feat(examples): Android example consumes the generated Kotlin/JNI wrapper

Regenerates the wrapper (MyTimerNode.kt) and JNI shim (my_timer_jni.c) via
`nimble genbindings_kotlin`, removing the hand-written sources, and points
the instrumented test at the derived MyTimerNode class.

Validated by cross-compiling both ABIs with the NDK: arm64-v8a + x86_64 build
clean, the four Java_org_logos_mytimer_MyTimerNode_* symbols are exported, and
libmy_timer_jni.so correctly NEEDS libmy_timer.so. (The Kotlin/Gradle layer
still runs on a device/emulator.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/timer/android/jni/my_timer_jni.c

@@ -1,9 +1,10 @@
-// JNI bridge: exposes the timer library's native C ABI to Kotlin/Java.
+// Generated by nim-ffi Kotlin/JNI codegen. Do not edit by hand.
 //
+// JNI bridge exposing the library's native (zero-serialization) C ABI to Kotlin.
 // The library calls back on its own FFI thread; each bridge function blocks on a
 // condvar until the callback fires, then returns a plain Java value — so the
-// Kotlin side sees a simple synchronous API. A struct return (EchoResponse) is
-// read out of the typed C-POD inside the callback (valid only there).
+// Kotlin side sees a simple synchronous API. A struct return is read out of the
+// typed C-POD inside the callback (valid only there).
 #include "my_timer.h"
 
 #include <jni.h>
@@ -13,9 +14,8 @@
 
 typedef struct {
   int ret, done;
-  char text[1024];   // string return / error text
-  char echoed[256];  // EchoResponse.echoed
-  char timerName[256];
+  char text[1024];           // string return / error text
+  char fields[2][256];  // string fields of a struct return
   pthread_mutex_t mu;
   pthread_cond_t cv;
 } Resp;
@@ -59,14 +59,15 @@ static void string_cb(int ret, const char *msg, size_t len, void *ud) {
   pthread_cond_signal(&r->cv);
   pthread_mutex_unlock(&r->mu);
 }
+
 static void echo_cb(int ret, const char *msg, size_t len, void *ud) {
   Resp *r = ud;
   pthread_mutex_lock(&r->mu);
   r->ret = ret;
   if (ret == RET_OK) {
-    const EchoResponse *e = (const EchoResponse *)msg; // typed struct return
-    strncpy(r->echoed, e->echoed, sizeof(r->echoed) - 1);
-    strncpy(r->timerName, e->timerName, sizeof(r->timerName) - 1);
+    const EchoResponse *e = (const EchoResponse *)msg;
+    strncpy(r->fields[0], e->echoed, sizeof(r->fields[0]) - 1);
+    strncpy(r->fields[1], e->timerName, sizeof(r->fields[1]) - 1);
   } else {
     copy_raw(r->text, sizeof(r->text), msg, len);
   }
@@ -76,23 +77,39 @@ static void echo_cb(int ret, const char *msg, size_t len, void *ud) {
 }
 
 JNIEXPORT jlong JNICALL
-Java_org_logos_mytimer_TimerNode_nativeCreate(JNIEnv *env, jobject thiz,
-                                              jstring jname) {
-  const char *name = (*env)->GetStringUTFChars(env, jname, NULL);
+Java_org_logos_mytimer_MyTimerNode_nativeCreate(JNIEnv *env, jobject thiz, jstring j_name) {
+  const char *name = (*env)->GetStringUTFChars(env, j_name, NULL);
+  TimerConfig config = {.name = name};
   Resp r;
   resp_init(&r);
-  TimerConfig cfg = {.name = name};
-  void *ctx = my_timer_create(cfg, ack_cb, &r);
+  void *ctx = my_timer_create(config, ack_cb, &r);
   resp_wait(&r);
-  (*env)->ReleaseStringUTFChars(env, jname, name);
+  (*env)->ReleaseStringUTFChars(env, j_name, name);
   resp_destroy(&r);
   (void)thiz;
   return (jlong)(intptr_t)ctx;
 }
 
+JNIEXPORT jobjectArray JNICALL
+Java_org_logos_mytimer_MyTimerNode_nativeEcho(JNIEnv *env, jobject thiz, jlong ctx, jstring j_message, jlong delayMs) {
+  const char *message = (*env)->GetStringUTFChars(env, j_message, NULL);
+  EchoRequest req = {.message = message, .delayMs = (int64_t)delayMs};
+  Resp r;
+  resp_init(&r);
+  if (my_timer_echo((void *)(intptr_t)ctx, echo_cb, &r, req) == RET_OK)
+    resp_wait(&r);
+  (*env)->ReleaseStringUTFChars(env, j_message, message);
+  jclass strClass = (*env)->FindClass(env, "java/lang/String");
+  jobjectArray arr = (*env)->NewObjectArray(env, 2, strClass, NULL);
+  (*env)->SetObjectArrayElement(env, arr, 0, (*env)->NewStringUTF(env, r.fields[0]));
+  (*env)->SetObjectArrayElement(env, arr, 1, (*env)->NewStringUTF(env, r.fields[1]));
+  resp_destroy(&r);
+  (void)thiz;
+  return arr;
+}
+
 JNIEXPORT jstring JNICALL
-Java_org_logos_mytimer_TimerNode_nativeVersion(JNIEnv *env, jobject thiz,
-                                               jlong ctx) {
+Java_org_logos_mytimer_MyTimerNode_nativeVersion(JNIEnv *env, jobject thiz, jlong ctx) {
   Resp r;
   resp_init(&r);
   if (my_timer_version((void *)(intptr_t)ctx, string_cb, &r) == RET_OK)
@@ -103,30 +120,8 @@ Java_org_logos_mytimer_TimerNode_nativeVersion(JNIEnv *env, jobject thiz,
   return out;
 }
 
