Nodejs Talking To C Executable 1
=============================================================

:Date: 21 Sep 2019

What is the idea?
-----------------------

- My boss prefers to implement webserver in C by himself, but I think people have already spent tons of time making the state of art **nodejs**, it doesn't make sense not to use it. And since I am not a engineer but a physicist, I don't want to spend too much time on the already-solved-for-decades engineering problem. So I will just use Nodejs without thinking

- However we will still use C to do the basic memory mapping, as it is already done.

- So the problem now is to make Nodejs talk to C executable, turns out to be very easy

Install Nodejs and Clion
----------------------------

- I recommend using Clion for C part, if you are a student, you can get free license with a :code:`edu` email address

- For Nodejs on Ubuntu

.. code-block:: console

	curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
	sudo apt install nodejs
	node -v

- For Nodejs on Angstrom Linux and ARMv7
	- `First download from here <https://nodejs.org/en/download/>`_
	- `Then read this <https://github.com/nodejs/help/wiki/Installation#how-to-install-nodejs-via-binary-archive-on-linux>`_ 


C Part 
---------------------

.. code-block:: c

	#include <stdio.h>

	int main(int argumentCount, char ** arg) {
	    //if you ran your program like this:
	    //    ./program hello world
	    // Then:
	    //    argumentCount = 3
	    //    argv[0] = "./program"
	    //    argv[1] = "hello"
	    //    argv[2] = "world"
	    printf("argv[0] =  %s\n",arg[0]);
	    printf("argv[1] =  %s\n",arg[1]);
	    printf("argv[2] =  %s\n",arg[2]);
	    return 0;
	}

In Clion, go to :code:`Build -> Build Project`, then the executable file will be in folder :code:`cmake-build-debug`, copy this file to same directory as your Nodejs code (below) 

Nodejs Part
------------------

- make a file named :code:`app.js`, and put the following in it:

.. code-block:: jsx

	const { execFile } = require('child_process');
	const child = execFile('./hello', ["hello","world"], (error, stdout, stderr) => {
	  if (error) {
	    throw error;
	  }
	  console.log("stdout:");
	  console.log(stdout);
	});

- then command: :code:`node app.js`