1 /*
   2  * Copyright (c) 2019, Red Hat, Inc
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 #include <jni.h>
  25 
  26 static jlong fib(jint num) {
  27     if (num == 0) {
  28         return 0;
  29     }
  30     if (num <= 2) {
  31         return 1;
  32     }
  33     return fib(num - 2) + fib(num -1);
  34 }
  35 
  36 static void callCallback(JNIEnv *env, jclass cls, jobject target, jlong result) {
  37     jmethodID mid = (*env)->GetMethodID(env, cls, "callback", "(J)V");
  38     if (mid == NULL) {
  39         jclass nsme = (jclass) (*env)->NewGlobalRef(env,
  40                                                     (*env)->FindClass(env,
  41                                                                       "java/lang/NoSuchMethodException"));
  42         if (nsme != NULL) {
  43             (*env)->ThrowNew(env, nsme, "Can't find method callback()");
  44         }
  45         return;
  46     }
  47     (*env)->CallVoidMethod(env, target, mid, result);
  48 }
  49 
  50 static void calculateAndCallCallback(JNIEnv *env, jclass cls, jobject target, jint num) {
  51     jlong result = -1;
  52     result = fib(num);
  53     callCallback(env, cls, target, result);
  54 }
  55 
  56 JNIEXPORT void JNICALL
  57 Java_fib_FibJNI_callJNI(JNIEnv *env, jclass cls, jobject target, jint num) {
  58     calculateAndCallCallback(env, cls, target, num);
  59 }