-// Returns String[2] = { echoed, timerName }.
-JNIEXPORT jobjectArray JNICALL
-Java_org_logos_mytimer_TimerNode_nativeEcho(JNIEnv *env, jobject thiz, jlong ctx,
-                                            jstring jmsg, jlong delayMs) {
-  const char *msg = (*env)->GetStringUTFChars(env, jmsg, NULL);
-  Resp r;
-  resp_init(&r);
-  EchoRequest req = {.message = msg, .delayMs = (int64_t)delayMs};
-  if (my_timer_echo((void *)(intptr_t)ctx, echo_cb, &r, req) == RET_OK)
-    resp_wait(&r);
-  (*env)->ReleaseStringUTFChars(env, jmsg, msg);
-
-  jclass strClass = (*env)->FindClass(env, "java/lang/String");
-  jobjectArray arr = (*env)->NewObjectArray(env, 2, strClass, NULL);
-  (*env)->SetObjectArrayElement(env, arr, 0, (*env)->NewStringUTF(env, r.echoed));
-  (*env)->SetObjectArrayElement(env, arr, 1, (*env)->NewStringUTF(env, r.timerName));
-  resp_destroy(&r);
-  (void)thiz;
-  return arr;
-}
-
 JNIEXPORT void JNICALL
-Java_org_logos_mytimer_TimerNode_nativeDestroy(JNIEnv *env, jobject thiz,
-                                               jlong ctx) {
+Java_org_logos_mytimer_MyTimerNode_nativeDestroy(JNIEnv *env, jobject thiz, jlong ctx) {
   my_timer_destroy((void *)(intptr_t)ctx);
   (void)env;
   (void)thiz;

examples/timer/android/src/androidTest/kotlin/org/logos/mytimer/TimerNodeTest.kt

@@ -11,7 +11,7 @@ import org.junit.runner.RunWith
 class TimerNodeTest {
     @Test
     fun createVersionEcho() {
-        TimerNode("android-demo").use { node ->
+        MyTimerNode("android-demo").use { node ->
             assertEquals("nim-timer v0.1.0", node.version())
             val r = node.echo("hello from Kotlin", delayMs = 2)
             assertEquals("hello from Kotlin", r.echoed)

examples/timer/android/src/main/kotlin/org/logos/mytimer/MyTimerNode.kt

@@ -0,0 +1,28 @@
+// Generated by nim-ffi Kotlin codegen. Do not edit by hand.
+package org.logos.mytimer
+
+/** Typed result mirroring the library's EchoResponse. */
+data class EchoResponse(val echoed: String, val timerName: String)
+
+class MyTimerNode(name: String) : AutoCloseable {
+    private val ctx: Long = nativeCreate(name)
+
+    fun echo(message: String, delayMs: Long = 0): EchoResponse {
+        val a = nativeEcho(ctx, message, delayMs)
+        return EchoResponse(a[0], a[1])
+    }
+    fun version(): String = nativeVersion(ctx)
+    override fun close() = nativeDestroy(ctx)
+
+    private external fun nativeCreate(name: String): Long
+    private external fun nativeEcho(ctx: Long, message: String, delayMs: Long): Array<String>
+    private external fun nativeVersion(ctx: Long): String
+    private external fun nativeDestroy(ctx: Long)
+
+    companion object {
+        init {
+            System.loadLibrary("my_timer")
+            System.loadLibrary("my_timer_jni")
+        }
+    }
+}

examples/timer/android/src/main/kotlin/org/logos/mytimer/TimerNode.kt

@@ -1,38 +0,0 @@
-package org.logos.mytimer
-
-/** Typed result of [TimerNode.echo] — mirrors the library's EchoResponse. */
-data class EchoResult(val echoed: String, val timerName: String)
-
-/**
- * Idiomatic Kotlin wrapper over the timer library's native C ABI, bridged through
- * JNI (see jni/my_timer_jni.c). Each call blocks until the library's FFI-thread
- * callback fires, so these methods are simple and synchronous.
- *
- * Call [close] (or use Kotlin's `use { }`) to tear the context down.
- */
-class TimerNode(name: String) : AutoCloseable {
-    private val ctx: Long = nativeCreate(name)
-
-    fun version(): String = nativeVersion(ctx)
-
-    fun echo(message: String, delayMs: Long = 0): EchoResult {
-        val a = nativeEcho(ctx, message, delayMs)
-        return EchoResult(a[0], a[1])
-    }
-
-    override fun close() = nativeDestroy(ctx)
-
-    private external fun nativeCreate(name: String): Long
-    private external fun nativeVersion(ctx: Long): String
-    private external fun nativeEcho(ctx: Long, message: String, delayMs: Long): Array<String>
-    private external fun nativeDestroy(ctx: Long)
-
-    companion object {
-        init {
-            // libmy_timer.so (the Nim library) is a NEEDED dependency of the JNI
-            // shim, but load it explicitly first so the linker finds it.
-            System.loadLibrary("my_timer")
-            System.loadLibrary("my_timer_jni")
-        }
-    }
-}