1 /* 2 * Copyright (c) 2005, 2018, Oracle and/or its affiliates. All rights reserved. 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 #include <stdio.h> 26 27 extern "C" { 28 29 /* 30 * A C function that takes a reference to java Object( a circular Linked list) 31 * and utilizes this reference to do a java method callback to determine the 32 * number of elements in the linked list 33 */ 34 JNIEXPORT jint JNICALL 35 Java_gc_gctests_nativeGC01_nativeGC01_nativeMethod01 36 (JNIEnv *env, jobject obj, jobject linked_list) { 37 jclass cls, clss; 38 jmethodID mid, mid2; 39 int elementCount; 40 41 /* Before doing anything force a GC by 42 invoking a callback where System.gc() is called 43 */ 44 cls = env->GetObjectClass(obj); 45 mid = env->GetMethodID(cls, "callbackGC", "()V"); 46 if (mid == 0) { 47 printf("couldnt locate method callbackGC()"); 48 return -1; 49 } 50 env->CallVoidMethod(obj,mid); 51 52 /* Now that a GC has been done, invoke the callback 53 that counts the number of elements in the 54 circular linked list 55 */ 56 57 clss = env->GetObjectClass(linked_list); 58 mid2 = env->GetMethodID(clss, "getLength", "()I" ); 59 if (mid2 == 0) { 60 printf("couldnt locate method getLength()"); 61 return -1; 62 } 63 elementCount = env->CallIntMethod(linked_list, mid2); 64 return elementCount; 65 } 66 67 }