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std/io/to_readable_stream.ts

Deno standard library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { DEFAULT_CHUNK_SIZE } from "./_constants.ts";import { isCloser } from "./_common.ts";import type { Closer, Reader } from "./types.ts";
/** Options for {@linkcode toReadableStream}. */export interface ToReadableStreamOptions { /** If the `reader` is also a `Closer`, automatically close the `reader` * when `EOF` is encountered, or a read error occurs. * * @default {true} */ autoClose?: boolean;
/** The size of chunks to allocate to read, the default is ~16KiB, which is * the maximum size that Deno operations can currently support. */ chunkSize?: number;
/** The queuing strategy to create the `ReadableStream` with. */ strategy?: QueuingStrategy<Uint8Array>;}
/** * Create a {@linkcode ReadableStream} of {@linkcode Uint8Array}s from a * {@linkcode Reader}. * * When the pull algorithm is called on the stream, a chunk from the reader * will be read. When `null` is returned from the reader, the stream will be * closed along with the reader (if it is also a `Closer`). * * @example * ```ts * import { toReadableStream } from "https://deno.land/std@$STD_VERSION/io/to_readable_stream.ts"; * * const file = await Deno.open("./file.txt", { read: true }); * const fileStream = toReadableStream(file); * ``` */export function toReadableStream( reader: Reader | (Reader & Closer), { autoClose = true, chunkSize = DEFAULT_CHUNK_SIZE, strategy, }: ToReadableStreamOptions = {},): ReadableStream<Uint8Array> { return new ReadableStream({ async pull(controller) { const chunk = new Uint8Array(chunkSize); try { const read = await reader.read(chunk); if (read === null) { if (isCloser(reader) && autoClose) { reader.close(); } controller.close(); return; } controller.enqueue(chunk.subarray(0, read)); } catch (e) { controller.error(e); if (isCloser(reader)) { reader.close(); } } }, cancel() { if (isCloser(reader) && autoClose) { reader.close(); } }, }, strategy);}