/*
* 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 FieldIterablePosting.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.postings;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.WritableUtils;
import org.terrier.compression.BitIn;
import org.terrier.structures.DocumentIndex;
import org.terrier.structures.FieldDocumentIndex;
import org.terrier.structures.FieldDocumentIndexEntry;
import org.terrier.utility.ArrayUtils;
/** A posting iterator for field postings.
* @see Posting
* @see IterablePosting
* @see FieldPosting
* @since 3.0
* @author Craig Macdonald
*/
public class FieldIterablePosting extends BasicIterablePosting implements FieldPosting {
/** number of fields */
final int fieldCount;
/** frequency in each field */
final int[] fieldFrequencies;
/** can we lookup fields lengths in a cheap manner? */
final boolean doiIsFieldDocumentIndex;
/** pre-cast DocumentIndex to FieldDocumentIndex */
final FieldDocumentIndex fdoi;
/**
* contructor
* @param _fieldCount
*/
public FieldIterablePosting(int _fieldCount) {
super();
this.fieldCount = _fieldCount;
this.fieldFrequencies = new int[_fieldCount];
this.doiIsFieldDocumentIndex = false;
this.fdoi = null;
}
/**
* constructor
* @param fileReader
* @param entries
* @param _doi
* @param _fieldCount
* @throws IOException
*/
public FieldIterablePosting(BitIn fileReader, int entries, DocumentIndex _doi, int _fieldCount) throws IOException {
super(fileReader, entries, _doi);
this.fieldCount = _fieldCount;
this.fieldFrequencies = new int[_fieldCount];
if (doiIsFieldDocumentIndex = _doi instanceof FieldDocumentIndex)
{
fdoi = (FieldDocumentIndex)super.doi;
} else {
fdoi = null;
}
}
/** {@inheritDoc} */
public int[] getFieldFrequencies() {
return fieldFrequencies;
}
/** {@inheritDoc} */
@Override
public int next() throws IOException {
if (numEntries-- <= 0)
return EOL;
id = bitFileReader.readGamma() + id;
tf = bitFileReader.readUnary();
for(int i = 0;i<fieldCount;i++)
{
fieldFrequencies[i] = bitFileReader.readUnary()-1;
}
return id;
}
/** {@inheritDoc} */
public int[] getFieldLengths() {
if (doiIsFieldDocumentIndex)
{
try{
return fdoi.getFieldLengths(id);
} catch (IOException ioe) {
System.err.println("Problem looking for doclength for document "+ id);
ioe.printStackTrace();
return new int[0];
}
}
else
{
FieldDocumentIndexEntry fdie = null;
try{
fdie = ((FieldDocumentIndexEntry)doi.getDocumentEntry(id));
} catch (IOException ioe) {
//TODO log?
System.err.println("Problem looking for doclength for document "+ id);
ioe.printStackTrace();
return new int[0];
}
return fdie.getFieldLengths();
}
}
/** Read this posting from specified inputstream */
@Override
public void readFields(DataInput in) throws IOException {
super.readFields(in);
final int l = WritableUtils.readVInt(in);
//fieldFrequencies = new int[l];
for(int i=0;i<l;i++)
fieldFrequencies[i] = WritableUtils.readVInt(in);
}
/** Write this posting to specified outputstream */
@Override
public void write(DataOutput out) throws IOException {
super.write(out);
WritableUtils.writeVInt(out, fieldFrequencies.length);
for(int field_f : fieldFrequencies)
WritableUtils.writeVInt(out, field_f);
}
/** Get this posting as a WritablePosting */
@Override
public WritablePosting asWritablePosting()
{
FieldPostingImpl fbp = new FieldPostingImpl(fieldCount);
fbp.id = id;
fbp.tf = tf;
System.arraycopy(fieldFrequencies, 0, fbp.fieldFrequencies, 0, fieldCount);
return fbp;
}
@Override
public String toString()
{
return "(" + id + "," + tf + ",F[" + ArrayUtils.join(fieldFrequencies, ",") + "])";
}
}