Share object between JNI and JVM in sample app

jni-utils/src/commonMain/kotlin/io/github/landrynorris/jniutils/GetFields.kt

@@ -3,9 +3,7 @@ package io.github.landrynorris.jniutils
 import kotlinx.cinterop.CPointer
 import kotlinx.cinterop.invoke
 import kotlinx.cinterop.pointed
-import platform.android.JNIEnvVar
-import platform.android.jfieldID
-import platform.android.jobject
+import platform.android.*
 
 fun CPointer<JNIEnvVar>.getObjectField(obj: jobject, fieldId: jfieldID?): jobject? {
     val method = pointed.pointed?.GetObjectField ?: error("JNI is not Oracle standard")
@@ -51,3 +49,44 @@ fun CPointer<JNIEnvVar>.getDoubleField(obj: jobject, fieldId: jfieldID?): Double
     val method = pointed.pointed?.GetDoubleField ?: error("JNI is not Oracle standard")
     return method.invoke(this, obj, fieldId)
 }
+
+fun CPointer<JNIEnvVar>.getBooleanField(obj: jobject, name: String, clazz: jclass): Boolean {
+    return getBooleanField(obj, getFieldId(clazz, name, Boolean.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getByteField(obj: jobject, name: String, clazz: jclass): Byte {
+    return getByteField(obj, getFieldId(clazz, name, Byte.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getShortField(obj: jobject, name: String, clazz: jclass): Short {
+    return getShortField(obj, getFieldId(clazz, name, Short.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getCharField(obj: jobject, name: String, clazz: jclass): Char {
+    return getCharField(obj, getFieldId(clazz, name, Char.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getIntField(obj: jobject, name: String, clazz: jclass): Int {
+    return getIntField(obj, getFieldId(clazz, name, Int.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getLongField(obj: jobject, name: String, clazz: jclass): Long {
+    return getLongField(obj, getFieldId(clazz, name, Long.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getFloatField(obj: jobject, name: String, clazz: jclass): Float {
+    return getFloatField(obj, getFieldId(clazz, name, Float.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getDoubleField(obj: jobject, name: String, clazz: jclass): Double {
+    return getDoubleField(obj, getFieldId(clazz, name, Double.toString()))
+}
+
+fun CPointer<JNIEnvVar>.getObjectField(obj: jobject, name: String, clazz: jclass, signature: String): jobject? {
+    return getObjectField(obj, getFieldId(clazz, name, signature))
+}
+
+fun CPointer<JNIEnvVar>.getStringField(obj: jobject, name: String, clazz: jclass): String {
+    val field = getObjectField(obj, name, clazz, String.toString()) as jstring
+    return getString(field)
+}

jni-utils/src/commonMain/kotlin/io/github/landrynorris/jniutils/RegisterNatives.kt

@@ -12,7 +12,7 @@ fun CPointer<JNIEnvVar>.registerNatives(clazz: jclass, methods: List<JNINativeMe
         name = m.name
         signature = m.signature
         fnPtr = m.fnPtr
-        println("Signature is ${m.signature}")
+        println("Signature is ${m.signature?.toKString()}")
     }
     method.invoke(this@registerNatives, clazz, methodBuffer, methods.size)
 }

jni-utils/src/commonMain/kotlin/io/github/landrynorris/jniutils/Signature.kt

@@ -1,5 +1,6 @@
 package io.github.landrynorris.jniutils
 
+import platform.android.jobject
 import platform.android.jstring
 import kotlin.reflect.KClass
 import kotlin.reflect.KType
@@ -11,6 +12,8 @@ data class Signature(val parameterClasses: List<JClass>, val returnClass: JClass
     }
 }
 
+inline fun <reified T> signature() = classToSignature(typeOf<T>())
+
 inline fun classToSignature(type: KType) = when(type) {
     typeOf<Unit>() -> Void
     typeOf<Byte>() -> Byte
@@ -21,15 +24,14 @@ inline fun classToSignature(type: KType) = when(type) {
     typeOf<Long>() -> Long
     typeOf<Float>() -> Float
     typeOf<Double>() -> Double
-    typeOf<jstring>() -> String
     typeOf<BooleanArray>() -> BooleanArray
     typeOf<ByteArray>() -> ByteArray
     typeOf<ShortArray>() -> ShortArray
     typeOf<CharArray>() -> CharArray
     typeOf<IntArray>() -> IntArray
     typeOf<FloatArray>() -> FloatArray
     typeOf<DoubleArray>() -> DoubleArray
+    typeOf<jobject>() -> createSignature("java.lang.Object")
+    typeOf<jstring>() -> String
     else -> createSignature(type.toString())
 }
-
-

sample/build.gradle.kts

@@ -56,7 +56,9 @@ kotlin {
     }
 
     sourceSets {
+        val commonMain by getting
         val ndkMain by creating {
+            dependsOn(commonMain)
             dependencies {
                 implementation(project(":jni-utils"))
                 //implementation("io.github.landrynorris:jni-utils:0.0.1-alpha02")

sample/src/androidMain/kotlin/io/github/landrynorris/sample/JniBridge.kt

@@ -1,5 +1,7 @@
 package io.github.landrynorris.sample
 
+import io.github.landrynorris.jni.sample.SharedClass
+
 object JniBridge {
     init {
         println("Loading library for JNI")
@@ -8,6 +10,8 @@ object JniBridge {
     }
 
     external fun methodWithParameters(value: Int)
+    external fun handleShared(sharedClass: SharedClass): String
+    //external fun doubleAll(array: DoubleArray): DoubleArray
     external fun callJavaFunction(value: Double)
     external fun buttonClicked(ptr: Long)
     external fun getText(ptr: Long): String

