// 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";
/**
 * 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 Usage
 * ```ts no-assert
 * import { toReadableStream } from "@std/io/to-readable-stream";
 *
 * const file = await Deno.open("./README.md", { read: true });
 * const fileStream = toReadableStream(file);
 * ```
 *
 * @param reader The reader to read from
 * @param options The options
 * @returns The readable stream
 */ export function toReadableStream(reader, options) {
  const { autoClose = true, chunkSize = DEFAULT_CHUNK_SIZE, strategy } = options ?? {};
  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);
}
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