backpressure.any.js

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// META: global=window,worker,shadowrealm

'use strict';

const classes = [

    name: 'TextDecoderStream',

    input: new Uint8Array([65])

},

    name: 'TextEncoderStream',

    input: 'A'

];

const microtasksRun = () => new Promise(resolve => step_timeout(resolve, 0));

for (const streamClass of classes) {

  promise_test(async () => {

    const stream = new self[streamClass.name]();

    const writer = stream.writable.getWriter();

    const reader = stream.readable.getReader();

    const events = [];

    await microtasksRun();

    const writePromise = writer.write(streamClass.input);

    writePromise.then(() => events.push('write'));

    await microtasksRun();

    events.push('paused');

    await reader.read();

    events.push('read');

    await writePromise;

    assert_array_equals(events, ['paused', 'read', 'write'],

                        'write should happen after read');

  }, 'write() should not complete until read relieves backpressure for ' +

     `${streamClass.name}`);

  promise_test(async () => {

    const stream = new self[streamClass.name]();

    const writer = stream.writable.getWriter();

    const reader = stream.readable.getReader();

    const events = [];

    await microtasksRun();

    const readPromise1 = reader.read();

    readPromise1.then(() => events.push('read1'));

    const writePromise1 = writer.write(streamClass.input);

    const writePromise2 = writer.write(streamClass.input);

    writePromise1.then(() => events.push('write1'));

    writePromise2.then(() => events.push('write2'));

    await microtasksRun();

    events.push('paused');

    const readPromise2 = reader.read();

    readPromise2.then(() => events.push('read2'));

    await Promise.all([writePromise1, writePromise2,

                       readPromise1, readPromise2]);

    assert_array_equals(events, ['read1', 'write1', 'paused', 'read2',

                                 'write2'],

                        'writes should not happen before read2');

  }, 'additional writes should wait for backpressure to be relieved for ' +

     `class ${streamClass.name}`);