message: storage-units: Use 64-bit math to calculate reffile offset
  This prevents integer overflows on 32-bit platforms.
diff: @@ -26,8 +26,8 @@ impl Reader {
  }
  pub fn getref_at_index(&mut self, index: u32) -> io::Result<Option<BlockHash>> {
  - let offset = index as usize * HASH_SIZE;
  - self.handle.seek(SeekFrom::Start(offset as u64))?;
  + let offset = (index as u64) * (HASH_SIZE as u64);
  + self.handle.seek(SeekFrom::Start(offset))?;
  self.next()
  }
  