Pure Kotlin Multiplatform DEFLATE, GZIP, and ZLIB compression.

KFlate is a Kotlin Multiplatform port of the npm fflate library. It provides compression and decompression with configurable levels, dictionary support, and both blocking and streaming APIs across KMP targets.

• Pure Kotlin Implementation: No native dependencies, works everywhere Kotlin runs.
• Multiplatform Support: JVM, Android, JS (Browser/Node), WASM, and native targets.
• Multiple Compression Formats: Raw DEFLATE, GZIP with optional headers, and ZLIB with dictionary support.
• Flexible APIs: Both blocking and streaming (kotlinx-io) interfaces.
• Configurable Compression: Compression levels 0-9 with intelligent hash table sizing.
• Dictionary Support: Full preset dictionary support for DEFLATE/ZLIB (max 32 KB).
• Production Ready: Tested against standard tools and libraries.

KFlate delivers performance comparable to standard implementations across all platforms:

• Native targets: Matches zlib
• JVM: Matches Java standard library
• Web: Matches fflate

For detailed benchmark results of each iteration, see the performance folder.

Add KFlate to your commonMain dependencies:

kotlin {
    sourceSets {
        commonMain.dependencies {
            implementation("com.rafambn:KFlate:1.0.0")
        }
    }
}

With KFlate, you select a format config and call the same API to compress/decompress:

import com.rafambn.kflate.KFlate
import com.rafambn.kflate.RAW
import com.rafambn.kflate.Raw

val input = "hello".encodeToByteArray()
val deflated = KFlate.compress(input, RAW())
val inflated = KFlate.decompress(deflated, Raw())

import com.rafambn.kflate.KFlate
import com.rafambn.kflate.GZIP
import com.rafambn.kflate.Gzip

val input = "hello".encodeToByteArray()

val options = GZIP(
    filename = "hello.txt",
    comment = "example",
    extraFields = mapOf("AB" to byteArrayOf(1, 2)),
    includeHeaderCrc = true
)

val gz = KFlate.compress(input, options)
val roundTrip = KFlate.decompress(gz, Gzip())

import com.rafambn.kflate.KFlate
import com.rafambn.kflate.ZLIB
import com.rafambn.kflate.Zlib

val input = "hello".encodeToByteArray()
val z = KFlate.compress(input, ZLIB())
val out = KFlate.decompress(z, Zlib())

val dict = "common".encodeToByteArray()
val zWithDict = KFlate.compress(input, ZLIB(dictionary = dict))

• level: Compression level 0–9 (default: 6)
  • 0: No compression
  • 1–3: Fast compression
  • 4–6: Balanced (6 is default)
  • 7–9: Maximum compression (9 uses full 1M entry hash table)
• bufferSize: Internal hash table size (optional, auto-sized per level)
• dictionary: Preset dictionary up to 32 KB (DEFLATE/ZLIB only)

• filename: Original filename
• comment: File comment
• extraFields: Custom header fields
• mtime: Modification time
• includeHeaderCrc: Include CRC16 of header

• dictionary: Preset dictionary for DEFLATE/ZLIB (required if compression used one)