pipe.js

"use strict";
const ffi = require("ffi");
const ref = require("ref");
const ArrayType = require("ref-array");
const { createReadStream, createWriteStream, readSync, writeSync, closeSync } = require("fs");

let IntArray = ArrayType("int");
let StringArray = ArrayType("string");
let voidPtr = ref.refType(ref.types.void);

let stdlib = ffi.Library(null, {
	"fork": ["int", []],
	"execvp": ["int", ["string", StringArray]],
	"dup2": ["int", ["int", "int"]],
	"wait4": ["int", ["int", "int", "int", voidPtr]],
	"pipe": ["int", [IntArray]],
	//"close": ["int", ["int"]],
	"_exit": ["int", ["int"]],
});

const WNOHANG = 1;

process.on("SIGCHLD", () => {
	console.log("SIGCHLD!");
	while (true) {
		let pid = stdlib.wait4(-1, 0, WNOHANG, ref.NULL);
		if (pid <= 0) break;
		console.log(`reaped zombie ${pid}`);
		console.timeEnd("fork");
	}
});

let pipefd = new IntArray(2);
let result = stdlib.pipe(pipefd);
if (result === -1)
	throw new Error("pipe "+result);

console.time("fork");
let pid = stdlib.fork();
if (pid === 0) {
	console.log("hello from child");
	process.title = "child";
	
	closeSync(pipefd[1]);
	
	let buf = Buffer.alloc(1024);
	let bytesRead = readSync(pipefd[0], buf, 0, 1024);
	console.log(bytesRead);
	console.log(buf.toString("utf8", 0, bytesRead));
	
	//let stream = createReadStream(null, { fd: pipefd[0], autoClose: false });
	//stream.pipe(process.stdout);
	
	closeSync(pipefd[0]);
	stdlib._exit(0);
} else if (pid < 0) {
	console.log("error forking");
} else {
	console.log("child has pid", pid);
	process.title = "parent";
	
	closeSync(pipefd[0]);
	
	writeSync(pipefd[1], "hello\n");
	
	closeSync(pipefd[1]);
	
	//let stream = createWriteStream(null, { fd: pipefd[1] });
	//stream.end("hello!\n");
	
	setInterval(() => {}, 10000);
}