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The main module contains the GeoTools public interfaces that are used by other GeoTools modules (and GeoTools applications). Where possible we make use industry standard terms as provided by OGC and ISO standards. The formal GeoTools public api consists of gt-metadata, jts and the gt-main module. The main module contains the default implementations that are available provided to other GeoTools modules using our factory system. Factories are obtained from an appropriate FactoryFinder, giving applications a chance configure the factory used using the Factory Hints facilities. FilterFactory ff = CommonFactoryFinder.getFilterFactory(); Expression expr = ff.add( expression1, expression2 ); If you find yourself using implementation specific classes chances are you doing it wrong: Expression expr = new AddImpl( expression1, expressiom2 );

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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2004-2015, Open Source Geospatial Foundation (OSGeo)
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library 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
 *    Lesser General Public License for more details.
 */
package org.geotools.data.sort;

import java.io.IOException;
import java.io.RandomAccessFile;
import org.opengis.feature.simple.SimpleFeature;

/**
 * Reads the features stored in the specified block of a {@link RandomAccessFile}
 *
 * @author Andrea Aime - GeoSolutions
 */
class FeatureBlockReader {

    SimpleFeature curr;

    long offset;

    int count;

    SimpleFeatureIO io;

    public FeatureBlockReader(SimpleFeatureIO io, long start, int count) {
        this.offset = start;
        this.count = count;
        this.io = io;
    }

    public SimpleFeature feature() throws IOException {
        if (curr == null && count > 0) {
            curr = readNextFeature();
        }
        return curr;
    }

    public SimpleFeature next() throws IOException {
        curr = readNextFeature();
        return curr;
    }

    private SimpleFeature readNextFeature() throws IOException {
        if (count <= 0) {
            return null;
        }

        // move to the next feature offset
        io.seek(offset);

        // read the feature
        SimpleFeature sf = io.read();

        // update the offset for the next feature
        offset = io.getOffset();
        count--;

        // return the feature
        return sf;
    }
}