Kompact

Kompact is a Kotlin Multiplatform library for reading and writing compact, LSB-first bit-packed messages. Use the runtime directly for small fixed layouts, or generate typed views from schemas. The framed API adds strings, byte arrays, nested messages, and repeated fields with explicit length boundaries.

Quick start

import ch.trancee.kompact.runtime.KompactRuntime
import ch.trancee.kompact.runtime.KompactWriter
import ch.trancee.kompact.runtime.ScalarType

val writer = KompactWriter()
writer.writeScalar(ScalarType.of(4, signed = false), 5L) // battery status
writer.writeScalar(ScalarType.of(10, signed = false), 10L) // speed
writer.writeBool(true) // malfunction flag
val bytes = writer.build() // [0xA5, 0x40]

val battery = KompactRuntime.readScalar(bytes, 0, ScalarType.of(4, signed = false)).getOrThrow()
val speed = KompactRuntime.readScalar(bytes, 4, ScalarType.of(10, signed = false)).getOrThrow()
val malfunction = KompactRuntime.readBool(bytes, 14).getOrThrow()

The getting-started tutorial walks through this frame and shows the expected bytes and decoded values.

Install

The latest Maven Central release is 0.8.0:

repositories {
    mavenCentral()
}

dependencies {
    implementation("ch.trancee.kompact:kompact:0.8.0")
}

The current development version in this checkout is 0.8.0; it is not published to Maven Central. To try unreleased changes, publish the snapshot modules to Maven Local and follow the consumer setup guide.

Choose a schema

• Fixed layout: use bitOffset and bitWidth when every field has a stable position. Generated value-class views are described in How to define a fixed-layout schema.
• Sequential framed layout: use order and length/count prefixes when a message contains strings, byte arrays, nested messages, or repeated values. See How to define a framed schema.

Both forms use the same runtime writer and checked decode APIs. The architecture guide explains the wire format, borrowed data, and the tradeoffs between the two layouts.

Documentation

If you want to…	Start here
Build and decode your first frame	Getting started
Add Kompact to a Kotlin or KMP project	Consume Kompact
Define a fixed-layout model	Fixed-layout schema guide
Define a sequential framed model	Framed schema guide
Read or write strings, blobs, nested data, and repeats	Long-form payloads
Handle malformed input	Decode errors
Pass frames across a BLE boundary	BLE integration
Look up public signatures and behavior	API reference
Understand design decisions	Architecture
Contribute or run project checks	Contributing

The generated, per-symbol API reference is also available in kompact/docs/api/.

Project modules

Module	Purpose
:kompact	KMP runtime, annotations, and generated API documentation
:kompact-ksp	KSP processor for fixed-layout and framed schemas
:kompact-gradle-plugin	Common-source generation for supported KMP targets

License

Kompact is released into the public domain. See LICENSE.