The way to name C code from Swift

From Swift 4 there may be native assist for wrapping C libraries in Swift system module packages. This implies that you could eaily ship your individual system modules, you simply need to learn to use the Swift Package deal Supervisor.😅

Bridging header inside Xcode

Let’s hearth up Xcode and begin a model new single view app iOS undertaking. Fill out the required fields, and naturally select the Swift language. Subsequent, add a brand new file and select the C file template.

After you enter the title and test the additionally create header file field, Xcode will ask you concerning the Goal-C bridging header file. Simply create it. The title of this file is difficult, as a result of it additionally helps different C household langages, like pure C or C++, Goal-C and plus-plus. 😉

Let’s create a public header for the C code (factorial.h):

#ifndef factorial_h
#outline factorial_h

#embody <stdio.h>

lengthy factorial(int n);

#endif /* factorial_h */

That is gona be the implementation of the strategy (factorial.c):

#embody "factorial.h"

lengthy factorial(int n)  n == 1) return 1;
    return n * factorial(n-1);

Contained in the bridging header, merely import the C header file:

#embody "factorial.h"

Someplace inside a Swift file you should utilize the factorial methodology:

print("Good day (factorial(5))!")

Compile and run. 🔨 It simply works. 🌟 Magic! 🌟

You are able to do the very same factor to make use of Goal-C lessons inside your Swift tasks. Apple has nice docs about this system, you need to learn that if you wish to know extra about combine and match.

Transport C code with SPM

The actual enjoyable begins while you begin utilizing the Swift Package deal Supervisor to construct C household based mostly sources. From Swift 3.0 you may construct C language targets with SPM. If you do not know how you can use the SPM software, you need to learn my complete tutorial concerning the Swift Package deal Supervisor first.

The one factor that you’re going to must do this can be a correct listing construction (plus you will want the package deal description file), and the package deal supervisor will take care all the remaining. Right here is every part what you should construct the factorial instance with SPM.

import PackageDescription

let package deal = Package deal(
    title: "cfactorial",
    merchandise: [
        .library(name: "cfactorial", targets: ["cfactorial"]),
    ],
    targets: [
        .target(
            name: "cfactorial",
            path: "./Sources/factorial"
        ),
    ]
)

The listing construction must be one thing like this.

Sources
    factorial
        embody
            factorial.h
        factorial.c

You also needs to change the #embody "factorial.h" line contained in the factorial.c file to #embody "embody/factorial.h" as a result of we made a brand new embody listing. That is NOT obligatory, however in case you do not put your umbrella header into the embody listing, you will want to supply a modulemap file, and supply the right location of your header. In the event you use the embody construction SPM will generate every part for you.

With this system you may import your cfactorial module from every other Swift package deal and name the factorial methodology, like we did by means of Xcode. You simply have so as to add this module as a dependency, oh by the way in which you may even name this module from one other C undertaking made with SPM! 💥

.package deal(url: "https://gitlab.com/theswiftdev/cfactorial", .department("grasp")),

Congratulations, you simply shipped your first C code with Swift Package deal Supervisor. Please take a look at the instance repository, you may construct and run the undertaking by your self.

This setup additionally works with C, C++, Goal-C, Goal-C++ code.

Wrapping C [system] modules with SPM

If you wish to wrap a C [system] library and name it immediately from Swift you may crete a model new wrapper package deal with the assistance of the Swift Package deal Supervisor. To start out you should utilize the swift package deal init --type system-module command, this may create a generic template undertaking.

These are particular packages in keeping with Apple, you simply need to ship your individual modulemap and a header file to show the wanted APIs, however first – clearly – you will want the standard package deal definition file:

import PackageDescription

let package deal = Package deal(
    title: "ccurl",
    suppliers: [
        .brew(["curl"]),
        .apt(["libcurl4-openssl-dev"])
    ]
)

Contained in the Package deal.swift file you may set the suppliers for the library (like brew on macOS or aptitude for ubuntu / debian and the others). Right here is an effective recommendation for you: sudo apt-get set up pkg-config below linux to make issues work, as a result of the system will seek for package deal header information with the assistance of the pkgConfig property. For instance if you wish to use libxml2 and pkg-config isn’t put in, you will not have the ability to compile / use your system module.

Subsequent you will want a module.modulemap file, which is fairly simple.

module ccurl [system] {
    header "shim.h"
    hyperlink "curl"
    export *
}

Concerning the hyperlink property see Xcode launch notes seek for “auto-linking”

Lastly add an additional shim.h header file to import all of the required APIs. Normally I do not prefer to import immediately the required header information from the modulemap file that is why I’m utilizing this “shim.h” – title it such as you need – you will see in a second why am I prefering this methodology, however here’s a primary one.

#ifndef CLIB_SWIFT_CURL
#outline CLIB_SWIFT_CURL

#import <curl/curl.h>;

#endif

Let’s discuss why I like importing the shim file. If in case you have platform variations you should utilize a neat trick with the assistance of utilizing macros, for instance you may import header information from completely different places in case you test for the __APPLE__ platform macro.

#ifndef CLIB_SWIFT_EXAMPLE
#outline CLIB_SWIFT_EXAMPLE

#ifdef __APPLE__
    #embody "/usr/native/embody/instance.h"
#else
    #embody "/usr/embody/instance.h"
#endif

#endif

Cool, huh? 🍎 + 🔨 = ❤️