$

node_modules/webpack/lib/util/StackedCacheMap.js

@@ -0,0 +1,110 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+/**
+ * @template K
+ * @template V
+ */
+class StackedCacheMap {
+	constructor() {
+		/** @type {Map<K, V>} */
+		this.map = new Map();
+		/** @type {ReadonlyMap<K, V>[]} */
+		this.stack = [];
+	}
+
+	/**
+	 * @param {ReadonlyMap<K, V>} map map to add
+	 * @param {boolean} immutable if 'map' is immutable and StackedCacheMap can keep referencing it
+	 */
+	addAll(map, immutable) {
+		if (immutable) {
+			this.stack.push(map);
+
+			// largest map should go first
+			for (let i = this.stack.length - 1; i > 0; i--) {
+				const beforeLast = this.stack[i - 1];
+				if (beforeLast.size >= map.size) break;
+				this.stack[i] = beforeLast;
+				this.stack[i - 1] = map;
+			}
+		} else {
+			for (const [key, value] of map) {
+				this.map.set(key, value);
+			}
+		}
+	}
+
+	/**
+	 * @param {K} item the key of the element to add
+	 * @param {V} value the value of the element to add
+	 * @returns {void}
+	 */
+	set(item, value) {
+		this.map.set(item, value);
+	}
+
+	/**
+	 * @param {K} item the item to delete
+	 * @returns {void}
+	 */
+	delete(item) {
+		throw new Error("Items can't be deleted from a StackedCacheMap");
+	}
+
+	/**
+	 * @param {K} item the item to test
+	 * @returns {boolean} true if the item exists in this set
+	 */
+	has(item) {
+		throw new Error(
+			"Checking StackedCacheMap.has before reading is inefficient, use StackedCacheMap.get and check for undefined"
+		);
+	}
+
+	/**
+	 * @param {K} item the key of the element to return
+	 * @returns {V} the value of the element
+	 */
+	get(item) {
+		for (const map of this.stack) {
+			const value = map.get(item);
+			if (value !== undefined) return value;
+		}
+		return this.map.get(item);
+	}
+
+	clear() {
+		this.stack.length = 0;
+		this.map.clear();
+	}
+
+	get size() {
+		let size = this.map.size;
+		for (const map of this.stack) {
+			size += map.size;
+		}
+		return size;
+	}
+
+	[Symbol.iterator]() {
+		const iterators = this.stack.map(map => map[Symbol.iterator]());
+		let current = this.map[Symbol.iterator]();
+		return {
+			next() {
+				let result = current.next();
+				while (result.done && iterators.length > 0) {
+					current = iterators.pop();
+					result = current.next();
+				}
+				return result;
+			}
+		};
+	}
+}
+
+module.exports = StackedCacheMap;