Merge pull request #114 from twpayne/ewkb

Add ToEWKBWithSRID

context.go

@@ -14,6 +14,7 @@ import (
 type Context struct {
 	sync.Mutex
 	handle              C.GEOSContextHandle_t
+	ewkbWriter          *C.struct_GEOSWKBWriter_t
 	geoJSONReader       *C.struct_GEOSGeoJSONReader_t
 	geoJSONWriter       *C.struct_GEOSGeoJSONWriter_t
 	wkbReader           *C.struct_GEOSWKBReader_t

geom.go

@@ -262,6 +262,22 @@ func (g *Geom) String() string {
 	return g.ToWKT()
 }
 
+// ToEWKB returns g in Extended WKB format with its SRID.
+func (g *Geom) ToEWKBWithSRID() []byte {
+	g.mustNotBeDestroyed()
+	g.context.Lock()
+	defer g.context.Unlock()
+	if g.context.ewkbWriter == nil {
+		g.context.ewkbWriter = C.GEOSWKBWriter_create_r(g.context.handle)
+		C.GEOSWKBWriter_setFlavor_r(g.context.handle, g.context.ewkbWriter, C.GEOS_WKB_EXTENDED)
+		C.GEOSWKBWriter_setIncludeSRID_r(g.context.handle, g.context.ewkbWriter, 1)
+	}
+	var size C.size_t
+	ewkbCBuf := C.GEOSWKBWriter_write_r(g.context.handle, g.context.ewkbWriter, g.geom, &size)
+	defer C.GEOSFree_r(g.context.handle, unsafe.Pointer(ewkbCBuf))
+	return C.GoBytes(unsafe.Pointer(ewkbCBuf), C.int(size))
+}
+
 // ToGeoJSON returns g in GeoJSON format.
 func (g *Geom) ToGeoJSON(indent int) string {
 	g.mustNotBeDestroyed()

geom_test.go

@@ -461,6 +461,26 @@ func TestWKXRoundTrip(t *testing.T) {
 	}
 }
 
+func TestEWKBWithSRIDRoundTrip(t *testing.T) {
+	c := geos.NewContext()
+	for _, tc := range []struct {
+		name string
+		geom *geos.Geom
+	}{
+		{
+			name: "point",
+			geom: mustNewGeomFromWKT(t, c, "POINT (0 0)").SetSRID(4326),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			newG, err := c.NewGeomFromWKB(tc.geom.ToEWKBWithSRID())
+			assert.NoError(t, err)
+			assert.True(t, newG.Equals(tc.geom))
+			assert.Equal(t, tc.geom.SRID(), newG.SRID())
+		})
+	}
+}
+
 func TestGeomRelate(t *testing.T) {
 	c := geos.NewContext()
 	g1 := mustNewGeomFromWKT(t, c, "POINT (0 0)")

geometry/binary.go

@@ -13,7 +13,7 @@ func NewGeometryFromWKB(wkb []byte) (*Geometry, error) {
 
 // MarshalBinary implements encoding.BinaryMarshaler.
 func (g *Geometry) MarshalBinary() ([]byte, error) {
-	return g.Geom.ToWKB(), nil
+	return g.Geom.ToEWKBWithSRID(), nil
 }
 
 // UnmarshalBinary implements encoding.BinaryUnmarshaler.

geometry/gob.go

@@ -18,5 +18,5 @@ func (g *Geometry) GobEncode() ([]byte, error) {
 	if g.Geom == nil {
 		return nil, nil
 	}
-	return g.Geom.ToWKB(), nil
+	return g.Geom.ToEWKBWithSRID(), nil
 }

geometry/sql.go

@@ -45,5 +45,5 @@ func (g Geometry) Value() (driver.Value, error) {
 	if g.Geom == nil {
 		return nil, nil
 	}
-	return hex.EncodeToString(g.Geom.ToWKB()), nil
+	return hex.EncodeToString(g.Geom.ToEWKBWithSRID()), nil
 }