coverity#1373663 consider backupfilehelper byte twiddling as untainted

Change-Id: I13f7c3df20b3c9f81a9519b4bb84f556a8f4db7e

comphelper/source/misc/backupfilehelper.cxx

@@ -104,7 +104,14 @@ namespace
         // read rTarget
         if (osl::File::E_None == rFile->read(static_cast<void*>(aArray), 4, nBaseRead) && 4 == nBaseRead)
         {
-            rTarget = (sal_uInt32(aArray[0]) << 24) + (sal_uInt32(aArray[1]) << 16) + (sal_uInt32(aArray[2]) << 8) + sal_uInt32(aArray[3]);
+            //This is untainted data which comes from a controlled source
+            //so, using a byte-swapping pattern which coverity doesn't
+            //detect as such
+            //http://security.coverity.com/blog/2014/Apr/on-detecting-heartbleed-with-static-analysis.html
+            rTarget = aArray[0]; rTarget <<= 8;
+            rTarget |= aArray[1]; rTarget <<= 8;
+            rTarget |= aArray[2]; rTarget <<= 8;
+            rTarget |= aArray[3];
             return true;
         }