webpack/lib/util/Semaphore.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

class Semaphore {
	/**
	 * Creates an instance of Semaphore.
	 *
	 * @param {number} available the amount available number of "tasks"
	 * in the Semaphore
	 */
	constructor(available) {
		this.available = available;
		/** @type {(function(): void)[]} */
		this.waiters = [];
		/** @private */
		this._continue = this._continue.bind(this);
	}

	/**
	 * @param {function(): void} callback function block to capture and run
	 * @returns {void}
	 */
	acquire(callback) {
		if (this.available > 0) {
			this.available--;
			callback();
		} else {
			this.waiters.push(callback);
		}
	}

	release() {
		this.available++;
		if (this.waiters.length > 0) {
			process.nextTick(this._continue);
		}
	}

	_continue() {
		if (this.available > 0) {
			if (this.waiters.length > 0) {
				this.available--;
				const callback = this.waiters.pop();
				callback();
			}
		}
	}
}

module.exports = Semaphore;