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Async coordination primitives and extensions on top of ES6 Promises
82 lines (80 loc) • 2.83 kB
JavaScript
"use strict";
/*! *****************************************************************************
Copyright (c) Microsoft Corporation.
Licensed under the Apache License, Version 2.0.
See LICENSE file in the project root for details.
***************************************************************************** */
Object.defineProperty(exports, "__esModule", { value: true });
const utils_1 = require("./utils");
/**
* An asynchronous Stack.
*/
class AsyncStack {
/**
* Initializes a new instance of the AsyncStack class.
*
* @param iterable An optional iterable of values or promises.
*/
constructor(iterable) {
this._available = undefined;
this._pending = undefined;
if (!utils_1.isIterable(iterable, /*optional*/ true))
throw new TypeError("Object not iterable: iterable.");
if (!utils_1.isMissing(iterable)) {
this._available = [];
for (const value of iterable) {
this._available.push(Promise.resolve(value));
}
}
}
/**
* Gets the number of entries in the stack.
* When positive, indicates the number of entries available to get.
* When negative, indicates the number of requests waiting to be fulfilled.
*/
get size() {
if (this._available && this._available.length > 0) {
return this._available.length;
}
if (this._pending && this._pending.length > 0) {
return -this._pending.length;
}
return 0;
}
/**
* Adds a value to the top of the stack. If the stack is empty but has a pending
* pop request, the value will be popped and the request fulfilled.
*
* @param value A value or promise to add to the stack.
*/
push(value) {
if (this._pending !== undefined) {
const resolve = this._pending.shift();
if (resolve !== undefined) {
resolve(value);
return;
}
}
if (this._available === undefined) {
this._available = [];
}
this._available.push(Promise.resolve(value));
}
/**
* Removes and returns a Promise for the top value of the stack. If the stack is empty,
* returns a Promise for the next value to be pushed on to the stack.
*/
pop() {
if (this._available !== undefined) {
const promise = this._available.pop();
if (promise !== undefined) {
return promise;
}
}
if (this._pending === undefined) {
this._pending = [];
}
return new Promise(resolve => { this._pending.push(resolve); });
}
}
exports.AsyncStack = AsyncStack;