Index: /trunk/FACT++/src/tools.h
===================================================================
--- /trunk/FACT++/src/tools.h	(revision 18187)
+++ /trunk/FACT++/src/tools.h	(revision 18188)
@@ -18,4 +18,35 @@
     std::vector<std::string> Split(const std::string &, const std::string &);
     std::string Uncomment(const std::string &opt);
+
+    template<typename T>
+        uint16_t Fletcher16(const T *t, size_t cnt)
+    {
+        const uint8_t *data = reinterpret_cast<const uint8_t*>(t);
+
+        size_t bytes = cnt*sizeof(T);
+
+        uint16_t sum1 = 0xff;
+        uint16_t sum2 = 0xff;
+
+        while (bytes) 
+        {
+            size_t tlen = bytes > 20 ? 20 : bytes;
+            bytes -= tlen;
+
+            do {
+                sum2 += sum1 += *data++;
+            } while (--tlen);
+
+            sum1 = (sum1 & 0xff) + (sum1 >> 8);
+            sum2 = (sum2 & 0xff) + (sum2 >> 8);
+        }
+
+        // Second reduction step to reduce sums to 8 bits
+        sum1 = (sum1 & 0xff) + (sum1 >> 8);
+        sum2 = (sum2 & 0xff) + (sum2 >> 8);
+
+        return sum2 << 8 | sum1;
+    }
+
 }