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diff --git a/node_modules/nan/doc/node_misc.md b/node_modules/nan/doc/node_misc.md new file mode 100644 index 0000000..17578e3 --- /dev/null +++ b/node_modules/nan/doc/node_misc.md @@ -0,0 +1,123 @@ +## Miscellaneous Node Helpers + + - <a href="#api_nan_asyncresource"><b><code>Nan::AsyncResource</code></b></a> + - <a href="#api_nan_make_callback"><b><code>Nan::MakeCallback()</code></b></a> + - <a href="#api_nan_module_init"><b><code>NAN_MODULE_INIT()</code></b></a> + - <a href="#api_nan_export"><b><code>Nan::Export()</code></b></a> + +<a name="api_nan_asyncresource"></a> +### Nan::AsyncResource + +This class is analogous to the `AsyncResource` JavaScript class exposed by Node's [async_hooks][] API. + +When calling back into JavaScript asynchronously, special care must be taken to ensure that the runtime can properly track +async hops. `Nan::AsyncResource` is a class that provides an RAII wrapper around `node::EmitAsyncInit`, `node::EmitAsyncDestroy`, +and `node::MakeCallback`. Using this mechanism to call back into JavaScript, as opposed to `Nan::MakeCallback` or +`v8::Function::Call` ensures that the callback is executed in the correct async context. This ensures that async mechanisms +such as domains and [async_hooks][] function correctly. + +Definition: + +```c++ +class AsyncResource { + public: + AsyncResource(v8::Local<v8::String> name, + v8::Local<v8::Object> resource = New<v8::Object>()); + AsyncResource(const char* name, + v8::Local<v8::Object> resource = New<v8::Object>()); + ~AsyncResource(); + + v8::MaybeLocal<v8::Value> runInAsyncScope(v8::Local<v8::Object> target, + v8::Local<v8::Function> func, + int argc, + v8::Local<v8::Value>* argv); + v8::MaybeLocal<v8::Value> runInAsyncScope(v8::Local<v8::Object> target, + v8::Local<v8::String> symbol, + int argc, + v8::Local<v8::Value>* argv); + v8::MaybeLocal<v8::Value> runInAsyncScope(v8::Local<v8::Object> target, + const char* method, + int argc, + v8::Local<v8::Value>* argv); +}; +``` + +* `name`: Identifier for the kind of resource that is being provided for diagnostics information exposed by the [async_hooks][] + API. This will be passed to the possible `init` hook as the `type`. To avoid name collisions with other modules we recommend + that the name include the name of the owning module as a prefix. For example `mysql` module could use something like + `mysql:batch-db-query-resource`. +* `resource`: An optional object associated with the async work that will be passed to the possible [async_hooks][] + `init` hook. If this parameter is omitted, or an empty handle is provided, this object will be created automatically. +* When calling JS on behalf of this resource, one can use `runInAsyncScope`. This will ensure that the callback runs in the + correct async execution context. +* `AsyncDestroy` is automatically called when an AsyncResource object is destroyed. + +For more details, see the Node [async_hooks][] documentation. You might also want to take a look at the documentation for the +[N-API counterpart][napi]. For example usage, see the `asyncresource.cpp` example in the `test/cpp` directory. + +<a name="api_nan_make_callback"></a> +### Nan::MakeCallback() + +Deprecated wrappers around the legacy `node::MakeCallback()` APIs. Node.js 10+ +has deprecated these legacy APIs as they do not provide a mechanism to preserve +async context. + +We recommend that you use the `AsyncResource` class and `AsyncResource::runInAsyncScope` instead of using `Nan::MakeCallback` or +`v8::Function#Call()` directly. `AsyncResource` properly takes care of running the callback in the correct async execution +context – something that is essential for functionality like domains, async_hooks and async debugging. + +Signatures: + +```c++ +NAN_DEPRECATED +v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target, + v8::Local<v8::Function> func, + int argc, + v8::Local<v8::Value>* argv); +NAN_DEPRECATED +v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target, + v8::Local<v8::String> symbol, + int argc, + v8::Local<v8::Value>* argv); +NAN_DEPRECATED +v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target, + const char* method, + int argc, + v8::Local<v8::Value>* argv); +``` + + +<a name="api_nan_module_init"></a> +### NAN_MODULE_INIT() + +Used to define the entry point function to a Node add-on. Creates a function with a given `name` that receives a `target` object representing the equivalent of the JavaScript `exports` object. + +See example below. + +<a name="api_nan_export"></a> +### Nan::Export() + +A simple helper to register a `v8::FunctionTemplate` from a JavaScript-accessible method (see [Methods](./methods.md)) as a property on an object. Can be used in a way similar to assigning properties to `module.exports` in JavaScript. + +Signature: + +```c++ +void Export(v8::Local<v8::Object> target, const char *name, Nan::FunctionCallback f) +``` + +Also available as the shortcut `NAN_EXPORT` macro. + +Example: + +```c++ +NAN_METHOD(Foo) { + ... +} + +NAN_MODULE_INIT(Init) { + NAN_EXPORT(target, Foo); +} +``` + +[async_hooks]: https://nodejs.org/dist/latest-v9.x/docs/api/async_hooks.html +[napi]: https://nodejs.org/dist/latest-v9.x/docs/api/n-api.html#n_api_custom_asynchronous_operations |