1 | ## V8 internals
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2 |
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3 | The hooks to access V8 internals—including GC and statistics—are different across the supported versions of V8, therefore NAN provides its own hooks that call the appropriate V8 methods.
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4 |
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5 | - <a href="#api_nan_gc_callback"><b><code>NAN_GC_CALLBACK()</code></b></a>
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6 | - <a href="#api_nan_add_gc_epilogue_callback"><b><code>Nan::AddGCEpilogueCallback()</code></b></a>
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7 | - <a href="#api_nan_remove_gc_epilogue_callback"><b><code>Nan::RemoveGCEpilogueCallback()</code></b></a>
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8 | - <a href="#api_nan_add_gc_prologue_callback"><b><code>Nan::AddGCPrologueCallback()</code></b></a>
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9 | - <a href="#api_nan_remove_gc_prologue_callback"><b><code>Nan::RemoveGCPrologueCallback()</code></b></a>
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10 | - <a href="#api_nan_get_heap_statistics"><b><code>Nan::GetHeapStatistics()</code></b></a>
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11 | - <a href="#api_nan_set_counter_function"><b><code>Nan::SetCounterFunction()</code></b></a>
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12 | - <a href="#api_nan_set_create_histogram_function"><b><code>Nan::SetCreateHistogramFunction()</code></b></a>
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13 | - <a href="#api_nan_set_add_histogram_sample_function"><b><code>Nan::SetAddHistogramSampleFunction()</code></b></a>
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14 | - <a href="#api_nan_idle_notification"><b><code>Nan::IdleNotification()</code></b></a>
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15 | - <a href="#api_nan_low_memory_notification"><b><code>Nan::LowMemoryNotification()</code></b></a>
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16 | - <a href="#api_nan_context_disposed_notification"><b><code>Nan::ContextDisposedNotification()</code></b></a>
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17 | - <a href="#api_nan_get_internal_field_pointer"><b><code>Nan::GetInternalFieldPointer()</code></b></a>
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18 | - <a href="#api_nan_set_internal_field_pointer"><b><code>Nan::SetInternalFieldPointer()</code></b></a>
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19 | - <a href="#api_nan_adjust_external_memory"><b><code>Nan::AdjustExternalMemory()</code></b></a>
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20 |
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21 |
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22 | <a name="api_nan_gc_callback"></a>
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23 | ### NAN_GC_CALLBACK(callbackname)
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24 |
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25 | Use `NAN_GC_CALLBACK` to declare your callbacks for `Nan::AddGCPrologueCallback()` and `Nan::AddGCEpilogueCallback()`. Your new method receives the arguments `v8::GCType type` and `v8::GCCallbackFlags flags`.
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26 |
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27 | ```c++
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28 | static Nan::Persistent<Function> callback;
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29 |
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30 | NAN_GC_CALLBACK(gcPrologueCallback) {
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31 | v8::Local<Value> argv[] = { Nan::New("prologue").ToLocalChecked() };
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32 | Nan::MakeCallback(Nan::GetCurrentContext()->Global(), Nan::New(callback), 1, argv);
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33 | }
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34 |
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35 | NAN_METHOD(Hook) {
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36 | callback.Reset(To<Function>(args[0]).ToLocalChecked());
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37 | Nan::AddGCPrologueCallback(gcPrologueCallback);
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38 | info.GetReturnValue().Set(info.Holder());
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39 | }
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40 | ```
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41 |
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42 | <a name="api_nan_add_gc_epilogue_callback"></a>
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43 | ### Nan::AddGCEpilogueCallback()
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44 |
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45 | Signature:
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46 |
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47 | ```c++
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48 | void Nan::AddGCEpilogueCallback(v8::Isolate::GCEpilogueCallback callback, v8::GCType gc_type_filter = v8::kGCTypeAll)
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49 | ```
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50 |
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51 | Calls V8's [`AddGCEpilogueCallback()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a90d1860babc76059c62514b422f56960).
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52 |
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53 | <a name="api_nan_remove_gc_epilogue_callback"></a>
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54 | ### Nan::RemoveGCEpilogueCallback()
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55 |
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56 | Signature:
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57 |
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58 | ```c++
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59 | void Nan::RemoveGCEpilogueCallback(v8::Isolate::GCEpilogueCallback callback)
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60 | ```
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61 |
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62 | Calls V8's [`RemoveGCEpilogueCallback()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a05c60859fd4b8e96bfcd451281ed6c7c).
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63 |
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64 | <a name="api_nan_add_gc_prologue_callback"></a>
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65 | ### Nan::AddGCPrologueCallback()
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66 |
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67 | Signature:
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68 |
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69 | ```c++
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70 | void Nan::AddGCPrologueCallback(v8::Isolate::GCPrologueCallback, v8::GCType gc_type_filter callback)
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71 | ```
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72 |
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73 | Calls V8's [`AddGCPrologueCallback()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#ab4b87b8f9f8e5bf95eba4009357e001f).
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74 |
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75 | <a name="api_nan_remove_gc_prologue_callback"></a>
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76 | ### Nan::RemoveGCPrologueCallback()
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77 |
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78 | Signature:
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79 |
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80 | ```c++
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81 | void Nan::RemoveGCPrologueCallback(v8::Isolate::GCPrologueCallback callback)
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82 | ```
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83 |
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84 | Calls V8's [`RemoveGCEpilogueCallback()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a9f6c51932811593f81ff30b949124186).
