streams/transferable/transform-stream.html

<!DOCTYPE html>
<meta charset="utf-8">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/test-utils.js"></script>
<script>
'use strict';

promise_test(t => {
  const orig = new TransformStream();
  const promise = new Promise(resolve => {
    addEventListener('message', t.step_func(evt => {
      const transferred = evt.data;
      assert_equals(transferred.constructor, TransformStream,
                    'transferred should be a TransformStream in this realm');
      assert_true(transferred instanceof TransformStream,
                  'instanceof check should pass');

      // Perform a brand-check on |transferred|.
      const readableGetter = Object.getOwnPropertyDescriptor(
        TransformStream.prototype, 'readable').get;
      assert_true(readableGetter.call(transferred) instanceof ReadableStream,
                 'brand check should pass and readable stream should result');
      const writableGetter = Object.getOwnPropertyDescriptor(
        TransformStream.prototype, 'writable').get;
      assert_true(writableGetter.call(transferred) instanceof WritableStream,
                 'brand check should pass and writable stream should result');
      resolve();
    }), {once: true});
  });
  postMessage(orig, '*', [orig]);
  assert_true(orig.readable.locked, 'the readable side should be locked');
  assert_true(orig.writable.locked, 'the writable side should be locked');
  return promise;
}, 'window.postMessage should be able to transfer a TransformStream');

test(() => {
  const ts = new TransformStream();
  const writer = ts.writable.getWriter();
  assert_throws_dom('DataCloneError', () => postMessage(ts, '*', [ts]),
                    'postMessage should throw');
  assert_false(ts.readable.locked, 'readable side should not get locked');
}, 'a TransformStream with a locked writable should not be transferable');

test(() => {
  const ts = new TransformStream();
  const reader = ts.readable.getReader();
  assert_throws_dom('DataCloneError', () => postMessage(ts, '*', [ts]),
                    'postMessage should throw');
  assert_false(ts.writable.locked, 'writable side should not get locked');
}, 'a TransformStream with a locked readable should not be transferable');

test(() => {
  const ts = new TransformStream();
  const reader = ts.readable.getReader();
  const writer = ts.writable.getWriter();
  assert_throws_dom('DataCloneError', () => postMessage(ts, '*', [ts]),
                    'postMessage should throw');
}, 'a TransformStream with both sides locked should not be transferable');

promise_test(t => {
  const source = new ReadableStream({
    start(controller) {
      controller.enqueue('hello ');
      controller.enqueue('there ');
      controller.close();
    }
  });
  let result = '';
  const sink = new WritableStream({
    write(chunk) {
      result += chunk;
    }
  });
  const transform1 = new TransformStream({
    transform(chunk, controller) {
      controller.enqueue(chunk.toUpperCase());
    }
  });
  const transform2 = new TransformStream({
    transform(chunk, controller) {
      controller.enqueue(chunk + chunk);
    }
  });
  const promise = new Promise(resolve => {
    addEventListener('message', t.step_func(evt => {
      const data = evt.data;
      resolve(data.source
                .pipeThrough(data.transform1)
                .pipeThrough(data.transform2)
                .pipeTo(data.sink));
    }));
  });
  postMessage({source, sink, transform1, transform2}, '*',
              [source, transform1, sink, transform2]);
  return promise
    .then(() => delay(0))
    .then(() => {
      assert_equals(result, 'HELLO HELLO THERE THERE ',
                    'transforms should have been applied');
    });
}, 'piping through transferred transforms should work');

</script>