Create an Application
=====================

.. highlight:: c

The rest of this guide will walk you through the steps to create an
application and will provide example code snippets.  It assumes that
you have defined your types (see :doc:`definedatatype`) and have 
used *rtiddsgen* to generate their support code 
(see :doc:`generatesupportcode`).

Registry Configuration
----------------------

The :link_connextmicro_dds_api_c_up_one:`DomainParticipantFactory <group__DDSDomainParticipantFactoryModule.html>`,
in addition to its standard role
of creating and deleting *DomainParticipants*, contains the RT Registry that
a new application registers with some necessary components.

The |me| architecture defines a run-time (RT) component interface that
provides a generic framework for organizing and extending functionality of
an application. An RT component is created and deleted (only available 
in |me_micro|) with an RT component factory. Each RT component factory 
must be registered within an RT registry in order for its components to 
be usable by an application.

|me| automatically registers components that provide necessary
functionality. These include components for DDS *Writers* and *Readers*,
the RTPS protocol, and the UDP transport.

In addition, every DDS application must register three components:

- **Writer History**.  Queue of written samples of a *DataWriter*.  Must be
  registered with the name "wh".
- **Reader History**.  Queue of received samples of a *DataReader*. Must be
  registered with the name "rh".
- **Discovery (DPSE)**.  Discovery component with static (DPSE) endpoint
  discovery. 

Example source:

- Get the RT Registry from the :link_connextmicro_dds_api_c_up_one:`DomainParticipantFactory <group__DDSDomainParticipantFactoryModule.html>`
  singleton:

  ::
  
     DDS_DomainParticipantFactory *factory = NULL;
     RT_Registry_T *registry = NULL;

     factory = DDS_DomainParticipantFactory_get_instance();
     registry = DDS_DomainParticipantFactory_get_registry(factory);

- Register the Writer History and Reader History components with the
  registry:

  ::
  
    /* Register Writer History */
    if (!RT_Registry_register(registry, "wh",
                              WHSM_HistoryFactory_get_interface(), 
                              NULL, NULL))
    {
        /* failure */
    }

    /* Register Reader History */
    if (!RT_Registry_register(registry, "rh",
                              RHSM_HistoryFactory_get_interface(), 
                              NULL, NULL))
    {
        /* failure */
    }

  Only one discovery component can be registered. Each
  has its own properties that can be configured upon registration. Please
  note that only DPSE can be registered in |me_cert|. Each has its own 
  properties that can be configured upon registration.

- Register :link_connextmicro_dds_api_c_up_one:`DPSE <group__DPSEModule.html>`
  for dynamic participant, static endpoint discovery:

  ::
  
    struct DPSE_DiscoveryPluginProperty discovery_plugin_properties =
        DPSE_DiscoveryPluginProperty_INITIALIZER;

    /*  Configure properties */
    discovery_plugin_properties.participant_liveliness_assert_period.sec = 5;
    discovery_plugin_properties.participant_liveliness_assert_period.nanosec = 0;
    discovery_plugin_properties.participant_liveliness_lease_duration.sec = 30;
    discovery_plugin_properties.participant_liveliness_lease_duration.nanosec = 0;

    /* Register DPSE with updated properties  */
    if (!RT_Registry_register(registry,
                              "dpse",
                              DPSE_DiscoveryFactory_get_interface(),
                              &discovery_plugin_properties._parent,
                              NULL))
    {
        printf("failed to register dpse\n");
        goto done;
    }