Zenoh Flat JNI

Zenoh JNI bindings and Kotlin wrappers for the Zenoh pub/sub, store/query and compute framework.

This project provides low-level JNI bindings (Rust) and high-level Kotlin wrappers generated from the zenoh-flat Rust crate using prebindgen.

Overview

The Zenoh Flat JNI library generates multi-language FFI bindings from a single annotated Rust source (zenoh-flat). It consists of:

• Rust JNI layer (src/) - Native bindings to Zenoh APIs
• Kotlin wrappers (kotlin/) - Type-safe Kotlin classes for JVM and Android
• Generated Kotlin (generated-kotlin/) - Auto-generated Kotlin sources from prebindgen

Features

• 🦀 Native Rust performance - Direct JNI binding to Zenoh
• 🎯 Type-safe API - Kotlin data classes and enums for type safety
• 📱 Multi-platform - Support for JVM (Linux, macOS, Windows) and Android
• 🔒 Memory-safe - Automatic resource management via Kotlin classes
• 🚀 Zero-copy - Efficient data transfer between Rust and JVM

Installation

Maven Central

Add the dependency to your build.gradle.kts:

dependencies {
    implementation("org.eclipse.zenoh:zenoh-flat-jni:1.9.0")
}

Or in pom.xml:

<dependency>
    <groupId>org.eclipse.zenoh</groupId>
    <artifactId>zenoh-flat-jni</artifactId>
    <version>1.9.0</version>
</dependency>

Usage

Kotlin Example

import io.zenoh.jni.*

fun main() {
    // Initialize Zenoh
    val config = ZConfig()
    val session = config.openSession()
    
    // Put a key-value pair
    val keyExpr = ZKeyExpr.from("demo/example")
    session.put(keyExpr, "Hello, Zenoh!")
    
    // Close resources
    keyExpr.drop()
    session.drop()
}

Development

Prerequisites

• Rust 1.70+ with JNI support
• Gradle 7.0+
• JDK 11+
• Android SDK (for Android builds)

Build from Source

# Clone the repository with dependencies
git clone https://github.com/ZettaScaleLabs/zenoh-flat-jni.git
cd zenoh-flat-jni

# Build Rust library
cargo build --release

# Build Kotlin (optional, for local development)
./gradlew build

Local Development with Workspace

To use local versions of zenoh-flat and prebindgen:

# Ensure you have the PREBINDGEN workspace checked out locally
mkdir -p ~/zenoh-workspace
cd ~/zenoh-workspace

git clone https://github.com/ZettaScaleLabs/prebindgen.git
git clone https://github.com/ZettaScaleLabs/zenoh-flat-jni.git

cd zenoh-flat-jni

# Adjust paths in Cargo.toml (temporarily):
# zenoh-flat = { version = "1.9.0", path = "../../PREBINDGEN/zenoh-flat", ... }
# prebindgen = { path = "../../PREBINDGEN/prebindgen/prebindgen" }

cargo build --release

Testing

# Run Rust tests
cargo test --all

# Run Kotlin tests
./gradlew jvmTest

# Lint
cargo clippy --all-targets --all-features -- -D warnings
cargo fmt --check

Building for Android

./gradlew -Pandroid=true build

Architecture

The generated bindings are created via prebindgen in the build process:

1. Rust source (zenoh-flat) marked with #[prebindgen] annotations
2. Proc-macro captures annotated items to JSONL format
3. prebindgen::lang::JniGen reads JSONL and generates:
   • Rust JNI wrapper functions
   • Kotlin data classes and enums
4. Gradle packages Rust dylib + Kotlin sources into a JAR
5. Maven Central publishes the multi-platform JAR

Integration with zenoh-java

zenoh-flat-jni is a standalone library that can be consumed by:

• zenoh-java - Higher-level Zenoh API for JVM/Android
• zenoh-kotlin - Kotlin-first Zenoh API

Both projects depend on zenoh-flat-jni as a Maven artifact, enabling independent versioning and release cycles.

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

License

This project is licensed under either of

• Eclipse Public License 2.0 (LICENSE or http://www.eclipse.org/legal/epl-2.0)
• Apache License, Version 2.0 (LICENSE or https://www.apache.org/licenses/LICENSE-2.0)

at your option.

Acknowledgments

This project is part of the Eclipse Zenoh ecosystem and is maintained by the ZettaScale team.