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Massive On-line Analysis is an environment for massive data mining. MOA provides a framework for data stream mining and includes tools for evaluation and a collection of machine learning algorithms. Related to the WEKA project, also written in Java, while scaling to more demanding problems.
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/*
 *    ArffFileStream.java
 *    Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
 *    @author Richard Kirkby ([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; 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 .
 *    
 */
package moa.streams;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;

import moa.core.InputStreamProgressMonitor;
import moa.core.InstancesHeader;
import moa.core.ObjectRepository;
import moa.options.AbstractOptionHandler;
import moa.options.FileOption;
import moa.options.IntOption;
import moa.tasks.TaskMonitor;

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

/**
 * Stream reader of ARFF files.
 *
 * @author Richard Kirkby ([email protected])
 * @version $Revision: 7 $
 */
public class ArffFileStream extends AbstractOptionHandler implements
        InstanceStream {

    @Override
    public String getPurposeString() {
        return "A stream read from an ARFF file.";
    }

    private static final long serialVersionUID = 1L;

    public FileOption arffFileOption = new FileOption("arffFile", 'f',
            "ARFF file to load.", null, "arff", false);

    public IntOption classIndexOption = new IntOption(
            "classIndex",
            'c',
            "Class index of data. 0 for none or -1 for last attribute in file.",
            -1, -1, Integer.MAX_VALUE);

    protected Instances instances;

    protected Reader fileReader;

    protected boolean hitEndOfFile;

    protected Instance lastInstanceRead;

    protected int numInstancesRead;

    protected InputStreamProgressMonitor fileProgressMonitor;

    public ArffFileStream() {
    }

    public ArffFileStream(String arffFileName, int classIndex) {
        this.arffFileOption.setValue(arffFileName);
        this.classIndexOption.setValue(classIndex);
        restart();
    }

    @Override
    public void prepareForUseImpl(TaskMonitor monitor,
            ObjectRepository repository) {
        restart();
    }

    @Override
    public InstancesHeader getHeader() {
        return new InstancesHeader(this.instances);
    }

    @Override
    public long estimatedRemainingInstances() {
        double progressFraction = this.fileProgressMonitor.getProgressFraction();
        if ((progressFraction > 0.0) && (this.numInstancesRead > 0)) {
            return (long) ((this.numInstancesRead / progressFraction) - this.numInstancesRead);
        }
        return -1;
    }

    @Override
    public boolean hasMoreInstances() {
        return !this.hitEndOfFile;
    }

    @Override
    public Instance nextInstance() {
        Instance prevInstance = this.lastInstanceRead;
        this.hitEndOfFile = !readNextInstanceFromFile();
        return prevInstance;
    }

    @Override
    public boolean isRestartable() {
        return true;
    }

    @Override
    public void restart() {
        try {
            if (this.fileReader != null) {
                this.fileReader.close();
            }
            InputStream fileStream = new FileInputStream(this.arffFileOption.getFile());
            this.fileProgressMonitor = new InputStreamProgressMonitor(
                    fileStream);
            this.fileReader = new BufferedReader(new InputStreamReader(
                    this.fileProgressMonitor));
            this.instances = new Instances(this.fileReader, 1);
            if (this.classIndexOption.getValue() < 0) {
                this.instances.setClassIndex(this.instances.numAttributes() - 1);
            } else if (this.classIndexOption.getValue() > 0) {
                this.instances.setClassIndex(this.classIndexOption.getValue() - 1);
            }
            this.numInstancesRead = 0;
            this.lastInstanceRead = null;
            this.hitEndOfFile = !readNextInstanceFromFile();
        } catch (IOException ioe) {
            throw new RuntimeException("ArffFileStream restart failed.", ioe);
        }
    }

    protected boolean readNextInstanceFromFile() {
        try {
            if (this.instances.readInstance(this.fileReader)) {
                this.lastInstanceRead = this.instances.instance(0);
                this.instances.delete(); // keep instances clean
                this.numInstancesRead++;
                return true;
            }
            if (this.fileReader != null) {
                this.fileReader.close();
                this.fileReader = null;
            }
            return false;
        } catch (IOException ioe) {
            throw new RuntimeException(
                    "ArffFileStream failed to read instance from stream.", ioe);
        }
    }

    @Override
    public void getDescription(StringBuilder sb, int indent) {
        // TODO Auto-generated method stub
    }
}