Simplifying ranges structure by adding compiler hints

In JavaScript, keys of object literals are always strings, and
internal type conversions are performed. Now if we tell the
compiler that keys are numbers, we get inconsistent types when
iterating through keys. So instead we set the key type to string
and do a type cast to make the compiler happy. Note that we
could also do toString() instead of a type cast, but it would
add a performance penalty (see
http://jsperf.com/internal-type-conversion-vs-tostring-for-object-keys).

src/ol/geom2/linestringcollection.js

@@ -19,7 +19,7 @@ ol.geom2.LineString;
  * This is an internal class that will be removed from the API.
  * @constructor
  * @param {ol.structs.Buffer} buf Buffer.
- * @param {Object.<number, Array.<number>>=} opt_ranges Ranges.
+ * @param {Object.<string, number>=} opt_ranges Ranges.
  * @param {number=} opt_dim Dimension.
  */
 ol.geom2.LineStringCollection = function(buf, opt_ranges, opt_dim) {
@@ -30,7 +30,7 @@ ol.geom2.LineStringCollection = function(buf, opt_ranges, opt_dim) {
   this.buf = buf;
 
   /**
-   * @type {Object.<number, Array.<number>>}
+   * @type {Object.<string, number>}
    */
   this.ranges = goog.isDef(opt_ranges) ? opt_ranges : {};
 
@@ -79,7 +79,7 @@ ol.geom2.LineStringCollection.pack =
   }
   capacity *= dim;
   var arr = new Array(capacity);
-  /** @type {Object.<number, Array.<number>>} */
+  /** @type {Object.<string, number>} */
   var ranges = {};
   var offset = 0;
   var start;
@@ -87,7 +87,7 @@ ol.geom2.LineStringCollection.pack =
     goog.asserts.assert(unpackedLineStrings[i].length > 1);
     start = offset;
     offset = ol.geom2.packPoints(arr, offset, unpackedLineStrings[i], dim);
-    ranges[start] = [start, offset];
+    ranges[/** @type {string} */ (start)] = offset;
   }
   goog.asserts.assert(offset <= capacity);
   var buf = new ol.structs.Buffer(arr, offset);
@@ -103,7 +103,7 @@ ol.geom2.LineStringCollection.prototype.add = function(lineString) {
   var n = lineString.length * this.dim;
   var offset = this.buf.allocate(n);
   goog.asserts.assert(offset != -1);
-  this.ranges[offset] = [offset, offset + n];
+  this.ranges[/** @type {string} */ (offset)] = offset + n;
   ol.geom2.packPoints(this.buf.getArray(), offset, lineString, this.dim);
   return offset;
 };
@@ -115,9 +115,9 @@ ol.geom2.LineStringCollection.prototype.add = function(lineString) {
  */
 ol.geom2.LineStringCollection.prototype.get = function(offset) {
   goog.asserts.assert(offset in this.ranges);
-  var range = this.ranges[offset];
+  var range = this.ranges[/** @type {string} */ (offset)];
   return ol.geom2.unpackPoints(
-      this.buf.getArray(), range[0], range[1], this.dim);
+      this.buf.getArray(), offset, range, this.dim);
 };
 
 
@@ -147,11 +147,12 @@ ol.geom2.LineStringCollection.prototype.getIndices = function() {
   goog.array.sort(offsets);
   var n = offsets.length;
   var indices = [];
-  var i, j, range, stop;
+  var i, j, range, offset, stop;
   for (i = 0; i < n; ++i) {
-    range = this.ranges[offsets[i]];
+    offset = offsets[i];
-    stop = range[1] / dim - 1;
+    range = this.ranges[offset];
-    for (j = range[0] / dim; j < stop; ++j) {
+    stop = range / dim - 1;
+    for (j = offset / dim; j < stop; ++j) {
       indices.push(j, j + 1);
     }
   }
@@ -164,9 +165,9 @@ ol.geom2.LineStringCollection.prototype.getIndices = function() {
  */
 ol.geom2.LineStringCollection.prototype.remove = function(offset) {
   goog.asserts.assert(offset in this.ranges);
-  var range = this.ranges[offset];
+  var range = this.ranges[/** @type {string} */ (offset)];
-  this.buf.remove(range[1] - range[0], range[0]);
+  this.buf.remove(range - offset, offset);
-  delete this.ranges[offset];
+  delete this.ranges[/** @type {string} */ (offset)];
 };
 
