Re: [Boost-users] intrusive list with pointer_plus_bit

Christian Holmquist wrote:

Hi,

I have a class X : public intrusive::list_base_hook<> and would like to embed an additional member bool using the pointer_plus_bit.

Can this be achieved using the value_traits somehow, and have the list working 'appropriately'?

It can be achieved using value_traits. Just repeat the following example: http://www.boost.org/doc/libs/1_35_0/doc/html/intrusive/value_traits.html#in... but instead of defining this value_traits: //Define the node traits. A single node_traits will be enough. struct simple_node_traits { typedef simple_node node; typedef node * node_ptr; typedef const node * const_node_ptr; static node *get_next(const node *n) { return n->next_; } static void set_next(node *n, node *next) { n->next_ = next; } // ... }; Use this (supposing you want to embed the bit in the next pointer): struct simple_node_traits { // ... static node *get_next(const node *n) { return pointer_plus_bit::get_pointer(n->next_); } static void set_next(node *n, node *next) { return pointer_plus_bit::set_pointer(n->next_, next); } //... }; I haven't compiled it, so it might contain errors. To access to the set bit you should define a function that accesses next pointer and extracts the bit, something like: pointer_plus_bit::set_bit(x.next_, true); bool ret = pointer_plus_bit::get_bit(x.next_); Take in care that you should make sure that has_pointer_plus_bit::value; is true, otherwise, you won't have space to store the bit, because the pointed type has not even alignment. FYI, I've just erased pointer_plus_bit.hpp and substituted it with a more generic pointer_plus_bits.hpp in Trunk. Now that I see that it's being used, I will need to provide backwards compatibility. I hope it works, Ion