flavio / wapc-guest-dotnet

A waPC guest for .NET

waPC Guest Library for .NET

⚠️ Warning: experimental ⚠️

This code leverages dot-net-wasi-sdk, which is currently marked as experimental.

It also requires usage of .NET 7, which is currently in preview.

This repository contains a C# implementation of the waPC standard for WebAssembly guest modules. It allows any waPC-compliant WebAssembly host to invoke to procedures inside a C# compiled guest and similarly for the guest to invoke procedures exposed by the host.

The generation of the Wasm module has been tested on a x86_64 Linux machine. It should work out of the box on other operating systems supported by the .NET platform.

Requirements

The code requires .NET 7, which is currently (as of July 2022) in preview mode. Executing dotnet --version should return 7.0.100-preview.4 or later.

Repository layout

The repository contains the following resources:

• src: contains the source code of the waPC guest library
• examples: contains a demo program and a waPC runtime to run it

Usage

Create a Console application:

dotnet new console -o MyFirstWapcModule
cd MyFirstWapcModule
dotnet add package Wasi.Sdk --prerelease
dotnet add package WapcGuest

Edit the Program.cs file and replace its contents to match the following ones:

using WapcGuest;
using System.Text;

static byte[] callHost(byte[] payload)
{
  var binding = "binding_value";
  var wapcNamespace = "wapc_namespace_value";
  var operation = "operation_value";
  var payloadGuest = "This is the payload coming from the waPC guest";
  var payloadGuestBytes = Encoding.UTF8.GetBytes(payloadGuest);

  var hostResponseBytes = Wapc.HostCall(binding, wapcNamespace, operation, payloadGuestBytes);
  var hostResponse = Encoding.UTF8.GetString(hostResponseBytes);

  string response = $"the host responded with {hostResponse}";
  var responseBytes = Encoding.UTF8.GetBytes(response);

  return responseBytes;
}

static byte[] echo(byte[] payload)
{
  return payload;
}

var wapc = new Wapc();
wapc.RegisterFunction("echo", echo);
wapc.RegisterFunction("callHost", callHost);

Finally, build the WebAssembly module in this way:

dotnet build

You can now invoke both the echo and the callHost functions from any waPC host.

For a more complex example, checkout the examples directory.

Contribute

The author of this code is not a .NET expert, patches are welcome to improve the code quality and to make it more idiomatic.