Method new_from_header

block/src/qcow/mod.rs:765–794

(
        mut file: RawFile,
        header: &QcowHeader,
        sparse: bool,
    )

    }

    fn new_from_header(
        mut file: RawFile,
        header: &QcowHeader,
        sparse: bool,
    ) -> BlockResult<QcowFile> {
        file.rewind()
            .map_err(|e| BlockError::new(BlockErrorKind::Io, Error::SeekingFile(e)))?;
        header
            .write_to(&mut file)
            .map_err(|e| BlockError::new(BlockErrorKind::Io, e))?;

        let mut qcow = Self::from_with_nesting_depth(file, MAX_NESTING_DEPTH, sparse)?;

        // Set the refcount for each refcount table cluster.
        let cluster_size = 0x01u64 << qcow.header.cluster_bits;
        let refcount_table_base = qcow.header.refcount_table_offset;
        let end_cluster_addr =
            refcount_table_base + u64::from(qcow.header.refcount_table_clusters) * cluster_size;

        let mut cluster_addr = 0;
        while cluster_addr < end_cluster_addr {
            let mut unref_clusters = qcow.set_cluster_refcount(cluster_addr, 1).map_err(|e| {
                BlockError::new(BlockErrorKind::Io, Error::SettingRefcountRefcount(e))
            })?;
            qcow.unref_clusters.append(&mut unref_clusters);
            cluster_addr += cluster_size;
        }

        Ok(qcow)
    }

    #[cfg(test)]
    pub fn set_backing_file(&mut self, backing: Option<Box<Self>>) {