webpack/lib/util/TupleQueue.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports 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";

const TupleSet = require("./TupleSet");

/**
 * FIFO queue for tuples that preserves uniqueness by delegating membership
 * tracking to `TupleSet`.
 * @template T
 * @template V
 */
class TupleQueue {
	/**
	 * Seeds the queue with an optional iterable of tuples to visit.
	 * @param {Iterable<[T, V, ...EXPECTED_ANY]>=} items The initial elements.
	 */
	constructor(items) {
		/**
		 * @private
		 * @type {TupleSet<T, V>}
		 */
		this._set = new TupleSet(items);
		/**
		 * @private
		 * @type {Iterator<[T, V, ...EXPECTED_ANY]>}
		 */
		this._iterator = this._set[Symbol.iterator]();
	}

	/**
	 * Returns the number of distinct tuples currently queued.
	 * @returns {number} The number of elements in this queue.
	 */
	get length() {
		return this._set.size;
	}

	/**
	 * Enqueues a tuple if it is not already present in the underlying set.
	 * @param {[T, V, ...EXPECTED_ANY]} item The element to add.
	 * @returns {void}
	 */
	enqueue(...item) {
		this._set.add(...item);
	}

	/**
	 * Removes and returns the next queued tuple, rebuilding the iterator when
	 * the underlying tuple set has changed since the last full pass.
	 * @returns {[T, V, ...EXPECTED_ANY] | undefined} The head of the queue of `undefined` if this queue is empty.
	 */
	dequeue() {
		const result = this._iterator.next();
		if (result.done) {
			if (this._set.size > 0) {
				this._iterator = this._set[Symbol.iterator]();
				const value =
					/** @type {[T, V, ...EXPECTED_ANY]} */
					(this._iterator.next().value);
				this._set.delete(...value);
				return value;
			}
			return;
		}
		this._set.delete(.../** @type {[T, V, ...EXPECTED_ANY]} */ (result.value));
		return result.value;
	}
}

module.exports = TupleQueue;