An example of using simdutf in Swift.
simdutf is written in C++, so this is only possible through Swift's C++ interoperability.
Furthermore, you can call simdutf functions via Swift's Span type instead of the unsafe UnsafePointers.

• Make sure you have Swift 6.3 (nightlies) or better installed.
• Clone this project.
• cd to the project directory.
• Run swift run.

After swift run, you'll see a message like this:

$ swift run
Building for debugging...
[1/1] Write swift-version-7E01106DFC2086DF.txt
Build of product 'SIMDUTF_Swift_Example' complete! (0.11s)
Welcome to the SIMDUTF Swift Example!
Enter a line to validate for ASCII:

Then you can enter some text to check for being ASCII, via simdutf.
For example you can enter "🙂":

...
Enter a line to validate for ASCII:
🙂
simdutf.validate_ascii says "🙂" is not ASCII!

Currently this is the whole code:

import Foundation
import simdutf

@main
struct SIMDUTF_Swift_Example {
    static func main() {
        print("Welcome to the SIMDUTF Swift Example!")

        print("Enter a line to validate for ASCII:")
        guard let line = readLine(), !line.isEmpty else {
            print("Empty line entered, please enter a non-empty line!")
            return
        }

        /// Pass a swift `Span` to `simdutf`'s C++ functions.
        let isASCII = simdutf.validate_ascii(line.utf8Span.span)

        print("simdutf.validate_ascii says \(line.debugDescription) is \(isASCII ? "ASCII" : "NOT ASCII")!")
    }
}

To support Swift, simdutf required these adjustements:

• 1. Add an appropriate Package.swift.
• 2. Add an appropriate module.modulemap.
• 3. Add __noescape (via a custom simd_noescape attribute) to std::span parameters in functions.
• 4. Declare and use a "type alias" instead of just spelling out the type name, for std::spans.
  • For example: using uint8_span = std::span<const std::uint8_t>;.
  • Then use it in function parameters: bool validate_ascii(uint8_span input simdutf_noescape)
  • This is currently also a requirement of the Swift compiler, and is not optional.

On the Swift side, you'd need:

• Swift 6.3.
  • Swift 6.2 contains some blocking bugs that are fixed in 6.3.
• Depend on simdutf like any other Swift package:
  • .package(url: "https://github.com/MahdiBM/simdutf.git", branch: "mmbm-swift-take-2")
  • Currently this points to my branch. I'll update that when the changes are available in simdutf.
• Depend on simdutf in your targets:
  • .product(name: "simdutf", package: "simdutf")
• For targets that depend on simdutf, add the following swiftSettings:
  • .interoperabilityMode(.Cxx)
  • .enableExperimentalFeature("SafeInteropWrappers")
• Set the cxx langauge standard of the package to cxx20 or better for the std::span support:
  • cxxLanguageStandard: .cxx20

In the end you'll have a Package.swift like this.