serenity/Tests/LibWeb/Text/input/Streams/ReadableByteStream-byob-tee.html

<script src="../include.js"></script>
<script>
    const CHUNK1 = "abcdefghijklmnopqrstuvwxyz";
    const CHUNK2 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    const CHUNK3 = "0123456789!@#$%^&*()-=_+,<";

    const readStream = (stream, name) => {
        const reader = stream.getReader({ mode: "byob" });

        let buffer = new ArrayBuffer(256);
        let offset = 0;

        return new Promise((resolve, reject) => {
            const processText = ({ done, value }) => {
                if (done) {
                    println(`${name}: Done!`);
                    resolve();
                    return;
                }

                buffer = value.buffer;
                offset += value.byteLength;

                value = new TextDecoder().decode(value);
                println(`${name}: ${value}`);

                return reader
                    .read(new Uint8Array(buffer, offset, buffer.byteLength - offset))
                    .then(processText);
            };

            reader
                .read(new Uint8Array(buffer, offset, buffer.byteLength - offset))
                .then(processText);
        });
    };

    const writeStream = (controller, data) => {
        const view = controller.byobRequest.view;

        const target = new Uint8Array(view.buffer, view.byteOffset, view.byteLength);
        const source = Uint8Array.from(Array.from(data).map(ch => ch.charCodeAt(0)));

        for (let i = 0; i < source.length; ++i) {
            target[i] = source[i];
        }

        controller.byobRequest.respond(source.length);
    };

    asyncTest(done => {
        const stream = new ReadableStream({
            type: "bytes",

            start(controller) {
                pullCount = 0;
            },

            pull(controller) {
                const view = controller.byobRequest.view;
                ++pullCount;

                if (pullCount == 1) {
                    writeStream(controller, CHUNK1);
                } else if (pullCount == 2) {
                    writeStream(controller, CHUNK2);
                } else if (pullCount == 3) {
                    writeStream(controller, CHUNK3);
                } else {
                    controller.close();
                    controller.byobRequest.respond(0);
                }
            },

            cancel() {},
        });

        const teed = stream.tee();

        readStream(teed[0], "stream1").then(() => {
            readStream(teed[1], "stream2").then(done);
        });
    });
</script>