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1 files changed, 72 insertions, 0 deletions

diff --git a/node_modules/when/guard.js b/node_modules/when/guard.js
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+/** @license MIT License (c) copyright 2011-2013 original author or authors */
+
+/**
+ * Generalized promise concurrency guard
+ * Adapted from original concept by Sakari Jokinen (Rocket Pack, Ltd.)
+ *
+ * @author Brian Cavalier
+ * @author John Hann
+ * @contributor Sakari Jokinen
+ */
+(function(define) {
+define(function(require) {
+
+	var when = require('./when');
+	var slice = Array.prototype.slice;
+
+	guard.n = n;
+
+	return guard;
+
+	/**
+	 * Creates a guarded version of f that can only be entered when the supplied
+	 * condition allows.
+	 * @param {function} condition represents a critical section that may only
+	 *  be entered when allowed by the condition
+	 * @param {function} f function to guard
+	 * @returns {function} guarded version of f
+	 */
+	function guard(condition, f) {
+		return function() {
+			var args = slice.call(arguments);
+
+			return when(condition()).withThis(this).then(function(exit) {
+				return when(f.apply(this, args))['finally'](exit);
+			});
+		};
+	}
+
+	/**
+	 * Creates a condition that allows only n simultaneous executions
+	 * of a guarded function
+	 * @param {number} allowed number of allowed simultaneous executions
+	 * @returns {function} condition function which returns a promise that
+	 *  fulfills when the critical section may be entered.  The fulfillment
+	 *  value is a function ("notifyExit") that must be called when the critical
+	 *  section has been exited.
+	 */
+	function n(allowed) {
+		var count = 0;
+		var waiting = [];
+
+		return function enter() {
+			return when.promise(function(resolve) {
+				if(count < allowed) {
+					resolve(exit);
+				} else {
+					waiting.push(resolve);
+				}
+				count += 1;
+			});
+		};
+
+		function exit() {
+			count = Math.max(count - 1, 0);
+			if(waiting.length > 0) {
+				waiting.shift()(exit);
+			}
+		}
+	}
+
+});
+}(typeof define === 'function' && define.amd ? define : function(factory) { module.exports = factory(require); }));