fixed m_status_code unset to zero.

Signed-off-by: Jack <jack.wgm@gmail.com>
fixed some bugs

Signed-off-by: Jack <jack.wgm@gmail.com>
fixed already downloaded still run.

Signed-off-by: Jack <jack.wgm@gmail.com>
add is_full to class rangefield

Signed-off-by: Jack <jack.wgm@gmail.com>
improve multi_download on exit

Signed-off-by: Jack <jack.wgm@gmail.com>
fixed calc object done

Signed-off-by: Jack <jack.wgm@gmail.com>