deno.land / std@0.166.0 / async / mux_async_iterator.ts

mux_async_iterator.ts
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { Deferred, deferred } from "./deferred.ts";
interface TaggedYieldedValue<T> { iterator: AsyncIterator<T>; value: T;}
/** The MuxAsyncIterator class multiplexes multiple async iterators into a * single stream. It currently makes an assumption: * - The final result (the value returned and not yielded from the iterator) * does not matter; if there is any, it is discarded. */export class MuxAsyncIterator<T> implements AsyncIterable<T> { #iteratorCount = 0; #yields: Array<TaggedYieldedValue<T>> = []; // deno-lint-ignore no-explicit-any #throws: any[] = []; #signal: Deferred<void> = deferred();
add(iterable: AsyncIterable<T>) { ++this.#iteratorCount; this.#callIteratorNext(iterable[Symbol.asyncIterator]()); }
async #callIteratorNext( iterator: AsyncIterator<T>, ) { try { const { value, done } = await iterator.next(); if (done) { --this.#iteratorCount; } else { this.#yields.push({ iterator, value }); } } catch (e) { this.#throws.push(e); } this.#signal.resolve(); }
async *iterate(): AsyncIterableIterator<T> { while (this.#iteratorCount > 0) { // Sleep until any of the wrapped iterators yields. await this.#signal;
// Note that while we're looping over `yields`, new items may be added. for (let i = 0; i < this.#yields.length; i++) { const { iterator, value } = this.#yields[i]; yield value; this.#callIteratorNext(iterator); }
if (this.#throws.length) { for (const e of this.#throws) { throw e; } this.#throws.length = 0; } // Clear the `yields` list and reset the `signal` promise. this.#yields.length = 0; this.#signal = deferred(); } }
[Symbol.asyncIterator](): AsyncIterator<T> { return this.iterate(); }}
std
Deno standard library
GitHub Repositorydenoland/deno_std
GitHub Stars
2458

Version Info

Tagged at
2 months ago