diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/HashValueUtils.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/HashValueUtils.java
new file mode 100644
index 0000000..6780035
--- /dev/null
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/HashValueUtils.java
@@ -0,0 +1,17 @@
+package org.projectfloodlight.openflow.types;
+
+import com.google.common.base.Preconditions;
+
+public class HashValueUtils {
+    private HashValueUtils() { }
+
+    public static long combineWithValue(long key, long value, int keyBits) {
+        Preconditions.checkArgument(keyBits >= 0 && keyBits <= 64, "keyBits must be [0,64]");
+
+        int valueBits = 64 - keyBits;
+        long valueMask = valueBits == 64 ? 0xFFFFFFFFFFFFFFFFL : (1L << valueBits) - 1;
+
+        return key ^ (value & valueMask);
+    }
+
+}