vrpn_Imager_Stream_Buffer.h

Go to the documentation of this file.

#ifndef VRPN_IMAGER_STREAM_BUFFER_H
#define VRPN_IMAGER_STREAM_BUFFER_H
#include <string.h> // for NULL, strcpy, strlen

#include "vrpn_Auxiliary_Logger.h"
#include "vrpn_Configure.h"  // for VRPN_CALLBACK, VRPN_API
#include "vrpn_Connection.h" // for vrpn_Connection (ptr only), etc
#include "vrpn_Imager.h"
#include "vrpn_Shared.h" // for vrpn_Semaphore, etc
#include "vrpn_Types.h"  // for vrpn_int32, vrpn_uint16

// This is a fairly complicated class that implements a multi-threaded
// full-rate logger and partial-rate forwarder for a vrpn_Imager_Server
// object.  It is intended to allow previewing of microscopy experiments
// at a subset of the camera's video rate while logging the video at
// full rate, possibly on a remote computer and possibly on the original
// video server computer.  Its architecture is described in the "Full-rate
// logging" section of the vrpn_Imager.html document in the VRPN web
// page.

//-------------------------------------------------------------------
// This is a helper class for the vrpn_Imager_Stream_Shared_State class
// below.  It keeps a linked list of vrpn_HANDLERPARAM types and the
// buffers to which they point.  The buffers need to be allocated by
// the one who inserts to this list and deleted by the one who pulls
// elements from this list.

class VRPN_API vrpn_Message_List {
public:
    vrpn_Message_List(void)
    {
        d_first = d_last = NULL;
        d_count = 0;
    };
    ~vrpn_Message_List(void)
    {
        while (d_first != NULL) {
            struct d_ELEMENT *next = d_first->next;
            delete d_first;
            d_first = next;
        }
    }

    // Give the length of the list.
    unsigned size(void) const { return d_count; }

    // Insert an element into the list.  Return false if fails.
    bool insert_back(const vrpn_HANDLERPARAM &p)
    {
        struct d_ELEMENT *el = new struct d_ELEMENT;
        if (el == NULL) {
            return false;
        }
        el->p = p;
        el->next = NULL;
        if (d_last != NULL) {
            d_last->next = el;
        }
        d_last = el;
        if (d_first == NULL) {
            d_first = el;
        }
        d_count++;
        return true;
    }

    // Remove an element from the list.  Return false if fails.
    bool retrieve_front(vrpn_HANDLERPARAM *p)
    {
        if (p == NULL) {
            return false;
        }
        if (size() == 0) {
            return false;
        }

        *p = d_first->p;
        if (d_last == d_first) {
            d_last = NULL;
        }
        struct d_ELEMENT *temp = d_first;
        d_first = d_first->next;
        delete temp;

        d_count--;
        return true;
    }

protected:
    struct d_ELEMENT {
        vrpn_HANDLERPARAM p;
        struct d_ELEMENT *next;
    };
    struct d_ELEMENT *d_first, *d_last;
    unsigned d_count;
};

//-------------------------------------------------------------------
// This is the data structure that is shared between the initial
// thread (which listens for client connections) and the non-blocking logging
// thread that sometimes exists to listen to the vrpn_Imager_Server.
// All of its methods must be thread-safe, so it creates a semaphore
// for access and uses it in all of the non-atomic methods.
// Note that some of the things in here are pointers to objects that
// are in the parent class, and they are here just to provide the
// semaphore protection.  The parent class should only access these
// things through this shared state object.

class VRPN_API vrpn_Imager_Stream_Shared_State {
public:
    vrpn_Imager_Stream_Shared_State() { init(); }

    // Reset the shared state to what it should be at
    // the time the logging thread is started.
    void init(void)
    {
        d_time_to_exit = false;
        d_description_updated = false;
        d_nRows = d_nCols = d_nDepth = d_nChannels = 0;
        d_new_log_request = false;
        d_request_lil = NULL;
        d_request_lol = NULL;
        d_request_ril = NULL;
        d_request_rol = NULL;
        d_new_log_result = false;
        d_result_lil = NULL;
        d_result_lol = NULL;
        d_result_ril = NULL;
        d_result_rol = NULL;
        d_new_throttle_request = false;
        d_throttle_count = -1;
        d_frames_in_queue = 0;
    }

