Function gzwrite 

pub unsafe extern "C" fn gzwrite(
    file: gzFile,
    buf: *const c_void,
    len: c_uint,
) -> c_int

Available on crate feature gz only.

Compress and write the len uncompressed bytes at buf to file.

Returns

• The number of uncompressed bytes written, on success.
• Or 0 in case of error.

Safety

• file, if non-null, must be an open file handle obtained from gzopen or gzdopen.
• buf must point to at least len bytes of readable memory.