WebAssembly

The WebAssembly API of the scripts is available when the browsing context has a WebAssembly runtime. The Meziantou.Framework.WebPlatform.Wasmtime package provides one, based on Wasmtime, which compiles the modules to native code:

dotnet package add Meziantou.Framework.WebPlatform.Wasmtime

using var runtime = new WasmtimeRuntime(); // can be shared by the browsing contexts
using var engine = new JavaScriptScriptEngine();
using var context = new BrowsingContext(new BrowsingContextOptions
{
    ScriptEngine = engine,
    WebAssemblyRuntime = runtime,
});

var document = await context.NavigateAsync("https://example.com/", _ => """
    <output></output>
    <script>
      // (module (func (export "add") (param i32 i32) (result i32) local.get 0 local.get 1 i32.add))
      const bytes = new Uint8Array([0, 97, 115, 109, 1, 0, 0, 0, 1, 7, 1, 96, 2, 127, 127, 1, 127, 3, 2, 1, 0,
        7, 7, 1, 3, 97, 100, 100, 0, 0, 10, 9, 1, 7, 0, 32, 0, 32, 1, 106, 11]);
      WebAssembly.instantiate(bytes).then(({ instance }) => {
        document.querySelector('output').textContent = instance.exports.add(2, 3);
      });
    </script>
    """);
await context.EventLoop.RunUntilIdleAsync();

Assert.Equal("5", document.QuerySelector("output")!.TextContent);

• The runtime can be shared by the browsing contexts and the script engines; dispose it when you are done.
• validate(), compile(), instantiate(), compileStreaming() and instantiateStreaming(), the Module, Instance, Memory, Table, Global, Tag and Exception objects, and the imported JavaScript functions are supported.
• The features of WebAssembly 3.0 are enabled (reference types, garbage collection types, exceptions, tail calls, memory64, multiple memories, SIMD), except the threads.
• The running code is interrupted by the limits of the script engine, such as Timeout.

WasmtimeRuntimeOptions sets the size of the stack of the WebAssembly code (MaxStackSize, 512 KiB by default: a deeper recursion throws a RangeError), the largest size of a memory (MaxMemorySize: the memories are .NET arrays, shared with the ArrayBuffer objects of the scripts), and how often the running code checks whether it must stop (InterruptionCheckInterval, 10 ms by default). A table has at most 10,000,000 elements, the limit of the JavaScript API of browsers: table.grow returns -1 beyond it.

Wasmtime is a native library: it comes with the Wasmtime package, a dependency of Meziantou.Framework.WebPlatform.Wasmtime.