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Calling C++ from Node.js

VRPC can embed existing C++ code in a Node.js program: the C++ classes become JavaScript classes whose calls run the compiled code in-process, in the same event loop, without a broker.

This guide shows the steps. The examples 03-native-simple and 04-native-advanced carry them out in full, and vrpc-hpp documents every registration macro.

1. Adapt the C++ code​

The C++ code stays as it is. An adapter file names the constructors and functions to offer:

src/adapter.cpp

#include "Foo.hpp"

VRPC_CTOR(Foo);
VRPC_CONST_MEMBER_FUNCTION(Foo, int, getValue);
VRPC_MEMBER_FUNCTION(Foo, void, setValue, int);

Arguments and results travel as JSON; custom types are described once with VRPC_DEFINE_TYPE. A callback parameter is declared with VRPC_CALLBACK.

2. Build an addon​

A binding.gyp builds VRPC's addon source together with your code:

{
  'variables': {
    'vrpc_path': '<!(if [ -e ../vrpc ]; then echo ../vrpc; else echo node_modules/vrpc; fi)'
  },
  'targets': [
    {
      'target_name': 'vrpc_foo',
      'cflags_cc!': ['-std=gnu++0x', '-fno-rtti', '-fno-exceptions'],
      'cflags_cc': ['-std=c++14', '-fPIC'],
      'include_dirs': ['<(vrpc_path)', 'src'],
      'sources': ['<(vrpc_path)/vrpc/addon.cpp']
    }
  ]
}

npm install (or npx node-gyp rebuild) compiles it to build/Release/vrpc_foo.node. You need a C++14 compiler and the usual node-gyp prerequisites.

3. Use it​

const { VrpcNative } = require('vrpc')
const addon = require('./build/Release/vrpc_foo')

const native = new VrpcNative(addon)
const Foo = native.getClass('Foo')

const foo = new Foo()
foo.setValue(42)
console.log(foo.getValue()) // 42

Calls are synchronous: they run the C++ code directly. Static functions are static functions of the proxy class. A callback called once (a done) is passed as a function; one called again and again goes through vrpcOn:

bar.vrpcOn('onRemove', bottle => console.log(`${bottle.name} went empty`))

native.getAvailableClasses() lists what the addon offers.

Offering C++ code remotely​

To call C++ code from other programs, run it as an agent of its own with vrpc-hpp, which speaks the same protocol as every other VRPC agent.