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 * 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
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package java.io;

import jdk.internal.misc.JavaIOFileDescriptorAccess;
import jdk.internal.misc.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.
 Subclassed from PhantomCleanable so that clear can be called to disable the cleanup when the handle is closed by any means other than calling FileDescriptor.close. Otherwise, it might incorrectly close the handle after it has been reused. /**
 * 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.
Params:
fdo – the FileDescriptor; may be null
Implementation Note:

A exception (OutOfMemoryException) will leave the FileDescriptor
having allocated resources and leak the fd/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.
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) {
            fdo.unregisterCleanup();
        }
    }

    
Constructor for a phantom cleanable reference.
Params:
obj –     the object to monitor
cleaner – the cleaner
fd –      file descriptor to close
handle –  handle to close/**
     * 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.
/**
     * Close the native handle or fd.
     */
    @Override
    protected void performCleanup() {
        try {
            cleanupClose0(fd, handle);
        } catch (IOException ioe) {
            throw new UncheckedIOException("close", ioe);
        }
    }
}