JNNGL · May 13, 2023 18:29 · May 13, 2023 · May 13, 2023 · May 13, 2023 · May 13, 2023
diff --git a/RuntimeJNI.java b/RuntimeJNI.java
@@ -46,7 +46,7 @@ JNIEXPORT void JNICALL Java_Test_hello(JNIEnv* env, jclass class) {
         processBuilder.redirectErrorStream(true);
         processBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
         processBuilder.directory(directory.toFile());
-        processBuilder.start().waitFor(); // TODO: Write native library directly in native form
+        processBuilder.start().waitFor(); // TODO: Write native library directly in binary form
 
         try (URLClassLoader classLoader = new URLClassLoader(new URL[]{directory.toUri().toURL()})) {
             Class<?> nativeBinding = classLoader.loadClass("Test");

diff --git a/RuntimeJNI.java b/RuntimeJNI.java
@@ -34,7 +34,7 @@ public static void main(String[] args) throws Throwable {
         String bindingCode = """
                                 #include <jni.h>
                                 extern void hello();
-                                JNIEXPORT void JNICALL Java_Test_hello(JNIEnv*, jclass class) {
+                                JNIEXPORT void JNICALL Java_Test_hello(JNIEnv* env, jclass class) {
                                     hello();
                                 }""";
 

diff --git a/RuntimeJNI.java b/RuntimeJNI.java
@@ -56,7 +56,6 @@ JNIEXPORT void JNICALL Java_Test_hello(JNIEnv*, jclass class) {
             nativeBinding.getMethod("hello").invoke(null);
         }
 
-
         try (Stream<Path> stream = Files.walk(directory)) {
             stream.sorted(Comparator.reverseOrder())
                     .map(Path::toFile)

diff --git a/RuntimeJNI.java b/RuntimeJNI.java
@@ -0,0 +1,66 @@
+import org.objectweb.asm.*;
+import java.io.File;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
+import java.util.stream.Stream;
+
+import static org.objectweb.asm.Opcodes.*;
+
+public class Main {
+
+    public static void main(String[] args) throws Throwable {
+        ClassWriter cw = new ClassWriter(0);
+        cw.visit(49, ACC_PUBLIC + ACC_SUPER, "Test", null, "java/lang/Object", null);
+
+        // public static native void hello();
+        cw.visitMethod(ACC_PUBLIC + ACC_STATIC + ACC_NATIVE, "hello", "()V", null, null).visitEnd();
+
+        // public static void loadLibrary(String lib) { System.load(lib); }
+        MethodVisitor mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "loadLibrary", "(Ljava/lang/String;)V", null, null);
+        mv.visitVarInsn(ALOAD, 0);
+        mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "load", "(Ljava/lang/String;)V", false);
+        mv.visitInsn(RETURN);
+        mv.visitMaxs(1, 1);
+        mv.visitEnd();
+
+        cw.visitEnd();
+
+        Path directory = Files.createTempDirectory("test");
+        Files.write(directory.resolve("Test.class"), cw.toByteArray());
+
+        String bindingCode = """
+                                #include <jni.h>
+                                extern void hello();
+                                JNIEXPORT void JNICALL Java_Test_hello(JNIEnv*, jclass class) {
+                                    hello();
+                                }""";
+
+        String targetLib = new File("hello.so").getAbsolutePath();
+
+        Files.writeString(directory.resolve("glue.c"), bindingCode);
+        ProcessBuilder processBuilder = new ProcessBuilder("bash", "-c", "gcc -I${JAVA_HOME}/include -I${JAVA_HOME}/include/linux -Os -fPIC -shared glue.c -o binding.so " + targetLib);
+        processBuilder.environment().put("JAVA_HOME", System.getProperty("java.home"));
+        processBuilder.redirectErrorStream(true);
+        processBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
+        processBuilder.directory(directory.toFile());
+        processBuilder.start().waitFor(); // TODO: Write native library directly in native form
+
+        try (URLClassLoader classLoader = new URLClassLoader(new URL[]{directory.toUri().toURL()})) {
+            Class<?> nativeBinding = classLoader.loadClass("Test");
+            nativeBinding.getMethod("loadLibrary", String.class)
+                    .invoke(null, directory.resolve("binding.so").toFile().getAbsolutePath());
+
+            nativeBinding.getMethod("hello").invoke(null);
+        }
+
+
+        try (Stream<Path> stream = Files.walk(directory)) {
+            stream.sorted(Comparator.reverseOrder())
+                    .map(Path::toFile)
+                    .forEach(File::deleteOnExit);
+        }
+    }
+}
diff --git a/hello.c b/hello.c
@@ -0,0 +1,5 @@
+#include <stdio.h>
+
+void hello() {
+    puts("Hello, world!");
+}