Class WKBWriter

Hierarchy: Object , WKBWriter

public class WKBWriter

Writes a Geometry into Well-Known Binary format. Supports use of an OutStream, which allows easy use with arbitrary byte stream sinks.

The WKB format is specified in the OGC Simple Features for SQL specification. This implementation also supports the Extended WKB standard. Extended WKB allows writing 3-dimensional coordinates and including the geometry SRID value. The presence of 3D coordinates is signified by setting the high bit of the wkbType word. The presence of an SRID is signified by setting the third bit of the wkbType word. EWKB format is upward compatible with the original SFS WKB format.

Empty Points are output as a Point with NaN X and Y ordinate values.

The WKB specification does not support representing LinearRings; they will be written as LineStrings.

This class is designed to support reuse of a single instance to read multiple geometries. This class is not thread-safe; each thread should create its own instance.

Syntax

The following syntax specification describes the version of Well-Known Binary supported by JTS.

The specification uses a syntax language similar to that used in the C language. Bitfields are specified from hi-order to lo-order bits.


 byte = 1 byte
 uint32 = 32 bit unsigned integer (4 bytes)
 double = double precision number (8 bytes)

 abstract Point { }

 Point2D extends Point {
 	double x;
 	double y;
 }

 Point3D extends Point {
 	double x;
 	double y;
 	double z;
 }

 LinearRing {
 	uint32 numPoints;
 	Point points[numPoints];
 }

 enum wkbGeometryType {
 	wkbPoint = 1,
 	wkbLineString = 2,
 	wkbPolygon = 3,
 	wkbMultiPoint = 4,
 	wkbMultiLineString = 5,
 	wkbMultiPolygon = 6,
 	wkbGeometryCollection = 7
 }

 enum byteOrder {
 	wkbXDR = 0,	// Big Endian
 	wkbNDR = 1 	// Little Endian
 }

 WKBType {
 	uint32 wkbGeometryType : 8; // values from enum wkbGeometryType
 }

 EWKBType {
 	uint32 is3D : 1; 	// 0 = 2D, 1 = 3D
 	uint32 noData1 : 1;
 	uint32 hasSRID : 1;  	// 0, no, 1 = yes
 	uint32 noData2 : 21;
 	uint32 wkbGeometryType : 8; // values from enum wkbGeometryType
 }

 abstract WKBGeometry {
 	byte byteOrder;		// values from enum byteOrder
 	EWKBType wkbType
 	[ uint32 srid; ] 	// only if hasSRID = yes
 }

 WKBPoint extends WKBGeometry {
 	Point point;
 }

 WKBLineString extends WKBGeometry {
 	uint32 numCoords;
 	Point points[numCoords];
 }

 WKBPolygon extends WKBGeometry {
 	uint32 numRings;
 	LinearRing rings[numRings];
 }

 WKBMultiPoint extends WKBGeometry {
 	uint32 numElems;
 	WKBPoint elems[numElems];
 }

 WKBMultiLineString extends WKBGeometry {
 	uint32 numElems;
 	WKBLineString elems[numElems];
 }

 wkbMultiPolygon extends WKBGeometry {
 	uint32 numElems;
 	WKBPolygon elems[numElems];
 }

 WKBGeometryCollection extends WKBGeometry {
 	uint32 numElems;
 	WKBGeometry elems[numElems];
 }

See also:: WKBReader

public WKBWriter()

Creates a writer that writes Geometrys with output dimension = 2 and BIG_ENDIAN byte order

public WKBWriter(int outputDimension)

Creates a writer that writes Geometrys with the given dimension (2 or 3) for output coordinates and ByteOrderValues.BIG_ENDIAN byte order. If the input geometry has a small coordinate dimension, coordinates will be padded with Coordinate.NULL_ORDINATE .

Parameters:: outputDimension - outputDimension the coordinate dimension to output (2 or 3)

public WKBWriter(int outputDimension, boolean includeSRID)

Creates a writer that writes Geometrys with the given dimension (2 or 3) for output coordinates and ByteOrderValues.BIG_ENDIAN byte order. This constructor also takes a flag to control whether srid information will be written. If the input geometry has a smaller coordinate dimension, coordinates will be padded with Coordinate.NULL_ORDINATE .

Parameters:: outputDimension - outputDimension the coordinate dimension to output (2 or 3); includeSRID - includeSRID indicates whether SRID should be written

public WKBWriter(int outputDimension, int byteOrder)

Creates a writer that writes Geometrys with the given dimension (2 or 3) for output coordinates and byte order If the input geometry has a small coordinate dimension, coordinates will be padded with Coordinate.NULL_ORDINATE .

Parameters:: outputDimension - outputDimension the coordinate dimension to output (2 or 3); byteOrder - byteOrder the byte ordering to use

public WKBWriter(int outputDimension, int byteOrder, boolean includeSRID)

Creates a writer that writes Geometrys with the given dimension (2 or 3) for output coordinates and byte order. This constructor also takes a flag to control whether srid information will be written. If the input geometry has a small coordinate dimension, coordinates will be padded with Coordinate.NULL_ORDINATE .

Parameters:: outputDimension - outputDimension the coordinate dimension to output (2 or 3); byteOrder - byteOrder the byte ordering to use; includeSRID - includeSRID indicates whether SRID should be written

public static String bytesToHex(byte[] bytes)

Converts a byte array to a hexadecimal string.

Parameters:: bytes - bytes

Returns:: a string of hexadecimal digits

public static String toHex(byte[] bytes)

Converts a byte array to a hexadecimal string.

Parameters:: bytes - bytes a byte array

Returns:: a string of hexadecimal digits

public byte[] write(Geometry geom)

Writes a Geometry into a byte array.

Parameters:: geom - geom the geometry to write

Returns:: the byte array containing the WKB

public void write(Geometry geom, OutStream os)

Writes a Geometry to an OutStream.

Parameters:: geom - geom the geometry to write; os - os the out stream to write to

Throws:: IOException - IOException if an I/O error occurs