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SDK for creating waPC WebAssembly Guest Modules in Swift
.package(url: "https://github.com/flavio/wapc-guest-swift.git", from: "0.0.2")

waPC Guest Library for Swift

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

The Swift compiler provided by the Swiftwasm project is required.


The following is a simple example of synchronous, bi-directional procedure calls between a WebAssembly host runtime and the guest module.

import wapc

func __guest_call(operation_size: UInt, payload_size: UInt) -> Bool {
  return wapc.handleCall(operation_size: operation_size, payload_size: payload_size)

func hello(payload: String) -> String {
  // call the host from the Wasm module
  let hostMsg = wapc.hostCall(
    binding: "binding_name",
    namespace: "namespace_name",
    operation: "operation_name",
    payload: "that's the payload"

  if hostMsg == nil {
    return "the validate function called the host but something went wrong"
  return "the validate function called the host and received back: '\(hostMsg!)'"

// register the function
wapc.registerFunction(name: "hello", fn: hello)

The Wasm module must declare a __guest_call function and export it. The linker must be instructed to export this function (see the official documentation).

When using SwiftPM to manage a package, the linker can be instruted by adding few lines to the Packages.swift file:

    name: "demo",
    dependencies: ["wapc"],
    linkerSettings: [

Working example

This GitHub repository contains a full working example.

Call for help

I'm new to Swift, I would appreciate help on the following topics from some more seasoned Swift develper:

  • Generic code review, ensure I'm not doing something stupid
  • Question about the API to expose, this is tracked on this issue


Stars: 3
Last commit: 3 weeks ago

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