Kotlin Bindings

JNI bridge to cactus_engine.h for Android, with KMP support for iOS.

The JNI bridge itself (android/cactus_jni.cpp, compiled into libcactus_engine.so) is JVM-language-agnostic. Java consumers can use it by writing an equivalent CactusJNI.java with native declarations matching the signatures in Cactus.kt — same library, same Java_com_cactus_CactusJNI_* symbols.

Android Integration

cactus build --android

1. Copy android/libcactus_engine.so to app/src/main/jniLibs/arm64-v8a/
2. Copy Cactus.kt and CactusCallbacks.kt to your Kotlin source tree

val handle = CactusJNI.nativeInit("/path/to/model", null, false)
val buf = ByteArray(65536)
CactusJNI.nativeComplete(handle, messagesJson, buf, null, null, null, null)
val response = String(buf, 0, buf.indexOf(0))
CactusJNI.nativeDestroy(handle)

Streaming transcription — push 16 kHz mono PCM16, read {"success":true,"confirmed":...,"pending":...} back each call:

val stream = CactusJNI.nativeStreamTranscribeStart(handle, "{\"language\":\"en\"}")
val out = ByteArray(65536)
for (chunk in pcmChunks) { // each: 16 kHz mono PCM16 bytes
    CactusJNI.nativeStreamTranscribeProcess(stream, chunk, out)
    // parse confirmed/pending from String(out, 0, out.indexOf(0))
}
CactusJNI.nativeStreamTranscribeStop(stream, out)

Kotlin Multiplatform

commonMain/  Cactus.common.kt     expect declarations
commonMain/  CactusCallbacks.kt   shared callback interfaces
androidMain/ Cactus.android.kt    actual via JNI
iosMain/     Cactus.ios.kt        actual via cinterop

build.gradle.kts

kotlin {
    androidTarget()

    listOf(iosArm64(), iosSimulatorArm64()).forEach { target ->
        target.compilations.getByName("main") {
            cinterops {
                val cactus by creating {
                    defFile("src/nativeInterop/cinterop/cactus.def")
                    includeDirs("/path/to/cactus/cactus-engine")
                }
            }
        }
        val libSuffix = if (target.name == "iosSimulatorArm64") "simulator" else "device"
        target.binaries.framework {
            linkerOpts("-L/path/to/cactus/apple", "-lcactus_engine-$libSuffix")
        }
    }
}

Usage (shared code)

val model = cactusInit("/path/to/model", null, false)
val result = cactusComplete(model, messagesJson, null, null, null, null)

// streaming transcription: start, feed PCM16 chunks, stop
val stream = cactusStreamTranscribeStart(model, "{\"language\":\"en\"}")
val out = cactusStreamTranscribeProcess(stream, pcmChunk)   // {"success":true,"confirmed":...,"pending":...}
val tail = cactusStreamTranscribeStop(stream)

cactusDestroy(model)