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std/streams/merge.ts

Deno standard library
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
import { deferred } from "../async/deferred.ts";
/** * Merge multiple streams into a single one, not taking order into account. * If a stream ends before other ones, the other will continue adding data, * and the finished one will not add any more data. */export function mergeReadableStreams<T>( ...streams: ReadableStream<T>[]): ReadableStream<T> { const resolvePromises = streams.map(() => deferred<void>()); return new ReadableStream<T>({ start(controller) { Promise.all(resolvePromises).then(() => { controller.close(); }); try { for (const [key, stream] of Object.entries(streams)) { (async () => { for await (const data of stream) { controller.enqueue(data); } resolvePromises[+key].resolve(); })(); } } catch (e) { controller.error(e); } }, });}
/** * Merge multiple streams into a single one, taking order into account, and each stream * will wait for a chunk to enqueue before the next stream can append another chunk. * If a stream ends before other ones, the others will continue adding data in order, * and the finished one will not add any more data. */export function zipReadableStreams<T>( ...streams: ReadableStream<T>[]): ReadableStream<T> { const readers = streams.map((s) => s.getReader()); return new ReadableStream<T>({ async start(controller) { try { let resolved = 0; while (resolved != streams.length) { for (const [key, reader] of Object.entries(readers)) { const { value, done } = await reader.read(); if (!done) { controller.enqueue(value!); } else { resolved++; readers.splice(+key, 1); } } } controller.close(); } catch (e) { controller.error(e); } }, });}
/** * Merge multiple streams into a single one, taking order into account, and each stream * will wait for a chunk to enqueue before the next stream can append another chunk. * If a stream ends before other ones, the others will be cancelled. */export function earlyZipReadableStreams<T>( ...streams: ReadableStream<T>[]): ReadableStream<T> { const readers = streams.map((s) => s.getReader()); return new ReadableStream<T>({ async start(controller) { try { loop: while (true) { for (const reader of readers) { const { value, done } = await reader.read(); if (!done) { controller.enqueue(value!); } else { await Promise.all(readers.map((reader) => reader.cancel())); break loop; } } } controller.close(); } catch (e) { controller.error(e); } }, });}