    // Accessors for the "time to exit" flag; set by the initial thread and
    // read by the logging thread.
    bool time_to_exit(void)
    {
        d_sem.p();
        bool ret = d_time_to_exit;
        d_sem.v();
        return ret;
    }
    void time_to_exit(bool do_exit)
    {
        d_sem.p();
        d_time_to_exit = do_exit;
        d_sem.v();
    }

    // Accessors for the parameters stored based on the
    // imager server's reports.  Returns false if nothing has
    // been set since the last time it was read, true (and fills in
    // the values) if it has.  Channel buffer must be delete [] by
    // the one calling this function iff the function returns true.
    bool get_imager_description(vrpn_int32 &nRows, vrpn_int32 &nCols,
                                vrpn_int32 &nDepth, vrpn_int32 &nChannels,
                                const char **channelBuffer)
    {
        d_sem.p();
        bool ret = d_description_updated;
        if (d_description_updated) {
            nRows = d_nRows;
            nCols = d_nCols;
            nDepth = d_nDepth;
            nChannels = d_nChannels;
            *channelBuffer = d_channel_buffer;
        }
        d_description_updated = false;
        d_sem.v();
        return ret;
    }
    bool set_imager_description(vrpn_int32 nRows, vrpn_int32 nCols,
                                vrpn_int32 nDepth, vrpn_int32 nChannels,
                                const char *channelBuffer)
    {
        d_sem.p();
        d_nRows = nRows;
        d_nCols = nCols;
        d_nDepth = nDepth;
        d_nChannels = nChannels;
        d_channel_buffer = channelBuffer;
        d_description_updated = true;
        d_sem.v();
        return true;
    }

    // Accessors for the initial thread to pass new logfile names down to the
    // logging thread, which will cause it to initiate a changeover of logging
    // connections.  Space for the return strings will be allocated in these
    // functions
    // and must be deleted by the logging thread ONLY IF the get function fills
    // the
    // values in (it returns true if it does).
    // NOTE:  this is used to query BOTH the presence of new logfile names
    // AS WELL AS the names themselves.  this function will only return values
    // if new logfile names have been requested since the last time this
    // function was called.
    bool get_logfile_request(char **lil, char **lol, char **ril, char **rol)
    {
        d_sem.p();
        bool ret = d_new_log_request;
        if (d_new_log_request) {
            // Allocate space to return the names in the handles passed in.
            // Copy the values from our local storage to the return values.
            if ((*lil = new char[strlen(d_request_lil) + 1]) != NULL) {
                strcpy(*lil, d_request_lil);
            }
            if ((*lol = new char[strlen(d_request_lol) + 1]) != NULL) {
                strcpy(*lol, d_request_lol);
            }
            if ((*ril = new char[strlen(d_request_ril) + 1]) != NULL) {
                strcpy(*ril, d_request_ril);
            }
            if ((*rol = new char[strlen(d_request_rol) + 1]) != NULL) {
                strcpy(*rol, d_request_rol);
            }

            // Delete and NULL the local storage pointers.
            delete[] d_request_lil;
            d_request_lil = NULL;
            delete[] d_request_lol;
            d_request_lol = NULL;
            delete[] d_request_ril;
            d_request_ril = NULL;
            delete[] d_request_rol;
            d_request_rol = NULL;
        }
        d_new_log_request = false;
        d_sem.v();
        return ret;
    }

    void set_logfile_request(const char *lil, const char *lol, const char *ril,
                             const char *rol)
    {
        d_sem.p();

        // delete file names, in case the logging thread hasn't had a chance to
        //  honor the request yet.
        if (d_request_lil) {
            delete[] d_request_lil;
            d_request_lil = NULL;
        }
        if (d_request_lol) {
            delete[] d_request_lol;
            d_request_lol = NULL;
        }
        if (d_request_ril) {
            delete[] d_request_ril;
            d_request_ril = NULL;
        }
        if (d_request_rol) {
            delete[] d_request_rol;
            d_request_rol = NULL;
        }

