2a09d1a4
 liuqimichale
添加宜春 天水 宣化
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## Miscellaneous V8 Helpers
- <a href="#api_nan_utf8_string"><b><code>Nan::Utf8String</code></b></a>
- <a href="#api_nan_get_current_context"><b><code>Nan::GetCurrentContext()</code></b></a>
- <a href="#api_nan_set_isolate_data"><b><code>Nan::SetIsolateData()</code></b></a>
- <a href="#api_nan_get_isolate_data"><b><code>Nan::GetIsolateData()</code></b></a>
- <a href="#api_nan_typedarray_contents"><b><code>Nan::TypedArrayContents</code></b></a>
<a name="api_nan_utf8_string"></a>
### Nan::Utf8String
Converts an object to a UTF-8-encoded character array. If conversion to a string fails (e.g. due to an exception in the toString() method of the object) then the length() method returns 0 and the * operator returns NULL. The underlying memory used for this object is managed by the object.
An implementation of [`v8::String::Utf8Value`](https://v8docs.nodesource.com/node-8.11/d4/d1b/classv8_1_1_string_1_1_utf8_value.html) that is consistent across all supported versions of V8.
Definition:
```c++
class Nan::Utf8String {
public:
Nan::Utf8String(v8::Local<v8::Value> from);
int length() const;
char* operator*();
const char* operator*() const;
};
```
<a name="api_nan_get_current_context"></a>
### Nan::GetCurrentContext()
A call to [`v8::Isolate::GetCurrent()->GetCurrentContext()`](https://v8docs.nodesource.com/node-8.11/d5/dda/classv8_1_1_isolate.html#a81c7a1ed7001ae2a65e89107f75fd053) that works across all supported versions of V8.
Signature:
```c++
v8::Local<v8::Context> Nan::GetCurrentContext()
```
<a name="api_nan_set_isolate_data"></a>
### Nan::SetIsolateData()
A helper to provide a consistent API to [`v8::Isolate#SetData()`](https://v8docs.nodesource.com/node-8.11/d5/dda/classv8_1_1_isolate.html#a7acadfe7965997e9c386a05f098fbe36).
Signature:
```c++
void Nan::SetIsolateData(v8::Isolate *isolate, T *data)
```
<a name="api_nan_get_isolate_data"></a>
### Nan::GetIsolateData()
A helper to provide a consistent API to [`v8::Isolate#GetData()`](https://v8docs.nodesource.com/node-8.11/d5/dda/classv8_1_1_isolate.html#aabd223436bc1100a787dadaa024c6257).
Signature:
```c++
T *Nan::GetIsolateData(v8::Isolate *isolate)
```
<a name="api_nan_typedarray_contents"></a>
### Nan::TypedArrayContents<T>
A helper class for accessing the contents of an ArrayBufferView (aka a typedarray) from C++. If the input array is not a valid typedarray, then the data pointer of TypedArrayContents will default to `NULL` and the length will be 0. If the data pointer is not compatible with the alignment requirements of type, an assertion error will fail.
Note that you must store a reference to the `array` object while you are accessing its contents.
Definition:
```c++
template<typename T>
class Nan::TypedArrayContents {
public:
TypedArrayContents(v8::Local<Value> array);
size_t length() const;
T* const operator*();
const T* const operator*() const;
};
```
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