/* AbstractSelector.java --
   Copyright (C) 2002, 2003, 2004  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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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.

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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
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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.HashSet;
import java.util.Set;


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

  /**
   * Initializes the slector.
   *
   * @param provider the provider that created this selector
   */
  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.
   *
   * @return true if channel is open, false otherwise.
   */
  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()
  {
  }

  /**
   * Returns the provider for this selector object.
   *
   * @return the SelectorProvider object that created this seletor
   */
  public final SelectorProvider provider()
  {
    return provider;
  }

  /**
   * Returns the cancelled keys set.
   *
   * @return the cancelled keys set
   */
  protected final Set cancelledKeys()
  {
    if (! isOpen())
      throw new ClosedSelectorException();

    return cancelledKeys;
  }

  /**
   * Cancels a selection key.
   */

  // This method is only called by AbstractSelectionKey.cancel().
  final void cancelKey(AbstractSelectionKey key)
  {
    synchronized (cancelledKeys)
      {
	cancelledKeys.add(key);
      }
  }

  /**
   * Closes the channel.
   *
   * @exception IOException if an error occurs
   */
  protected abstract void implCloseSelector() throws IOException;

  /**
   * Registers a channel for the selection process.
   *
   * @param ch the channel register
   * @param ops the interested operations
   * @param att an attachement to the selection key
   *
   * @return the registered selection key
   */
  protected abstract SelectionKey register(AbstractSelectableChannel ch,
                                           int ops, Object att);

  /**
   * Deregisters the given selection key.
   *
   * @param key the key to deregister
   */
  protected final void deregister(AbstractSelectionKey key)
  {
    ((AbstractSelectableChannel) key.channel()).removeSelectionKey(key);
  }
}