Re: Transfer data from server to client via Rpc_in_buf troubles

Hello Nikolay,

you ran into the same issue as Pruthivi Raj

http://sourceforge.net/mailarchive/message.php?msg_id=28616670

twelve month ago.

On Wed, Dec 19, 2012 at 02:50:50PM +0400, Nikolay Golikov wrote:

    enum { MAX_BUFFER_SIZE = 256 };
    typedef Genode::Rpc_in_buffer<MAX_BUFFER_SIZE> Byte_array;

Rpc_in_buffer can only be used for _input_ parameters of RPC functions.

    virtual bool read(Genode::uint8_t address, Genode::uint8_t register,
                      Byte_array &out) = 0;

You may use a fixed-size struct for the out parameter here

struct Byte_array { char v[256]; };

which unfortunately leaves you sending all 256 bytes - significant or not - on reply to the RPC.

A good option for bulk-data interfaces like yours is synchronized usage of shared memory:

* Put input parameters into shared memory * Call RPC * Read output parameters from shared memory

A good example for this approach can be found in os/include/terminal_session/client.h etc.

Regards