 
@@ -178,10 +179,10 @@ ol.geom2.LineStringCollection.prototype.remove = function(offset) {
 ol.geom2.LineStringCollection.prototype.set = function(offset, lineString) {
   var dim = this.dim;
   goog.asserts.assert(offset in this.ranges);
-  var range = this.ranges[offset];
+  var range = this.ranges[/** @type {string} */ (offset)];
-  if (lineString.length * dim == range[1] - range[0]) {
+  if (lineString.length * dim == range - offset) {
-    ol.geom2.packPoints(this.buf.getArray(), range[0], lineString, dim);
+    ol.geom2.packPoints(this.buf.getArray(), offset, lineString, dim);
-    this.buf.markDirty(range[1] - range[0], range[0]);
+    this.buf.markDirty(range - offset, offset);
     return offset;
   } else {
     this.remove(offset);
@@ -200,9 +201,9 @@ ol.geom2.LineStringCollection.prototype.unpack = function() {
   var i = 0;
   var offset, range;
   for (offset in this.ranges) {
-    range = this.ranges[Number(offset)];
+    range = this.ranges[offset];
     lineStrings[i++] = ol.geom2.unpackPoints(
-        this.buf.getArray(), range[0], range[1], dim);
+        this.buf.getArray(), Number(offset), range, dim);
   }
   return lineStrings;
 };

test/spec/ol/geom2/linecollection.test.js

@@ -41,8 +41,8 @@ describe('ol.geom2.LineStringCollection', function() {
           [[[0, 1], [2, 3], [4, 5]], [[6, 7], [8, 9]]]);
       expect(lsc.buf.getArray()).to.eql([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
       expect(lsc.getCount()).to.be(2);
-      expect(lsc.ranges[0]).to.eql([0, 6]);
+      expect(lsc.ranges[0]).to.be(6);
-      expect(lsc.ranges[6]).to.eql([6, 10]);
+      expect(lsc.ranges[6]).to.be(10);
       expect(lsc.dim).to.be(2);
     });
 
@@ -51,8 +51,8 @@ describe('ol.geom2.LineStringCollection', function() {
           [[[0, 1, 2], [3, 4, 5]], [[6, 7, 8], [9, 10, 11]]]);
       expect(lsc.buf.getArray()).to.eql([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
       expect(lsc.getCount()).to.be(2);
-      expect(lsc.ranges[0]).to.eql([0, 6]);
+      expect(lsc.ranges[0]).to.be(6);
-      expect(lsc.ranges[6]).to.eql([6, 12]);
+      expect(lsc.ranges[6]).to.be(12);
       expect(lsc.dim).to.be(3);
     });
 
@@ -63,8 +63,8 @@ describe('ol.geom2.LineStringCollection', function() {
           [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
       expect(lsc.buf.getArray()).to.have.length(32);
       expect(lsc.getCount()).to.be(2);
-      expect(lsc.ranges[0]).to.eql([0, 6]);
+      expect(lsc.ranges[0]).to.be(6);
-      expect(lsc.ranges[6]).to.eql([6, 10]);
+      expect(lsc.ranges[6]).to.be(10);
       expect(lsc.dim).to.be(2);
     });
 
@@ -106,7 +106,7 @@ describe('ol.geom2.LineStringCollection', function() {
         var offset = lsc.add([[0, 1], [2, 3]]);
         expect(offset).to.be(0);
         expect(lsc.getCount()).to.be(1);
-        expect(lsc.ranges[0]).to.eql([0, 4]);
+        expect(lsc.ranges[0]).to.be(4);
         expect(lsc.dim).to.be(2);
       });
 
@@ -163,8 +163,8 @@ describe('ol.geom2.LineStringCollection', function() {
         var offset2 = lsc.add([[4, 5], [6, 7]]);
         expect(offset2).to.be(4);
         expect(lsc.getCount()).to.be(2);
-        expect(lsc.ranges[0]).to.eql([0, 4]);
+        expect(lsc.ranges[0]).to.be(4);
-        expect(lsc.ranges[4]).to.eql([4, 8]);
+        expect(lsc.ranges[4]).to.be(8);
         expect(lsc.dim).to.be(2);
       });