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'use strict';

const fs = require('node:fs');

const threads = require('node:worker_threads');

const { Worker, isMainThread } = threads;

class CountingSemaphore {

constructor(shared, offset = 0, initial) {

this.counter = new Int32Array(shared, offset, 1);

if (typeof initial === 'number') {

this.counter[0] = initial;

}

enter() {

while (this.counter[0] === 0);

this.counter[0]--;

}

leave() {

this.counter[0]++;

}

// Usage

if (isMainThread) {

const buffer = new SharedArrayBuffer(4);

// Try to change 10 to 2 at next line to see the problem

const semaphore = new CountingSemaphore(buffer, 0, 10);

console.dir({ semaphore: semaphore.counter[0] });

for (let i = 0; i < 20; i++) {

new Worker(__filename, { workerData: buffer });

}

} else {

const { threadId, workerData } = threads;

const semaphore = new CountingSemaphore(workerData);

console.dir({ threadId, semaphore: semaphore.counter[0] });

const REPEAT_COUNT = 1000000;

const file = `file-${threadId}.dat`;

semaphore.enter();

const data = `Data from ${threadId}`.repeat(REPEAT_COUNT);

fs.writeFile(file, data, () => {

fs.unlink(file, () => {

semaphore.leave();

});

}