/// Corruption error
    #[error("Corruption error: offset {0} is past the end of the file")]
    Corrupt(u64),

        if off > self.length {
            return Err(Error::Corrupt(off))
        }

    pub(crate) size: u64,

        };
        // Load the header from the root page of this transaction, and
        // get its length. This is used as a check to avoid loading a
        // page past the end of the file.
        let size = unsafe {
            let next_page_ptr = env_.mmaps.lock()[0].ptr.offset((root * PAGE_SIZE) as isize);
            let header = GlobalHeader::from_le(&*(next_page_ptr as *const GlobalHeader));
            header.length

        Ok(Txn { env, root })

        Ok(Txn { env, root, size })

        if off > self.size {
            return Err(Error::Corrupt(off))
        }