This project contains some helper utilities that make native addon development a bit more easier.
NAN_METHOD(GetFirstNPrimes) {
int numberOfPrimes = Nan::Marshal<int>(info[0]);
std::vector<int> primes = computeNPrimes(numberOfPrimes);
info.GetReturnValue().Set(Nan::Marshal(primes));
}
Ok, enough words, gimme the code! All source code is available on GitHub: nan-marshal.
By tradition, native add-ons for Node are built with GYP build system. So you should install node-gyp package: npm install -g node-gyp
.
This module requires Nan package. If you are not using Nan already for writing C++ add-ons for Nodejs I strongly advise you to start doing that. Anyway, npm install --save nan
is a right way to start.
Simply add nan-marshal as a dependency module to package.json of your Node add-on:
$ npm install --save nan-marshal
Add include directories for NAN and NAN-Marshal in your binding.gyp so that you can use #include <nan-marshal.h>
in your .cpp files:
"include_dirs" : [
"<!(node -e \"require('nan')\")",
"<!(node -e \"require('nan-marshal')\")"
]
This works like a -I<path-to-nan-marshal>
when compiling your add-on.
There is a single all-purpose function: Nan::Marshal
. To convert from V8 object to C++ type, use it as follows: Nan::Marshal<Dst>(V8 object)
.
To convert from C++ to V8 object: Nan::Marshal(..)
.
Nan::Marshal
supports following types out of the box:
- Built-in C++ types
- std::string
- std::vector
- std::map
- std::shared_ptr
- Marshalling of used-defined types (There are intrusive and non-intrusive options available)
For built-in and STL types, use is straightforward:
Local<Value> arg1 = info[0];
// Marshal from V8 to C++ type
std::string msg = Nan::Marshal<std::string>(arg1);
// Marshal from C++ to V8
info.GetReturnValue().Set(Nan::Marshal(msg));
User-defined serialization inspired by boost::serialization approach and you will find it similar and easy-to-use. Here's quick example of non-intrusive serialization of the OpenCV data type:
namespace Nan
{
namespace marshal
{
template<typename T>
struct Serializer < cv::Rect_<T> >
{
template<typename InputArchive>
static inline void load(InputArchive& ar, cv::Rect_<T>& val)
{
ar & make_nvp("x", val.x);
ar & make_nvp("y", val.y);
ar & make_nvp("width", val.width);
ar & make_nvp("height", val.height);
}
template<typename OutputArchive>
static inline void save(OutputArchive& ar, const cv::Rect_<T>& val)
{
ar & make_nvp("x", val.x);
ar & make_nvp("y", val.y);
ar & make_nvp("width", val.width);
ar & make_nvp("height", val.height);
}
};
}
}
Having a snippet above in your code lets you to return JavaScript object like { x:12, y:13, width:124, height: 144 }
from C++ code. The same is true for V8 -> C++ marshalling. Nan::Marshal will convert V8 object to desired object type.
To run the tests do:
npm install
npm run-script rebuild-tests
npm test
Or just:
npm install
npm test
This library does not perform strict checking of V8 types during conversion. There is nan-check module that serves this purpose.
Copyright (c) 2015 Ievgen Khvedchenia.
Native Abstractions for Node.js is licensed under an MIT license. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE file for more details.