JNIGlobalRefHolder.java

/*
 * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package gc.g1.unloading.keepref;

import gc.g1.unloading.check.cleanup.CleanupAction;
import gc.g1.unloading.loading.LibLoader;

/**
 * This holder keeps reference through JNI global reference.
 */
public class JNIGlobalRefHolder implements RefHolder {

    static {
        //Force loading library
        new LibLoader().hashCode();
    }

    public static native int keepGlobalJNIReference(Object object);

    public static native void deleteGlobalJNIReference(int index);

    @Override
    public Object hold(Object object) {
        final Integer index = keepGlobalJNIReference(object);
        return new CleanupAction() {
        @Override
            public void cleanup() throws Exception {
                // Clenup global reference when it's not needed anymore
                JNIGlobalRefHolder.deleteGlobalJNIReference(index);
            }
        };

    }

}