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- import AwaitValue from "./AwaitValue";
- export default function AsyncGenerator(gen) {
- var front, back;
-
- function send(key, arg) {
- return new Promise(function (resolve, reject) {
- var request = {
- key: key,
- arg: arg,
- resolve: resolve,
- reject: reject,
- next: null
- };
-
- if (back) {
- back = back.next = request;
- } else {
- front = back = request;
- resume(key, arg);
- }
- });
- }
-
- function resume(key, arg) {
- try {
- var result = gen[key](arg);
- var value = result.value;
- var wrappedAwait = value instanceof AwaitValue;
- Promise.resolve(wrappedAwait ? value.wrapped : value).then(function (arg) {
- if (wrappedAwait) {
- resume(key === "return" ? "return" : "next", arg);
- return;
- }
-
- settle(result.done ? "return" : "normal", arg);
- }, function (err) {
- resume("throw", err);
- });
- } catch (err) {
- settle("throw", err);
- }
- }
-
- function settle(type, value) {
- switch (type) {
- case "return":
- front.resolve({
- value: value,
- done: true
- });
- break;
-
- case "throw":
- front.reject(value);
- break;
-
- default:
- front.resolve({
- value: value,
- done: false
- });
- break;
- }
-
- front = front.next;
-
- if (front) {
- resume(front.key, front.arg);
- } else {
- back = null;
- }
- }
-
- this._invoke = send;
-
- if (typeof gen["return"] !== "function") {
- this["return"] = undefined;
- }
- }
-
- if (typeof Symbol === "function" && Symbol.asyncIterator) {
- AsyncGenerator.prototype[Symbol.asyncIterator] = function () {
- return this;
- };
- }
-
- AsyncGenerator.prototype.next = function (arg) {
- return this._invoke("next", arg);
- };
-
- AsyncGenerator.prototype["throw"] = function (arg) {
- return this._invoke("throw", arg);
- };
-
- AsyncGenerator.prototype["return"] = function (arg) {
- return this._invoke("return", arg);
- };
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