/*
* Terrier - Terabyte Retriever
* Webpage: http://terrier.org/
* Contact: terrier{a.}dcs.gla.ac.uk
* University of Glasgow - School of Computing Science
* http://www.gla.ac.uk/
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (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.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
* the License for the specific language governing rights and limitations
* under the License.
*
* The Original Code is BlockFieldDirectInvertedOutputStream.java
*
* The Original Code is Copyright (C) 2004-2011 the University of Glasgow.
* All Rights Reserved.
*
* Contributor(s):
* Craig Macdonald <craigm{a.}dcs.gla.ac.uk> (original contributor)
*/
package org.terrier.structures;
import java.io.IOException;
import org.terrier.compression.BitOut;
import org.terrier.structures.postings.BlockFieldIterablePosting;
import org.terrier.structures.postings.BlockPosting;
import org.terrier.structures.postings.IterablePosting;
import org.terrier.structures.postings.Posting;
/**
* Writes out a blocks and fields direct index to an output stream
*/
public class BlockFieldDirectInvertedOutputStream extends
FieldDirectInvertedOutputStream {
/**
* Constructs an instance of the class with
* @param out
*/
public BlockFieldDirectInvertedOutputStream(BitOut out) {
super(out);
}
/**
* Constructs an instance of the class with
* @param filename
* @throws IOException
*/
public BlockFieldDirectInvertedOutputStream(String filename)
throws IOException {
super(filename);
}
@Override
public Class<? extends IterablePosting> getPostingIteratorClass()
{
return BlockFieldIterablePosting.class;
}
@Override
protected void writePostingNotDocid(Posting _p) throws IOException
{
super.writePostingNotDocid(_p);
final BlockPosting p = (BlockPosting)_p;
final int positions[] = p.getPositions();
final int l = positions.length;
//System.err.println("posting has " + l + "blocks");
output.writeUnary(l+1);
if (l == 0)
return;
output.writeGamma(positions[0]+1);
for(int i=1;i<l;i++)
{
output.writeGamma(positions[i] - positions[i-1]);
}
}
}