91 lines
3 KiB
JavaScript
91 lines
3 KiB
JavaScript
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'use strict';
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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exports.default = memoize;
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var _setImmediate = require('./internal/setImmediate.js');
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var _setImmediate2 = _interopRequireDefault(_setImmediate);
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var _initialParams = require('./internal/initialParams.js');
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var _initialParams2 = _interopRequireDefault(_initialParams);
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var _wrapAsync = require('./internal/wrapAsync.js');
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var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
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function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
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/**
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* Caches the results of an async function. When creating a hash to store
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* function results against, the callback is omitted from the hash and an
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* optional hash function can be used.
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*
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* **Note: if the async function errs, the result will not be cached and
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* subsequent calls will call the wrapped function.**
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*
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* If no hash function is specified, the first argument is used as a hash key,
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* which may work reasonably if it is a string or a data type that converts to a
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* distinct string. Note that objects and arrays will not behave reasonably.
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* Neither will cases where the other arguments are significant. In such cases,
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* specify your own hash function.
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*
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* The cache of results is exposed as the `memo` property of the function
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* returned by `memoize`.
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*
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* @name memoize
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* @static
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* @memberOf module:Utils
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* @method
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* @category Util
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* @param {AsyncFunction} fn - The async function to proxy and cache results from.
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* @param {Function} hasher - An optional function for generating a custom hash
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* for storing results. It has all the arguments applied to it apart from the
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* callback, and must be synchronous.
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* @returns {AsyncFunction} a memoized version of `fn`
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* @example
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*
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* var slow_fn = function(name, callback) {
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* // do something
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* callback(null, result);
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* };
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* var fn = async.memoize(slow_fn);
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*
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* // fn can now be used as if it were slow_fn
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* fn('some name', function() {
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* // callback
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* });
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*/
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function memoize(fn, hasher = v => v) {
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var memo = Object.create(null);
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var queues = Object.create(null);
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var _fn = (0, _wrapAsync2.default)(fn);
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var memoized = (0, _initialParams2.default)((args, callback) => {
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var key = hasher(...args);
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if (key in memo) {
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(0, _setImmediate2.default)(() => callback(null, ...memo[key]));
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} else if (key in queues) {
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queues[key].push(callback);
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} else {
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queues[key] = [callback];
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_fn(...args, (err, ...resultArgs) => {
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// #1465 don't memoize if an error occurred
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if (!err) {
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memo[key] = resultArgs;
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}
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var q = queues[key];
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delete queues[key];
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for (var i = 0, l = q.length; i < l; i++) {
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q[i](err, ...resultArgs);
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}
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});
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}
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});
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memoized.memo = memo;
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memoized.unmemoized = fn;
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return memoized;
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}
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module.exports = exports['default'];
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