simple-squiggle

A restricted subset of Squiggle
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ArrayQueue.js (2198B)

      1 /*
      2 	MIT License http://www.opensource.org/licenses/mit-license.php
      3 	Author Tobias Koppers @sokra
      4 */
      5 
      6 "use strict";
      7 
      8 /**
      9  * @template T
     10  */
     11 class ArrayQueue {
     12 	/**
     13 	 * @param {Iterable<T>=} items The initial elements.
     14 	 */
     15 	constructor(items) {
     16 		/** @private @type {T[]} */
     17 		this._list = items ? Array.from(items) : [];
     18 		/** @private @type {T[]} */
     19 		this._listReversed = [];
     20 	}
     21 
     22 	/**
     23 	 * Returns the number of elements in this queue.
     24 	 * @returns {number} The number of elements in this queue.
     25 	 */
     26 	get length() {
     27 		return this._list.length + this._listReversed.length;
     28 	}
     29 
     30 	/**
     31 	 * Empties the queue.
     32 	 */
     33 	clear() {
     34 		this._list.length = 0;
     35 		this._listReversed.length = 0;
     36 	}
     37 
     38 	/**
     39 	 * Appends the specified element to this queue.
     40 	 * @param {T} item The element to add.
     41 	 * @returns {void}
     42 	 */
     43 	enqueue(item) {
     44 		this._list.push(item);
     45 	}
     46 
     47 	/**
     48 	 * Retrieves and removes the head of this queue.
     49 	 * @returns {T | undefined} The head of the queue of `undefined` if this queue is empty.
     50 	 */
     51 	dequeue() {
     52 		if (this._listReversed.length === 0) {
     53 			if (this._list.length === 0) return undefined;
     54 			if (this._list.length === 1) return this._list.pop();
     55 			if (this._list.length < 16) return this._list.shift();
     56 			const temp = this._listReversed;
     57 			this._listReversed = this._list;
     58 			this._listReversed.reverse();
     59 			this._list = temp;
     60 		}
     61 		return this._listReversed.pop();
     62 	}
     63 
     64 	/**
     65 	 * Finds and removes an item
     66 	 * @param {T} item the item
     67 	 * @returns {void}
     68 	 */
     69 	delete(item) {
     70 		const i = this._list.indexOf(item);
     71 		if (i >= 0) {
     72 			this._list.splice(i, 1);
     73 		} else {
     74 			const i = this._listReversed.indexOf(item);
     75 			if (i >= 0) this._listReversed.splice(i, 1);
     76 		}
     77 	}
     78 
     79 	[Symbol.iterator]() {
     80 		let i = -1;
     81 		let reversed = false;
     82 		return {
     83 			next: () => {
     84 				if (!reversed) {
     85 					i++;
     86 					if (i < this._list.length) {
     87 						return {
     88 							done: false,
     89 							value: this._list[i]
     90 						};
     91 					}
     92 					reversed = true;
     93 					i = this._listReversed.length;
     94 				}
     95 				i--;
     96 				if (i < 0) {
     97 					return {
     98 						done: true,
     99 						value: undefined
    100 					};
    101 				}
    102 				return {
    103 					done: false,
    104 					value: this._listReversed[i]
    105 				};
    106 			}
    107 		};
    108 	}
    109 }
    110 
    111 module.exports = ArrayQueue;