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4-phases.js
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100 lines (81 loc) · 1.83 KB
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'use strict';
class Reactor {
#phases = {
timers: [],
io: [],
check: [],
close: [],
};
#queueCount = 0;
#active = false;
enqueue(phase, fn) {
if (this.#phases[phase]) {
this.#phases[phase].push(fn);
this.#queueCount++;
}
}
start() {
this.#active = true;
const phases = Object.keys(this.#phases);
while (this.#active && this.#hasPending()) {
for (const phase of phases) {
const queue = this.#phases[phase].splice(0);
this.#queueCount -= queue.length;
for (const fn of queue) fn();
}
}
}
stop() {
const phases = Object.values(this.#phases);
for (const phase of phases) phase.splice(0);
this.#queueCount = 0;
this.#active = false;
}
get active() {
return this.#active;
}
#hasPending() {
return this.#queueCount > 0;
}
}
const eventLoop = new Reactor();
// Timers
const timers = { id: 0 };
const timeouts = new Set();
const setTimeout = (fn, delay) => {
const id = ++timers.id;
const start = Date.now();
const check = () => {
if (!timeouts.has(id)) return;
if (Date.now() - start >= delay) {
timeouts.delete(id);
fn();
} else {
eventLoop.enqueue('timers', check);
}
};
timeouts.add(id);
eventLoop.enqueue('timers', check);
return id;
};
// File system
const { readFileSync } = require('node:fs');
const readFile = (path, encoding, callback) => {
const read = () => {
setTimeout(() => {
try {
const data = readFileSync(path, encoding);
callback(null, data);
} catch (err) {
callback(err);
}
}, 1000);
};
eventLoop.enqueue('io', read);
};
// Usage
readFile('./4-phases.js', 'utf8', (err, data) => {
if (err) console.error('Error:', err.message);
else console.log('File contents:', data);
});
eventLoop.start();