function xFormatByteSize(const bytes: Longint): string;
 const
   B = 1; //byte
   KB = 1024 * B; //kilobyte
   MB = 1024 * KB; //megabyte
   GB = 1024 * MB; //gigabyte
begin
   if bytes > GB then
     result := FormatFloat('#.## GB', bytes / GB)
   else
     if bytes > MB then
       result := FormatFloat('#.## MB', bytes / MB)
     else
       if bytes > KB then
         result := FormatFloat('#.## KB', bytes / KB)
       else
         result := FormatFloat('#.## bytes', bytes) ;
 end;


function xFileSize(fileName : wideString) : Int64;
 var
   sr : TSearchRec;
 begin


   if FindFirst(fileName, faAnyFile, sr ) = 0 then
      result := Int64(sr.FindData.nFileSizeHigh) shl Int64(32) + Int64(sr.FindData.nFileSizeLow)
   else
      result := -1;


   FindClose(sr) ;


end;