Box2DX.Collision.Collision.CollideEdgeAndCircle C# (CSharp) Method

        public static void CollideEdgeAndCircle(ref Manifold manifold, EdgeShape edge, Transform transformA, CircleShape circle, Transform transformB)
        {
            manifold.PointCount = 0;
            Vector2 cLocal = Common.Math.MulT(transformA, Common.Math.Mul(transformB, circle._position));
            Vector2 normal = edge._normal;
            Vector2 v1 = edge._v1;
            Vector2 v2 = edge._v2;
            float radius = edge._radius + circle._radius;

            // Barycentric coordinates
            float u1 = Vector2.Dot(cLocal - v1, v2 - v1);
            float u2 = Vector2.Dot(cLocal - v2, v1 - v2);

            if (u1 <= 0.0f)
            {
                // Behind v1
                if ((cLocal- v1).sqrMagnitude > radius * radius)
                {
                    return;
                }

                manifold.PointCount = 1;
                manifold.Type = ManifoldType.FaceA;
                manifold.LocalPlaneNormal = cLocal - v1;
                manifold.LocalPlaneNormal.Normalize();
                manifold.LocalPoint = v1;
                manifold.Points[0].LocalPoint = circle._position;
                manifold.Points[0].ID.Key = 0;
            }
            else if (u2 <= 0.0f)
            {
                // Ahead of v2
                if ((cLocal- v2).sqrMagnitude > radius * radius)
                {
                    return;
                }

                manifold.PointCount = 1;
                manifold.Type = ManifoldType.FaceA;
                manifold.LocalPlaneNormal = cLocal - v2;
                manifold.LocalPlaneNormal.Normalize();
                manifold.LocalPoint = v2;
                manifold.Points[0].LocalPoint = circle._position;
                manifold.Points[0].ID.Key = 0;
            }
            else
            {
                float separation = Vector2.Dot(cLocal - v1, normal);
                if (separation < -radius || radius < separation)
                {
                    return;
                }

                manifold.PointCount = 1;
                manifold.Type = ManifoldType.FaceA;
                manifold.LocalPlaneNormal = separation < 0.0f ? -normal : normal;
                manifold.LocalPoint = 0.5f * (v1 + v2);
                manifold.Points[0].LocalPoint = circle._position;
                manifold.Points[0].ID.Key = 0;
            }
        }