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 }