Swiftpack.co - Package - tsolomko/SWCompression


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A framework with (de)compression algorithms and functions for processing various archives and containers.

What is this?

SWCompression — is a framework with a collection of functions for:

  1. Decompression (and sometimes compression) using different algorithms.
  2. Reading (and sometimes writing) archives of different formats.
  3. Reading containers such as ZIP, TAR and 7-Zip.

It also works both on Apple platforms and Linux.

All features are listed in the tables below. "TBD" means that feature is planned but not implemented (yet).

| | Deflate | BZip2 | LZMA/LZMA2 | | ------------- | ------- | ----- | ---------- | | Decompression | ✅ | ✅ | ✅ | | Compression | ✅ | ✅ | TBD |

| | Zlib | GZip | XZ | | ----- | ---- | ---- | --- | | Read | ✅ | ✅ | ✅ | | Write | ✅ | ✅ | TBD |

| | ZIP | TAR | 7-Zip | | ----- | --- | --- | ----- | | Read | ✅ | ✅ | ✅ | | Write | TBD | TBD | TBD |

Also, SWCompression is written with Swift only.


SWCompression can be integrated into your project using Swift Package Manager, CocoaPods or Carthage.

Swift Package Manager

Add SWCompression to you package dependencies and specify it as a dependency for your target, e.g.:

import PackageDescription

let package = Package(
    name: "PackageName",
    dependencies: [
        .package(url: "https://github.com/tsolomko/SWCompression.git",
                 from: "4.2.0")
    targets: [
            name: "TargetName",
            dependencies: ["SWCompression"]

More details you can find in Swift Package Manager's Documentation.


Add pod 'SWCompression', '~> 4.2' and use_frameworks! to your Podfile.

To complete installation, run pod install.

If you need only some parts of framework, you can install only them using sub-podspecs. Available subspecs:

  • SWCompression/BZip2
  • SWCompression/Deflate
  • SWCompression/Gzip
  • SWCompression/LZMA
  • SWCompression/LZMA2
  • SWCompression/SevenZip
  • SWCompression/TAR
  • SWCompression/XZ
  • SWCompression/Zlib
  • SWCompression/ZIP

"Optional Dependencies"

Both ZIP and 7-Zip containers have a single compression method which is most likely to be used, for compression of data inside them. This is Deflate for ZIP and LZMA/LZMA2 for 7-Zip. Thus, SWCompression/ZIP subspec have SWCompression/Deflate subspec as a dependency and SWCompression/LZMA subspec is a dependency for SWCompression/SevenZip.

But both of these formats support other compression methods, and some of them are implemented in SWCompression. For CocoaPods configurations there are some sort of 'optional dependencies' for such compression methods.

"Optional dependency" in this context means that SWCompression/ZIP or SWCompression/7-Zip will support particular compression methods only if a corresponding subspec is expicitly specified in your Podfile and installed.

List of "optional dependecies":

  • For SWCompression/ZIP:
    • SWCompression/BZip2
    • SWCompression/LZMA
  • For SWCompression/SevenZip:
    • SWCompression/BZip2
    • SWCompression/Deflate

Note: If you use Swift Package Manager or Carthage you always have everything (ZIP and 7-Zip are built with Deflate, BZip2 and LZMA/LZMA2 support).


Add to your Cartfile github "tsolomko/SWCompression" ~> 4.2.

Then run carthage update.

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

SWCompression depends on BitByteData framework, so Carthage will also download this dependency, and you should drag and drop BitByteData.framework file into the "Embedded Binaries" as well.


Basic Example

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

// let data = <Your compressed data>
let decompressedData = try? Deflate.decompress(data: data)

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)

Handling Errors

Most SWCompression functions can throw an error and you are responsible for handling them. If you look at list of available error types and their cases, you may be frightened by their number. However, most of these cases (such as XZError.wrongMagic) exist for diagnostic purposes.

