_basetreemap_ozonetreeiteratorimpl.java

Java的面向对象数据库系统的源代码

/*
 * $Id: _BaseTreeMap_OzoneTreeIteratorImpl.java,v 1.1 2003/11/27 15:55:11 leomekenkamp Exp $
 * This file is based on TreeMap.java from GNU Classpath. Quote:

TreeMap.java -- a class providing a basic Red-Black Tree data structure,
mapping Object --> Object
Copyright (C) 1998, 1999, 2000, 2001, 2002 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., 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
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.

 * end quote.
 *
 * This file is licenced under the same conditions as its original (GPL +
 * "special exception").
 */

package org.ozoneDB.collections;

import java.io.Serializable;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.ozoneDB.OzoneObject;

/**
 * <p>DO NOT USE THIS CLASS DIRECTLY.</p>
 * <p>This should be an inner class; ozone unfortunately does not (yet) support
 * inner classes as Ozone objects. Until it does we have to resort to this hack.</p>
 * <p>Note that this class resembles <code>_BaseTreeMap_TreeIterator</code>.</p>
 * <p>TODO: as soon as Ozone supports server side objects that are not storable, this
 * class has to be rewritten to such a server side non-persistent object.</p>
 */
public class _BaseTreeMap_OzoneTreeIteratorImpl extends OzoneObject implements OzoneIterator {

    private static final long serialVersionUID = 1L;

    private BaseTreeMap owner;

    public _BaseTreeMap_OzoneTreeIteratorImpl(BaseTreeMap owner, int type) {
        this.owner = owner;
        knownMod = owner._org_ozoneDB_getModification();
        this.type = type;
        this.next = owner._org_ozoneDB_firstNode();
        this.max = BaseTreeMapImpl.nilNode;
        valid = true;
    }

    public _BaseTreeMap_OzoneTreeIteratorImpl(BaseTreeMap owner, int type, BaseTreeMap.Node first, BaseTreeMap.Node max) {
        this.owner = owner;
        knownMod = owner._org_ozoneDB_getModification();
        this.type = type;
        this.next = first;
        this.max = max;
        valid = true;
    }

    /**
     * The type of this Iterator: {@link AbstractOzoneMap#KEYS}, {@link AbstractOzoneMap#VALUES},
     * or {@link AbstractOzoneMap#ENTRIES}.
     */
    private final int type;
    /** The number of modifications to the backing Map that we know about. */
    private int knownMod;
    /** The last Entry returned by a next() call. */
    private BaseTreeMap.Node last;
    /** The next entry that should be returned by next(). */
    private BaseTreeMap.Node next;
    /**
     * The last node visible to this iterator. This is used when iterating
     * on a SubMap.
     */
    private final BaseTreeMap.Node max;
    
    /**
     * set by ctor; if not set it indicates that since this instance has
     * been deserialized and its <code>last</code> and <code>next</code> are not
     * longer the same nodes as their counterparts in the collection this
     * iterator is connected to
     */
    private transient boolean valid = false;

    /**
     * Construct a new TreeIterator with the supplied type.
     * @param type {@link AbstractOzoneMap#KEYS}, {@link AbstractOzoneMap#VALUES},
     * or {@link AbstractOzoneMap#ENTRIES}
     */
    private _BaseTreeMap_OzoneTreeIteratorImpl(int type) {
        // FIXME gcj cannot handle this. Bug java/4695
        // this(type, firstNode(), nil);
        this.type = type;
        this.next = owner._org_ozoneDB_firstNode();
        this.max = BaseTreeMapImpl.nilNode;
        valid = true;
    }

    /**
     * Construct a new TreeIterator with the supplied type. Iteration will
     * be from "first" (inclusive) to "max" (exclusive).
     *
     * @param type {@link AbstractOzoneMap#KEYS}, {@link AbstractOzoneMap#VALUES},
     * or {@link AbstractOzoneMap#ENTRIES}
     * @param first where to start iteration, nil for empty iterator
     * @param max the cutoff for iteration, nil for all remaining nodes
     */
    private _BaseTreeMap_OzoneTreeIteratorImpl(int type, BaseTreeMap.Node first, BaseTreeMap.Node max) {
        this.type = type;
        this.next = first;
        this.max = max;
        valid = true;
    }

    /**
     * Returns true if the Iterator has more elements.
     * @return true if there are more elements
     * @throws ConcurrentModificationException if the TreeMap was modified
     */
    public boolean hasNext() {
        if (!valid) {
            throw new ConcurrentModificationException("iterator has been persisted and reloaded; see javadoc on FullTreeMapImpl");
        }
        if (knownMod != owner._org_ozoneDB_getModification())
            throw new ConcurrentModificationException();
        return !next.equals(max);
    }

    /**
     * Returns the next element in the Iterator's sequential view.
     * @return the next element
     * @throws ConcurrentModificationException if the TreeMap was modified
     * @throws NoSuchElementException if there is none
     */
    public Object next() {
        if (!valid) {
            throw new ConcurrentModificationException("iterator has been persisted and reloaded; see javadoc on FullTreeMapImpl");
        }
        if (knownMod != owner._org_ozoneDB_getModification())
            throw new ConcurrentModificationException();
        if (next.equals(max))
            throw new NoSuchElementException();
        last = next;
        next = owner._org_ozoneDB_successor(last);

        if (type == BaseTreeMapImpl.VALUES)
            return last.getValue();
        else if (type == BaseTreeMapImpl.KEYS)
            return last.getKey();
        return last;
    }

    /**
     * Removes from the backing TreeMap the last element which was fetched
     * with the <code>next()</code> method.
     * @throws ConcurrentModificationException if the TreeMap was modified
     * @throws IllegalStateException if called when there is no last element
     */
    public void remove() {
        if (last == null) {
            throw new IllegalStateException();
        }
        if (!valid) {
            throw new ConcurrentModificationException("iterator has been persisted and reloaded; see javadoc on FullTreeMapImpl");
        }
        if (knownMod != owner._org_ozoneDB_getModification()) {
            throw new ConcurrentModificationException();
        }

        owner._org_ozoneDB_removeNode(last);
        last = null;
        knownMod++;
    }

}