When the framework calls setServices, it passes in a gov.cca.Services object (in C++ gov::cca::Services) that we need to keep a copy of. Note that frameworkServices is not declared here. We will add a declaration for it to the .hxx file in the next step.

In order to register the ports that our component will provide with the framework, we use the addProvidesPort method of the gov.cca.Services interface. You can find this interface in the cca.sidl file (where you previously looked up gov.cca.Component and gov.cca.ports.GoPort) in order to check its signature, which is:

...
void addProvidesPort(in gov.cca.Port inPort,
                     in string portName,
                     in string type,
                     in gov.cca.TypeMap properties )
       throws gov.cca.CCAException ;
...

(Of course we're actually calling the C++ version of the interface.)

The first argument is the object that actually provides the port. The way we wrote the SIDL, the drivers.CXXDriver class provides the port, and since we're writing a method within this class, the babel C++ binding allows the enclosing object to be accessed through the standard C++ *this mechanism (cast to the appropriate type).

The second and third arguments are a local name for the port, which must be unique within the component, and a type, which should be globally unique. If the actual types of the ports don't match between user and provider, it will cause a failed cast or possibly a segmentation fault. The string type here is a convenience to the user, giving a human-readable way to identify the type of the port that can be presented in the framework's user interface. By convention, the SIDL interface name for the port is used for the type.

The final argument is a gov.cca.TypeMap. This is a CCA-defined type that provides a simple hash table that can be used to associate properties with a provides port. In practice, it is rarely used, but must be present.

We must also tell the framework which ports we expect to use from other components. Looking in cca.sidl, we find that the method's signature is:

...
void registerUsesPort(in string portName,
                      in string type,
                      in gov.cca.TypeMap properties ) 
     throws gov.cca.CCAException ;
...

The first and second arguments are a local name for the port, following the same rules and conventions as in the addProvidesPort invocation above. The final argument is, once again, a gov.cca.TypeMap, like addProvidesPort.

Setup the parameters with which to call the integrator.

In this section we get a handle to the particular integrator.IntegratorPort that the driver's uses port has been connected to. First, we have to declare a variable of the appropriate type (::integrator::IntegratorPort is the C++ translation of the SIDL integrator.IntegratorPort, defined in $STUDENT_SRC/ports/sidl/integrator.sidl. Then, we invoke the getPort on our frameworkServices object. The argument to this method is the local name we used in the registerUsesPort invocation. Note the use of the babel_cast method to cast from the gov::cca::Port to its sub-type ::integrator::IntegratorPort.

This code checks that the getPort worked, and returned a valid port. If the getPort fails, or if the driver's uses port has not been connected to an appropriate provider, then getPort will return a nil port object. The _is_nil method is automatically available on all SIDL objects. Because the driver can't do anything without being properly connected to an integrator, the response to getPort failing is to abort by returning a non-zero value.

	Note
	getPort returning nil need not be treated as a fatal error in all cases. For example, a component may be designed so that certain ports are optional -- to be used if present, but to be ignored if not. Another possibility is that the component may be able to accomplish the same thing through several different ports, so that only one of a given group needs to be connected.

Here we actually call the integrate method on the integrator port we just got a handle for. The signature of the integrate method is defined in $STUDENT_SRC/ports/sidl/integrator.sidl.

Finally, once we're done using the port, we call releasePort.

It is considered impolite for a component to call exit because it will bring down the entire application, and possibly crash the framework. Instead, components should simply return.