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wkb.go
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wkb.go
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//Package wkb is for decoding ESRI's Well Known Binary (WKB) format for OGC geometry (WKBGeometry)
// sepcification at http://edndoc.esri.com/arcsde/9.1/general_topics/wkb_representation.htm
// There are a few types supported by the specification. Each general type is in it's own file.
// So, to find the implementation of Point (and MultiPoint) it will be located in the point.go
// file. Each of the basic type here adhere to the geom.Geometry interface. So, a wkb point
// is, also, a geom.Point
package wkb
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"github.com/go-spatial/geom"
"github.com/go-spatial/geom/encoding/wkb/internal/consts"
"github.com/go-spatial/geom/encoding/wkb/internal/decode"
"github.com/go-spatial/geom/encoding/wkb/internal/encode"
)
type ErrUnknownGeometryType struct {
Typ uint32
}
func (e ErrUnknownGeometryType) Error() string {
return fmt.Sprintf("Unknown Geometry Type %v", e.Typ)
}
// geometry types
// http://edndoc.esri.com/arcsde/9.1/general_topics/wkb_representation.htm
const (
Point = consts.Point
LineString = consts.LineString
Polygon = consts.Polygon
MultiPoint = consts.MultiPoint
MultiLineString = consts.MultiLineString
MultiPolygon = consts.MultiPolygon
Collection = consts.Collection
)
// DecodeBytes will attempt to decode a geometry encoded as WKB into a geom.Geometry.
func DecodeBytes(b []byte) (geo geom.Geometry, err error) {
buff := bytes.NewReader(b)
return Decode(buff)
}
// Decode will attempt to decode a geometry encoded as WKB into a geom.Geometry.
func Decode(r io.Reader) (geo geom.Geometry, err error) {
bom, typ, err := decode.ByteOrderType(r)
if err != nil {
return nil, err
}
switch typ {
case Point:
pt, err := decode.Point(r, bom)
return geom.Point(pt), err
case MultiPoint:
mpt, err := decode.MultiPoint(r, bom)
return geom.MultiPoint(mpt), err
case LineString:
ln, err := decode.LineString(r, bom)
return geom.LineString(ln), err
case MultiLineString:
mln, err := decode.MultiLineString(r, bom)
return geom.MultiLineString(mln), err
case Polygon:
pl, err := decode.Polygon(r, bom)
return geom.Polygon(pl), err
case MultiPolygon:
mpl, err := decode.MultiPolygon(r, bom)
return geom.MultiPolygon(mpl), err
case Collection:
col, err := decode.Collection(r, bom)
return col, err
default:
return nil, ErrUnknownGeometryType{typ}
}
}
func EncodeBytes(g geom.Geometry) (bs []byte, err error) {
buff := new(bytes.Buffer)
if err = Encode(buff, g); err != nil {
return nil, err
}
return buff.Bytes(), nil
}
func Encode(w io.Writer, g geom.Geometry) error {
return EncodeWithByteOrder(binary.LittleEndian, w, g)
}
func EncodeWithByteOrder(byteOrder binary.ByteOrder, w io.Writer, g geom.Geometry) error {
en := encode.Encoder{W: w, ByteOrder: byteOrder}
en.Geometry(g)
return en.Err()
}