CSHARP-1607: Fix indexes for very large arrays.

Author: rstam

src/MongoDB.Bson.Tests/IO/ArrayElementNameAcceleratorTests.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2014 MongoDB Inc.
+/* Copyright 2010-2016 MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -36,6 +36,7 @@ public void GetElementNameBytes_should_return_expected_result(int numberOfCached
             }
         }
 
+        [Test]
         public void GetElementNameBytes_should_return_expected_result_for_boundary_conditions(
             [Values(0, 9, 10, 99, 100, 999, 1000, 9999, 10000, 99999, 100000, 999999, 1000000, 9999999, 100000000, int.MaxValue)]
             int index,

src/MongoDB.Bson/IO/ArrayElementNameAccelerator.cs

@@ -1,4 +1,4 @@
-/* Copyright 2010-2014 MongoDB Inc.
+/* Copyright 2010-2016 MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -74,26 +74,27 @@ private byte[] CreateElementNameBytes(int index)
 
             const int asciiZero = 48;
 
-            var a = (byte)(asciiZero + index % 10);
-            index = index / 10;
-            var b = (byte)(asciiZero + index % 10);
-            index = index / 10;
-            var c = (byte)(asciiZero + index % 10);
-            index = index / 10;
-            var d = (byte)(asciiZero + index % 10);
-            index = index / 10;
+            var n = index;
+            var a = (byte)(asciiZero + n % 10);
+            n = n / 10;
+            var b = (byte)(asciiZero + n % 10);
+            n = n / 10;
+            var c = (byte)(asciiZero + n % 10);
+            n = n / 10;
+            var d = (byte)(asciiZero + n % 10);
+            n = n / 10;
 
-            if (index == 0)
+            if (n == 0)
             {
                 if (d != (byte)asciiZero) { return new[] { d, c, b, a }; }
                 if (c != (byte)asciiZero) { return new[] { c, b, a }; }
                 if (b != (byte)asciiZero) { return new[] { b, a }; }
                 return new[] { a };
             }
 
-            var e = (byte)(asciiZero + index % 10);
-            index = index / 10;
-            if (index == 0) { return new[] { e, d, c, b, a }; }
+            var e = (byte)(asciiZero + n % 10);
+            n = n / 10;
+            if (n == 0) { return new[] { e, d, c, b, a }; }
 
             // really large indexes should be extremely rare and not worth optimizing further
             return Utf8Encodings.Strict.GetBytes(index.ToString());