Node.js package using node-addon-api

Ref: https://github.com/nodejs/node-addon-api#api

Installation#

curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash - \
&& sudo apt-get install -y nodejs

mkdir test \
&& cd test \
&& npm init

sudo npm install -g node-gyp

npm install node-addon-api

<package>
├── binding.gyp
├── index.js
├── node_modules
│   └── node-addon-api
│       └── ...
├── package.json
├── package-lock.json
├── test
│   └── ...
├── .clang-format
└── c_src
    ├── funcs.cpp
    ├── funcs.h
    ├── funcs_wrapper.cpp
    ├── funcs_wrapper.h
    └── <target>.cpp

package.json#

Ref: https://docs.npmjs.com/files/package.json

{
    "name": "<package>",
...
    "gypfile": true,
...
    "scripts": {
        "install": "node-gyp rebuild",
        "build": "node-gyp rebuild --verbose",
        "clean": "node-gyp clean",
        "cf": "clang-format -style=file -i -verbose c_src/*"
    },
...
    "dependencies": {
        "node-addon-api": "*",
    },
...
}

binding.gyp#

Ref: https://github.com/nodejs/node-addon-api/blob/master/doc/setup.md

{
    "targets": [
        {
            "target_name": "<target>",
            "include_dirs": ["<!@(node -p \"require('node-addon-api').include\")"],
            "dependencies": ["<!(node -p \"require('node-addon-api').gyp\")"],
            "cflags!": ["-fno-exceptions"],
            "cflags_cc!": ["-fno-exceptions"],
            "cflags": [],
            "cflags_cc": [],
            "defines": [],
            "sources": [
                "c_src/funcs.cpp",
                "c_src/funcs.h",
                "c_src/funcs_wrapper.cpp",
                "c_src/funcs_wrapper.h",
                "c_src/<target>.cpp",
            ],
            "libraries": [
                # "/usr/lib/libxxx.so"
            ]
        }
    ]
}

caution

target_name에 '-' 등은 들어갈 수 없습니다.

index.js#

module.exports = require('./build/Release/<target>');

Wrapper#

Ref: https://medium.com/@atulanand94/beginners-guide-to-writing-nodejs-addons-using-c-and-n-api-node-addon-api-9b3b718a9a7f

c_src/funcs.h#

#pragma once

#include <string>

std::string hello(void);
int         add(int a, int b);

c_src/funcs.cpp#

#include "funcs.h"

std::string hello(void) { return "Hello World!"; }

int add(int a, int b) { return a + b; }

c_src/funcs_wrapper.h#

#pragma once

#include <napi.h>

Napi::Object init_funcs(Napi::Env env, Napi::Object exports);

Napi::String hello_wrapper(const Napi::CallbackInfo &info);
Napi::Number add_wrapper(const Napi::CallbackInfo &info);

c_src/funcs_wrapper.cpp#

#include "funcs.h"
#include "funcs_wrapper.h"

Napi::Object init_funcs(Napi::Env env, Napi::Object exports) {
    exports.Set("hello", Napi::Function::New(env, hello_wrapper));
    exports.Set("add", Napi::Function::New(env, add_wrapper));

    return exports;
}

Napi::String hello_wrapper(const Napi::CallbackInfo &info) {
    Napi::Env env = info.Env();

    return Napi::String::New(env, hello());
}

Napi::Number add_wrapper(const Napi::CallbackInfo &info) {
    Napi::Env env = info.Env();

    if(info.Length() < 2 || ! info[0].IsNumber() || ! info[1].IsNumber()) {
        Napi::TypeError::New(env,
                             "Arguments must be (int a, int b) such as (1, 2).")
            .ThrowAsJavaScriptException();
    }

    // Implicit type conversion
    int a = info[0].As<Napi::Number>();
    int b = info[1].As<Napi::Number>();

    return Napi::Number::New(env, add(a, b));
}

c_src/<target>.cpp#

#include "funcs_wrapper.h"

#include <napi.h>

Napi::Object init_all(Napi::Env env, Napi::Object exports) {
    return init_funcs(env, exports);
}

NODE_API_MODULE(NODE_GYP_MODULE_NAME, init_all)

Build#

npm run build

test/test.js#

const addon = require('../build/Release/<target>');

console.log('wrapper info', addon);

console.log(addon.hello());
console.log(addon.add(1, 2));

$ node test/test.js
wrapper info { hello: [Function], add: [Function] }
Hello World!
3