        // Allocate space for each string and then copy into it.
        if (lil != NULL) {
            if ((d_request_lil = new char[strlen(lil) + 1]) != NULL) {
                strcpy(d_request_lil, lil);
            }
        }
        if (lol != NULL) {
            if ((d_request_lol = new char[strlen(lol) + 1]) != NULL) {
                strcpy(d_request_lol, lol);
            }
        }
        if (ril != NULL) {
            if ((d_request_ril = new char[strlen(ril) + 1]) != NULL) {
                strcpy(d_request_ril, ril);
            }
        }
        if (rol != NULL) {
            if ((d_request_rol = new char[strlen(rol) + 1]) != NULL) {
                strcpy(d_request_rol, rol);
            }
        }

        d_new_log_request = true;
        d_sem.v();
    }

    // Accessors for the logfile thread to pass new logfile names back up to the
    // initial thread, reporting a changeover of logging connections.
    // Space for the return strings will be allocated in these functions
    // and must be deleted by the initial thread ONLY IF the get function fills
    // the
    // values in (it returns true if it does).
    // NOTE:  this function is intended to query BOTH the logfile names AS WELL
    // AS
    // the change in logging status.  it ONLY returns filenames if logging has
    // changed since the last time this function was called).
    bool get_logfile_result(char **lil, char **lol, char **ril, char **rol)
    {
        d_sem.p();
        bool ret = d_new_log_result;
        if (d_new_log_result) {
            // Allocate space to return the names in the handles passed in.
            // Copy the values from our local storage to the return values.
            if (d_result_lil == NULL)
                *lil = NULL;
            else {
                if ((*lil = new char[strlen(d_result_lil) + 1]) != NULL) {
                    strcpy(*lil, d_result_lil);
                }
            }
            if (d_result_lol == NULL)
                *lol = NULL;
            else {
                if ((*lol = new char[strlen(d_result_lol) + 1]) != NULL) {
                    strcpy(*lol, d_result_lol);
                }
            }
            if (d_result_ril == NULL)
                *ril = NULL;
            else {
                if ((*ril = new char[strlen(d_result_ril) + 1]) != NULL) {
                    strcpy(*ril, d_result_ril);
                }
            }
            if (d_result_rol == NULL)
                *rol = NULL;
            else {
                if ((*rol = new char[strlen(d_result_rol) + 1]) != NULL) {
                    strcpy(*rol, d_result_rol);
                }
            }

            // do not Delete and NULL the local storage pointers.
            // someone may request the filenames later.
        }
        d_new_log_result = false;
        d_sem.v();
        return ret;
    }

    void set_logfile_result(const char *lil, const char *lol, const char *ril,
                            const char *rol)
    {
        d_sem.p();

        if (d_result_lil) delete[] d_result_lil;
        d_result_lil = NULL;
        if (d_result_lol) delete[] d_result_lol;
        d_result_lol = NULL;
        if (d_result_ril) delete[] d_result_ril;
        d_result_ril = NULL;
        if (d_result_rol) delete[] d_result_rol;
        d_result_rol = NULL;

        // Allocate space for each string and then copy into it.
        if (lil != NULL) {
            if ((d_result_lil = new char[strlen(lil) + 1]) != NULL) {
                strcpy(d_result_lil, lil);
            }
        }
        if (lol != NULL) {
            if ((d_result_lol = new char[strlen(lol) + 1]) != NULL) {
                strcpy(d_result_lol, lol);
            }
        }
        if (ril != NULL) {
            if ((d_result_ril = new char[strlen(ril) + 1]) != NULL) {
                strcpy(d_result_ril, ril);
            }
        }
        if (rol != NULL) {
            if ((d_result_rol = new char[strlen(rol) + 1]) != NULL) {
                strcpy(d_result_rol, rol);
            }
        }

        d_new_log_result = true;
        d_sem.v();
    }

    // fills in the arguments with the logfile names currently in use
    // for a particular log, the value will be NULL if that log is not being
    // collected.
    // NOTE:  this function allocates memory for each string returned.  IT IS
    // THE
    // RESPONSIBILITY OF THE CALLING FUNCTION TO FREE THIS MEMORY.
    void get_logfile_names(char **local_in, char **local_out, char **remote_in,
                           char **remote_out)
    {
        d_sem.p();
        if (d_result_lil == NULL)
            *local_in = NULL;
        else {
            *local_in = new char[strlen(d_result_lil) + 1];
            strcpy(*local_in, d_result_lil);
        }
        if (d_result_lol == NULL)
            *local_out = NULL;
        else {
            *local_out = new char[strlen(d_result_lol) + 1];
            strcpy(*local_out, d_result_lol);
        }
        if (d_result_ril == NULL)
            *remote_in = NULL;
        else {
            *remote_in = new char[strlen(d_result_ril) + 1];
            strcpy(*remote_in, d_result_ril);
        }
        if (d_result_rol == NULL)
            *remote_out = NULL;
        else {
            *remote_out = new char[strlen(d_result_rol) + 1];
            strcpy(*remote_out, d_result_rol);
        }
        d_sem.v();
    }

