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/* FileLock.java --

   Copyright (C) 2002, 2005 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package java.nio.channels;

import java.io.IOException;

/**

 * @since 1.4

 */

public abstract class FileLock

{

  private final FileChannel channel;

  private final long position;

  private final long size;

  private final boolean shared;

  /**

   * Initializes the file lock.

   *

   * @exception IllegalArgumentException If the preconditions on the parameters do not hold

   */

  protected FileLock(FileChannel channel, long position, long size,

                     boolean shared)

  {

    if (position < 0 || size < 0)

      throw new IllegalArgumentException();

    this.channel = channel;

    this.position = position;

    this.size = size;

    this.shared = shared;

  }

  /**

   * Tells whether or not this lock is valid.

   */

  public abstract boolean isValid();

  /**

   * Releases this lock.

   *

   * @exception IOException If an error occurs

   * @exception ClosedChannelException If the locked channel is no longer open.

   */

  public abstract void release() throws IOException;

  /**

   * Returns the file channel upon whose file this lock is held.

   */

  public final FileChannel channel()

  {

    return channel;

  }

  /**

   * Tells whether this lock is shared.

   */

  public final boolean isShared()

  {

    return shared;

  }

  /**

   * Tells whether or not this lock overlaps the given lock range.

   */

  public final boolean overlaps(long position, long size)

  {

    if (position > this.position + this.size)

      return false;

    if (position + size < this.position)

      return false;

    return true;

  }

  /**

   * Returns the position within the file of the first byte of the

   * locked region.

   */

  public final long position()

  {

    return position;

  }

  /**

   * Returns the size of the locked region in bytes.

   */

  public final long size()

  {

    return size;

  }

  /**

   * Returns a string describing the range, type, and validity of this lock.

   */

  public final String toString()

  {

    StringBuffer buf = new StringBuffer(getClass().getName());

    buf.append("[");

    buf.append(position);

    buf.append(":");

    buf.append(size);

    if (shared)

      buf.append(" shared");

    else

      buf.append(" exclusive");

    if (isValid())

      buf.append(" valid]");

    else

      buf.append(" invalid]");

    return buf.toString();

  }

}