shxinputstream.java

OpenMap是一个基于JavaBeansTM的开发工具包。利用OpenMap你就能够快速构建用于访问legacy数据库的应用程序与applets。OpenMap提供了允许用户查看和操作地理空间信息的

// **********************************************************************
// 
// <copyright>
// 
//  BBN Technologies
//  10 Moulton Street
//  Cambridge, MA 02138
//  [phone]
// 
//  Copyright (C) BBNT Solutions LLC. All rights reserved.
// 
// </copyright>
// **********************************************************************
// 
// $Source: /cvs/distapps/openmap/src/openmap/com/bbn/openmap/dataAccess/shape/input/ShxInputStream.java,v $
// $RCSfile: ShxInputStream.java,v $
// $Revision: 1.4.2.3 $
// $Date: 2006/08/24 20:56:34 $
// $Author: dietrick $
// 
// **********************************************************************

package com.bbn.openmap.dataAccess.shape.input;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Reads index data from a .shx file
 * 
 * @author Doug Van Auken
 */
public class ShxInputStream {

    /**
     * An input stream to process primitives in Little Endian or Big Endian
     */
    private LittleEndianInputStream _leis = null;

    /**
     * Chains an input stream with a Little EndianInputStream
     */
    public ShxInputStream(InputStream is) {
        BufferedInputStream bis = new BufferedInputStream(is);
        _leis = new LittleEndianInputStream(bis);
    }

    /**
     * Processes the SHX file to obtain a list of offsets, which classes derived
     * from AbstractSupport will use to iterate through the associated SHP file
     * 
     * @return an array of offsets, which will be passed into the open method of
     *         classes which extend AbstractSupport.
     */
    public int[][] getIndex() {
        int[][] indexData = null;
        try {
            /*int fileCode = */_leis.readInt();
            _leis.skipBytes(20);
            int fileLength = _leis.readInt();
            int numShapes = (fileLength - 50) / 4;
            indexData = new int[2][numShapes];
            _leis.skipBytes(4);
            /*_type = */_leis.readLEInt();
            _leis.skip(64);
            for (int i = 0; i <= numShapes - 1; i++) {
                indexData[0][i] = _leis.readInt();
                indexData[1][i] = _leis.readInt();
            }
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
        return indexData;
    }

    public void close() throws IOException {
        _leis.close();
    }
}