WasmKit

WasmKit is a standalone and embeddable WebAssembly runtime implementation written in Swift.

Usage

The best way to learn how to use WasmKit is to look at the Examples directory.

Command Line Tool

WasmKit provides a command line tool to run WebAssembly binaries compliant with WASI.

$ git clone https://github.com/swiftwasm/WasmKit.git
$ cd WasmKit
$ swift run wasmkit-cli run ./Examples/wasm/hello.wasm
Hello, World!

As a Library

Swift Package Manager

You can use WasmKit as a Swift Package Manager dependency by adding the following to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/swiftwasm/WasmKit.git", from: "0.1.0"),
],

You can find API documentation on the Swift Package Index.

Features

• Reasonably fast
• Minimal dependencies
  • The core runtime engine depends only on swift-system.
  • No Foundation dependency
• Compact and embeddable
  • Debug build complete in 5 seconds¹
• Batteries included
  • WASI support, WAT parser, etc.

Supported Platforms

WasmKit engine works on all major platforms supported by Swift. It is continuously tested on macOS, Ubuntu, and Windows, and should work on the following platforms:

• macOS 10.13+, iOS 12.0+, tvOS 12.0+, watchOS 6.0+
• Ubuntu 20.04+
• Windows 10+

Implementation Status

Category	Feature	Status
WebAssembly MVP	Parsing binary format	✅ Implemented
	Parsing text format (WAT)	✅ Implemented
	Execution	✅ Implemented
	Validation	✅ Implemented
WebAssembly Proposal	Reference types	✅ Implemented
	Bulk memory operations	✅ Implemented
	Mutable globals	✅ Implemented
	Sign-extension operators	✅ Implemented
	Non-trapping float-to-int conversions	✅ Implemented
	Memory64	✅ Implemented
	Threads and atomics	🚧 Parser implemented
WASI	WASI Preview 1	✅ Implemented

Minimum Supported Swift Version

The minimum supported Swift version of WasmKit is 5.8, which is the version used to bootstrap the Swift toolchain in ci.swift.org.

Testing

To run the WasmKit test suite, you need to checkout the test suite repositories first.

# Checkout test suite repositories
$ ./Vendor/checkout-dependency
# Run tests
$ swift test

Acknowledgement

This project was originally developed by @akkyie, and is now maintained by the community.

Footnotes

1. On a 2020 Mac mini (M1, 16GB RAM) with Swift 5.10. Measured by swift package resolve && swift package clean && time swift build --product PrintAdd. ↩