Secondly, if you are a Swift developer and you want to compress/decompress something in your project you have to use either wrapper around system libraries (which is probably written in Objective-C) or you have to use built-in Compression framework. You might think that last option is what you need, but, frankly that framework has a bit complicated API and somewhat questionable choice of supported compression algorithms. And yes, it is also in Objective-C.

And here comes SWCompression: no Objective-C, pure Swift.

Features

Decompress data which were compressed with DEFLATE algorithm.
Extract data from GZip archives.
Unarchive zlib compressed data.
Platform independent.
Swift only

By the way, it seems like GZip and Deflate decompressor implementations are specification compliant.

Installation

CocoaPods

Add to your Podfile pod 'SWCompression'.

Also, do not forget to have use_frameworks! line in the Podfile.

To complete installation, run pod install.

Carthage

Add to your Cartfile github "tsolomko/SWCompression".

Then run carthage update.

Finally, drag and drop SWCompression.framework from Carthage/Build folder into the "Embedded Binaries" section on your targets' "General" tab.

Swift Package Manager

Add to you package specification's dependecies .Package(url: "https://github.com/tsolomko/SWCompression.git"), for example like this:

import PackageDescription

let package = Package(
    name: "PackageName",
    dependencies: [
        .Package(url: "https://github.com/tsolomko/SWCompression.git")
    ]
)

More info you may find at Swift Package Manager's Documentation.

Usage

If you'd like to decompress "deflated" data just use:

let data = try! Data(contentsOf: URL(fileURLWithPath: "path/to/file"))
let decompressedData = try? Deflate.decompress(compressedData: data)

Note: you should properly handle possible errors in loading data from file and decide yourself if you need any Data.ReadingOptions.

However, it is unlikely that you will encounter deflated data outside of any archive. So, in case of GZip archive you should use:

let decompressedData = try? GzipArchive.unarchive(archiveData: data)

And, finally, for zlib the corresponding code is:

let decompressedData = try? ZlibArchive.unarchive(archiveData: data)

One final note: every unarchive/decompress function can throw an error and you are responsible for handling them.

Future plans

Performance improvement.
BZip2 decompression support.
Deflate compression.
BZip2 compression.
Something else...

References

The main source of information was pyflate — python implementation of GZip and BZip2.

There are also several specifications which were also very useful: