websockets/send-data-isolation.sub.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>WebSocket send() data isolation</title>
<link rel="help" href="https://websockets.spec.whatwg.org/#dom-websocket-send">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<script>
"use strict";

// These tests verify that `send()` on a WebSocket correctly copies its input data,
// so that subsequent modifications to the input do not affect what gets sent.

// We use an echo server that sends back what it receives.
const echoURL = "ws://{{host}}:{{ports[ws][0]}}/echo";

promise_test(async () => {
  const ws = new WebSocket(echoURL);
  await new Promise((resolve, reject) => {
    ws.onopen = resolve;
    ws.onerror = () => reject(new Error("WebSocket connection failed"));
  });

  const input = new Uint8Array([1, 2, 3, 4]);

  const messagePromise = new Promise((resolve, reject) => {
    ws.onmessage = e => {
      const reader = new FileReader();
      reader.onload = () => resolve(new Uint8Array(reader.result));
      reader.onerror = () => reject(reader.error);
      reader.readAsArrayBuffer(e.data);
    };
    ws.onerror = () => reject(new Error("WebSocket error"));
  });

  ws.send(input);
  input[0] = 99;

  const result = await messagePromise;
  ws.close();

  assert_array_equals(
    Array.from(result),
    [1, 2, 3, 4],
    "Sent data should not be affected by modifying the input Uint8Array"
  );
}, "Modifying a Uint8Array after send() does not affect the sent data");

promise_test(async () => {
  const ws = new WebSocket(echoURL);
  await new Promise((resolve, reject) => {
    ws.onopen = resolve;
    ws.onerror = () => reject(new Error("WebSocket connection failed"));
  });

  const input = new Uint8Array([5, 6, 7, 8]);
  const inputBuffer = input.buffer;

  const messagePromise = new Promise((resolve, reject) => {
    ws.onmessage = e => {
      const reader = new FileReader();
      reader.onload = () => resolve(new Uint8Array(reader.result));
      reader.onerror = () => reject(reader.error);
      reader.readAsArrayBuffer(e.data);
    };
    ws.onerror = () => reject(new Error("WebSocket error"));
  });

  ws.send(inputBuffer);
  input[0] = 99;

  const result = await messagePromise;
  ws.close();

  assert_array_equals(
    Array.from(result),
    [5, 6, 7, 8],
    "Sent data should not be affected by modifying the underlying ArrayBuffer"
  );
}, "Modifying an ArrayBuffer after send() does not affect the sent data");

promise_test(async () => {
  const ws = new WebSocket(echoURL);
  await new Promise((resolve, reject) => {
    ws.onopen = resolve;
    ws.onerror = () => reject(new Error("WebSocket connection failed"));
  });

  // Test with a view into a larger buffer (exercises offset handling)
  const largerBuffer = new ArrayBuffer(16);
  const view = new Uint8Array(largerBuffer, 4, 4);
  view.set([10, 11, 12, 13]);

  const messagePromise = new Promise((resolve, reject) => {
    ws.onmessage = e => {
      const reader = new FileReader();
      reader.onload = () => resolve(new Uint8Array(reader.result));
      reader.onerror = () => reject(reader.error);
      reader.readAsArrayBuffer(e.data);
    };
    ws.onerror = () => reject(new Error("WebSocket error"));
  });

  ws.send(view);
  view[0] = 99;

  const result = await messagePromise;
  ws.close();

  assert_array_equals(
    Array.from(result),
    [10, 11, 12, 13],
    "Sent data should not be affected by modifying a typed array view"
  );
}, "Modifying a typed array view after send() does not affect the sent data");
</script>