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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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 */
package java.net;

import jdk.internal.misc.JavaIOFileDescriptorAccess;
import jdk.internal.misc.SharedSecrets;
import jdk.internal.ref.CleanerFactory;
import jdk.internal.ref.PhantomCleanable;

import java.io.FileDescriptor;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.ref.Cleaner;


Cleanable for a socket/datagramsocket FileDescriptor when it becomes phantom reachable. Create a cleanup if the raw fd != -1. Windows closes sockets using the fd. Subclassed from PhantomCleanable so that clear can be called to disable the cleanup when the socket fd is closed by any means other than calling FileDescriptor.close. Otherwise, it might incorrectly close the handle or fd after it has been reused. /**
 * Cleanable for a socket/datagramsocket FileDescriptor when it becomes phantom reachable.
 * Create a cleanup if the raw fd != -1. Windows closes sockets using the fd.
 * Subclassed from {@code PhantomCleanable} so that {@code clear} can be
 * called to disable the cleanup when the socket fd is closed by any means
 * other than calling {@link FileDescriptor#close}.
 * Otherwise, it might incorrectly close the handle or fd after it has been reused.
 */
final class SocketCleanable extends PhantomCleanable<FileDescriptor> {

    // Access to FileDescriptor private fields
    private static final JavaIOFileDescriptorAccess fdAccess =
            SharedSecrets.getJavaIOFileDescriptorAccess();

    // Native function to call NET_SocketClose(fd)
    // Used only for last chance cleanup.
    private static native void cleanupClose0(int fd) throws IOException;

    // The raw fd to close
    private final int fd;

    
Register a socket specific Cleanable with the FileDescriptor
if the FileDescriptor is non-null and the raw fd is != -1.
Params:
fdo – the FileDescriptor; may be null/**
     * Register a socket specific Cleanable with the FileDescriptor
     * if the FileDescriptor is non-null and the raw fd is != -1.
     *
     * @param fdo the FileDescriptor; may be null
     */
    static void register(FileDescriptor fdo) {
        if (fdo != null && fdo.valid()) {
            int fd = fdAccess.get(fdo);
            fdAccess.registerCleanup(fdo,
                    new SocketCleanable(fdo, CleanerFactory.cleaner(), fd));
        }
    }

    
Unregister a Cleanable from the FileDescriptor.
Params:
fdo – the FileDescriptor; may be null/**
     * Unregister a Cleanable from the FileDescriptor.
     * @param fdo the FileDescriptor; may be null
     */
    static void unregister(FileDescriptor fdo) {
        if (fdo != null) {
            fdAccess.unregisterCleanup(fdo);
        }
    }

    
Constructor for a phantom cleanable reference.
Params:
obj –     the object to monitor
cleaner – the cleaner
fd –      file descriptor to close/**
     * Constructor for a phantom cleanable reference.
     *
     * @param obj     the object to monitor
     * @param cleaner the cleaner
     * @param fd      file descriptor to close
     */
    private SocketCleanable(FileDescriptor obj, Cleaner cleaner, int fd) {
        super(obj, cleaner);
        this.fd = fd;
    }

    
Close the native handle or fd.
/**
     * Close the native handle or fd.
     */
    @Override
    protected void performCleanup() {
        try {
            cleanupClose0(fd);
        } catch (IOException ioe) {
            throw new UncheckedIOException("close", ioe);
        }
    }
}