GAT Interface Model

In addition to introducing notions of class, subclass, superclass, inheritance...GAT also introduces the notion of ``interface.'' The GAT interface model consists of a set of ``interfaces,'' see figure .

Each GAT ``interface'' consists of a struct containing function pointers. As C does not support interfaces, the ``interfaces'' depicted in figure are simply a stand-in for interfaces with language support.

To clarify the concept of interfaces in GAT let us consider a few examples. The class GATFile realizes the interface GATInterface_ISerialisable, as rendered in figure .

As a result of this realization, there exists a set of GATFile functions implementing this realization. These functions are detailed in figure .

Similarly, the class GATEndpoint realizes the interface GATInterface_ISerialisable. Thus, there exist a set of ``corresponding'' GATEndpoint functions implementing this realization, see figure .

As previously mentioned, an interface in GAT is a struct containing a set of function pointers. For example, these function pointers for the GATInterface_ISerialisable interface of GATFile are the functions specified in figure above. To obtain reference to the struct containing these function pointers one must use the ``GetInterface'' member function of the apropos GAT object. As an example, in the case of a GATFile one would obtain such a struct as follows,

GATFile file;
GATResult result;
void const *serialisableInterface;

/* Create a new GATFile */
file = ...

/* Obtain the struct for the GATInterface_ISerialisable interface */
result = GATFile_GetInterface(file, GATInterface_ISerialisable, &serialisableInterface);

Upon successful return from the function GATFile_GetInterface the variable *serialisable Interface will point to a struct containing the aforementioned functions.