jni: implement IsInstanceOf

Author: Serial-ATA

jni/src/env/object.rs

@@ -51,6 +51,24 @@ impl super::JniEnv {
 	}
 
 	// TODO: GetObjectClass
-	// TODO: IsInstanceOf
+	/// Tests whether an object is an instance of a class.
+	///
+	/// ## PARAMETERS
+	///
+	/// `obj`: a Java object.
+	/// `class`: a Java class object.
+	pub fn is_instance_of(&self, obj: JObject, class: JClass) -> bool {
+		let ret;
+		unsafe {
+			let invoke_interface = self.as_native_interface();
+			ret = ((*invoke_interface).IsInstanceOf)(
+				self.0.cast::<jni_sys::JNIEnv>(),
+				obj.raw(),
+				class.raw(),
+			);
+		}
+
+		ret
+	}
 	// TODO: GetObjectRefType
 }

runtime/src/native/jni/object.rs

@@ -79,7 +79,17 @@ pub unsafe extern "system" fn IsInstanceOf(
 	obj: jobject,
 	clazz: jclass,
 ) -> jboolean {
-	unimplemented!("jni::IsInstanceOf");
+	let obj = unsafe { reference_from_jobject(obj) };
+	let Some(obj) = obj else {
+		return false;
+	};
+
+	let class_obj = unsafe { reference_from_jobject(clazz) };
+	let Some(class_obj) = class_obj else {
+		return false;
+	};
+
+	obj.is_instance_of(class_obj.extract_instance_class())
 }
 
 pub unsafe extern "system" fn GetObjectRefType(env: *mut JNIEnv, obj: jobject) -> jobjectRefType {