Method read

block/src/qcow/mod.rs:2030–2052

(&mut self, buf: &mut [u8])

impl Read for QcowFile {
    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
        let address: u64 = self.current_offset;
        let read_count: usize = self.limit_range_file(address, buf.len());

        let mut nread: usize = 0;
        while nread < read_count {
            let curr_addr = address + nread as u64;
            let count = self.limit_range_cluster(curr_addr, read_count - nread);

            if (self.file_read(curr_addr, count, &mut buf[nread..(nread + count)])?).is_some() {
                // Data is successfully read from the cluster
            } else if let Some(backing) = self.backing_file.as_mut() {
                backing.read_at(curr_addr, &mut buf[nread..(nread + count)])?;
            } else {
                // Previously unwritten region, return zeros
                buf[nread..(nread + count)].fill(0);
            }

            nread += count;
        }
        self.current_offset += read_count as u64;
        Ok(read_count)
    }
}

impl Seek for QcowFile {