How to construct a header

The header of a linked list needs to know the type of data for each list element, and where in each element the pointer to the next element can be found.

In order to construct a header, two important pieces of information are needed:

• the type of object which forms the elements.

• the offset of the link object from the start of the element.

To create a header for a singly linked list of CMyClass elements, defined as:

      
       
      
      class CMyClass : public CBase
    {
    ...
    TSglQueLink iSlink;
    ...
    };
     

construct a TSglQue as follows:

      
       
      
      TSglQue<CMyClass> queHeader(_FOFF(CMyClass,iSlink));
     

The TSglQue class takes a class template parameter which defines the type of object which is to form an element of the list. In this example, objects of type CMyClass form the elements of the list.

The _FOFF macro (i.e. the "field offset" macro) calculates the offset of the component link object within the element. In this example, the required value is the offset of the iSlink data member from the start of CMyClass .

Figure 1. Links in singly linked lists