sample/src/androidMain/kotlin/io/github/landrynorris/sample/MainActivity.kt

@@ -7,6 +7,8 @@ import androidx.appcompat.app.AppCompatActivity
 import androidx.compose.material.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.tooling.preview.Preview
+import io.github.landrynorris.jni.sample.DataHolder
+import io.github.landrynorris.jni.sample.SharedClass
 import io.github.landrynorris.sample.ui.theme.JniUtilsTheme
 
 class MainActivity: AppCompatActivity() {
@@ -27,8 +29,17 @@ class MainActivity: AppCompatActivity() {
         findViewById<Button>(R.id.btnCrash).setOnClickListener {
             JniBridge.crash("App requested a Fatal Error")
         }
+
+        //findViewById<TextView>(R.id.doubleValuesLabel).text = getDoubleValuesText()
+        findViewById<TextView>(R.id.doubleValuesLabel).text = JniBridge.handleShared(
+            SharedClass(0.5, DataHolder(5, 2.5, "multiplied values"))
+        )
     }
 
+//    private fun getDoubleValuesText(): String {
+//        return JniBridge.doubleAll(doubleArrayOf(0.0, 0.5, 2.0, -3.0)).joinToString(", ")
+//    }
+
     private fun testJni() {
         JniBridge.methodWithParameters(50)
         JniBridge.callJavaFunction(12.5)

sample/src/androidMain/res/layout/activity_main.xml

@@ -17,4 +17,12 @@
             android:text="Crash"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"/>
+
+    <TextView android:id="@+id/doubleValuesLabel"
+              android:layout_width="wrap_content"
+              android:layout_height="wrap_content"/>
+
+    <TextView android:id="@+id/sharedClassLabel"
+              android:layout_width="wrap_content"
+              android:layout_height="wrap_content"/>
 </LinearLayout>

sample/src/commonMain/kotlin/io/github/landrynorris/jni/sample/SharedClass.kt

@@ -0,0 +1,5 @@
+package io.github.landrynorris.jni.sample
+
+class SharedClass(val x: Double, val dataHolder: DataHolder)
+
+data class DataHolder(val i: Int, val d: Double, val s: String)

sample/src/ndkMain/kotlin/io/github/landrynorris/jni/sample/Jni.kt

@@ -25,6 +25,10 @@ fun callJavaFunction(env: CPointer<JNIEnvVar>, thiz: jobject, value: Double) {
     }
 }
 
+fun doubleAll(env: CPointer<JNIEnvVar>, thiz: jobject, array: DoubleArray): DoubleArray {
+    return array.map { it*2 }.toDoubleArray()
+}
+
 fun createRepository(env: CPointer<JNIEnvVar>, thiz: jobject): Long {
     val repository = ButtonClickRepository()
     println("Converting repository to pointer")
@@ -45,6 +49,13 @@ fun getText(env: CPointer<JNIEnvVar>, thiz: jobject, ptr: Long): jstring {
     return repository.getText().toJString(env) ?: error("Unable to create JString")
 }
 
+fun handleSharedClass(env: CPointer<JNIEnvVar>, thiz: jobject, data: jobject): jstring {
+    val shared = data.toSharedClass(env)!!
+    val total = shared.x * shared.dataHolder.i * shared.dataHolder.d
+    val s = shared.dataHolder.s + ": " + total
+    return s.toJString(env) ?: error("Unable to create JString")
+}
+
 fun crash(env: CPointer<JNIEnvVar>, thiz: jobject, message: jstring) {
     val messageString = env.getString(message)
     env.fatalError(messageString)
@@ -73,7 +84,7 @@ fun registerJniNatives(env: CPointer<JNIEnvVar>) {
         }
 
         method("getText") {
-            signature = signature(::getText)
+            signature = Signature(listOf(Long), String).toString()
             function = staticCFunction(::getText)
         }
 
@@ -91,6 +102,16 @@ fun registerJniNatives(env: CPointer<JNIEnvVar>) {
             signature = Signature(listOf(String)).toString()
             function = staticCFunction(::crash)
         }
+
+//        method("doubleAll") {
+//            signature = signature(::doubleAll)
+//            function = staticCFunction(::doubleAll)
+//        }
+
+        method("handleShared") {
+            signature = Signature(listOf(signature<SharedClass>()), String).toString()
+            function = staticCFunction(::handleSharedClass)
+        }
     }
     println("Finished registering native methods")
 }

sample/src/ndkMain/kotlin/io/github/landrynorris/jni/sample/SharedClassJni.kt

@@ -0,0 +1,24 @@
+package io.github.landrynorris.jni.sample
+
+import io.github.landrynorris.jniutils.*
+import kotlinx.cinterop.CPointer
+import platform.android.JNIEnvVar
+import platform.android.jobject
+
+fun jobject.toSharedClass(env: CPointer<JNIEnvVar>): SharedClass? {
+    val clazz = env.findClass("io/github/landrynorris/jni/sample/SharedClass") ?: error("Unable to find class")
+    if(!env.isInstanceOf(this, clazz)) return null
+    val x = env.getDoubleField(this, "x", clazz)
+    val holder = env.getObjectField(this, "dataHolder", clazz, signature<DataHolder>().toString())
+    return SharedClass(x, holder?.toDataHolder(env)!!)
+}
+
+fun jobject.toDataHolder(env: CPointer<JNIEnvVar>): DataHolder? {
+    val clazz = env.findClass("io/github/landrynorris/jni/sample/DataHolder") ?: error("Unable to find class")
+    if(!env.isInstanceOf(this, clazz)) return null
+    val i = env.getIntField(this, "i", clazz)
+    val d = env.getDoubleField(this, "d", clazz)
+    val s = env.getStringField(this, "s", clazz)
+
+    return DataHolder(i, d, s)
+}