    // Accessors for the initial thread to pass new throttle values down to the
    // logging thread, which will cause it to throttle as needed.
    bool get_throttle_request(vrpn_int32 *throttle_count)
    {
        d_sem.p();
        bool ret = d_new_throttle_request;
        if (d_new_throttle_request) {
            *throttle_count = d_throttle_count;
        }
        d_new_throttle_request = false;
        d_sem.v();
        return ret;
    }
    void set_throttle_request(vrpn_int32 throttle_count)
    {
        d_sem.p();
        d_throttle_count = throttle_count;
        d_new_throttle_request = true;
        d_sem.v();
    }

    // Accessors for the logging thread to increment and read the number of
    // frames in the queue and for the initial thread to decrement them.  The
    // increment/decrement is done when a begin_frame message is found.  The
    // increment/decrement routines return the new value.
    vrpn_int32 get_frames_in_queue(void)
    {
        d_sem.p();
        vrpn_int32 ret = d_frames_in_queue;
        d_sem.v();
        return ret;
    }
    vrpn_int32 increment_frames_in_queue(void)
    {
        d_sem.p();
        d_frames_in_queue++;
        vrpn_int32 ret = d_frames_in_queue;
        d_sem.v();
        return ret;
    }
    vrpn_int32 decrement_frames_in_queue(void)
    {
        d_sem.p();
        d_frames_in_queue--;
        vrpn_int32 ret = d_frames_in_queue;
        d_sem.v();
        return ret;
    }

    // Accessors for the logging thread to add messages to the queue
    // and for the initial thread to retrieve and count them.
    vrpn_int32 get_logger_to_client_queue_size(void)
    {
        d_sem.p();
        vrpn_int32 ret = d_logger_to_client_messages.size();
        d_sem.v();
        return ret;
    }
    bool insert_logger_to_client_message(const vrpn_HANDLERPARAM &p)
    {
        d_sem.p();
        bool ret = d_logger_to_client_messages.insert_back(p);
        d_sem.v();
        return ret;
    }
    bool retrieve_logger_to_client_message(vrpn_HANDLERPARAM *p)
    {
        d_sem.p();
        bool ret = d_logger_to_client_messages.retrieve_front(p);
        d_sem.v();
        return ret;
    }

protected:
    vrpn_Semaphore d_sem; // Semaphore to control access to data items.

    // Is it time for the logging thread to exit?
    bool d_time_to_exit;

    // Stored copies of the value in the vrpn_Imager_Remote and a flag telling
    // whether they have changed since last read.
    bool d_description_updated; // Do we have a new description from imager
                                // server?
    vrpn_int32 d_nRows;
    vrpn_int32 d_nCols;
    vrpn_int32 d_nDepth;
    vrpn_int32 d_nChannels;
    const char *d_channel_buffer; //< Allocated by sender, freed by receiver

    // Names of the log files passed from the initial thread to the logging
    // thread and a flag telling whether they have been changed since last
    // read.
    bool d_new_log_request;
    char *d_request_lil;
    char *d_request_lol;
    char *d_request_ril;
    char *d_request_rol;

    // Names of the log files passed from the logging thread to the initial
    // thread and a flag telling whether they have been changed since last
    // read.  NOTE:  we maintain a copy of the log file names here, instead
    // of using the accessor of vrpn_Connection to query the names.  Only
    // the logging thread is supposed to have access to the logging connection,
    // but the logging thread is banned from calling methods on the client
    // connection.
    bool d_new_log_result;
    char *d_result_lil;
    char *d_result_lol;
    char *d_result_ril;
    char *d_result_rol;

    // New throttle request passed on by the client-handling thread
    bool d_new_throttle_request;
    vrpn_int32 d_throttle_count;

    // Records the number of frames in the queue.  This is incremented
    // by the non-blocking thread and decremented by the initial thread
    // as the begin_frame() messages are queued and dequeued.
    vrpn_int32 d_frames_in_queue;

    // List of messages passing from the logging thread to the initial
    // thread.
    vrpn_Message_List d_logger_to_client_messages;
};

