DataCompression
Data
type
A libcompression wrapper extension for the Supported compression algorithms are:
- GZIP format (.gz files) RFC-1952
- ZLIB deflate stream RFC-1950
- ZLIB deflate raw RFC-1951
- LZMA
- LZFSE
- LZ4
Requirements
- iOS deployment target >= 9.0
- macOS deployment target >= 10.11
- tvOS deployment target >= 9.0
- watchOS deployment target >= 2.0
Swift version support
Library Version | Swift Version |
---|---|
3.7.0 | 5.7 (Xcode 14) |
3.6.0 | 5.1 (Xcode 11) |
3.5.0 | 5.0 |
3.1.0 | 4.2 |
3.0.0 | 3.0 -> 4.1 |
2.0.1 | < 3.0 |
Usage example
Try all algorithms and compare the compression ratio
let raw: Data! = String(repeating: "There is no place like 127.0.0.1", count: 25).data(using: .utf8)
print("raw => \(raw.count) bytes")
for algo: Data.CompressionAlgorithm in [.zlib, .lzfse, .lz4, .lzma] {
let compressedData: Data! = raw.compress(withAlgorithm: algo)
let ratio = Double(raw.count) / Double(compressedData.count)
print("\(algo) => \(compressedData.count) bytes, ratio: \(ratio)")
assert(compressedData.decompress(withAlgorithm: algo)! == raw)
}
Will print something like:
raw => 800 bytes
zlib => 40 bytes, ratio: 20.00
lzfse => 69 bytes, ratio: 11.59
lz4 => 181 bytes, ratio: 4.42
lzma => 100 bytes, ratio: 8.00
Container formats
RFC-1951) can also be used with the shortcuts .deflate()
and .inflate()
The famous zlib deflate algorithm (let data: Data! = "https://www.ietf.org/rfc/rfc1951.txt".data(using: .utf8)
let deflated: Data! = data.deflate()
let inflated: Data? = deflated?.inflate()
assert(data == inflated)
RFC-1952) can be handled with .gzip()
and .gunzip()
Data in gzip format (let data: Data! = "https://www.ietf.org/rfc/rfc1952.txt".data(using: .utf8)
let gzipped: Data! = data.gzip()
let gunzipped: Data? = gzipped.gunzip()
assert(data == gunzipped)
Note: Compressed data in gzip format will always be 18 bytes larger than raw deflated data and will append/perform a crc32 checksum based data integrity test .
RFC-1950) can be handled with .zip()
and .unzip()
Data in zip format (let data: Data! = "https://www.ietf.org/rfc/rfc1950.txt".data(using: .utf8)
let zipped: Data! = data.zip()
let unzipped: Data? = zipped.unzip()
assert(data == unzipped)
Note: Compressed data in zip format will always be 6 bytes larger than raw deflated data and will append/perform a adler32 checksum based data integrity test .
Compress a file on the command line and decompress it in Swift
The easiest way is using the already installed gzip command line tool. Assuming you have a file called file.txt, after calling
gzip -9 file.txt
the file should have been compressed to file.txt.gz. You can now load and uncompress the contents of your file with:
let compressedData = try? Data(contentsOf: URL(fileURLWithPath: "/path/to/your/file.txt.gz"))
if let uncompressedData = compressedData?.gunzip() {
print(String(data: uncompressedData, encoding: .utf8) ?? "Can't decode UTF-8")
}
Checksum extensions
Unrelated to compression but for convenience Crc32 and Adler32 methods are also exposed on the Data
type which may come in handy.
let classicExample = "The quick brown fox jumps over the lazy dog".data(using: .utf8)!
let crc32 = classicExample.crc32()
let adler32 = classicExample.adler32()
print("crc32: \(crc32), adler32: \(adler32)")
Will print:
crc32: 414fa339, adler32: 5bdc0fda
Install
Cocoa Pods
To integrate DataCompression into your Xcode project using CocoaPods, add it to your Podfile
:
target '<your_target_name>' do
pod 'DataCompression'
end
Then, run the following command:
$ pod install
You then will need to add import DataCompression
at the top of your swift source files to use the extension.
Carthage
Note: DataCompression versions < 3.3.0 are not compatible with carthage. That means Swift 5 only.
To integrate DataCompression into your Xcode project using Carthage, add it as a dependency to your Cartfile
. Just add:
github "mw99/DataCompression"
You will then have to add the framework paths in the carthage copy-frameworks
run script phase of your Xcode project.
The paths may differ depending on you have setup your project in relation to Carthage.
Input:
$(SRCROOT)/Carthage/Build/iOS/DataCompression.framework
Output:
$(BUILT_PRODUCTS_DIR)/$(FRAMEWORKS_FOLDER_PATH)/DataCompression.framework
You then will need to add import DataCompression
at the top of your swift source files to use the extension.
Swift Package Manager
To integrate DataCompression into your Xcode project using the swift package manager, add it as a dependency to your Package.swift
file:
import PackageDescription
let package = Package(
name: "<your_package_name>",
dependencies: [
.Package(url: "https://github.com/mw99/DataCompression.git", majorVersion: 3)
]
)
You then will need to add import DataCompression
at the top of your swift source files to use the extension.
The next time you run swift build
, the new dependencies will be resolved.
$ swift build
Or just copy the file into your project
You only need one file located at Sources/DataCompression.swift
. Drag and drop it into the Xcode project navigator.
Change log / Upgrading guide
3.6.0
to 3.7.0
Version - Support for Xcode 14 with Swift 5.7
3.5.0
to 3.6.0
Version - Target platforms finally added to the SPM Package file
- Carthage support improved
- Support for Xcode 11 SPM integration
3.4.0
to 3.5.0
Version - Fix that prevents a bug in Apples lzfse compressor when working with large chunks of data.
3.3.0
to 3.4.0
Version - Swift 5 release had further deprecation warnings than in the Swift 5 beta. Fixed.
3.2.0
to 3.3.0
Version - Added support for Carthage
3.1.0
to 3.2.0
Version - Podspec swift version set to 5.0
- Library file structure updated to fit the new swift package manager layout
3.0.0
to 3.1.0
Version - Podspec swift version set to 4.2
2.0.X
to 3.0.0
Version - The encoded data in zip format is not copied anymore, which should improve performance.
- Checksum validation is now always performed with libz and way faster.
- The
skipCheckSumValidation:
parameter of.unzip()
was removed. - Items of the algorithm enum type are now Swift like lowercase, e.g.
.LZMA
→.lzma
License
Apache License, Version 2.0
Copyright 2016, Markus Wanke
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.