1 | #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED |
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2 | #define BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED |
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3 | |
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4 | // MS compatible compilers support #pragma once |
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5 | |
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6 | #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
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7 | # pragma once |
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8 | #endif |
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9 | |
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10 | // |
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11 | // detail/sp_counted_base_gcc_x86.hpp - g++ on 486+ or AMD64 |
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12 | // |
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13 | // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd. |
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14 | // Copyright 2004-2005 Peter Dimov |
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15 | // |
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16 | // Distributed under the Boost Software License, Version 1.0. (See |
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17 | // accompanying file LICENSE_1_0.txt or copy at |
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18 | // http://www.boost.org/LICENSE_1_0.txt) |
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19 | // |
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20 | // |
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21 | // Lock-free algorithm by Alexander Terekhov |
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22 | // |
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23 | // Thanks to Ben Hitchings for the #weak + (#shared != 0) |
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24 | // formulation |
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25 | // |
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26 | |
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27 | #include <boost/detail/sp_typeinfo.hpp> |
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28 | |
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29 | namespace boost |
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30 | { |
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31 | |
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32 | namespace detail |
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33 | { |
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34 | |
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35 | inline int atomic_exchange_and_add( int * pw, int dv ) |
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36 | { |
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37 | // int r = *pw; |
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38 | // *pw += dv; |
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39 | // return r; |
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40 | |
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41 | int r; |
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42 | |
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43 | __asm__ __volatile__ |
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44 | ( |
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45 | "lock\n\t" |
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46 | "xadd %1, %0": |
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47 | "=m"( *pw ), "=r"( r ): // outputs (%0, %1) |
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48 | "m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1) |
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49 | "memory", "cc" // clobbers |
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50 | ); |
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51 | |
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52 | return r; |
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53 | } |
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54 | |
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55 | inline void atomic_increment( int * pw ) |
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56 | { |
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57 | //atomic_exchange_and_add( pw, 1 ); |
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58 | |
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59 | __asm__ |
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60 | ( |
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61 | "lock\n\t" |
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62 | "incl %0": |
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63 | "=m"( *pw ): // output (%0) |
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64 | "m"( *pw ): // input (%1) |
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65 | "cc" // clobbers |
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66 | ); |
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67 | } |
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68 | |
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69 | inline int atomic_conditional_increment( int * pw ) |
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70 | { |
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71 | // int rv = *pw; |
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72 | // if( rv != 0 ) ++*pw; |
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73 | // return rv; |
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74 | |
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75 | int rv, tmp; |
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76 | |
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77 | __asm__ |
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78 | ( |
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79 | "movl %0, %%eax\n\t" |
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80 | "0:\n\t" |
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81 | "test %%eax, %%eax\n\t" |
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82 | "je 1f\n\t" |
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83 | "movl %%eax, %2\n\t" |
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84 | "incl %2\n\t" |
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85 | "lock\n\t" |
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86 | "cmpxchgl %2, %0\n\t" |
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87 | "jne 0b\n\t" |
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88 | "1:": |
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89 | "=m"( *pw ), "=&a"( rv ), "=&r"( tmp ): // outputs (%0, %1, %2) |
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90 | "m"( *pw ): // input (%3) |
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91 | "cc" // clobbers |
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92 | ); |
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93 | |
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94 | return rv; |
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95 | } |
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96 | |
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97 | class sp_counted_base |
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98 | { |
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99 | private: |
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100 | |
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101 | sp_counted_base( sp_counted_base const & ); |
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102 | sp_counted_base & operator= ( sp_counted_base const & ); |
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103 | |
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104 | int use_count_; // #shared |
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105 | int weak_count_; // #weak + (#shared != 0) |
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106 | |
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107 | public: |
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108 | |
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109 | sp_counted_base(): use_count_( 1 ), weak_count_( 1 ) |
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110 | { |
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111 | } |
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112 | |
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113 | virtual ~sp_counted_base() // nothrow |
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114 | { |
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115 | } |
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116 | |
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117 | // dispose() is called when use_count_ drops to zero, to release |
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118 | // the resources managed by *this. |
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119 | |
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120 | virtual void dispose() = 0; // nothrow |
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121 | |
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122 | // destroy() is called when weak_count_ drops to zero. |
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123 | |
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124 | virtual void destroy() // nothrow |
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125 | { |
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126 | delete this; |
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127 | } |
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128 | |
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129 | virtual void * get_deleter( sp_typeinfo const & ti ) = 0; |
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130 | |
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131 | void add_ref_copy() |
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132 | { |
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133 | atomic_increment( &use_count_ ); |
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134 | } |
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135 | |
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136 | bool add_ref_lock() // true on success |
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137 | { |
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138 | return atomic_conditional_increment( &use_count_ ) != 0; |
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139 | } |
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140 | |
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141 | void release() // nothrow |
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142 | { |
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143 | if( atomic_exchange_and_add( &use_count_, -1 ) == 1 ) |
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144 | { |
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145 | dispose(); |
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146 | weak_release(); |
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147 | } |
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148 | } |
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149 | |
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150 | void weak_add_ref() // nothrow |
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151 | { |
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152 | atomic_increment( &weak_count_ ); |
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153 | } |
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154 | |
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155 | void weak_release() // nothrow |
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156 | { |
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157 | if( atomic_exchange_and_add( &weak_count_, -1 ) == 1 ) |
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158 | { |
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159 | destroy(); |
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160 | } |
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161 | } |
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162 | |
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163 | long use_count() const // nothrow |
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164 | { |
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165 | return static_cast<int const volatile &>( use_count_ ); |
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166 | } |
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167 | }; |
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168 | |
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169 | } // namespace detail |
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170 | |
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171 | } // namespace boost |
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172 | |
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173 | #endif // #ifndef BOOST_SMART_PTR_DETAIL_SP_COUNTED_BASE_GCC_X86_HPP_INCLUDED |
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