ensure DirectBuffer.CheckLimit can be inlined (#840)

Author: szehetner

csharp/sbe-dll/DirectBuffer.cs

@@ -120,7 +120,7 @@ public int Capacity
         {
             get { return _capacity; }
         }
-
+        
         /// <summary>
         /// Check that a given limit is not greater than the capacity of a buffer from a given offset.
         /// </summary>
@@ -129,17 +129,22 @@ public void CheckLimit(int limit)
         {
             if (limit > _capacity)
             {
-                if (bufferOverflow == null)
-                    throw new IndexOutOfRangeException(string.Format("limit={0} is beyond capacity={1}", limit, _capacity));
+                TryResizeBuffer(limit);
+            }
+        }
 
-                var newBuffer = bufferOverflow(_capacity, limit);
+        private void TryResizeBuffer(int limit)
+        {
+            if (bufferOverflow == null)
+                throw new IndexOutOfRangeException(string.Format("limit={0} is beyond capacity={1}", limit, _capacity));
 
-                if (newBuffer == null)
-                    throw new IndexOutOfRangeException(string.Format("limit={0} is beyond capacity={1}", limit, _capacity));
+            var newBuffer = bufferOverflow(_capacity, limit);
 
-                Marshal.Copy((IntPtr)_pBuffer, newBuffer, 0, _capacity);
-                Wrap(newBuffer);
-            }
+            if (newBuffer == null)
+                throw new IndexOutOfRangeException(string.Format("limit={0} is beyond capacity={1}", limit, _capacity));
+
+            Marshal.Copy((IntPtr)_pBuffer, newBuffer, 0, _capacity);
+            Wrap(newBuffer);
         }
 
         /// <summary>