Add ol.structs.Buffer#getSplit32

src/ol/structs/buffer.js

@@ -22,6 +22,12 @@ ol.structs.BufferUsage = {
 ol.BUFFER_REPLACE_UNUSED_ENTRIES_WITH_NANS = goog.DEBUG;
 
 
+/**
+ * @typedef {{high: Float32Array, low: Float32Array}}
+ */
+ol.structs.BufferSplit32;
+
+
 
 /**
  * @constructor
@@ -62,6 +68,18 @@ ol.structs.Buffer = function(opt_arr, opt_used, opt_usage) {
     }
   }
 
+  /**
+   * @private
+   * @type {?ol.structs.BufferSplit32}
+   */
+  this.split32_ = null;
+
+  /**
+   * @private
+   * @type {ol.structs.IntegerSet}
+   */
+  this.split32DirtySet_ = null;
+
   /**
    * @private
    * @type {number}
@@ -146,6 +164,45 @@ ol.structs.Buffer.prototype.getFreeSet = function() {
 };
 
 
+/**
+ * Splits this buffer into two Float32Arrays.
+ * @see http://blogs.agi.com/insight3d/index.php/2008/09/03/precisions-precisions/
+ * @return {ol.structs.BufferSplit32} Split.
+ */
+ol.structs.Buffer.prototype.getSplit32 = function() {
+  var arr = this.arr_;
+  var n = arr.length;
+  if (goog.isNull(this.split32DirtySet_)) {
+    this.split32DirtySet_ = new ol.structs.IntegerSet([0, n]);
+    this.addDirtySet(this.split32DirtySet_);
+  }
+  if (goog.isNull(this.split32_)) {
+    this.split32_ = {
+      high: new Float32Array(n),
+      low: new Float32Array(n)
+    };
+  }
+  var split32 = this.split32_;
+  this.split32DirtySet_.forEachRange(function(start, stop) {
+    var doubleHigh, i, value;
+    for (i = start; i < stop; ++i) {
+      value = arr[i];
+      if (value < 0) {
+        doubleHigh = 65536 * Math.floor(-value / 65536);
+        split32.high[i] = -doubleHigh;
+        split32.low[i] = value + doubleHigh;
+      } else {
+        doubleHigh = 65536 * Math.floor(value / 65536);
+        split32.high[i] = doubleHigh;
+        split32.low[i] = value - doubleHigh;
+      }
+    }
+  });
+  this.split32DirtySet_.clear();
+  return this.split32_;
+};
+
+
 /**
  * @return {number} Usage.
  */

test/spec/ol/structs/buffer.test.js

@@ -220,6 +220,45 @@ describe('ol.structs.Buffer', function() {
 
   });
 
+  describe('with a populated instance', function() {
+
+    var b;
+    beforeEach(function() {
+      b = new ol.structs.Buffer([1234567.1234567, -7654321.7654321]);
+    });
+
+    describe('getSplit32', function() {
+
+      it('returns the expected value', function() {
+        var split32 = b.getSplit32();
+        expect(split32.high).to.be.a(Float32Array);
+        expect(split32.low).to.be.a(Float32Array);
+        expect(split32.high).to.have.length(2);
+        expect(split32.low).to.have.length(2);
+        expect(split32.high[0]).to.roughlyEqual(1179648.0, 1e1);
+        expect(split32.low[0]).to.roughlyEqual(54919.12345670001, 1e-2);
+        expect(split32.high[1]).to.roughlyEqual(-7602176.0, 1e1);
+        expect(split32.low[1]).to.roughlyEqual(-52145.76543209981, 1e-2);
+      });
+
+      it('tracks updates', function() {
+        b.getSplit32();
+        b.getArray()[0] = 0;
+        b.markDirty(1, 0);
+        var split32 = b.getSplit32();
+        expect(split32.high).to.be.a(Float32Array);
+        expect(split32.low).to.be.a(Float32Array);
+        expect(split32.high).to.have.length(2);
+        expect(split32.low).to.have.length(2);
+        expect(split32.high[0]).to.be(0);
+        expect(split32.low[0]).to.be(0);
+        expect(split32.high[1]).to.roughlyEqual(-7602176.0, 1e1);
+        expect(split32.low[1]).to.roughlyEqual(-52145.76543209981, 1e-2);
+      });
+
+    });
+  });
+
   describe('usage tests', function() {
 
     it('allows multiple adds and removes', function() {