shapebinaryparser.java

postGIS是一个能够使用postSQL数据库来管理GIS数据的小程序,充分发挥了该数据库的空间管理功能,非常有用哦

/*
 * JtsBinaryParser.java
 * 
 * Binary Parser for JTS - relies on org.postgis V1.0.0+ package.
 * 
 * (C) 2005 Markus Schaber, [e-mail]
 * 
 * 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, either 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.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA or visit the web at
 * http://www.gnu.org.
 * 
 * $Id: ShapeBinaryParser.java 2077 2005-11-25 17:22:34Z mschaber $
 */
package org.postgis.java2d;

import java.awt.geom.GeneralPath;

import org.postgis.binary.ByteGetter;
import org.postgis.binary.ValueGetter;
import org.postgis.binary.ByteGetter.BinaryByteGetter;
import org.postgis.binary.ByteGetter.StringByteGetter;

/**
 * Parse binary representation of geometries. Currently, only text rep (hexed)
 * implementation is tested.
 * 
 * It should be easy to add char[] and CharSequence ByteGetter instances,
 * although the latter one is not compatible with older jdks.
 * 
 * I did not implement real unsigned 32-bit integers or emulate them with long,
 * as both java Arrays and Strings currently can have only 2^31-1 elements
 * (bytes), so we cannot even get or build Geometries with more than approx.
 * 2^28 coordinates (8 bytes each).
 * 
 * @author Markus Schaber, [e-mail]
 * 
 */
public class ShapeBinaryParser {

    /**
     * Get the appropriate ValueGetter for my endianness
     * 
     * @param bytes The appropriate Byte Getter
     * 
     * @return the ValueGetter
     */
    public static ValueGetter valueGetterForEndian(ByteGetter bytes) {
        if (bytes.get(0) == ValueGetter.XDR.NUMBER) { // XDR
            return new ValueGetter.XDR(bytes);
        } else if (bytes.get(0) == ValueGetter.NDR.NUMBER) {
            return new ValueGetter.NDR(bytes);
        } else {
            throw new IllegalArgumentException("Unknown Endian type:" + bytes.get(0));
        }
    }

    /**
     * Parse a hex encoded geometry
     * 
     * Is synchronized to protect offset counter. (Unfortunately, Java does not
     * have neither call by reference nor multiple return values.)
     * 
     * @returns a potential SRID or -1 if not present
     */
    public synchronized int parse(String value, GeneralPath path) {
        StringByteGetter bytes = new ByteGetter.StringByteGetter(value);
        return parseGeometry(valueGetterForEndian(bytes), path);
    }

    /**
     * Parse a binary encoded geometry.
     * 
     * Is synchronized to protect offset counter. (Unfortunately, Java does not
     * have neither call by reference nor multiple return values.)
     * 
     * @returns a potential SRID or -1 if not present
     */
    public synchronized int parse(byte[] value, GeneralPath path) {
        BinaryByteGetter bytes = new ByteGetter.BinaryByteGetter(value);
        return parseGeometry(valueGetterForEndian(bytes), path);
    }

    /**
     * Parse a geometry starting at offset.
     * 
     * @param path
     */
    protected int parseGeometry(ValueGetter data, GeneralPath path) {
        byte endian = data.getByte(); // skip and test endian flag
        if (endian != data.endian) {
            throw new IllegalArgumentException("Endian inconsistency!");
        }
        int typeword = data.getInt();

        int realtype = typeword & 0x1FFFFFFF; // cut off high flag bits

        boolean haveZ = (typeword & 0x80000000) != 0;
        boolean haveM = (typeword & 0x40000000) != 0;
        boolean haveS = (typeword & 0x20000000) != 0;

        int srid = -1;

        if (haveS) {
            srid = data.getInt();
        }

        switch (realtype) {
            case org.postgis.Geometry.POINT :
                parsePoint(data, haveZ, haveM, path);
                break;
            case org.postgis.Geometry.LINESTRING :
                parseLineString(data, haveZ, haveM, path);
                break;
            case org.postgis.Geometry.POLYGON :
                parsePolygon(data, haveZ, haveM, path);
                break;
            case org.postgis.Geometry.MULTIPOINT :
                parseMultiPoint(data, path);
                break;
            case org.postgis.Geometry.MULTILINESTRING :
                parseMultiLineString(data, path);
                break;
            case org.postgis.Geometry.MULTIPOLYGON :
                parseMultiPolygon(data, path);
                break;
            case org.postgis.Geometry.GEOMETRYCOLLECTION :
                parseCollection(data, path);
                break;
            default :
                throw new IllegalArgumentException("Unknown Geometry Type!");
        }
        return srid;
    }

    private void parsePoint(ValueGetter data, boolean haveZ, boolean haveM, GeneralPath path) {
        path.moveTo((float) data.getDouble(), (float) data.getDouble());
        path.closePath();
        skipZM(data, haveZ, haveM);
    }

    private void skipZM(ValueGetter data, boolean haveZ, boolean haveM) {
        if (haveZ) { // skip Z value
            data.getDouble();
        }
        if (haveM) { // skip M value
            data.getDouble();
        }
    }

    /** Parse an Array of "full" Geometries */
    private void parseGeometryArray(ValueGetter data, int count, GeneralPath path) {
        for (int i = 0; i < count; i++) {
            parseGeometry(data, path);
        }
    }

    /**
     * Parse an Array of "slim" Points (without endianness and type, part of
     * LinearRing and Linestring, but not MultiPoint!
     * 
     * @param haveZ
     * @param haveM
     */
    private void parseCS(ValueGetter data, boolean haveZ, boolean haveM, GeneralPath path) {
        int count = data.getInt();
        if (count > 0) {
            path.moveTo((float) data.getDouble(), (float) data.getDouble());
            skipZM(data, haveZ, haveM);
            for (int i = 1; i < count; i++) {
                path.lineTo((float) data.getDouble(), (float) data.getDouble());
                skipZM(data, haveZ, haveM);
            }
        }
    }


    private void parseMultiPoint(ValueGetter data, GeneralPath path) {
        parseGeometryArray(data, data.getInt(), path);
    }

    private void parseLineString(ValueGetter data, boolean haveZ, boolean haveM, GeneralPath path) {
        parseCS(data, haveZ, haveM, path);
    }

    private void parseLinearRing(ValueGetter data, boolean haveZ, boolean haveM, GeneralPath path) {
        parseCS(data, haveZ, haveM, path);
        path.closePath();
    }

    private void parsePolygon(ValueGetter data, boolean haveZ, boolean haveM, GeneralPath path) {
        int holecount = data.getInt() - 1;
        // parse shell
        parseLinearRing(data, haveZ, haveM, path);
        // parse inner rings
        for (int i = 0; i < holecount; i++) {
            parseLinearRing(data, haveZ, haveM, path);
        }
    }

    private void parseMultiLineString(ValueGetter data, GeneralPath path) {
        int count = data.getInt();
        parseGeometryArray(data, count, path);
    }

    private void parseMultiPolygon(ValueGetter data, GeneralPath path) {
        int count = data.getInt();
        parseGeometryArray(data, count, path);
    }

    private void parseCollection(ValueGetter data, GeneralPath path) {
        int count = data.getInt();
        parseGeometryArray(data, count, path);
    }
}