Added wkb with srid meta data

geos/geom.go

@@ -90,12 +90,18 @@ func (g *Geometry) String() string {
 	return str
 }
 
-// WKB returns the geoemtry encoded as a Well-Known Binary (WKB).
+// WKB returns the geometry encoded as a Well-Known Binary (WKB).
 func (g *Geometry) WKB() ([]byte, error) {
 	encoder := newWkbEncoder()
 	return encoder.encode(g)
 }
 
+// EWKB returns the geometry encoded as a Well-Known Binary (WKB) with SRID meta data.
+func (g *Geometry) EWKB() ([]byte, error) {
+	encoder := newWkbEncoder()
+	return encoder.encodeEWkb(g)
+}
+
 // Hex returns the geometry as a Well-Known Binary (WKB) hex-encoded byte slice.
 func (g *Geometry) Hex() ([]byte, error) {
 	encoder := newWkbEncoder()

geos/wkb.go

@@ -79,6 +79,14 @@ func encodeWkb(e *wkbEncoder, g *Geometry, fn func(*C.GEOSWKBWriter, *C.GEOSGeom
 	return out, nil
 }
 
+func (e *wkbEncoder) encodeEWkb(g *Geometry) ([]byte, error) {
+	srid, _ := g.SRID()
+	if srid > 0 {
+		cGEOSWKBWriter_setIncludeSRID(e.w, C.char(1))
+	}
+	return encodeWkb(e, g, cGEOSWKBWriter_write)
+}
+
 func (e *wkbEncoder) encode(g *Geometry) ([]byte, error) {
 	return encodeWkb(e, g, cGEOSWKBWriter_write)
 }

geos/wkb_test.go

@@ -2,6 +2,8 @@ package geos
 
 import (
 	"bytes"
+	"encoding/hex"
+	"strings"
 	"testing"
 )
 
@@ -72,6 +74,16 @@ var wkbEncoderHexTests = []struct {
 	{"POINT(-117 35)", []byte("01010000000000000000405DC00000000000804140")},
 }
 
+var ewkbEncoderHexTests = []struct {
+	wkt  string
+	srid int
+	wkb  []byte
+}{
+	{"POINT(-117 35)", 4326, []byte("0101000020E61000000000000000405DC00000000000804140")},
+	{"POINT(-117 35)", 900913, []byte("010100002031BF0D000000000000405DC00000000000804140")},
+	{"POINT(-117 35)", 0, []byte("01010000000000000000405DC00000000000804140")},
+}
+
 func TestWkbEncoderEncodeHex(t *testing.T) {
 	wktDecoder := newWktDecoder()
 	wkbEncoder := newWkbEncoder()
@@ -85,4 +97,16 @@ func TestWkbEncoderEncodeHex(t *testing.T) {
 			t.Errorf("#%d: want %v got %v", i, string(test.wkb), string(actual))
 		}
 	}
+	for i, test := range ewkbEncoderHexTests {
+		g1 := Must(wktDecoder.decode(test.wkt))
+		g1.SetSRID(test.srid)
+		eg1, err := wkbEncoder.encodeEWkb(g1)
+		if err != nil {
+			panic(err)
+		}
+		actual := []byte(strings.ToUpper(hex.EncodeToString(eg1)))
+		if !bytes.Equal(actual, test.wkb) {
+			t.Errorf("#%d: want %v got %v", i, string(test.wkb), string(actual))
+		}
+	}
 }