Tips on how 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 you can simply ship your individual system modules, you simply must be taught the way to use the Swift Bundle Supervisor.😅

Bridging header inside Xcode

Let’s fireplace up Xcode and begin a model new single view app iOS challenge. 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 verify 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 hard, as a result of it additionally helps different C household languages, 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) 

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

#embody "factorial.h"

Someplace inside a Swift file you need to use the factorial technique:

print("Hiya (factorial(5))!")
// it really prints out "Hiya 120!" ;)

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

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

Delivery C code with SPM

The actual enjoyable begins whenever you begin utilizing the Swift Bundle Supervisor to construct C household primarily based sources. From Swift 3.0 you possibly can construct C language targets with SPM. If you do not know the way to use the SPM software, it is best to learn my complete tutorial concerning the Swift Bundle Supervisor first.

The one factor that you will have to do it is a correct listing construction (plus you may want the package deal description file), and the package deal supervisor will take care all the remainder. Right here is every little thing what it is advisable construct the factorial instance with SPM.

import PackageDescription

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

The listing construction ought to be one thing like this.

Sources
    factorial
        embody
            factorial.h
        factorial.c

You must also 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 crucial, however in the event you do not put your umbrella header into the embody listing, you may want to offer a modulemap file, and supply the right location of your header. If you happen to use the embody construction SPM will generate every little thing for you.

With this system you possibly can import your cfactorial module from another Swift package deal and name the factorial technique, like we did by means of Xcode. You simply have so as to add this module as a dependency, oh by the best way you possibly can even name this module from one other C challenge made with SPM! 💥

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

Congratulations, you simply shipped your first C code with Swift Bundle Supervisor. 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 possibly can crete a model new wrapper package deal with the assistance of the Swift Bundle Supervisor. To start out you need to use the swift package deal init --type system-module command, this can create a generic template challenge.

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

import PackageDescription

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

Contained in the Bundle.swift file you possibly can 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 beneath Linux to make issues work, as a result of the system will seek for package deal header recordsdata 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 be capable to compile / use your system module.

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

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

Concerning the hyperlink property see the 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 recordsdata from the modulemap file that is why I’m utilizing this shim.h – title it such as you need – you may see in a second why am I preferring this technique, however here’s a fundamental 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 need to use a neat trick with the assistance of utilizing macros, for instance you possibly can import header recordsdata from totally different places in the event you verify 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? 🍎 + 🔨 = ❤️