Features
- Given only one list item, one cannot immediately obtain the addresses of the other elements of the list.
- Two XOR operations suffice to do the traversal from one item to the next, the same instructions sufficing in both cases. Consider a list with items
{…B C D…}and with R1 and R2 being registers containing, respectively, the address of the current (say C) list item and a work register containing the XOR of the current address with the previous address (say C⊕D). Cast as System/360 instructions:
- End of list is signified by imagining a list item at address zero placed adjacent to an end point, as in
{0 A B C…}. The link field at A would be 0⊕B. An additional instruction is needed in the above sequence after the two XOR operations to detect a zero result in developing the address of the current item, - A list end point can be made reflective by making the link pointer be zero. A zero pointer is a mirror. (The XOR of the left and right neighbor addresses, being the same, is zero.)
Read more about this topic: XOR Linked List
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