1 | #ifndef BOOST_ENABLE_SHARED_FROM_THIS2_HPP_INCLUDED |
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2 | #define BOOST_ENABLE_SHARED_FROM_THIS2_HPP_INCLUDED |
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3 | |
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4 | // |
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5 | // enable_shared_from_this2.hpp |
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6 | // |
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7 | // Copyright 2002, 2009 Peter Dimov |
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8 | // Copyright 2008 Frank Mori Hess |
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9 | // |
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10 | // Distributed under the Boost Software License, Version 1.0. |
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11 | // See accompanying file LICENSE_1_0.txt or copy at |
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12 | // http://www.boost.org/LICENSE_1_0.txt |
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13 | // |
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14 | |
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15 | #include <boost/config.hpp> |
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16 | #include <boost/shared_ptr.hpp> |
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17 | #include <boost/assert.hpp> |
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18 | #include <boost/detail/workaround.hpp> |
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19 | |
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20 | namespace boost |
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21 | { |
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22 | |
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23 | namespace detail |
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24 | { |
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25 | |
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26 | class esft2_deleter_wrapper |
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27 | { |
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28 | private: |
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29 | |
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30 | shared_ptr<void> deleter_; |
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31 | |
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32 | public: |
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33 | |
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34 | esft2_deleter_wrapper() |
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35 | { |
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36 | } |
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37 | |
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38 | template< class T > void set_deleter( shared_ptr<T> const & deleter ) |
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39 | { |
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40 | deleter_ = deleter; |
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41 | } |
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42 | |
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43 | template< class T> void operator()( T* ) |
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44 | { |
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45 | BOOST_ASSERT( deleter_.use_count() <= 1 ); |
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46 | deleter_.reset(); |
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47 | } |
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48 | }; |
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49 | |
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50 | } // namespace detail |
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51 | |
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52 | template< class T > class enable_shared_from_this2 |
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53 | { |
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54 | protected: |
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55 | |
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56 | enable_shared_from_this2() |
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57 | { |
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58 | } |
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59 | |
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60 | enable_shared_from_this2( enable_shared_from_this2 const & ) |
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61 | { |
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62 | } |
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63 | |
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64 | enable_shared_from_this2 & operator=( enable_shared_from_this2 const & ) |
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65 | { |
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66 | return *this; |
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67 | } |
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68 | |
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69 | ~enable_shared_from_this2() |
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70 | { |
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71 | BOOST_ASSERT( shared_this_.use_count() <= 1 ); // make sure no dangling shared_ptr objects exist |
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72 | } |
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73 | |
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74 | private: |
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75 | |
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76 | mutable weak_ptr<T> weak_this_; |
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77 | mutable shared_ptr<T> shared_this_; |
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78 | |
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79 | public: |
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80 | |
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81 | shared_ptr<T> shared_from_this() |
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82 | { |
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83 | init_weak_once(); |
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84 | return shared_ptr<T>( weak_this_ ); |
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85 | } |
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86 | |
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87 | shared_ptr<T const> shared_from_this() const |
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88 | { |
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89 | init_weak_once(); |
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90 | return shared_ptr<T>( weak_this_ ); |
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91 | } |
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92 | |
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93 | private: |
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94 | |
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95 | void init_weak_once() const |
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96 | { |
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97 | if( weak_this_._empty() ) |
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98 | { |
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99 | shared_this_.reset( static_cast< T* >( 0 ), detail::esft2_deleter_wrapper() ); |
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100 | weak_this_ = shared_this_; |
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101 | } |
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102 | } |
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103 | |
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104 | public: // actually private, but avoids compiler template friendship issues |
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105 | |
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106 | // Note: invoked automatically by shared_ptr; do not call |
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107 | template<class X, class Y> void _internal_accept_owner( shared_ptr<X> * ppx, Y * py ) const |
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108 | { |
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109 | BOOST_ASSERT( ppx != 0 ); |
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110 | |
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111 | if( weak_this_.use_count() == 0 ) |
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112 | { |
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113 | weak_this_ = shared_ptr<T>( *ppx, py ); |
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114 | } |
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115 | else if( shared_this_.use_count() != 0 ) |
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116 | { |
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117 | BOOST_ASSERT( ppx->unique() ); // no weak_ptrs should exist either, but there's no way to check that |
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118 | |
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119 | detail::esft2_deleter_wrapper * pd = boost::get_deleter<detail::esft2_deleter_wrapper>( shared_this_ ); |
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120 | BOOST_ASSERT( pd != 0 ); |
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121 | |
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122 | pd->set_deleter( *ppx ); |
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123 | |
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124 | ppx->reset( shared_this_, ppx->get() ); |
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125 | shared_this_.reset(); |
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126 | } |
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127 | } |
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128 | }; |
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129 | |
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130 | } // namespace boost |
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131 | |
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132 | #endif // #ifndef BOOST_ENABLE_SHARED_FROM_THIS2_HPP_INCLUDED |
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