Function otNetDataGetMaxLength 

pub unsafe extern "C" fn otNetDataGetMaxLength(
    aInstance: *mut otInstance,
) -> u8

Get the maximum observed length of the Thread Network Data since OT stack initialization or since the last call to otNetDataResetMaxLength().

@param[in] aInstance A pointer to an OpenThread instance.

@return The maximum length of the Network Data (high water mark for Network Data length).