kotlin-random is a Kotlin Multiplatform library of deterministic pseudo-random generators with both mutable kotlin.random.Random implementations and serializable immutable state snapshots.

It is designed for reproducible simulation, testing, procedural generation, and cross-platform streams where the exact generator state matters. It is not a cryptographic random-number library.

repositories {
    mavenCentral()
}

dependencies {
    implementation("one.wabbit:kotlin-random:1.1.0")
}

import one.wabbit.random.L64X128Random

val rng = L64X128Random(seed = 1234L)

val id = rng.nextLong()
val bounded = rng.nextInt(100)

check(bounded in 0 until 100)

The mutable generators extend Kotlin's Random, so they work with APIs that accept kotlin.random.Random.

Immutable snapshots return the sampled value and the continuation generator:

import one.wabbit.random.Xoshiro256PlusPlusRandom

val start = Xoshiro256PlusPlusRandom.Immutable(seed = 42L)
val first = start.next64()
val second = first.generator.next64()

check(first.generator != start)
check(first.value != second.value)

Immutable states are @Serializable, which makes them useful for checkpointing reproducible streams.

• L64X128Random: mutable LXM generator compatible with Java's L64X128 stepping and seeding model.
• L64X128Random.Immutable: serializable immutable L64X128 state.
• PhiloxRandom: mutable Philox 4x64 counter-based generator with exact-counter APIs.
• PhiloxRandom.Immutable: serializable immutable Philox state, including buffered output.
• ThreefryRandom: mutable Threefry 2x32 generator with JAX-style split and foldIn.
• ThreefryRandom.Immutable: serializable immutable Threefry state.
• Xoshiro256PlusPlusRandom and Xoshiro256StarStarRandom: mutable xoshiro256 variants.
• Xoshiro256PlusPlusRandom.Immutable and Xoshiro256StarStarRandom.Immutable: serializable immutable xoshiro256 states.

Some generators expose raw block APIs in addition to Kotlin Random primitives. Mixed 32-bit, 64-bit, byte, and block consumption can affect stream alignment by design. Use one consumption style per stream when exact reproducibility across implementations matters.

This library is stable enough for deterministic application streams and tests. It does not promise cryptographic security, and generator-specific bit streams are part of the library's compatibility surface.

• User guide
• API reference notes
• Troubleshooting
• Development

Generated API docs can be built locally with Dokka. See API reference notes for the command.

• CHANGELOG.md

This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0) for open source use.

For commercial use, contact Wabbit Consulting Corporation at wabbit@wabbit.one.

Before contributions can be merged, contributors need to agree to the repository CLA.