webpack/lib/util/WeakTupleMap.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";

/**
 * Strong-key child map used for tuple elements that cannot be stored in a
 * `WeakMap`.
 * @template {EXPECTED_ANY[]} T
 * @template V
 * @typedef {Map<EXPECTED_ANY, WeakTupleMap<T, V>>} M
 */

/**
 * Weak-key child map used for tuple elements that are objects and can be held
 * without preventing garbage collection.
 * @template {EXPECTED_ANY[]} T
 * @template V
 * @typedef {WeakMap<EXPECTED_OBJECT, WeakTupleMap<T, V>>} W
 */

/**
 * Reports whether a tuple element can be stored in a `WeakMap`.
 * @param {EXPECTED_ANY} thing thing
 * @returns {boolean} true if is weak
 */
const isWeakKey = (thing) => typeof thing === "object" && thing !== null;

/**
 * Extracts the element type from a tuple-like array.
 * @template {unknown[]} T
 * @typedef {T extends ReadonlyArray<infer ElementType> ? ElementType : never} ArrayElement
 */

/**
 * Stores values by tuple keys while using `WeakMap` for object elements so the
 * cache can release entries when those objects are collected.
 * @template {EXPECTED_ANY[]} K
 * @template V
 */
class WeakTupleMap {
	/**
	 * Initializes an empty tuple trie node with optional value and child maps.
	 */
	constructor() {
		/** @private */
		this.f = 0;
		/**
		 * @private
		 * @type {V | undefined}
		 */
		this.v = undefined;
		/**
		 * @private
		 * @type {M<K, V> | undefined}
		 */
		this.m = undefined;
		/**
		 * @private
		 * @type {W<K, V> | undefined}
		 */
		this.w = undefined;
	}

	/**
	 * Stores a value at the node identified by the provided tuple key.
	 * @param {[...K, V]} args tuple
	 * @returns {void}
	 */
	set(...args) {
		/** @type {WeakTupleMap<K, V>} */
		let node = this;
		for (let i = 0; i < args.length - 1; i++) {
			node = node._get(/** @type {ArrayElement<K>} */ (args[i]));
		}
		node._setValue(/** @type {V} */ (args[args.length - 1]));
	}

	/**
	 * Checks whether the exact tuple key has a stored value.
	 * @param {K} args tuple
	 * @returns {boolean} true, if the tuple is in the Set
	 */
	has(...args) {
		/** @type {WeakTupleMap<K, V> | undefined} */
		let node = this;
		for (let i = 0; i < args.length; i++) {
			node = node._peek(/** @type {ArrayElement<K>} */ (args[i]));
			if (node === undefined) return false;
		}
		return node._hasValue();
	}

	/**
	 * Returns the value stored for the exact tuple key, if any.
	 * @param {K} args tuple
	 * @returns {V | undefined} the value
	 */
	get(...args) {
		/** @type {WeakTupleMap<K, V> | undefined} */
		let node = this;
		for (let i = 0; i < args.length; i++) {
			node = node._peek(/** @type {ArrayElement<K>} */ (args[i]));
			if (node === undefined) return;
		}
		return node._getValue();
	}

	/**
	 * Returns an existing value for the tuple or computes, stores, and returns a
	 * new one when the tuple is missing.
	 * @param {[...K, (...args: K) => V]} args tuple
	 * @returns {V} the value
	 */
	provide(...args) {
		/** @type {WeakTupleMap<K, V>} */
		let node = this;
		for (let i = 0; i < args.length - 1; i++) {
			node = node._get(/** @type {ArrayElement<K>} */ (args[i]));
		}
		if (node._hasValue()) return /** @type {V} */ (node._getValue());
		const fn = /** @type {(...args: K) => V} */ (args[args.length - 1]);
		const newValue = fn(.../** @type {K} */ (args.slice(0, -1)));
		node._setValue(newValue);
		return newValue;
	}

	/**
	 * Removes the value stored for the tuple key without pruning the trie.
	 * @param {K} args tuple
	 * @returns {void}
	 */
	delete(...args) {
		/** @type {WeakTupleMap<K, V> | undefined} */
		let node = this;
		for (let i = 0; i < args.length; i++) {
			node = node._peek(/** @type {ArrayElement<K>} */ (args[i]));
			if (node === undefined) return;
		}
		node._deleteValue();
	}

	/**
	 * Clears the stored value and all strong and weak child maps from this node.
	 * @returns {void}
	 */
	clear() {
		this.f = 0;
		this.v = undefined;
		this.w = undefined;
		this.m = undefined;
	}

	/**
	 * Returns the value stored directly on this trie node.
	 * @returns {V | undefined} stored value
	 */
	_getValue() {
		return this.v;
	}

	/**
	 * Reports whether this trie node currently stores a value.
	 * @returns {boolean} true when a value is present
	 */
	_hasValue() {
		return (this.f & 1) === 1;
	}

	/**
	 * Stores a value directly on this trie node.
	 * @param {V} v value
	 * @private
	 */
	_setValue(v) {
		this.f |= 1;
		this.v = v;
	}

	/**
	 * Removes the value stored directly on this trie node.
	 */
	_deleteValue() {
		this.f &= 6;
		this.v = undefined;
	}

	/**
	 * Returns the child node for a tuple element without creating one.
	 * @param {ArrayElement<K>} thing thing
	 * @returns {WeakTupleMap<K, V> | undefined} thing
	 * @private
	 */
	_peek(thing) {
		if (isWeakKey(thing)) {
			if ((this.f & 4) !== 4) return;
			return /** @type {WeakMap<ArrayElement<K>, WeakTupleMap<K, V>>} */ (
				this.w
			).get(thing);
		}
		if ((this.f & 2) !== 2) return;
		return /** @type {Map<ArrayElement<K>, WeakTupleMap<K, V>>} */ (this.m).get(
			thing
		);
	}

	/**
	 * Returns the child node for a tuple element, creating and storing it when
	 * necessary.
	 * @private
	 * @param {ArrayElement<K>} thing thing
	 * @returns {WeakTupleMap<K, V>} value
	 */
	_get(thing) {
		if (isWeakKey(thing)) {
			if ((this.f & 4) !== 4) {
				/** @type {W<K, V>} */
				const newMap = new WeakMap();
				this.f |= 4;
				/** @type {WeakTupleMap<K, V>} */
				const newNode = new WeakTupleMap();
				(this.w = newMap).set(thing, newNode);
				return newNode;
			}
			const entry = /** @type {W<K, V>} */ (this.w).get(thing);
			if (entry !== undefined) {
				return entry;
			}
			/** @type {WeakTupleMap<K, V>} */
			const newNode = new WeakTupleMap();
			/** @type {W<K, V>} */
			(this.w).set(thing, newNode);
			return newNode;
		}
		if ((this.f & 2) !== 2) {
			/** @type {M<K, V>} */
			const newMap = new Map();
			this.f |= 2;
			/** @type {WeakTupleMap<K, V>} */
			const newNode = new WeakTupleMap();
			(this.m = newMap).set(thing, newNode);
			return newNode;
		}
		const entry =
			/** @type {M<K, V>} */
			(this.m).get(thing);
		if (entry !== undefined) {
			return entry;
		}
		/** @type {WeakTupleMap<K, V>} */
		const newNode = new WeakTupleMap();
		/** @type {M<K, V>} */
		(this.m).set(thing, newNode);
		return newNode;
	}
}

module.exports = WeakTupleMap;