VXinit, VXcpy, VXlnklist, VXdellist − VisionX list manipulation functions

VisXelem_t *VXinit ();
VisXelem_t *VXcpy (list);
VisXelem_t *list;
void VXlnklist (lista, listb);
VisXelem_t *lista, *listb;
void VXdellist (list);
VisXelem_t *list;

VisionX represents information internally as a doubly linked list of data elements. Each element contains a type descriptor, forward and backward pointers to other elements, and data. The VisionX file i/o functions read and write these lists.

The first element of a list is always a dummy element that is required for consistency. The list manipulation functions provide a set of programming tools for performing operations on whole list structures.

The list manipulation toolkit contains the following functions: VXinit − creates an empty list structure, VXcpy − make a copy of a list VXlnklist − link a list into another list and VXdellist − delete a complete list.

VXinit creates an empty list structure to which elements and lists may be added. A dummy data element is created which is necessary for consistent list operations; VXinit returns a pointer to this element. The dummy element is not copied to a file when the list is written; it is deleted when the list is deleted.

VXcpy makes a copy of a list starting at the element pointed at by the argument list and includes all the following elements. VXcpy automatically creates the required first dummy element and returns a pointer to the copied list.

VXlnklist Moves the whole of the list to which argument listb points to and inserts it after the element pointed to by argument lista. (listb does not have to point to the start of its list). All that remains of the list pointed to by listb is the dummy element. Note, adding one list to the end of another list can be achieved with VXlnklist(VXlast(lista), listb).

VXdellist deletes all elements of the argument list starting at the element list to the end of the list. Note, VXdellist will delete the dummy element if list points to the dummy element; however, VXdellist(VXfirst(list)), will delete all elements of a list except the dummy element.

A. P. Reeves