/// <summary>
        /// Initialises a new instance of toxav.
        /// </summary>
        /// <param name="tox"></param>
        /// <param name="maxCalls"></param>
        public ToxAv(ToxHandle tox, int maxCalls)
        {
            _tox = tox;
            _toxAv = ToxAvFunctions.New(tox, maxCalls);

            if (_toxAv == null || _toxAv.IsInvalid)
                throw new Exception("Could not create a new instance of toxav.");

            MaxCalls = maxCalls;
        }

 internal static extern void SelfGetStatusMessage(ToxHandle tox, byte[] status);

 internal static extern bool FriendGetStatusMessage(ToxHandle tox, uint friendNumber, byte[] message, ref ToxErrorFriendQuery error);

 internal static extern bool FriendGetPublicKey(ToxHandle tox, uint friendNumber, byte[] publicKey, ref ToxErrorFriendGetPublicKey error);

 internal static extern ulong FriendGetLastOnline(ToxHandle tox, uint friendNumber, ref ToxErrorFriendGetLastOnline error);

 internal static extern bool FriendExists(ToxHandle tox, uint friendNumber);

 internal static extern uint FriendByPublicKey(ToxHandle tox, byte[] publicKey, ref ToxErrorFriendByPublicKey error);

 internal static extern bool SelfSetTyping(ToxHandle tox, uint friendNumber, [MarshalAs(UnmanagedType.Bool)]bool is_typing, ref ToxErrorSetTyping error);

 internal static extern void SelfSetStatusMessage(ToxHandle tox, byte[] status, uint length, ref ToxErrorSetInfo error);

 internal static extern void SelfSetStatus(ToxHandle tox, ToxUserStatus status);

 internal static extern void SelfSetNospam(ToxHandle tox, uint nospam);

 internal static extern bool SelfSetName(ToxHandle tox, byte[] name, uint length, ref ToxErrorSetInfo error);

 internal static extern ushort SelfGetUdpPort(ToxHandle tox, ref ToxErrorGetPort error);

 internal static extern uint SelfGetStatusMessageSize(ToxHandle tox);

 internal static extern uint FriendAdd(ToxHandle tox, byte[] address, byte[] message, uint length, ref ToxErrorFriendAdd error);

 internal static extern uint FriendAddNoRequest(ToxHandle tox, byte[] publicKey, ref ToxErrorFriendAdd error);

 internal static extern bool Bootstrap(ToxHandle tox, string host, ushort port, byte[] publicKey, ref ToxErrorBootstrap error);

 internal static extern bool FriendDelete(ToxHandle tox, uint friendNumber, ref ToxErrorFriendDelete error);

 internal static extern int DelGroupchat(ToxHandle tox, int groupnumber);

 internal static extern ToxConnectionStatus FriendGetConnectionStatus(ToxHandle tox, uint friendNumber, ref ToxErrorFriendQuery error);