From a367850f6f7648561ebb3c078d67bd55eedc088a Mon Sep 17 00:00:00 2001
From: Oliver Tonnhofer <olt@bogosoft.com>
Date: Tue, 21 Nov 2017 09:18:44 +0100
Subject: [PATCH] writer: do not check for validity of simple polygons

Skips slow GEOS IsValid calls for polygons with only 4 corners.
They can be invalid, but its more unlikely to get simple polygons
wrong and even if, it should affect only small polygons like buildings.
---
 geom/geos/geos.go | 5 +++++
 writer/ways.go    | 5 ++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/geom/geos/geos.go b/geom/geos/geos.go
index e311b6f..559cb13 100644
--- a/geom/geos/geos.go
+++ b/geom/geos/geos.go
@@ -112,6 +112,11 @@ func (this *Geos) NumGeoms(geom *Geom) int32 {
 	return count
 }
 
+func (this *Geos) NumCoordinates(geom *Geom) int32 {
+	count := int32(C.GEOSGetNumCoordinates_r(this.v, geom.v))
+	return count
+}
+
 func (this *Geos) Geoms(geom *Geom) []*Geom {
 	count := this.NumGeoms(geom)
 	var result []*Geom
diff --git a/writer/ways.go b/writer/ways.go
index 3ba3af4..5ca184a 100644
--- a/writer/ways.go
+++ b/writer/ways.go
@@ -139,7 +139,10 @@ func (ww *WayWriter) buildAndInsert(g *geos.Geos, w *element.Way, matches []mapp
 	if isPolygon {
 		geosgeom, err = geomp.Polygon(g, way.Nodes)
 		if err == nil {
-			geosgeom, err = g.MakeValid(geosgeom)
+			if g.NumCoordinates(geosgeom) > 5 {
+				// only check for valididty for non-simple geometries
+				geosgeom, err = g.MakeValid(geosgeom)
+			}
 		}
 	} else {
 		geosgeom, err = geomp.LineString(g, way.Nodes)