1 files changed, 53 insertions, 0 deletions
diff --git a/vendor/github.com/golang/geo/s2/polyline_measures.go b/vendor/github.com/golang/geo/s2/polyline_measures.go
new file mode 100644
index 000000000..38ce991b5
--- /dev/null
+++ b/vendor/github.com/golang/geo/s2/polyline_measures.go
@@ -0,0 +1,53 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package s2
+
+// This file defines various measures for polylines on the sphere. These are
+// low-level methods that work directly with arrays of Points. They are used to
+// implement the methods in various other measures files.
+
+import (
+	"github.com/golang/geo/r3"
+	"github.com/golang/geo/s1"
+)
+
+// polylineLength returns the length of the given Polyline.
+// It returns 0 for polylines with fewer than two vertices.
+func polylineLength(p []Point) s1.Angle {
+	var length s1.Angle
+
+	for i := 1; i < len(p); i++ {
+		length += p[i-1].Distance(p[i])
+	}
+	return length
+}
+
+// polylineCentroid returns the true centroid of the polyline multiplied by the
+// length of the polyline. The result is not unit length, so you may wish to
+// normalize it.
+//
+// Scaling by the Polyline length makes it easy to compute the centroid
+// of several Polylines (by simply adding up their centroids).
+//
+// Note that for degenerate Polylines (e.g., AA) this returns Point(0, 0, 0).
+// (This answer is correct; the result of this function is a line integral over
+// the polyline, whose value is always zero if the polyline is degenerate.)
+func polylineCentroid(p []Point) Point {
+	var centroid r3.Vector
+	for i := 1; i < len(p); i++ {
+		centroid = centroid.Add(EdgeTrueCentroid(p[i-1], p[i]).Vector)
+	}
+	return Point{centroid}
+}