Thus, you only need to handle the most common type of error for your archive/algorithm. For example:

do {
    // let data = <Your compressed data>
    let decompressedData = try XZArchive.unarchive(archive: data)
} catch let error as XZError {
    <handle XZ related error here>
} catch let error {
    <handle all other errors here>

Or, if you don't care about errors at all, use try?.


Every function or type of SWCompression's public API is documented. This documentation can be found at its own website.

Sophisticated example

There is a small command-line program, "swcomp", which is included in this repository in "Sources/swcomp". To build it you need to uncomment several lines in "Package.swift" and run swift build -c release.


Whether you find a bug, have a suggestion, idea or something else, please create an issue on GitHub.

In case you have encoutered a bug, it would be especially helpful if you attach a file (archive, etc.) that caused the bug to happen.

If you'd like to contribute code, please create a pull request on GitHub.

Note: If you are considering working on SWCompression, please note that Xcode project (SWCompression.xcodeproj) was created manually and you shouldn't use swift package generate-xcodeproj command.

Executing tests locally

If you'd like to run tests on your computer, you need to do an additional step after cloning this repository:

git submodule update --init --recursive

This command downloads files which are used for testing. These files are stored in a separate repository. Git LFS is used for storing them which is the reason for having them in the separate repository, since Swift Package Manager have some problems with Git LFS-enabled repositories (installing git-lfs locally with --skip-smudge option is required to solve these problems).

Note: You can also use "Utils/prepare-workspace-macos.sh" script from the repository, which not only downloads test files but also downloads dependencies.


Usage of whole module optimizations is recommended for best performance. These optimizations are enabled by default for Release configurations.

Tests Results document contains results of benchmarking of various functions.


First of all, existing solutions for work with compression, archives and containers have some problems. They might not support some particular compression algorithms or archive formats and they all have different APIs, which sometimes can be slightly "unfriendly" to users. This project attempts to provide missing (and sometimes existing) functionality through unified API, which is easy to use and remember.

Secondly, it may be important to have a compression framework written completely in Swift, without relying on either system libraries or solutions implemented in different languages. Additionaly, since SWCompression is written fully in Swift without Objective-C, it can also be compiled on Linux.

Future plans

  • Performance...
  • Better Deflate compression.
  • Something else...



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4.3.0-test.2 - Apr 20, 2018

In this test release a new function and enum have been added to TarContainer which provide information about formats of TAR containers.

4.3.0-test.1 - Apr 10, 2018

This is the first test release of 4.3.0 which includes support for ZIP custom extra fields, updates for Swift 4.1 and upcoming 1.2.0 release of BitByteData.

4.2.2 - Mar 17, 2018

  • Fixed a problem when in some rare cases (when SevenZipSubstreamInfo isn't found in a container) 7-Zip Container entries were skipped during open(container:), instead of being appended with nil data to the result array, as was always intended.
  • Fixed a crash in SevenZipContainer.info(container:) when either entry's size or CRC32 isn't present in the container.
  • Updated documentation.

4.2.1 - Mar 8, 2018

  • All 7-Zip minor format versions from 1 to 4 are now accepted (previously, it was only 4; for all other versions SevenZipError.wrongFormatVersion was thrown).

4.2.0 - Mar 4, 2018

  • Minuimum required version of BitByteData is now 1.1.0.
  • Added ownerID and groupID properties to ZipEntryInfo, which provide access to uid and gid from Info-ZIP New Unix and Info-Zip Unix extra fields.
  • Added unknownExtendedHeaderRecords property to TarEntryInfo which includes unrecognized entries from PAX global and local extended headers.
  • Prevent double slashes in TarEntryInfo.name when prefix header's field was used, but it had trailing slash.
  • Improved BZip2 compression performance: Now additional Huffman trees aren't created when they cannot be used, since maximum amount of Huffman tables was generated.
  • Disabled symbol stripping in archives generated by Carthage and published on GitHub Releases.
  • swcomp changes:
    • Replaced 9 block size options of bz2 command with a single one: -b (--block-size).
    • Now prints entry type-specific properties in output of tar, zip and 7z commands with -i (--info) option.
    • Renamed perf-test command group to benchmark.