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One of the first issues to be addressed when considering the implementation of DOM in an imperative language like C is the mapping of the object-oriented architecture of DOM. Gdome2 objects are implemented in a straightforward way: objects have fields classified into instance fields and class fields. Instance fields are allocated for each instance of a given class (where the ``class'' is the realization of a DOM interface), and they are grouped in a standard C structure. Class fields are fields shared by all the instances of a given interface. Each Gdome2 object has one instance field which is a pointer to a statically allocated structure containing its class fields. A typical example of a class field which is present in all Gdome2 objects is the virtual table, containing pointers to the methods implemented by the class of the object itself. The use of virtual tables enables us to have a mechanism equivalent to inheritance of methods, thus favoring the reuse of code and making easier the maintenance of the source code.

Paolo Casarini 2001-04-01