Swift 6.2: Complete Guide to WebAssembly, C++ & Java Interoperability

# Using swiftly (recommended)
swiftly install 6.2

# Create a new Swift package
mkdir my-wasm-app && cd my-wasm-app
swift package init --type executable

# Build for WebAssembly
swift build --triple wasm32-unknown-wasi

# Run with WasmKit (built-in runtime)
swift run --triple wasm32-unknown-wasi

// MyLibrary.h
#pragma once

// Swift will import this as taking a Span<Int32>
void processData(const int32_t* data, size_t count)
    __attribute__((swift_attr("import_as_span:data,count")));

// Swift will import this as returning a Span<UInt8>
const uint8_t* getBuffer(size_t* outSize)
    __attribute__((swift_attr("returns_span:outSize")));

import MyLibrary

// Safe Swift code using Span
let numbers: [Int32] = [1, 2, 3, 4, 5]
numbers.withUnsafeBufferPointer { buffer in
    processData(Span(buffer))
}

// Getting a buffer back safely
let data = getBuffer()
for byte in data {
    print(byte)
}

# Add to Package.swift
dependencies: [
    .package(url: "https://github.com/swiftlang/swift-java.git",
             from: "0.3.0")
]

# Generate Swift bindings from Java classes
swift-java generate --classpath myapp.jar \
    --output Sources/JavaBindings \
    com.mycompany.MyClass