Add ol.geom.reverseFlatCoordinates

src/ol/geom/geometry.js

@@ -486,3 +486,24 @@ ol.geom.inflateCoordinatesss =
   coordinatesss.length = i;
   return coordinatesss;
 };
+
+
+/**
+ * @param {Array.<number>} flatCoordinates Flat coordinates.
+ * @param {number} offset Offset.
+ * @param {number} end End.
+ * @param {number} stride Stride.
+ */
+ol.geom.reverseFlatCoordinates =
+    function(flatCoordinates, offset, end, stride) {
+  while (offset < end - stride) {
+    var i;
+    for (i = 0; i < stride; ++i) {
+      var tmp = flatCoordinates[offset + i];
+      flatCoordinates[offset + i] = flatCoordinates[end - stride + i];
+      flatCoordinates[end - stride + i] = tmp;
+    }
+    offset += stride;
+    end -= stride;
+  }
+};

test/spec/ol/geom/geom.test.js

@@ -54,4 +54,127 @@ describe('ol.geom', function() {
 
   });
 
+  describe('ol.geom.reverseFlatCoordinates', function() {
+
+    describe('with a stride of 2', function() {
+
+      it('can reverse empty flat coordinates', function() {
+        var flatCoordinates = [];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 2);
+        expect(flatCoordinates).to.be.empty();
+      });
+
+      it('can reverse one flat coordinates', function() {
+        var flatCoordinates = [1, 2];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 2);
+        expect(flatCoordinates).to.eql([1, 2]);
+      });
+
+      it('can reverse two flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 2);
+        expect(flatCoordinates).to.eql([3, 4, 1, 2]);
+      });
+
+      it('can reverse three flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 2);
+        expect(flatCoordinates).to.eql([5, 6, 3, 4, 1, 2]);
+      });
+
+      it('can reverse four flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6, 7, 8];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 2);
+        expect(flatCoordinates).to.eql([7, 8, 5, 6, 3, 4, 1, 2]);
+      });
+
+    });
+
+    describe('with a stride of 3', function() {
+
+      it('can reverse empty flat coordinates', function() {
+        var flatCoordinates = [];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 3);
+        expect(flatCoordinates).to.be.empty();
+      });
+
+      it('can reverse one flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 3);
+        expect(flatCoordinates).to.eql([1, 2, 3]);
+      });
+
+      it('can reverse two flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 3);
+        expect(flatCoordinates).to.eql([4, 5, 6, 1, 2, 3]);
+      });
+
+      it('can reverse three flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 3);
+        expect(flatCoordinates).to.eql([7, 8, 9, 4, 5, 6, 1, 2, 3]);
+      });
+
+      it('can reverse four flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 3);
+        expect(flatCoordinates).to.eql([10, 11, 12, 7, 8, 9, 4, 5, 6, 1, 2, 3]);
+      });
+
+    });
+
+    describe('with a stride of 4', function() {
+
+      it('can reverse empty flat coordinates', function() {
+        var flatCoordinates = [];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 4);
+        expect(flatCoordinates).to.be.empty();
+      });
+
+      it('can reverse one flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 4);
+        expect(flatCoordinates).to.eql([1, 2, 3, 4]);
+      });
+
+      it('can reverse two flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6, 7, 8];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 4);
+        expect(flatCoordinates).to.eql([5, 6, 7, 8, 1, 2, 3, 4]);
+      });
+
+      it('can reverse three flat coordinates', function() {
+        var flatCoordinates = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 4);
+        expect(flatCoordinates).to.eql([9, 10, 11, 12, 5, 6, 7, 8, 1, 2, 3, 4]);
+      });
+
+      it('can reverse four flat coordinates', function() {
+        var flatCoordinates =
+            [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+        ol.geom.reverseFlatCoordinates(
+            flatCoordinates, 0, flatCoordinates.length, 4);
+        expect(flatCoordinates).to.eql(
+            [13, 14, 15, 16, 9, 10, 11, 12, 5, 6, 7, 8, 1, 2, 3, 4]);
+      });
+
+    });
+
+  });
+
 });