com.bigdata.btree.ChildIterator Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program 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; version 2 of the License.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Nov 15, 2006
*/
package com.bigdata.btree;
import java.util.NoSuchElementException;
/**
* Visits the direct children of a {@link Node} in the external key ordering.
*
* @author Bryan Thompson
* @version $Id$
*/
class ChildIterator implements INodeIterator {
private final Node node;
private int index = 0;
private int lastVisited = -1;
// private final byte[] fromKey;
//
// private final byte[] toKey;
// first index to visit.
private final int fromIndex;
// first index to NOT visit.
private final int toIndex;
public ChildIterator(Node node) {
this(node,null,null);
}
/**
*
* @param node
* The node whose children will be traversed.
* @param fromKey
* The first key whose child will be visited or null
* if the lower bound on the key traversal is not constrained.
* @param toKey
* The first key whose child will NOT be visited or
* null if the upper bound on the key traversal is
* not constrained.
*
* @exception IllegalArgumentException
* if fromKey is given and is greater than toKey.
*/
public ChildIterator(final Node node, final byte[] fromKey, final byte[] toKey) {
assert node != null;
this.node = node;
// this.fromKey = fromKey; // may be null (no lower bound).
//
// this.toKey = toKey; // may be null (no upper bound).
{ // figure out the first index to visit.
int fromIndex;
if (fromKey != null) {
fromIndex = node.findChild(fromKey);
} else {
fromIndex = 0;
}
this.fromIndex = fromIndex;
}
{ /*
* figure out the last index to visit.
*
* Note: Unlike a leaf, we do visit the child in which the toKey
* would be found. This is necessary in order to ensure that we
* visit any keys in leaves spanned by the child that are less
* than the toKey.
*/
int toIndex;
if (toKey != null) {
toIndex = node.findChild(toKey);
if (fromIndex > toIndex) {
/*
* Note: we test for from/to key out of order _before_
* incrementing the toIndex.
*/
throw new IllegalArgumentException("fromKey > toKey");
}
// +1 so that we visit the child in which toKey would be found!
toIndex++;
} else {
// Note: nchildren == nkeys+1 for a Node.
toIndex = node.getKeyCount() + 1;
}
this.toIndex = toIndex;
}
// starting index is the lower bound.
index = fromIndex;
}
public boolean hasNext() {
return index >= fromIndex && index < toIndex;
}
public AbstractNode next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
lastVisited = index++;
return node.getChild(lastVisited);
}
public AbstractNode getNode() {
if( lastVisited == -1 ) {
throw new IllegalStateException();
}
return node.getChild(lastVisited);
}
public Object getKey() {
if( lastVisited == -1 ) {
throw new IllegalStateException();
}
return node.getKeys().get(lastVisited);
}
/**
* @exception UnsupportedOperationException
*/
public void remove() {
throw new UnsupportedOperationException();
}
}
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