/*

 * Copyright (c) 2005, 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 com.sun.imageio.stream;

import java.io.IOException;

import javax.imageio.stream.ImageInputStream;

/**

 * Small class to assist in properly closing an ImageInputStream instance

 * prior to garbage collection.  The ImageInputStreamImpl class defines a

 * finalize() method, but in a number of its public subclasses

 * (e.g. FileImageInputStream) we override the finalize() method to be

 * empty for performance reasons, and instead rely on the Disposer mechanism

 * for closing/disposing resources.  This is fine when one of these classes

 * is instantiated directly (e.g. new FileImageInputStream()) but in the

 * unlikely case where a user defines their own subclass of one of those

 * streams, we need some way to get back to the behavior of

 * ImageInputStreamImpl, which will call close() as part of finalization.

 *

 * Typically an Image{Input,Output}Stream will construct an instance of

 * StreamFinalizer in its constructor if it detects that it has been

 * subclassed by the user.  The ImageInputStream instance will hold a

 * reference to the StreamFinalizer, and the StreamFinalizer will hold a

 * reference back to the ImageInputStream from which it was created.  When

 * both are no longer reachable, the StreamFinalizer.finalize() method will

 * be called, which will take care of closing down the ImageInputStream.

 *

 * Clearly this is a bit of a hack, but it will likely only be used in the

 * rarest of circumstances: when a user has subclassed one of the public

 * stream classes.  (It should be no worse than the old days when the public

 * stream classes had non-empty finalize() methods.)

 */

public class StreamFinalizer {

    private ImageInputStream stream;

    public StreamFinalizer(ImageInputStream stream) {

        this.stream = stream;

    }

    protected void finalize() throws Throwable {

        try {

            stream.close();

        } catch (IOException e) {

        } finally {

            stream = null;

            super.finalize();

        }

    }

}