//-------------------------------------------------------------------
// This class is a vrpn_Imager_Server; it has one or two instances of
// vrpn_Imager_Clients to talk to the server it is forwarding packets
// to.  It does not use their callback parsers, but rather hooks its own
// callbacks directly to the connection object for the server it is
// buffering.

class VRPN_API vrpn_Imager_Stream_Buffer : public vrpn_Auxiliary_Logger_Server,
                                           public vrpn_Imager_Server {
public:
    // Name of this object (the server side of the vrpn_Imager that is
    // buffered and the vrpn_Auxiliary_Logger that the client will connect to).
    // (Optional, can be NULL) pointer to the server connection on which to
    // communicate.
    // Name of the vrpn_Imager_Server to connect to (packets from this server
    // will
    // be forwarded to the main connection, and logging will occur on the
    // connection
    // to this imager_server).  This server may be local or remote; if local,
    // include "@localhost" in the name because new connections will be made to
    // it.
    vrpn_Imager_Stream_Buffer(const char *name, const char *imager_server_name,
                              vrpn_Connection *c);

    // Get rid of any logging thread and then clean up.
    virtual ~vrpn_Imager_Stream_Buffer();

    // Required for servers.
    virtual void mainloop(void);

protected:
    // Handle a logging-request message.  The request contains four file
    // names, two for local (to the Auxiliary server itself) and two for
    // remote (the far side of its connection to the server).  It must
    // also respond to the client with a message saying what logging has
    // been set up (using the send_logging_response function).  Logging is
    // turned off on a particular file by sending an empty-string name ("").
    // The in/out local/remote are with respect to the connection that the
    // logging is to occur on, which is to the imager server whose name is
    // passed in to the constructor, not the connection that the client has
    // sent the request on.
    // Make sure to send a response saying what you did.
    virtual void handle_request_logging(const char *local_in_logfile_name,
                                        const char *local_out_logfile_name,
                                        const char *remote_in_logfile_name,
                                        const char *remote_out_logfile_name);

    // Static portion of handling (unpacking) the request_logging message.  It
    // then calls the non-static virtual method above.
    static int VRPN_CALLBACK
    static_handle_request_logging(void *userdata, vrpn_HANDLERPARAM p);

    virtual void handle_request_logging_status();

    // Handle dropped last connection on our primary connection by shutting down
    // the
    // connection to the imager server.  The static method in the base class
    // looks up this
    // pointer and calls the virtual method.
    virtual void handle_dropped_last_connection(void);

    // Handles a throttle request by passing it on down to the non-blocking
    // thread to deal with.
    static int VRPN_CALLBACK
    static_handle_throttle_message(void *userdata, vrpn_HANDLERPARAM p);

    // Handle got first connection request by (having the second thread) create
    // a connection to the server and waiting until we get a description message
    // from the imager server we're listening to.  Timeout after a while if the
    // connection cannot be made or the server does not respond.
    virtual void handle_got_first_connection(void);
    vrpn_int32 got_first_connection_m_id; // ID of message that we got the first
                                          // connection
    static int VRPN_CALLBACK
    static_handle_got_first_connection(void *userdata, vrpn_HANDLERPARAM p);

    // State shared between the initial thread and the logging thread.
    vrpn_Imager_Stream_Shared_State d_shared_state;

    //----------------------------------------------------------------------
    // The section below includes methods and member variables that should
    // only be used by the logging thread.  They are not protected by
    // semaphores and so should not be accessed except within the
    // logging_thread_func().

    // This class spawns a new thread to handle uninterrupted communication
    // and logging with the vrpn_Imager_Server that we are forwarding messages
    // for.  This is created in the constructor and shut down (hopefully gently)
    // in the destructor.  There are a number of semaphores that are used by
    // the initial thread and the logging thread to communicate.
    vrpn_Thread *d_logging_thread;

    // The function that is called to become the logging thread.  It is passed
    // a pointer to "this" so that it can acces the object that created it.
    // Note that it must use semaphores to get at the data that will be shared
    // between the main thread and itself.  The static function basically just
    // pulls the "this" pointer out and then calls the non-static function.
    static void static_logging_thread_func(vrpn_ThreadData &threadData);
    void logging_thread_func(void);

    // Stop the logging thread function, cleanly if possible.  Returns true if
    // the function stopped cleanly, false if it had to be killed.
    bool stop_logging_thread(void);

