1 | #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED |
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2 | #define BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED |
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3 | |
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4 | // |
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5 | // weak_ptr.hpp |
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6 | // |
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7 | // Copyright (c) 2001, 2002, 2003 Peter Dimov |
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8 | // |
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9 | // Distributed under the Boost Software License, Version 1.0. (See |
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10 | // accompanying file LICENSE_1_0.txt or copy at |
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11 | // http://www.boost.org/LICENSE_1_0.txt) |
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12 | // |
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13 | // See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation. |
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14 | // |
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15 | |
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16 | #include <memory> // boost.TR1 include order fix |
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17 | #include <boost/smart_ptr/detail/shared_count.hpp> |
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18 | #include <boost/smart_ptr/shared_ptr.hpp> |
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19 | |
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20 | #ifdef BOOST_MSVC // moved here to work around VC++ compiler crash |
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21 | # pragma warning(push) |
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22 | # pragma warning(disable:4284) // odd return type for operator-> |
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23 | #endif |
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24 | |
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25 | namespace boost |
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26 | { |
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27 | |
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28 | template<class T> class weak_ptr |
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29 | { |
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30 | private: |
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31 | |
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32 | // Borland 5.5.1 specific workarounds |
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33 | typedef weak_ptr<T> this_type; |
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34 | |
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35 | public: |
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36 | |
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37 | typedef T element_type; |
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38 | |
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39 | weak_ptr(): px(0), pn() // never throws in 1.30+ |
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40 | { |
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41 | } |
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42 | |
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43 | // generated copy constructor, assignment, destructor are fine |
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44 | |
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45 | |
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46 | // |
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47 | // The "obvious" converting constructor implementation: |
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48 | // |
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49 | // template<class Y> |
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50 | // weak_ptr(weak_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws |
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51 | // { |
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52 | // } |
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53 | // |
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54 | // has a serious problem. |
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55 | // |
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56 | // r.px may already have been invalidated. The px(r.px) |
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57 | // conversion may require access to *r.px (virtual inheritance). |
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58 | // |
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59 | // It is not possible to avoid spurious access violations since |
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60 | // in multithreaded programs r.px may be invalidated at any point. |
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61 | // |
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62 | |
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63 | template<class Y> |
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64 | #if !defined( BOOST_SP_NO_SP_CONVERTIBLE ) |
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65 | |
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66 | weak_ptr( weak_ptr<Y> const & r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) |
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67 | |
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68 | #else |
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69 | |
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70 | weak_ptr( weak_ptr<Y> const & r ) |
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71 | |
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72 | #endif |
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73 | : px(r.lock().get()), pn(r.pn) // never throws |
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74 | { |
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75 | } |
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76 | |
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77 | #if defined( BOOST_HAS_RVALUE_REFS ) |
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78 | |
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79 | template<class Y> |
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80 | #if !defined( BOOST_SP_NO_SP_CONVERTIBLE ) |
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81 | |
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82 | weak_ptr( weak_ptr<Y> && r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) |
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83 | |
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84 | #else |
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85 | |
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86 | weak_ptr( weak_ptr<Y> && r ) |
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87 | |
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88 | #endif |
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89 | : px( r.lock().get() ), pn( static_cast< boost::detail::weak_count && >( r.pn ) ) // never throws |
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90 | { |
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91 | r.px = 0; |
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92 | } |
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93 | |
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94 | // for better efficiency in the T == Y case |
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95 | weak_ptr( weak_ptr && r ): px( r.px ), pn( static_cast< boost::detail::weak_count && >( r.pn ) ) // never throws |
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96 | { |
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97 | r.px = 0; |
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98 | } |
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99 | |
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100 | // for better efficiency in the T == Y case |
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101 | weak_ptr & operator=( weak_ptr && r ) // never throws |
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102 | { |
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103 | this_type( static_cast< weak_ptr && >( r ) ).swap( *this ); |
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104 | return *this; |
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105 | } |
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106 | |
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107 | |
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108 | #endif |
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109 | |
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110 | template<class Y> |
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111 | #if !defined( BOOST_SP_NO_SP_CONVERTIBLE ) |
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112 | |
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113 | weak_ptr( shared_ptr<Y> const & r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) |
