🗜️ Kompress

Compression and archiver APIs for Kotlin Multiplatform.

Features

Modules

• kompress-core: Core compression and CRC APIs, provides a common DEFLATE implementation
• kompress-gzip: Support for the GZIP archive container format
• kompress-zip: Support for the ZIP archive container format (no en-/decryption support)
• kompress-benchmarks: Various benchmarks comparing Kompress implementations against platform references

How to use it

First, add the official Maven Central repository to your settings.gradle.kts:

dependencyResolutionManagement {
    repositories {
        maven("https://central.sonatype.com/repository/maven-snapshots")
        mavenCentral()
    }
}

Then add a dependency on the library in your root buildscript:

kotlin {
    sourceSets {
        commonMain {
            dependencies {
                implementation("dev.karmakrafts.kompress:kompress-core:<version>")
            }
        }
    }
}

Or, if you are only using Kotlin/JVM, add it to your top-level dependencies block instead.

Inflater and Deflater interfaces

Bulk compression

If you just want to (de)compress one large blob of data, the Deflater.compress and Inflater.decompress functions are what you're probably looking for:

fun main() {
    val myData = "Hello, World! This is an important message."
    val compressedData = Deflater.compress(
        data = myData.encodeToByteArray(), raw = false, // Control if you want the gzip/pkzip header
        level = , 
        bufferSize =  
    )
     decompressedData = Inflater.decompress(
         = compressedData, 
        raw = , 
        bufferSize = 
    )
    println(myData == decompressedData.decodeToString())
}

Streaming compression

Streaming compression is what you want if your data exceeds a certain size,
that size usually being the limit of the underlying runtime's array size.
With Kompress, that limit is about 2.147GB because the index type of an array in Kotlin is a signed integer. Streaming allows you to split up the data into discrete chunks and compress those chunks sequentially until you processed all the data.

You can either use the Deflater and Inflater interfaces from the core module manually:

fun main() {
    val deflater = Deflater(
        raw = false,
        level = 9,
        // ...
    )
    val outputBuffer = ByteArray(1024)
    while (deflater.needsInput) {
        if (!hasMoreInput) deflater.finish() // Signal that we are done compressing
        deflater.input = getInputChunk()
         (!deflater.finished) {
            deflater.compress(outputBuffer) 
            copyChunkToSomeTarget(outputBuffer)
        }
    }
    deflater.close() 
}

Or you can use the recommended way of using kotlinx.io wrappers:

fun main() {
    val buffer = Buffer()
    buffer.writeInt(42)
    buffer.writeFloat(4.20F)

    val compressedBuffer = Buffer()
    buffer.deflatingSource().use(compressedBuffer::transferFrom)

    val decompressedBuffer = Buffer()
    compressedBuffer.inflatingSource().use(decompressedBuffer::transferFrom)
}