internal delegate IntPtr Alloc()

in sources/Google.Solutions.Ssh/Native/NativeMethods.cs [180:347]
110 lines of code
1 McCabe index (conditional complexity)

        internal delegate IntPtr Alloc(
            IntPtr size,
            IntPtr context);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        internal delegate IntPtr Realloc(
            IntPtr ptr,
            IntPtr size,
            IntPtr context);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        internal delegate void Free(
            IntPtr ptr,
            IntPtr context);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Libssh2SessionHandle libssh2_session_init_ex(
            Alloc alloc,
            Free free,
            Realloc realloc,
            IntPtr context);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Int32 libssh2_free(
            Libssh2SessionHandle session,
            IntPtr ptr);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Int32 libssh2_session_free(
            IntPtr session);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        internal static extern Int32 libssh2_session_disconnect_ex(
            Libssh2SessionHandle session,
            SSH_DISCONNECT reason,
            [MarshalAs(UnmanagedType.LPStr)] string? description,
            [MarshalAs(UnmanagedType.LPStr)] string? lang);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Int32 libssh2_session_get_blocking(
            Libssh2SessionHandle session);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern void libssh2_session_set_blocking(
            Libssh2SessionHandle session,
            Int32 blocking);

        //---------------------------------------------------------------------
        // Algorithm functions.
        //---------------------------------------------------------------------

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr libssh2_session_methods(
            Libssh2SessionHandle session,
            LIBSSH2_METHOD methodType);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Int32 libssh2_session_supported_algs(
            Libssh2SessionHandle session,
            LIBSSH2_METHOD methodType,
            [Out] out IntPtr algorithmsPtrPtr);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        internal static extern Int32 libssh2_session_method_pref(
            Libssh2SessionHandle session,
            LIBSSH2_METHOD methodType,
            [MarshalAs(UnmanagedType.LPStr)] string prefs);


        //---------------------------------------------------------------------
        // Banner functions.
        //---------------------------------------------------------------------

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr libssh2_session_banner_get(
            Libssh2SessionHandle session);


        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        internal static extern Int32 libssh2_session_banner_set(
            Libssh2SessionHandle session,
            [MarshalAs(UnmanagedType.LPStr)] string banner);

        //---------------------------------------------------------------------
        // Handshake functions.
        //---------------------------------------------------------------------

        //
        // NB. This function hangs when using libssh2 1.9.0 on Windows 10 1903.
        // https://github.com/libssh2/libssh2/issues/388
        //
        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Int32 libssh2_session_handshake(
            Libssh2SessionHandle session,
            IntPtr socket);

        //---------------------------------------------------------------------
        // Hostkey functions.
        //---------------------------------------------------------------------

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr libssh2_session_hostkey(
            Libssh2SessionHandle session,
            out IntPtr length,
            out LIBSSH2_HOSTKEY_TYPE type);


        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern IntPtr libssh2_hostkey_hash(
            Libssh2SessionHandle session,
            LIBSSH2_HOSTKEY_HASH hashType);

        //---------------------------------------------------------------------
        // Timeout.
        //---------------------------------------------------------------------

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern int libssh2_session_get_timeout(
            Libssh2SessionHandle session);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern void libssh2_session_set_timeout(
            Libssh2SessionHandle session,
            int timeout);

        //---------------------------------------------------------------------
        // User auth.
        //
        // NB. The documentation on libssh2_userauth_publickey is extremely sparse.
        // For a usage example, see:
        // https://github.com/stuntbadger/GuacamoleServer/blob/master/src/common-ssh/ssh.c
        //---------------------------------------------------------------------

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl)]
        internal static extern Int32 libssh2_userauth_authenticated(
            Libssh2SessionHandle session);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        internal static extern IntPtr libssh2_userauth_list(
            Libssh2SessionHandle session,
            [MarshalAs(UnmanagedType.LPStr)] string username,
            int usernameLength);

        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
        internal delegate int SignCallback(
            IntPtr session,
            out IntPtr signature,
            out IntPtr signatureLength,
            IntPtr data,
            IntPtr dataLength,
            IntPtr context);

        [DllImport(Libssh2, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
        internal static extern int libssh2_userauth_publickey(
            Libssh2SessionHandle session,
            [MarshalAs(UnmanagedType.LPStr)] string username,
            [MarshalAs(UnmanagedType.LPArray)] byte[] publicKey,
            IntPtr pemPublicKeyLength,
            SignCallback callback,
            IntPtr context);

        [StructLayout(LayoutKind.Sequential)]
        internal struct LIBSSH2_USERAUTH_KBDINT_PROMPT
        {
            internal IntPtr TextPtr;
            internal int TextLength;
            internal byte Echo;
        }