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114 | |
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115 | #else |
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116 | |
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117 | weak_ptr( shared_ptr<Y> const & r ) |
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118 | |
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119 | #endif |
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120 | : px( r.px ), pn( r.pn ) // never throws |
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121 | { |
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122 | } |
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123 | |
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124 | #if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300) |
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125 | |
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126 | template<class Y> |
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127 | weak_ptr & operator=(weak_ptr<Y> const & r) // never throws |
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128 | { |
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129 | px = r.lock().get(); |
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130 | pn = r.pn; |
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131 | return *this; |
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132 | } |
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133 | |
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134 | #if defined( BOOST_HAS_RVALUE_REFS ) |
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135 | |
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136 | template<class Y> |
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137 | weak_ptr & operator=( weak_ptr<Y> && r ) |
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138 | { |
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139 | this_type( static_cast< weak_ptr<Y> && >( r ) ).swap( *this ); |
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140 | return *this; |
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141 | } |
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142 | |
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143 | #endif |
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144 | |
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145 | template<class Y> |
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146 | weak_ptr & operator=(shared_ptr<Y> const & r) // never throws |
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147 | { |
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148 | px = r.px; |
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149 | pn = r.pn; |
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150 | return *this; |
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151 | } |
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152 | |
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153 | #endif |
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154 | |
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155 | shared_ptr<T> lock() const // never throws |
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156 | { |
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157 | return shared_ptr<element_type>( *this, boost::detail::sp_nothrow_tag() ); |
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158 | } |
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159 | |
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160 | long use_count() const // never throws |
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161 | { |
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162 | return pn.use_count(); |
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163 | } |
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164 | |
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165 | bool expired() const // never throws |
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166 | { |
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167 | return pn.use_count() == 0; |
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168 | } |
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169 | |
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170 | bool _empty() const // extension, not in std::weak_ptr |
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171 | { |
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172 | return pn.empty(); |
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173 | } |
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174 | |
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175 | void reset() // never throws in 1.30+ |
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176 | { |
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177 | this_type().swap(*this); |
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178 | } |
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179 | |
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180 | void swap(this_type & other) // never throws |
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181 | { |
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182 | std::swap(px, other.px); |
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183 | pn.swap(other.pn); |
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184 | } |
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185 | |
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186 | void _internal_assign(T * px2, boost::detail::shared_count const & pn2) |
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187 | { |
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188 | px = px2; |
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189 | pn = pn2; |
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190 | } |
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191 | |
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192 | template<class Y> bool _internal_less(weak_ptr<Y> const & rhs) const |
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193 | { |
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194 | return pn < rhs.pn; |
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195 | } |
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196 | |
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197 | // Tasteless as this may seem, making all members public allows member templates |
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198 | // to work in the absence of member template friends. (Matthew Langston) |
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199 | |
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200 | #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS |
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201 | |
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202 | private: |
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203 | |
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204 | template<class Y> friend class weak_ptr; |
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205 | template<class Y> friend class shared_ptr; |
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206 | |
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207 | #endif |
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208 | |
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209 | T * px; // contained pointer |
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210 | boost::detail::weak_count pn; // reference counter |
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211 | |
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212 | }; // weak_ptr |
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213 | |
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214 | template<class T, class U> inline bool operator<(weak_ptr<T> const & a, weak_ptr<U> const & b) |
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215 | { |
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216 | return a._internal_less(b); |
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217 | } |
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218 | |
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219 | template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b) |
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220 | { |
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221 | a.swap(b); |
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222 | } |
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223 | |
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224 | } // namespace boost |
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225 | |
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226 | #ifdef BOOST_MSVC |
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227 | # pragma warning(pop) |
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228 | #endif |
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229 | |
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230 | #endif // #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED |
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