From db2f805ed902822c300f1a0abb355bbc49e284a7 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Thu, 30 May 2013 20:05:02 +0200
Subject: [PATCH] Return split values in a single interleaved Float32Array

---
 src/ol/structs/buffer.js            | 32 ++++++++++++-----------------
 test/spec/ol/structs/buffer.test.js | 28 +++++++++++--------------
 2 files changed, 25 insertions(+), 35 deletions(-)

diff --git a/src/ol/structs/buffer.js b/src/ol/structs/buffer.js
index 65178cfb0c..91848768c2 100644
--- a/src/ol/structs/buffer.js
+++ b/src/ol/structs/buffer.js
@@ -22,12 +22,6 @@ ol.structs.BufferUsage = {
 ol.BUFFER_REPLACE_UNUSED_ENTRIES_WITH_NANS = goog.DEBUG;
 
 
-/**
- * @typedef {{high: Float32Array, low: Float32Array}}
- */
-ol.structs.BufferSplit32;
-
-
 
 /**
  * @constructor
@@ -70,7 +64,7 @@ ol.structs.Buffer = function(opt_arr, opt_used, opt_usage) {
 
   /**
    * @private
-   * @type {?ol.structs.BufferSplit32}
+   * @type {?Float32Array}
    */
   this.split32_ = null;
 
@@ -165,9 +159,12 @@ ol.structs.Buffer.prototype.getFreeSet = function() {
 
 
 /**
- * Splits this buffer into two Float32Arrays.
+ * Returns a Float32Array twice the length of the buffer containing each value
+ * split into two 32-bit floating point values that, when added together,
+ * approximate the original value. Even indicies contain the high bits, odd
+ * indicies contain the low bits.
  * @see http://blogs.agi.com/insight3d/index.php/2008/09/03/precisions-precisions/
- * @return {ol.structs.BufferSplit32} Split.
+ * @return {Float32Array} Split.
  */
 ol.structs.Buffer.prototype.getSplit32 = function() {
   var arr = this.arr_;
@@ -177,24 +174,21 @@ ol.structs.Buffer.prototype.getSplit32 = function() {
     this.addDirtySet(this.split32DirtySet_);
   }
   if (goog.isNull(this.split32_)) {
-    this.split32_ = {
-      high: new Float32Array(n),
-      low: new Float32Array(n)
-    };
+    this.split32_ = new Float32Array(2 * n);
   }
   var split32 = this.split32_;
   this.split32DirtySet_.forEachRange(function(start, stop) {
-    var doubleHigh, i, value;
-    for (i = start; i < stop; ++i) {
+    var doubleHigh, i, j, value;
+    for (i = start, j = 2 * start; i < stop; ++i, j += 2) {
       value = arr[i];
       if (value < 0) {
         doubleHigh = 65536 * Math.floor(-value / 65536);
-        split32.high[i] = -doubleHigh;
-        split32.low[i] = value + doubleHigh;
+        split32[j] = -doubleHigh;
+        split32[j + 1] = value + doubleHigh;
       } else {
         doubleHigh = 65536 * Math.floor(value / 65536);
-        split32.high[i] = doubleHigh;
-        split32.low[i] = value - doubleHigh;
+        split32[j] = doubleHigh;
+        split32[j + 1] = value - doubleHigh;
       }
     }
   });
diff --git a/test/spec/ol/structs/buffer.test.js b/test/spec/ol/structs/buffer.test.js
index 956364c706..d91e37a4d7 100644
--- a/test/spec/ol/structs/buffer.test.js
+++ b/test/spec/ol/structs/buffer.test.js
@@ -231,14 +231,12 @@ describe('ol.structs.Buffer', 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);
+        expect(split32).to.be.a(Float32Array);
+        expect(split32).to.have.length(4);
+        expect(split32[0]).to.roughlyEqual(1179648.0, 1e1);
+        expect(split32[1]).to.roughlyEqual(54919.12345670001, 1e-2);
+        expect(split32[2]).to.roughlyEqual(-7602176.0, 1e1);
+        expect(split32[3]).to.roughlyEqual(-52145.76543209981, 1e-2);
       });
 
       it('tracks updates', function() {
@@ -246,14 +244,12 @@ describe('ol.structs.Buffer', function() {
         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);
+        expect(split32).to.be.a(Float32Array);
+        expect(split32).to.have.length(4);
+        expect(split32[0]).to.be(0);
+        expect(split32[1]).to.be(0);
+        expect(split32[2]).to.roughlyEqual(-7602176.0, 1e1);
+        expect(split32[3]).to.roughlyEqual(-52145.76543209981, 1e-2);
       });
 
     });