Extism Playground

This is a solution that combines the Extism Plugin Development Kit (PDK) and the Extism Software Development Kit (SDK) into a producer/consumer example.

Getting Started

1. You will need the wasi-experimental dotnet workload.
2. You'll also need the WASI SDK and set the WASI_SDK_PATH variable in your global PATH.

Projects

The ExtismPlayground.WasmPlugin exports a .NET function of greet to be used by any Extism consumer regardless of technology stack or operating system using the power of Wasi.

Currently, Wasi works on the concept of arguments and outputs to the standard input and output. So you'll never see a method with parameters in C#.

using System.Runtime.InteropServices;
using Extism;

public class Program
{
    [UnmanagedCallersOnly(EntryPoint = "greet")]
    public static int Greet()
    {
        var name = Pdk.GetInputString();
        var greeting = $"Hello, {name}!";
        Pdk.SetOutput(greeting);
        return 0;
    }
    
    public static void Main() {}
}

Additionally, you'll see all results being written to the host output. If you need complex results, those occur using JSON.

Consuming the .wasm file is as simple as including the ExtismPlayground.WasmPlugin.wasm file as content in a consuming project, then using the following code.

using Extism.Sdk;

var wasm = await File.ReadAllBytesAsync("ExtismPlayground.WasmPlugin.wasm");
var plugin = new Plugin(wasm,[], withWasi: true);

var result = plugin.Call("greet", "Khalid");

Console.WriteLine(result);

Remember, all arguments and outputs are essentially command line arguments. The host can hold these "plugins" in memory for long-lived variables, but you're expected to write Host Functions to provide proxy access to files, web requests, or external resources.

Have fun!