stream_engine.hpp

/*
    Copyright (c) 2007-2014 Contributors as noted in the AUTHORS file

    This file is part of 0MQ.

    0MQ is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    0MQ is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef __ZMQ_STREAM_ENGINE_HPP_INCLUDED__
#define __ZMQ_STREAM_ENGINE_HPP_INCLUDED__

#include <stddef.h>

#include "fd.hpp"
#include "i_engine.hpp"
#include "io_object.hpp"
#include "i_encoder.hpp"
#include "i_decoder.hpp"
#include "options.hpp"
#include "socket_base.hpp"
#include "../include/zmq.h"

namespace zmq
{
    //  Protocol revisions
    enum
    {
        ZMTP_1_0 = 0,
        ZMTP_2_0 = 1
    };

    class io_thread_t;
    class msg_t;
    class session_base_t;
    class mechanism_t;

    //  This engine handles any socket with SOCK_STREAM semantics,
    //  e.g. TCP socket or an UNIX domain socket.

    class stream_engine_t : public io_object_t, public i_engine
    {
    public:

        stream_engine_t (fd_t fd_, const options_t &options_, 
                         const std::string &endpoint);
        ~stream_engine_t ();

        //  i_engine interface implementation.
        void plug (zmq::io_thread_t *io_thread_,
           zmq::session_base_t *session_);
        void terminate ();
        void restart_input ();
        void restart_output ();
        void zap_msg_available ();

        //  i_poll_events interface implementation.
        void in_event ();
        void out_event ();

    private:

        //  Unplug the engine from the session.
        void unplug ();

        //  Function to handle network disconnections.
        void error ();

        //  Receives the greeting message from the peer.
        int receive_greeting ();

        //  Detects the protocol used by the peer.
        bool handshake ();

        //  Writes data to the socket. Returns the number of bytes actually
        //  written (even zero is to be considered to be a success). In case
        //  of error or orderly shutdown by the other peer -1 is returned.
        int write (const void *data_, size_t size_);

        //  Reads data from the socket (up to 'size' bytes).
        //  Returns the number of bytes actually read or -1 on error.
        //  Zero indicates the peer has closed the connection.
        int read (void *data_, size_t size_);

        int read_identity (msg_t *msg_);
        int write_identity (msg_t *msg_);

        int next_handshake_command (msg_t *msg);
        int process_handshake_command (msg_t *msg);

        int pull_msg_from_session (msg_t *msg_);
        int push_msg_to_session (msg_t *msg);

        int write_credential (msg_t *msg_);
        int pull_and_encode (msg_t *msg_);
        int decode_and_push (msg_t *msg_);
        int push_one_then_decode_and_push (msg_t *msg_);

        void mechanism_ready ();

        int write_subscription_msg (msg_t *msg_);

        size_t add_property (unsigned char *ptr,
            const char *name, const void *value, size_t value_len);

        //  Underlying socket.
        fd_t s;

        //  True iff this is server's engine.
        bool as_server;

        msg_t tx_msg;

        handle_t handle;

        unsigned char *inpos;
        size_t insize;
        i_decoder *decoder;

        unsigned char *outpos;
        size_t outsize;
        i_encoder *encoder;

        //  When true, we are still trying to determine whether
        //  the peer is using versioned protocol, and if so, which
        //  version.  When false, normal message flow has started.
        bool handshaking;

        static const size_t signature_size = 10;

        //  Size of ZMTP/1.0 and ZMTP/2.0 greeting message
        static const size_t v2_greeting_size = 12;

        //  Size of ZMTP/3.0 greeting message
        static const size_t v3_greeting_size = 64;

        //  Expected greeting size.
        size_t greeting_size;

        //  Greeting received from, and sent to peer
        unsigned char greeting_recv [v3_greeting_size];
        unsigned char greeting_send [v3_greeting_size];

        //  Size of greeting received so far
        unsigned int greeting_bytes_read;

        //  The session this engine is attached to.
        zmq::session_base_t *session;

        options_t options;

        // String representation of endpoint
        std::string endpoint;

        bool plugged;

        int (stream_engine_t::*read_msg) (msg_t *msg_);

        int (stream_engine_t::*write_msg) (msg_t *msg_);

        bool io_error;

        //  Indicates whether the engine is to inject a phantom
        //  subscription message into the incoming stream.
        //  Needed to support old peers.
        bool subscription_required;

        mechanism_t *mechanism;

        //  True iff the engine couldn't consume the last decoded message.
        bool input_stopped;

        //  True iff the engine doesn't have any message to encode.
        bool output_stopped;

        // Socket
        zmq::socket_base_t *socket;

        std::string peer_address;

        stream_engine_t (const stream_engine_t&);
        const stream_engine_t &operator = (const stream_engine_t&);
    };

}

#endif