compression-multiple-chunks.tentative.any.js

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// META: global=window,worker,shadowrealm

// META: script=third_party/pako/pako_inflate.min.js

// META: timeout=long

'use strict';

// This test asserts that compressing multiple chunks should work.

// Example: ('Hello', 3) => TextEncoder().encode('HelloHelloHello')

function makeExpectedChunk(input, numberOfChunks) {

  const expectedChunk = input.repeat(numberOfChunks);

  return new TextEncoder().encode(expectedChunk);

// Example: ('Hello', 3, 'deflate') => compress ['Hello', 'Hello', Hello']

async function compressMultipleChunks(input, numberOfChunks, format) {

  const cs = new CompressionStream(format);

  const writer = cs.writable.getWriter();

  const chunk = new TextEncoder().encode(input);

  for (let i = 0; i < numberOfChunks; ++i) {

    writer.write(chunk);

  const closePromise = writer.close();

  const out = [];

  const reader = cs.readable.getReader();

  let totalSize = 0;

  while (true) {

    const { value, done } = await reader.read();

    if (done)

      break;

    out.push(value);

    totalSize += value.byteLength;

  await closePromise;

  const concatenated = new Uint8Array(totalSize);

  let offset = 0;

  for (const array of out) {

    concatenated.set(array, offset);

    offset += array.byteLength;

  return concatenated;

const hello = 'Hello';

for (let numberOfChunks = 2; numberOfChunks <= 16; ++numberOfChunks) {

  promise_test(async t => {

    const compressedData = await compressMultipleChunks(hello, numberOfChunks, 'deflate');

    const expectedValue = makeExpectedChunk(hello, numberOfChunks);

    // decompress with pako, and check that we got the same result as our original string

    assert_array_equals(expectedValue, pako.inflate(compressedData), 'value should match');

  }, `compressing ${numberOfChunks} chunks with deflate should work`);

  promise_test(async t => {

    const compressedData = await compressMultipleChunks(hello, numberOfChunks, 'gzip');

    const expectedValue = makeExpectedChunk(hello, numberOfChunks);

    // decompress with pako, and check that we got the same result as our original string

    assert_array_equals(expectedValue, pako.inflate(compressedData), 'value should match');

  }, `compressing ${numberOfChunks} chunks with gzip should work`);

  promise_test(async t => {

    const compressedData = await compressMultipleChunks(hello, numberOfChunks, 'deflate-raw');

    const expectedValue = makeExpectedChunk(hello, numberOfChunks);

    // decompress with pako, and check that we got the same result as our original string

    assert_array_equals(expectedValue, pako.inflateRaw(compressedData), 'value should match');

  }, `compressing ${numberOfChunks} chunks with deflate-raw should work`);