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234 __len_half = __len - __len2;
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235 while (__pred(*__m1))
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236 {
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237 if (++__m1 == __last)
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238 goto __second_half_done;
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239 --__len_half;
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240 }
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241 // TTTFFFFFTTTF?????T
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242 // f ff m m1 l
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243 __second_false = _VSTD::__stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __bit);
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244 __second_half_done:
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245 // TTTFFFFFTTTTTFFFFF
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246 // f ff m sf l
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247 return _VSTD::rotate(__first_false, __m, __second_false);
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248 // TTTTTTTTFFFFFFFFFF
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249 // |
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250 }
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251
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252 template <class _Predicate, class _BidirectionalIterator>
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253 _BidirectionalIterator
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254 __stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
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255 bidirectional_iterator_tag)
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256 {
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257 typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
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258 typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
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259 const difference_type __alloc_limit = 4; // might want to make this a function of trivial assignment
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260 // Either prove all true and return __first or point to first false
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261 while (true)
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262 {
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263 if (__first == __last)
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264 return __first;
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265 if (!__pred(*__first))
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266 break;
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267 ++__first;
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268 }
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269 // __first points to first false, everything prior to __first is already set.
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270 // Either prove [__first, __last) is all false and return __first, or point __last to last true
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271 do
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272 {
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273 if (__first == --__last)
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274 return __first;
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275 } while (!__pred(*__last));
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276 // We now have a reduced range [__first, __last]
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277 // *__first is known to be false
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278 // *__last is known to be true
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279 // __len >= 2
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280 difference_type __len = _VSTD::distance(__first, __last) + 1;
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281 pair<value_type*, ptrdiff_t> __p(0, 0);
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282 unique_ptr<value_type, __return_temporary_buffer> __h;
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283 if (__len >= __alloc_limit)
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284 {
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285 __p = _VSTD::get_temporary_buffer<value_type>(__len);
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286 __h.reset(__p.first);
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287 }
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288 return _VSTD::__stable_partition<typename add_lvalue_reference<_Predicate>::type>
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289 (__first, __last, __pred, __len, __p, bidirectional_iterator_tag());
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290 }
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291
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292 template <class _ForwardIterator, class _Predicate>
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293 inline _LIBCPP_INLINE_VISIBILITY
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294 _ForwardIterator
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295 stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
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296 {
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297 return _VSTD::__stable_partition<typename add_lvalue_reference<_Predicate>::type>
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298 (__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
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299 }
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300
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301 _LIBCPP_END_NAMESPACE_STD
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302
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303 _LIBCPP_POP_MACROS
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304
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305 #endif // _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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