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85 |
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86 | <a name="api_nan_get_heap_statistics"></a>
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87 | ### Nan::GetHeapStatistics()
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88 |
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89 | Signature:
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90 |
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91 | ```c++
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92 | void Nan::GetHeapStatistics(v8::HeapStatistics *heap_statistics)
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93 | ```
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94 |
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95 | Calls V8's [`GetHeapStatistics()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a5593ac74687b713095c38987e5950b34).
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96 |
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97 | <a name="api_nan_set_counter_function"></a>
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98 | ### Nan::SetCounterFunction()
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99 |
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100 | Signature:
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101 |
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102 | ```c++
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103 | void Nan::SetCounterFunction(v8::CounterLookupCallback cb)
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104 | ```
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105 |
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106 | Calls V8's [`SetCounterFunction()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a045d7754e62fa0ec72ae6c259b29af94).
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107 |
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108 | <a name="api_nan_set_create_histogram_function"></a>
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109 | ### Nan::SetCreateHistogramFunction()
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110 |
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111 | Signature:
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112 |
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113 | ```c++
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114 | void Nan::SetCreateHistogramFunction(v8::CreateHistogramCallback cb)
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115 | ```
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116 |
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117 | Calls V8's [`SetCreateHistogramFunction()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a542d67e85089cb3f92aadf032f99e732).
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118 |
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119 | <a name="api_nan_set_add_histogram_sample_function"></a>
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120 | ### Nan::SetAddHistogramSampleFunction()
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121 |
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122 | Signature:
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123 |
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124 | ```c++
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125 | void Nan::SetAddHistogramSampleFunction(v8::AddHistogramSampleCallback cb)
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126 | ```
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127 |
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128 | Calls V8's [`SetAddHistogramSampleFunction()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#aeb420b690bc2c216882d6fdd00ddd3ea).
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129 |
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130 | <a name="api_nan_idle_notification"></a>
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131 | ### Nan::IdleNotification()
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132 |
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133 | Signature:
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134 |
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135 | ```c++
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136 | void Nan::IdleNotification(v8::HeapStatistics *heap_statistics)
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137 | ```
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138 |
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139 | Calls V8's [`IdleNotification()` or `IdleNotificationDeadline()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#ad6a2a02657f5425ad460060652a5a118) depending on V8 version.
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140 |
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141 | <a name="api_nan_low_memory_notification"></a>
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142 | ### Nan::LowMemoryNotification()
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143 |
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144 | Signature:
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145 |
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146 | ```c++
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147 | void Nan::LowMemoryNotification()
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148 | ```
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149 |
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150 | Calls V8's [`LowMemoryNotification()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#a24647f61d6b41f69668094bdcd6ea91f).
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151 |
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152 | <a name="api_nan_context_disposed_notification"></a>
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153 | ### Nan::ContextDisposedNotification()
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154 |
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155 | Signature:
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156 |
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157 | ```c++
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158 | void Nan::ContextDisposedNotification()
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159 | ```
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160 |
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161 | Calls V8's [`ContextDisposedNotification()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#ad7f5dc559866343fe6cd8db1f134d48b).
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162 |
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163 | <a name="api_nan_get_internal_field_pointer"></a>
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164 | ### Nan::GetInternalFieldPointer()
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165 |
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166 | Gets a pointer to the internal field with at `index` from a V8 `Object` handle.
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167 |
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168 | Signature:
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169 |
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170 | ```c++
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171 | void* Nan::GetInternalFieldPointer(v8::Local<v8::Object> object, int index)
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172 | ```
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173 |
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174 | Calls the Object's [`GetAlignedPointerFromInternalField()` or `GetPointerFromInternalField()`](https://v8docs.nodesource.com/io.js-3.3/db/d85/classv8_1_1_object.html#ab3c57184263cf29963ef0017bec82281) depending on the version of V8.
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175 |
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176 | <a name="api_nan_set_internal_field_pointer"></a>
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177 | ### Nan::SetInternalFieldPointer()
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178 |
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179 | Sets the value of the internal field at `index` on a V8 `Object` handle.
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180 |
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181 | Signature:
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182 |
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183 | ```c++
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184 | void Nan::SetInternalFieldPointer(v8::Local<v8::Object> object, int index, void* value)
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185 | ```
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186 |
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187 | Calls the Object's [`SetAlignedPointerInInternalField()` or `SetPointerInInternalField()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#ad7f5dc559866343fe6cd8db1f134d48b) depending on the version of V8.
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188 |
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189 | <a name="api_nan_adjust_external_memory"></a>
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190 | ### Nan::AdjustExternalMemory()
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191 |
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192 | Signature:
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193 |
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194 | ```c++
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195 | int Nan::AdjustExternalMemory(int bytesChange)
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196 | ```
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197 |
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198 | Calls V8's [`AdjustAmountOfExternalAllocatedMemory()`](https://v8docs.nodesource.com/io.js-3.3/d5/dda/classv8_1_1_isolate.html#ae1a59cac60409d3922582c4af675473e).
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199 |
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