reader_from_stream_reader_test.ts

// Copyright 2018-2025 the Deno authors. MIT license.

import { assert, assertEquals } from "@std/assert";
import { copy } from "./copy.ts";
import { readerFromStreamReader } from "./reader_from_stream_reader.ts";
import { Buffer } from "./buffer.ts";

function repeat(c: string, bytes: number): Uint8Array {
  assertEquals(c.length, 1);
  const ui8 = new Uint8Array(bytes);
  ui8.fill(c.charCodeAt(0));
  return ui8;
}

Deno.test("[streams] readerFromStreamReader()", async function () {
  const chunks: string[] = ["hello", "deno", "land"];
  const expected = chunks.slice();
  const readChunks: Uint8Array[] = [];
  const readableStream = ReadableStream.from(chunks)
    .pipeThrough(new TextEncoderStream());

  const decoder = new TextDecoder();
  const reader = readerFromStreamReader(readableStream.getReader());

  let i = 0;

  while (true) {
    const b = new Uint8Array(1024);
    const n = await reader.read(b);

    if (n === null) break;

    readChunks.push(b.subarray(0, n));
    assert(i < expected.length);

    i++;
  }

  assertEquals(
    expected,
    readChunks.map((chunk) => decoder.decode(chunk)),
  );
});

Deno.test("[streams] readerFromStreamReader() big chunks", async function () {
  const bufSize = 1024;
  const chunkSize = 3 * bufSize;
  const writer = new Buffer();

  // A readable stream can enqueue chunks bigger than Copy bufSize
  // Reader returned by toReader should enqueue exceeding bytes
  const chunks: string[] = [
    "a".repeat(chunkSize),
    "b".repeat(chunkSize),
    "c".repeat(chunkSize),
  ];
  const expected = chunks.slice();
  const readableStream = ReadableStream.from(chunks)
    .pipeThrough(new TextEncoderStream());

  const reader = readerFromStreamReader(readableStream.getReader());
  const n = await copy(reader, writer, { bufSize });

  const expectedWritten = chunkSize * expected.length;
  assertEquals(n, chunkSize * expected.length);
  assertEquals(writer.length, expectedWritten);
});

Deno.test("[streams] readerFromStreamReader() irregular chunks", async function () {
  const bufSize = 1024;
  const chunkSize = 3 * bufSize;
  const writer = new Buffer();

  // A readable stream can enqueue chunks bigger than Copy bufSize
  // Reader returned by toReader should enqueue exceeding bytes
  const chunks: Uint8Array[] = [
    repeat("a", chunkSize),
    repeat("b", chunkSize + 253),
    repeat("c", chunkSize + 8),
  ];
  const expected = new Uint8Array(
    chunks
      .slice()
      .map((chunk) => [...chunk])
      .flat(),
  );
  const readableStream = ReadableStream.from(chunks);

  const reader = readerFromStreamReader(readableStream.getReader());

  const n = await copy(reader, writer, { bufSize });
  assertEquals(n, expected.length);
  assertEquals(expected, writer.bytes());
});