--- /dev/null
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+ value: true
+});
+exports.default = memoize;
+
+var _identity = require('lodash/identity');
+
+var _identity2 = _interopRequireDefault(_identity);
+
+var _rest = require('./internal/rest');
+
+var _rest2 = _interopRequireDefault(_rest);
+
+var _setImmediate = require('./internal/setImmediate');
+
+var _setImmediate2 = _interopRequireDefault(_setImmediate);
+
+var _initialParams = require('./internal/initialParams');
+
+var _initialParams2 = _interopRequireDefault(_initialParams);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+function has(obj, key) {
+ return key in obj;
+}
+
+/**
+ * Caches the results of an `async` function. When creating a hash to store
+ * function results against, the callback is omitted from the hash and an
+ * optional hash function can be used.
+ *
+ * If no hash function is specified, the first argument is used as a hash key,
+ * which may work reasonably if it is a string or a data type that converts to a
+ * distinct string. Note that objects and arrays will not behave reasonably.
+ * Neither will cases where the other arguments are significant. In such cases,
+ * specify your own hash function.
+ *
+ * The cache of results is exposed as the `memo` property of the function
+ * returned by `memoize`.
+ *
+ * @name memoize
+ * @static
+ * @memberOf module:Utils
+ * @method
+ * @category Util
+ * @param {Function} fn - The function to proxy and cache results from.
+ * @param {Function} hasher - An optional function for generating a custom hash
+ * for storing results. It has all the arguments applied to it apart from the
+ * callback, and must be synchronous.
+ * @returns {Function} a memoized version of `fn`
+ * @example
+ *
+ * var slow_fn = function(name, callback) {
+ * // do something
+ * callback(null, result);
+ * };
+ * var fn = async.memoize(slow_fn);
+ *
+ * // fn can now be used as if it were slow_fn
+ * fn('some name', function() {
+ * // callback
+ * });
+ */
+function memoize(fn, hasher) {
+ var memo = Object.create(null);
+ var queues = Object.create(null);
+ hasher = hasher || _identity2.default;
+ var memoized = (0, _initialParams2.default)(function memoized(args, callback) {
+ var key = hasher.apply(null, args);
+ if (has(memo, key)) {
+ (0, _setImmediate2.default)(function () {
+ callback.apply(null, memo[key]);
+ });
+ } else if (has(queues, key)) {
+ queues[key].push(callback);
+ } else {
+ queues[key] = [callback];
+ fn.apply(null, args.concat((0, _rest2.default)(function (args) {
+ memo[key] = args;
+ var q = queues[key];
+ delete queues[key];
+ for (var i = 0, l = q.length; i < l; i++) {
+ q[i].apply(null, args);
+ }
+ })));
+ }
+ });
+ memoized.memo = memo;
+ memoized.unmemoized = fn;
+ return memoized;
+}
+module.exports = exports['default'];
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