Apple docs: C Interoperability
Using Swift with Cocoa and Objective-C (HTML) (iBook)
swift-jni: A project to wrap Swift around JNI
SwiftJava: A collection of Swift-Java bridges built around a pair of core packages (SwiftJava and CJavaVM), it looks like?
Unsafe Swift: Using Pointers and Interacting With C
Making a C library available in Swift using Swift Package Manager:
Example is making Sqlite3 C library available in Swift
By convention, we prepend a letter "C" to the name of the library that we want to wrap. This makes explicit that its a wrapper for a C library.
Create directory for SQLite 3 (mkdir Csqlite3) and initialise with Swift Package Manager: swift package init --type library.
Ultimately directory structure for this package will look like:
Csqlite3
├── Headers
│ └── Csqlite3-Bridging-Header.h
├── Package.swift
└── Sources
└── Csqlite3
└── module.modulemap
Create directory to hold header files: mkdir Headers and create a bridging header file, Csqlite3-Bridging-Header.h with
#import <sqlite3.h>
inside of it.
In Sources\Csqlite3\module.modulemap put
module CSQLite [system] {
header "../../Headers/Csqlite3-Bridging-Header.h"
link "sqlite3"
export *
}
Adding [system] is the same as when you use gcc and add the macro #pragma system_header. What this does is indicate to the compiler that the header is a system header. A system header is different than a regular header because it might include code that is not entirely standard. The code in a system header could include code that generates warnings for regular headers.
Because a system header is written for the OS, the system header might take some liberties. If you want to learn more check gcc's systems header description, or this Stack overflow question. In summary, if you are using a system library and know it's ok to suppress the warnings, use the [system] attribute.
Then Package.swift should look like
// swift-tools-version:5.1
// The swift-tools-version declares the minimum version of Swift required to build this package.
import PackageDescription
let package = Package(
name: "Csqlite3",
products: [
.library(name: "Csqlite3", targets: ["Csqlite3"]),
],
targets: [
.systemLibrary(name: "Csqlite3"),
]
)
Last modified 03 May 2022