Load a class via JNI

Author: JaroslavTulach

lib/java/os-environment/src/main/java/org/enso/os/environment/jni/JNI.java

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+package org.enso.os.environment.jni;
+
+import org.graalvm.nativeimage.c.CContext;
+import org.graalvm.nativeimage.c.function.CFunction;
+import org.graalvm.nativeimage.c.function.CFunctionPointer;
+import org.graalvm.nativeimage.c.function.InvokeCFunctionPointer;
+import org.graalvm.nativeimage.c.struct.CField;
+import org.graalvm.nativeimage.c.struct.CStruct;
+import org.graalvm.nativeimage.c.type.CCharPointer;
+import org.graalvm.nativeimage.c.type.WordPointer;
+import org.graalvm.word.PointerBase;
+
+/** Java virtual machine initialization API. */
+@CContext(JNIDirectives.class)
+final class JNIBoot {
+  @CFunction
+  static native int JNI_GetDefaultJavaVMInitArgs(Args vmargs);
+
+  public interface JNICreateJavaVMPointer extends CFunctionPointer {
+    @InvokeCFunctionPointer
+    int call(JNI.JavaVMPointer jvmptr, JNI.JNIEnvPointer env, Args args);
+  }
+
+  @CStruct("JavaVMInitArgs")
+  interface Args extends PointerBase {
+    @CField
+    int version();
+
+    @CField
+    void version(int v);
+
+    @CField
+    int nOptions();
+
+    @CField
+    void nOptions(int n);
+
+    @CField
+    Option options();
+
+    @CField
+    void options(Option ptr);
+
+    @CField
+    boolean ignoreUnrecognized();
+
+    @CField
+    void ignoreUnrecognized(boolean v);
+  }
+
+  @CStruct(value = "JavaVMOption")
+  public interface Option extends PointerBase {
+
+    @CField("optionString")
+    CCharPointer getOptionString();
+
+    @CField("optionString")
+    void setOptionString(CCharPointer value);
+
+    @CField("extraInfo")
+    WordPointer getExtraInfo();
+
+    @CField("extraInfo")
+    void setExtraInfo(WordPointer value);
+
+    Option addressOf(int index);
+  }
+}

lib/java/os-environment/src/main/java/org/enso/os/environment/jni/JNIBoot.java

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+package org.enso.os.environment.jni;
+
+import java.io.File;
+import java.util.List;
+import org.graalvm.nativeimage.c.CContext;
+
+final class JNIDirectives implements CContext.Directives {
+
+  @Override
+  public List<String> getLibraryPaths() {
+    var javaHome = new File(System.getProperty("java.home"));
+    var libServer = new File(new File(javaHome, "lib"), "server");
+    return List.of(libServer.getPath());
+  }
+
+  @Override
+  public List<String> getLibraries() {
+    return List.of("jvm");
+  }
+
+  @Override
+  public List<String> getOptions() {
+    var javaHome = new File(System.getProperty("java.home"));
+    var include = new File(javaHome, "include");
+    assert include.isDirectory();
+    var jni = new File(include, "jni.h");
+    assert jni.canRead();
+    for (var subDir : include.listFiles()) {
+      var md = new File(subDir, "jni_md.h");
+      if (md.canRead()) {
+        var q = "\"";
+        var includes = List.of("-I", jni.getParent(), "-I", md.getParent());
+        return includes;
+      }
+    }
+    throw new AssertionError("Cannot find libs in " + javaHome);
+  }
+
+  @Override
+  public List<String> getHeaderFiles() {
+    return List.of("<jni.h>", "<jni_md.h>");
+  }
+}