1 | /*! |
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2 | \file |
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3 | \brief BDM's own smart pointers. |
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4 | \author Vaclav Barta. |
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5 | |
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6 | ----------------------------------- |
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7 | BDM++ - C++ library for Bayesian Decision Making under Uncertainty |
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8 | |
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9 | Using IT++ for numerical operations |
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10 | ----------------------------------- |
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11 | */ |
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12 | |
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13 | #ifndef shared_ptr_h |
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14 | #define shared_ptr_h |
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15 | |
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16 | #include <limits.h> |
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17 | #include <algorithm> |
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18 | #include <stdexcept> |
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19 | #include <string> |
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20 | #include "bdmerror.h" |
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21 | |
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22 | namespace bdm { |
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23 | |
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24 | /*! \brief A naive implementation of roughly a subset of the std::tr1::shared_ptr spec |
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25 | |
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26 | Really just roughly - it ignores memory |
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27 | exceptions, for example; also note I didn't read the spec. |
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28 | |
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29 | The standard template would naturally be preferable, \b if it was |
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30 | included in the standard libraries of all supported compilers - but |
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31 | as of 2009, that's still a problem... |
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32 | */ |
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33 | template <typename T> |
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34 | class shared_ptr { |
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35 | template<class U> friend class shared_ptr; |
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36 | |
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37 | private: |
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38 | T *payload; |
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39 | unsigned *refCnt; |
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40 | |
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41 | public: |
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42 | /*! |
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43 | \brief Default constructor |
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44 | |
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45 | Creates an empty shared_ptr - one that doesn't point anywhere. |
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46 | */ |
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47 | shared_ptr() : |
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48 | payload ( 0 ), |
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49 | refCnt ( 0 ) { |
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50 | } |
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51 | |
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52 | /*! |
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53 | Constructs a shared_ptr that owns the pointer p (unless p |
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54 | is NULL, in which case this constructor creates an empty |
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55 | shared_ptr). When p isn't null, it must have been alllocated |
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56 | by new! |
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57 | */ |
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58 | shared_ptr ( T *p ) : |
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59 | payload ( p ), |
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60 | refCnt ( p ? new unsigned ( 1 ) : 0 ) { |
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61 | } |
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62 | |
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63 | /*! |
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64 | \brief Copy constructor |
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65 | |
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66 | If other is empty, constructs an empty shared_ptr; otherwise, |
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67 | constructs a shared_ptr that shares ownership with other. |
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68 | */ |
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69 | shared_ptr ( const shared_ptr<T> &other ) : |
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70 | payload ( other.payload ), |
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71 | refCnt ( other.refCnt ) { |
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72 | add_ref(); |
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73 | } |
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74 | |
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75 | /*! |
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76 | \brief Generalized copy |
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77 | |
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78 | Allows initialization of shared pointer of a base type from |
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79 | raw pointer to a derived type. |
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80 | |
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81 | If other is empty, constructs an empty shared_ptr; otherwise, |
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82 | constructs a shared_ptr that shares ownership with other. |
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83 | */ |
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84 | template<typename U> |
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85 | shared_ptr ( const shared_ptr<U> &other ) : |
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86 | payload ( other.payload ), |
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87 | refCnt ( other.refCnt ) { |
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88 | add_ref(); |
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89 | } |
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90 | |
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91 | /*! |
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92 | Destructor. |
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93 | */ |
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94 | ~shared_ptr() { |
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95 | del_ref(); |
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96 | } |
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97 | |
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98 | /*! |
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99 | \brief Assignment operator |
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100 | */ |
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101 | shared_ptr<T> &operator= ( const shared_ptr<T> &other ) { |
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102 | other.add_ref(); |
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103 | del_ref(); |
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104 | |
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105 | payload = other.payload; |
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106 | refCnt = other.refCnt; |
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107 | |
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108 | return *this; |
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109 | } |
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110 | |
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111 | /*! |
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112 | Returns the stored pointer (which remains owned by this |
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113 | instance). For empty instances, this method returns NULL. |
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114 | */ |
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115 | T *get() { |
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116 | return payload; |
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117 | } |
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118 | |
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119 | /*! |
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120 | Dereferences the stored pointer (which remains owned by |
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121 | this instance). This method may only be called when the |
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122 | stored pointer isn't NULL. |
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123 | */ |
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124 | T *operator->() { |
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125 | bdm_assert_debug ( payload, "dereferencing NULL" ); |
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126 | return payload; |
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127 | } |
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128 | |
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129 | //! Returns a reference to the object pointed to by the stored |
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130 | //! pointer. This method may only be called when the stored pointer |
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131 | //! isn't NULL. |
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132 | T &operator*() { |
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133 | bdm_assert_debug ( payload, "dereferencing NULL" ); |
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134 | return *payload; |
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135 | } |
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136 | |
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137 | /*! |
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138 | Returns the stored pointer (which remains owned by this |
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139 | instance). For empty instances, this method returns NULL. |
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140 | */ |
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141 | const T* get() const { |
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142 | return payload; |
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143 | } |
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144 | |
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145 | //! Returns the stored pointer (which remains owned by this |
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146 | //! instance). This method may only be called when the stored |
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147 | //! pointer isn't NULL. |
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148 | const T *operator->() const { |
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149 | bdm_assert_debug ( payload, "dereferencing NULL" ); |
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150 | return payload; |
