Function IONetworkGetDataCapacity 

pub unsafe extern "C-unwind" fn IONetworkGetDataCapacity(
    con_object: io_connect_t,
    data_handle: IONDHandle,
    capacity_p: *mut u32,
) -> IOReturn

Available on crate features libc and network only.

Get the capacity (in bytes) of a network data object.

Parameter conObject: The connection object.

Parameter dataHandle: The handle of a network data object.

Parameter capacityP: Upon success, the capacity is written to this address.

Returns: kIOReturnSuccess on success, or an error code otherwise.

Safety

capacity_p must be a valid pointer.