Function enqueue_map_buffer 

pub unsafe fn enqueue_map_buffer(
    command_queue: cl_command_queue,
    buffer: cl_mem,
    blocking_map: cl_bool,
    map_flags: cl_map_flags,
    offset: size_t,
    size: size_t,
    buffer_ptr: &mut cl_mem,
    num_events_in_wait_list: cl_uint,
    event_wait_list: *const cl_event,
) -> Result<cl_event, cl_int>

Note: returns event NOT pointer for consistency with other enqueue functions. The buffer pointer is returned in the buffer_ptr mutable reference.