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151 | } |
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152 | |
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153 | //! Returns a reference to the object pointed to by the stored |
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154 | //! pointer. This method may only be called when the stored pointer |
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155 | //! isn't NULL. |
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156 | const T &operator*() const { |
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157 | bdm_assert_debug ( payload, "dereferencing NULL" ); |
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158 | return *payload; |
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159 | } |
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160 | |
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161 | //! Returns use_count() == 1 |
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162 | bool unique() const { |
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163 | return refCnt && ( *refCnt == 1 ); |
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164 | } |
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165 | |
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166 | /*! |
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167 | Returns the number of shared_ptr instances (including |
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168 | this instance) that share ownership with this instance. For |
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169 | empty instances, this method returns 0. |
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170 | */ |
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171 | long use_count() const { |
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172 | return refCnt ? *refCnt : 0; |
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173 | } |
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174 | |
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175 | /*! |
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176 | \brief Boolean cast |
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177 | |
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178 | This operator returns true if and only if the instance isn't empty. |
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179 | */ |
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180 | operator bool() const { |
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181 | return !!payload; |
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182 | } |
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183 | |
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184 | /*! |
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185 | \brief const cast |
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186 | |
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187 | Shared pointer to T can be converted to shared pointer to |
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188 | const T, just like T * can be converted to T const *. |
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189 | */ |
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190 | template<typename U> |
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191 | operator shared_ptr<const U>() const { |
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192 | shared_ptr<const U> cptr; |
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193 | cptr.refCnt = refCnt; |
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194 | cptr.payload = payload; |
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195 | add_ref(); |
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196 | return cptr; |
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197 | } |
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198 | |
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199 | /*! |
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200 | \brief Efficient swap for shared_ptr. |
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201 | */ |
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202 | void swap ( shared_ptr &other ) { |
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203 | std::swap ( payload, other.payload ); |
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204 | std::swap ( refCnt, other.refCnt ); |
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205 | } |
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206 | |
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207 | private: |
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208 | void add_ref() const { |
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209 | if ( refCnt ) { |
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210 | if ( *refCnt == UINT_MAX ) { |
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211 | throw std::overflow_error ( |
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212 | std::string ( "Shared pointer has too many references." ) ); |
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213 | } |
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214 | |
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215 | ++*refCnt; |
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216 | } |
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217 | } |
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218 | |
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219 | void del_ref() { |
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220 | if ( refCnt ) { |
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221 | if ( ! ( --*refCnt ) ) { |
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222 | delete payload; |
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223 | delete refCnt; |
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224 | } |
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225 | } |
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226 | } |
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227 | }; |
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228 | |
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229 | //! Compare shared pointers |
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230 | template<typename T, typename U> |
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231 | bool operator== ( shared_ptr<T> const &a, shared_ptr<U> const &b ) { |
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232 | return a.get() == b.get(); |
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233 | } |
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234 | |
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235 | //! Compare shared pointers |
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236 | template<typename T, typename U> |
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237 | bool operator!= ( shared_ptr<T> const &a, shared_ptr<U> const &b ) { |
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238 | return a.get() != b.get(); |
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239 | } |
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240 | |
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241 | //! Compare shared pointers |
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242 | template<typename T, typename U> |
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243 | bool operator< ( shared_ptr<T> const &a, shared_ptr<U> const &b ) { |
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244 | return a.get() < b.get(); |
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245 | } |
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246 | |
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247 | /*! \brief A wrapper of shared_ptr which is never empty. |
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248 | |
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249 | T must have a default constructor. |
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250 | |
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251 | Note that shared_ptr's destructor isn't virtual - don't call delete |
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252 | on pointers to instances of this class. |
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253 | */ |
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254 | template <typename T> |
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255 | class object_ptr : public shared_ptr<T> |
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256 | { |
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257 | public: |
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258 | /*! |
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259 | \brief Default constructor |
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260 | |
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261 | Calls T's default constructor. |
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262 | */ |
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263 | object_ptr() : shared_ptr<T> ( new T() ) { } |
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264 | |
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265 | /*! |
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266 | \brief Upcast from shared_ptr<T> to object_ptr<T> |
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267 | |
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268 | \param b The shared pointer, which must not be empty. |
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269 | */ |
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270 | object_ptr ( const shared_ptr<T> &b ) : shared_ptr<T> ( b ) { |
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271 | bdm_assert_debug ( this->get(), "object_ptr cannot be empty" ); |
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272 | } |
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273 | |
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274 | /*! |
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275 | Constructs an object_ptr that owns the pointer p. p must |
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276 | have been alllocated by new! |
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277 | */ |
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278 | object_ptr ( T *p ) : shared_ptr<T> ( p ) { |
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279 | bdm_assert_debug ( p, "object_ptr cannot be empty" ); |
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280 | } |
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281 | |
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282 | /*! |
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283 | \brief Assignment operator |
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284 | */ |
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285 | object_ptr<T> &operator= ( const object_ptr<T> &other ) { |
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286 | shared_ptr<T>::operator= ( other ); |
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287 | return *this; |
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288 | } |
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289 | }; |
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290 | |
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291 | #define SHAREDPTR(class_name) typedef bdm::object_ptr< class_name > class_name##_ptr |
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292 | |
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293 | #define SHAREDPTR2(template_class_name, template_parameter_name) typedef bdm::object_ptr< template_class_name < template_parameter_name > > template_class_name##_##template_parameter_name##_ptr |
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294 | |
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295 | } |
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296 | |
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297 | #endif |
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