SwiftZSTD

Description

Swift Wrapper around Zstandard Compression Library

System Requirements

Zstandard is required to be installed in order to build this package. See https://github.com/facebook/zstd for additional information, including licensing.

On OS X the easiest way to install Zstandard is with homebrew

brew install zstd

On Ubuntu it can be installed with apt

sudo apt install libzstd-dev

Installation

This has been bundled as a swift package for Swift 5. To use it in a project include the pacakge as a dependency in your projects Package.swift:

    dependencies: [
        .package(url: "https://github.com/HeartedApp/SwiftZSTD", .branch("master"))
    ],

In order to test out the included example ZSTDSampleApp run swift run

$ swift run
Testing compression

Original size: 1465 bytes
Compressed size: 757 bytes
Decompressed string is the same as original.

Testing compression with dictionary

Building Dictionary
Original size: 1465 bytes
Compressed size: 438 bytes
Dictionary decompressed string is the same as original.

Limitations

Compression and de-compression of in-memory buffers is supported, with or without a context or a dictionary. Buffers are represented by Data instances that must use contiguous storage, and in practice most Data instances meet this requirement. To be decompressed by this code, a buffer must be a complete frame with decompressed size encoded in it and retrievable using ZSTD_getDecompressedSize().

This is actually a fairly useful implementation. Experimentation shows that even fairly large files (100s of MB),when compressed using the zstd utility provided with the C library, end up in a single frame, which is easily decompressible by this Swift code if read into memory as one piece.