/* AbstractSelector.java -- 
   Copyright (C) 2002, 2003 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.

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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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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
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package java.nio.channels.spi;

import java.io.IOException;
import java.nio.channels.ClosedSelectorException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Set;
import java.util.HashSet;

public abstract class AbstractSelector extends Selector
{
  private boolean closed = false;
  private SelectorProvider provider;
  private HashSet cancelledKeys;

  /**
   * Initializes the slector.
   */
  protected AbstractSelector (SelectorProvider provider)
  {
    this.provider = provider;
    this.cancelledKeys = new HashSet();
  }
 
  /**
   * Closes the channel.
   * 
   * @exception IOException If an error occurs
   */
  public final synchronized void close () throws IOException
  {
    if (closed)
      return;
    
    implCloseSelector();
    closed = true;
  }

  /**
   * Tells whether this channel is open or not.
   */
  public final boolean isOpen ()
  {
    return ! closed;
  }

  /**
   * Marks the beginning of an I/O operation that might block indefinitely.
   */
  protected final void begin()
  {
  }

  /**
   * Marks the end of an I/O operation that might block indefinitely.
   */
  protected final void end()
  {
  }
    
  public final SelectorProvider provider ()
  {
    return provider;
  }

  protected final Set cancelledKeys()
  {
    if (!isOpen())
      throw new ClosedSelectorException();

    return cancelledKeys;
  }

  final void cancelKey (AbstractSelectionKey key)
  {
    synchronized (cancelledKeys)
      {
        cancelledKeys.remove(key);
      }
  }

  /**
   * Closes the channel.
   */
  protected abstract void implCloseSelector () throws IOException;

  protected abstract SelectionKey register (AbstractSelectableChannel ch,
                                            int ops, Object att);   

  protected final void deregister (AbstractSelectionKey key)
  {
    // FIXME
  }
}