/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hp.hpl.jena.tdb.index.bplustree;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.apache.jena.atlas.iterator.PeekIterator ;
import com.hp.hpl.jena.tdb.base.recordbuffer.RecordBufferPage ;
/** From a stream of RecordBufferPage, manage the link fields.
* That is, be a one slot delay so that the "link" field can point to the next page.
* Be careful about the last block.
*
*/
class RecordBufferPageLinker implements Iterator<RecordBufferPage>
{
PeekIterator<RecordBufferPage> peekIter ;
RecordBufferPage slot = null ;
RecordBufferPageLinker(Iterator<RecordBufferPage> iter)
{
if ( ! iter.hasNext() )
{
peekIter = null ;
return ;
}
peekIter = new PeekIterator<>(iter) ;
}
@Override
public boolean hasNext()
{
if ( slot != null )
return true ;
if ( peekIter == null )
return false ;
if ( ! peekIter.hasNext() )
{
peekIter = null ;
return false ;
}
slot = peekIter.next() ;
RecordBufferPage nextSlot = peekIter.peek() ;
// If null, no slot ahead so no linkage field to set.
if ( nextSlot != null )
// Set the slot to the id of the next one
slot.setLink(nextSlot.getId()) ;
return true ;
}
@Override
public RecordBufferPage next()
{
if ( ! hasNext() ) throw new NoSuchElementException() ;
RecordBufferPage rbp = slot ;
slot = null ;
return rbp ;
}
@Override
public void remove()
{ throw new UnsupportedOperationException() ; }
}