Pointer Plus Bits: Is a data structure which points to specifically aligned object such that the value of the address is divisible by a power of two (the power of two which it is divisible by is given as a template argument). The empty bits of the pointer are then used to store extra boolean values relating to something (This is of the programmers choosing but it would seem best practice to make it related to the object being pointed at).
Hi Brian,
1) Should the pointer_plus_bits have a pre and post increment and decrement ( what about supporting other arithmetic operations such as add, minus, add assign etc...) ?
1.a) If this is a behavior supported by the pointer_plus_bits should it keep
the bits being stuffed or set them to zero each time?
I don't think this class implement arithmetic operations because the extra bits typically apply to the referenced object and not the pointer itself. Here you have a case where the pointer and value type can't be arbitrarily decoupled (the pointer is part of the value) and so these operations don't make much sense.
2) Should the bits being stuffed apply during comparison?
Contrary to what I've just said, you could implement comparisons using the pointers alone and excluding the bits. I think this would be reasonable. Consider a comparison to nullptr (or (void*)0).
3) Should the pointer provide compatibility between itself and pointer of the same type that is being stuffed (the behavior of this would mean masking out the pointer so the stuffed bits won't apply during the comparison)? (ie Should pointer_plus_bits<T,2> be comparable to T* ?) (in pointer_plus_bits 2 is the number of bits being stuffed).
In general, I would say no. I think a non-explicit constructor taking T* and a get() member should be sufficient. I think that should cover most of your interoperability concerns, but I'm just guessing here. Andrew Sutton andrew.n.sutton@gmail.com