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node_modules/webpack/lib/util/Semaphore.js

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+/*
+	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;