/*

 * Copyright 2003-2007 Sun Microsystems, Inc.  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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package java.io;

import java.util.concurrent.atomic.AtomicInteger;

/**

 * Instances of the file descriptor class serve as an opaque handle

 *

 * @author  Pavani Diwanji

 * @since   JDK1.0

 */

public final class FileDescriptor {

    private int fd;

    private long handle;

    /**

     * A use counter for tracking the FIS/FOS/RAF instances that

     * use this FileDescriptor. The FIS/FOS.finalize() will not release

     * the FileDescriptor if it is still under use by any stream.

     */

    private AtomicInteger useCount;

    /**

     * Constructs an (invalid) FileDescriptor

     * object.

     */

    public /**/ FileDescriptor() {

        fd = -1;

        handle = -1;

        useCount = new AtomicInteger();

    }

    static {

        initIDs();

    }

    // Set up JavaIOFileDescriptorAccess in SharedSecrets

    static {

        sun.misc.SharedSecrets.setJavaIOFileDescriptorAccess(

            new sun.misc.JavaIOFileDescriptorAccess() {

                public void set(FileDescriptor obj, int fd) {

                    obj.fd = fd;

                }

                public int get(FileDescriptor obj) {

                    return obj.fd;

                }

            }

        );

    }

    /**

     * A handle to the standard input stream. Usually, this file

     * descriptor is not used directly, but rather via the input stream

     *

     * @see     java.lang.System#in

     */

    public static final FileDescriptor in = standardStream(0);

    /**

     * A handle to the standard output stream. Usually, this file

     * descriptor is not used directly, but rather via the output stream

     * @see     java.lang.System#out

     */

    public static final FileDescriptor out = standardStream(1);

    /**

     * A handle to the standard error stream. Usually, this file

     * descriptor is not used directly, but rather via the output stream

     *

     * @see     java.lang.System#err

     */

    public static final FileDescriptor err = standardStream(2);

    /**

     * Tests if this file descriptor object is valid.

     *

     *          valid, open file, socket, or other active I/O connection;

     */

    public boolean valid() {

        return ((handle != -1) || (fd != -1));

    }

    /**

     * Force all system buffers to synchronize with the underlying

     * device.  This method returns after all modified data and

     * attributes of this FileDescriptor have been written to the

     * relevant device(s).  In particular, if this FileDescriptor

     * refers to a physical storage medium, such as a file in a file

     * system, sync will not return until all in-memory modified copies

     * of buffers associated with this FileDesecriptor have been

     * written to the physical medium.

     *

     * sync is meant to be used by code that requires physical

     * storage (such as a file) to be in a known state  For

     * example, a class that provided a simple transaction facility

     * might use sync to ensure that all changes to a file caused

     * by a given transaction were recorded on a storage medium.

     *

     * sync only affects buffers downstream of this FileDescriptor.  If

     * any in-memory buffering is being done by the application (for

     * example, by a BufferedOutputStream object), those buffers must

     * be flushed into the FileDescriptor (for example, by invoking

     * OutputStream.flush) before that data will be affected by sync.

     *

     * @exception SyncFailedException

     *        Thrown when the buffers cannot be flushed,

     *        or because the system cannot guarantee that all the

     *        buffers have been synchronized with physical media.

     * @since     JDK1.1

     */

    public native void sync() throws SyncFailedException;

    /* This routine initializes JNI field offsets for the class */

    private static native void initIDs();

    private static native long set(int d);

    private static FileDescriptor standardStream(int fd) {

        FileDescriptor desc = new FileDescriptor();

        desc.handle = set(fd);

        return desc;

    }

    // package private methods used by FIS, FOS and RAF.

    int incrementAndGetUseCount() {

        return useCount.incrementAndGet();

    }

    int decrementAndGetUseCount() {

        return useCount.decrementAndGet();

    }

}