Repository /Debellor/debellor-1.0.jar:org.debellor.weka.ArffReader

/*
 *  Debellor
 *
 *  Copyright (C) 2008-2009 by Marcin Wojnarski
 *
 *  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, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  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, see http://www.gnu.org/licenses/.
 */
package org.debellor.weka;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;

import org.debellor.core.Cell;
import org.debellor.core.Parameters;
import org.debellor.core.Sample;
import org.debellor.core.Sample.SampleType;
import org.debellor.core.parameters.ParametersInfo;

import weka.core.Instance;
import weka.core.Instances;

/**
 * <p>Parameters:</p>
 * <ul>
 * <li><i>filename</i>: directory path to the ARFF file
 * <li><i>fileURL</i>: URL of the ARFF file. 
 * 		Can be given instead of a <i>filename</i>,
 * 		e.g. to read from a class resource file:<br>
 *          <code> arffReader.set("fileURL", myClass.class.getResource("...").toString()); </code>
 * <li><i>decisionAttr</i>: index of the attribute to become {@link Sample#decision}. Indices start from 1.
 * 		Special values "last" and "-1" denote the last attribute.
 * 		If not specified or empty string, all attributes will fall into {@link Sample#data}.
 * </ul>
 * 
 * <p>Instead of specifying a 'filename' or 'fileURL' the user may call 
 * {@link #setInputStream(InputStream)} to manually
 * provide an instance of <code>java.io.InputStream</code> that 
 * should be used to read the ARFF file.
 * This enables reading from file that is not accessible in regular way,
 * e.g., is stored in memory.
 * This also gives the user more control over how the file is accessed and when,
 * as the InputStream instance may be prepared in a special way by the user. 
 * </p>
 * 
 * @author Marcin Wojnarski
 *
 */
public class ArffReader extends Cell 
{
	private static final ParametersInfo availParams = new ParametersInfo
		(
			"filename", null,	"directory path to the ARFF file",
			"fileURL", null,	"URL of the ARFF file. Can be given instead of a filename, " +
								"e.g. to read from a class resource file: " +
								"arffReader.set(\"fileURL\", myClass.class.getResource(\"...\").toString());",
			"decisionAttr", "",	"index of the attribute to become Sample.decision. Indices start from 1. " +
								"Special values \"last\" and \"-1\" denote the last attribute. " +
								"If not specified or empty string, all attributes will fall into Sample.data."
		);
	
	private InputStream inputStreamFromUser;
	private Reader reader;
	private SampleType type;
	private Instances instances;
	private boolean finished;

//	private static class Knobs {
//		String filename;
//		String fileURL;
//		int getDecisionIndex() { return -1; }
//	}

	
	public ArffReader() {
		super(false);
		setAvailableParams(availParams);
	}
	
	/**
	 * Sets the instance of <code>java.io.InputStream</code> that will be used
	 * by this ArffReader to read the contents of an ARFF file.
	 * ArffReader will use this input stream instead of opening
	 * the file by itself.
	 * This method has priority over parameters 'filename' and 'fileURL'.
	 * It has effect only on the nearest call to open-next...-close.
	 */
	public void setInputStream(InputStream inputStream) {
		inputStreamFromUser = inputStream;
	}

	@Override
	protected SampleType onOpen() throws Exception {
		Parameters param = parameters;
		
		if(inputStreamFromUser != null) {
			if(!(inputStreamFromUser instanceof BufferedInputStream))
				inputStreamFromUser = new BufferedInputStream(inputStreamFromUser);
			reader = new InputStreamReader(inputStreamFromUser);
			inputStreamFromUser = null;
		}
		else if(param.exists("filename"))
			reader = new BufferedReader(new FileReader(param.get("filename")));
		else if(param.exists("fileURL"))
			reader = new InputStreamReader( 
					 new BufferedInputStream(
					 new URL(param.get("fileURL")).openStream() ));
		else
			throw new Exception("Neither 'filename' nor 'fileURL' parameter was defined for ArffReader");
		
		instances = new Instances(reader, 1);			// read only the header

		//Knobs knobs = new Knobs().from(parameters);
		
		int decisionAttrIndex = -2;
		try {
			if(param.get("decisionAttr").trim().equalsIgnoreCase("last"))
				decisionAttrIndex = -1;
			else
				decisionAttrIndex = param.getAsInt("decisionAttr");
			if(decisionAttrIndex == -1)
				decisionAttrIndex = instances.numAttributes() - 1;		// the last column will become decision
		}
		catch(Exception e) {}

		if((decisionAttrIndex >= 0) && (decisionAttrIndex < instances.numAttributes()))
			instances.setClassIndex(decisionAttrIndex);

		type = DataConverter.sampleTypeFrom(instances);
		
		finished = false;
		return type;
	}

	@Override
	protected Sample onNext() throws Exception {
		if(finished) return null;
		if(!instances.readInstance(reader)) {
			finished = true;
			return null;
		}
		Instance instance = instances.instance(0);
		Sample s = DataConverter.sampleFrom(instance, type);
		instances.delete(0);
		return s;
	}

	@Override
	protected void onClose() throws Exception {
		reader.close();
		
		// let internal objects be garbage-collected 
		reader = null;
		instances = null;
		type = null;
	}

}