--- old/src/java.base/share/classes/jdk/internal/misc/Unsafe.java	2016-02-05 13:30:06.917439881 -0800
+++ new/src/java.base/share/classes/jdk/internal/misc/Unsafe.java	2016-02-05 13:30:06.701436118 -0800
@@ -458,9 +458,19 @@
         copyMemory(null, srcAddress, null, destAddress, bytes);
     }
 
+    private boolean isPrimitiveArray(Class<?> c) {
+        Class<?> componentType = c.getComponentType();
+        return componentType != null && componentType.isPrimitive();
+    }
+
+    private native void copySwapMemory0(Object srcBase, long srcOffset,
+                                        Object destBase, long destOffset,
+                                        long bytes, long elemSize);
+        
+
     /**
-     * Copies all elements from one block of memory to another block, byte swapping the
-     * elements on the fly.
+     * Copies all elements from one block of memory to another block,
+     * *unconditionally* byte swapping the elements on the fly.
      *
      * <p>This method determines each block's base address by means of two parameters,
      * and so it provides (in effect) a <em>double-register</em> addressing mode,
@@ -469,9 +479,42 @@
      *
      * @since 9
      */
-    public native void copySwapMemory(Object srcBase, long srcOffset,
-                                      Object destBase, long destOffset,
-                                      long bytes, long elemSize);
+    public void copySwapMemory(Object srcBase, long srcOffset,
+                               Object destBase, long destOffset,
+                               long bytes, long elemSize) {
+        if (bytes < 0 || srcOffset < 0 || destOffset < 0) {
+            throw new IllegalArgumentException();
+        }
+        if (elemSize != 2 && elemSize != 4 && elemSize != 8) {
+            throw new IllegalArgumentException();
+        }
+        if (bytes % elemSize != 0) {
+            throw new IllegalArgumentException();
+        }
+        if ((srcBase == null && srcOffset == 0) ||
+            (destBase == null && destOffset == 0)) {
+            throw new NullPointerException();
+        }
+
+        // Must be off-heap, or primitive heap arrays
+        if ((srcBase != null && !isPrimitiveArray(srcBase.getClass())) ||
+            (destBase != null && !isPrimitiveArray(destBase.getClass()))) {
+            throw new IllegalArgumentException();
+        }
+
+        // Sanity check size and offsets on 32-bit platforms. Most
+        // significant 32 bits must be zero.
+        if (ADDRESS_SIZE == 4 &&
+            (bytes >>> 32 != 0 || srcOffset >>> 32 != 0 || destOffset >>> 32 != 0)) {
+            throw new IllegalArgumentException();
+        }
+
+        if (bytes == 0) {
+            return;
+        }
+
+        copySwapMemory0(srcBase, srcOffset, destBase, destOffset, bytes, elemSize);
+    }
 
    /**
      * Copies all elements from one block of memory to another block, byte swapping the