Function enqueue_map_buffer 

pub unsafe fn enqueue_map_buffer<T>(
    cq: &CommandQueue,
    buffer: *mut c_void,
    block: bool,
    map_flags: u64,
    offset: usize,
    len: usize,
) -> Result<*mut c_void, Error>

map_flags: Read: 1, Write: 2,

Safety

valid mem object