KFlate

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.

Check out the demo app on web: KFlate Demo

Current version 1.0.0.

Key Features

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

Performance

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, see the performance/ folder.

Installation

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

Usage

Raw DEFLATE

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())

GZIP

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())

ZLIB

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())

// With a preset dictionary
val dict = "common".encodeToByteArray()
val options = ZLIB(dictionary = dict)
val zWithDict = KFlate.compress(input, options)

Configuration Options

Compression Options

• 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)

GZIP-Specific Options

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

Decompression Options

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