/*

 * Copyright (c) 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.  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 java.io;

import jdk.internal.access.JavaIOFileDescriptorAccess;

import jdk.internal.access.SharedSecrets;

import jdk.internal.ref.CleanerFactory;

import jdk.internal.ref.PhantomCleanable;

import java.lang.ref.Cleaner;

/**

 * Cleanable for a FileDescriptor when it becomes phantom reachable.

 * For regular fds on Unix and regular handles on Windows

 * register a cleanup if fd != -1 or handle != -1.

 * <p>

 * Subclassed from {@code PhantomCleanable} so that {@code clear} can be

 * called to disable the cleanup when the handle is closed by any means other

 * than calling {@link FileDescriptor#close}.

 * Otherwise, it might incorrectly close the handle after it has been reused.

 */

final class FileCleanable extends PhantomCleanable<FileDescriptor> {

    // Access to FileDescriptor private fields;

    // avoids making fd and handle package private

    private static final JavaIOFileDescriptorAccess fdAccess =

            SharedSecrets.getJavaIOFileDescriptorAccess();

    /*

     * Raw close of the file fd and/or handle.

     * Used only for last chance cleanup.

     */

    private static native void cleanupClose0(int fd, long handle) throws IOException;

    // The raw fd to close

    private final int fd;

    // The handle to close

    private final long handle;

    /**

     * Register a Cleanable with the FileDescriptor

     * if the FileDescriptor is non-null and valid.

     * @implNote

     * A exception (OutOfMemoryException) will leave the FileDescriptor

     * having allocated resources and leak the fd/handle.

     *

     * @param fdo the FileDescriptor; may be null

     */

    static void register(FileDescriptor fdo) {

        if (fdo != null && fdo.valid()) {

            int fd = fdAccess.get(fdo);

            long handle = fdAccess.getHandle(fdo);

            fdo.registerCleanup(new FileCleanable(fdo, CleanerFactory.cleaner(), fd, handle));

        }

    }

    /**

     * Unregister a Cleanable from the FileDescriptor.

     * @param fdo the FileDescriptor; may be null

     */

    static void unregister(FileDescriptor fdo) {

        if (fdo != null) {

            fdo.unregisterCleanup();

        }

    }

    /**

     * Constructor for a phantom cleanable reference.

     *

     * @param obj     the object to monitor

     * @param cleaner the cleaner

     * @param fd      file descriptor to close

     * @param handle  handle to close

     */

    private FileCleanable(FileDescriptor obj, Cleaner cleaner, int fd, long handle) {

        super(obj, cleaner);

        this.fd = fd;

        this.handle = handle;

    }

    /**

     * Close the native handle or fd.

     */

    @Override

    protected void performCleanup() {

        try {

            cleanupClose0(fd, handle);

        } catch (IOException ioe) {

            throw new UncheckedIOException("close", ioe);

        }

    }

}