Merge pull request #113 from twpayne/no-aliasing

Fix aliasing of coordinates in coordinate sequences

context.go

@@ -449,7 +449,7 @@ func (c *Context) newCoordsFromGEOSCoordSeq(s *C.struct_GEOSCoordSeq_t) [][]floa
 	}
 	coords := make([][]float64, 0, size)
 	for i := 0; i < int(size); i++ {
-		coord := flatCoords[i*int(dimensions) : (i+1)*int(dimensions)]
+		coord := flatCoords[i*int(dimensions) : (i+1)*int(dimensions) : (i+1)*int(dimensions)]
 		coords = append(coords, coord)
 	}
 	return coords

coordseq.go

@@ -141,7 +141,7 @@ func (s *CoordSeq) ToCoords() [][]float64 {
 	coords := make([][]float64, s.size)
 	j := 0
 	for i := 0; i < s.size; i++ {
-		coords[i] = flatCoords[j : j+s.dimensions]
+		coords[i] = flatCoords[j : j+s.dimensions : j+s.dimensions]
 		j += s.dimensions
 	}
 	return coords

coordseq_test.go

@@ -11,6 +11,12 @@ import (
 	"github.com/twpayne/go-geos"
 )
 
+func TestCoordSeqAliasing(t *testing.T) {
+	coords := geos.NewContext().NewCoordSeqFromCoords([][]float64{{0, 1}, {2, 3}}).ToCoords()
+	coords[0] = append(coords[0], 4)
+	assert.Equal(t, []float64{2, 3}, coords[1])
+}
+
 func TestCoordSeqEmpty(t *testing.T) {
 	defer runtime.GC() // Exercise finalizers.
 	c := geos.NewContext()

geom_test.go

@@ -402,6 +402,15 @@ func TestNewGeomFromGeoJSONError(t *testing.T) {
 	assert.Error(t, err)
 }
 
+func TestGeomNearestPointsAliasing(t *testing.T) {
+	c := geos.NewContext()
+	geom1 := mustNewGeomFromWKT(t, c, "POINT (0 1)")
+	geom2 := mustNewGeomFromWKT(t, c, "POINT (2 3)")
+	points := geom1.NearestPoints(geom2)
+	points[0] = append(points[0], 4)
+	assert.Equal(t, []float64{2, 3}, points[1])
+}
+
 func TestGeomToJSON(t *testing.T) {
 	geom := mustNewGeomFromWKT(t, geos.NewContext(), "POINT (1 2)")
 	assert.Equal(t, `{"type":"Point","coordinates":[1.0,2.0]}`, geom.ToGeoJSON(-1))