    // Name of the vrpn_Imager_Server object we are to connect to and
    // log/pass messages from.
    char *d_imager_server_name;

    // Are we ready to drop the old connection (new one has received its
    // descriptor message)?
    bool d_ready_to_drop_old_connection;

    // The connection that is used to talk to the client.
    vrpn_Connection *d_log_connection;
    vrpn_Connection *
    open_new_log_connection(const char *local_in_logfile_name,
                            const char *local_out_logfile_name,
                            const char *remote_in_logfile_name,
                            const char *remote_out_logfile_name);

    // These will create/destroy the d_imager_remote and other callback handlers
    // needed to provide the handling of messages from the logging connection
    // passed in; they are used by the initial-connection code and by the
    // code that handles handing off from an old connection to a new connection
    // when a new logging message is received.
    bool setup_handlers_for_logging_connection(vrpn_Connection *c);
    bool teardown_handlers_for_logging_connection(vrpn_Connection *c);

    // This is yet another "create me some logs" function; it handles the
    // hand-off from one log file to another within the logging thread.
    // It is called by the main logging thread function when a request comes in
    // from the initial thread to perform logging.
    bool make_new_logging_connection(const char *local_in_logfile_name,
                                     const char *local_out_logfile_name,
                                     const char *remote_in_logfile_name,
                                     const char *remote_out_logfile_name);

    // The imager remote to listen to the vrpn_Imager_Server, along
    // with the callback functions that support its operation.  The
    // generic VRPN callback handler that receives all messages from
    // the imager server and either queues them or handles them, there
    // is a static version that just gets a this pointer and calls the
    // non-static function.
    vrpn_Imager_Remote *d_imager_remote;
    static void VRPN_CALLBACK
    handle_image_description(void *pvISB, const struct timeval msg_time);
    static int VRPN_CALLBACK
    static_handle_server_messages(void *pvISB, vrpn_HANDLERPARAM p);
    int handle_server_messages(const vrpn_HANDLERPARAM &p);

    // Types of messages we expect to be coming from the server.
    vrpn_int32 d_server_description_m_id; //< ID of the message type describing
    // the range and channels
    vrpn_int32 d_server_begin_frame_m_id; //< ID of the message type describing
    // the start of a region
    vrpn_int32 d_server_end_frame_m_id; //< ID of the message type describing
    // the start of a region
    vrpn_int32 d_server_discarded_frames_m_id; //< ID of the message type
    // describing the discarding of
    // one or more regions
    vrpn_int32 d_server_regionu8_m_id; //< ID of the message type describing a
    // region with 8-bit unsigned entries
    vrpn_int32 d_server_regionu12in16_m_id; //< ID of the message type
    // describing a region with 12-bit
    // unsigned entries packed in 16 bits
    vrpn_int32 d_server_regionu16_m_id; //< ID of the message type describing a
    // region with 16-bit unsigned entries
    vrpn_int32 d_server_regionf32_m_id; //< ID of the message type describing a
    // region with 32-bit float entries
    vrpn_int32 d_server_text_m_id; //< ID of the system text message
    vrpn_int32 d_server_ping_m_id; //< ID of the system ping message
    vrpn_int32 d_server_pong_m_id; //< ID of the system pong message

    // Transcode the sender and type fields from the logging server connection
    // to
    // the initial client connection and pack the resulting message into the
    // queue
    // from the logging thread to the initial thread.  The data buffer is
    // copied;
    // this space is allocated by the logging thread and must be freed by the
    // initial thread.
    // Returns true on success and false on failure.  The sender is set to the
    // d_sender_id of our server object.
    bool transcode_and_send(const vrpn_HANDLERPARAM &p);

    // Transcode the type from the logging thread's connection type to
    // the initial thread's connection type.  Return -1 if we don't
    // recognize the type.
    vrpn_int32 transcode_type(vrpn_int32 type);

    // Handling throttling on the non-blocking thread.  This is a shadow
    // copy of the structures in the vrpn_Image_Server base class; we cannot
    // use those directly because they will be adjusted by their own callbacks
    // in the initial thread.
    vrpn_uint16 d_server_dropped_due_to_throttle;
    vrpn_int32 d_server_frames_to_send;
};

//-----------------------------------------------------------
// Client code should connect to the server twice, once as
// a vrpn_Imager_Server and once as a vrpn_Auxiliary_Logger_Server.
// There is not a special remote class for this.

#endif