/*

 * Copyright (c) 2008, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.tracing.dtrace;

import java.lang.ref.WeakReference;

import java.lang.ref.ReferenceQueue;

import java.security.Permission;

import java.util.HashSet;

class Activation {

    private SystemResource resource;

    private int referenceCount;

    Activation(String moduleName, DTraceProvider[] providers) {

        SecurityManager security = System.getSecurityManager();

        if (security != null) {

            Permission perm =

                new RuntimePermission("com.sun.tracing.dtrace.createProvider");

            security.checkPermission(perm);

        }

        referenceCount = providers.length;

        for (DTraceProvider p : providers) {

            p.setActivation(this);

        }

        resource = new SystemResource(

            this, JVM.activate(moduleName, providers));

    }

    void disposeProvider(DTraceProvider p) {

        if (--referenceCount == 0) {

            resource.dispose();

        }

    }

}

/**

 * The native resource part of an Activation.

 *

 * This holds the native handle.

 *

 * If the user loses a reference to a set of Providers without disposing them,

 * and GC determines the Activation is unreachable, then the next

 * activation or flush call will automatically dispose the unreachable objects

 *

 * The SystemResource instances are creating during activation, and

 * unattached during disposal.  When created, they always have a

 * strong reference to them via the {@code resources} static member.  Explicit

 * {@code dispose} calls will unregister the native resource and remove

 * references to the SystemResource object.  Absent an explicit dispose,

 * when their associated Activation object becomes garbage, the SystemResource

 * object will be enqueued on the reference queue and disposed at the

 * next call to {@code flush}.

 */

class SystemResource extends WeakReference<Activation> {

    private long handle;

    private static ReferenceQueue<Activation> referenceQueue =

        referenceQueue = new ReferenceQueue<Activation>();

    static HashSet<SystemResource> resources = new HashSet<SystemResource>();

    SystemResource(Activation activation, long handle) {

        super(activation, referenceQueue);

        this.handle = handle;

        flush();

        resources.add(this);

    }

    void dispose() {

        JVM.dispose(handle);

        resources.remove(this);

        handle = 0;

    }

    static void flush() {

        SystemResource resource = null;

        while ((resource = (SystemResource)referenceQueue.poll()) != null) {

            if (resource.handle != 0) {

                resource.dispose();

            }

        }

    }

}