cobalt/black_box_tests/testdata/wasm_basic_test.html

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<head>
  <title>Cobalt WASM Basic Test</title>
  <script src='black_box_js_test_utils.js'></script>
</head>

<body>
  <script>
const fail = msg => {
  if (msg) {
    console.error(msg);
  }
  notReached();
};
const timeoutId = setTimeout(fail, 3000);
const success = () => {
  clearTimeout(timeoutId);
  onEndTest();
};

const Module = {};

const noop = () => {};
const wasmImports = {
  emscripten_notify_memory_growth: () => {
    if (!Module.asm || !Module.asm.memory) {
      return;
    }
    Module.HEAPU8 = new Uint8Array(Module.asm.memory.buffer);
  },
  fd_close: noop,
  fd_seek: noop,
  fd_write: noop,
  proc_exit: noop,
};
const importObject = {
  env: wasmImports,
  wasi_snapshot_preview1: wasmImports,
};

const stringFromHeap = stringPointer => {
  const heap = Module.HEAPU8;
  let endPointer = stringPointer;
  // Find null terminating character.
  while (heap[endPointer]) ++endPointer;
  return (new TextDecoder('utf8')).decode(heap.subarray(stringPointer, endPointer));
}

fetch('wasm_basic_test.wasm')
    .then(response => response.arrayBuffer())
    .then(bufferSource => WebAssembly.instantiate(bufferSource, importObject))
    .then(({instance}) => {
      Module.asm = instance.exports;
      wasmImports.emscripten_notify_memory_growth();
      assertEqual(3, Module.asm.add(1, 2));
      // Include space for null terminating byte.
      const helloStringPointer = Module.asm.malloc(7);
      Module.asm.getHello(helloStringPointer);
      assertEqual("Hello.", stringFromHeap(helloStringPointer));
      Module.asm.free(helloStringPointer);
      success();
    })
    .catch(fail);

setupFinished();
  </script>
</body>