[Boost-users] [intrusive] list compatibility with existing application-defined intrusive lists

Subject: [Boost-users] [intrusive] list compatibility with existing application-defined intrusive lists
From: Rahul Ramadas (tripshock_at_[hidden])
Date: 2018-02-03 20:42:51

Hi all,

boost::intrusive lists can be easily customized to be compatible with an
existing doubly-linked intrusive list implementation, such as the one used
in the linux kernel (struct list_head). Indeed, I have been able to declare
and use a boost::intrusive::list of my own with custom traits that uses
struct list_head as the underlying representation, enabling me to simply
use .end().pointed_node() to get access to the list head and pass it to
legacy C code that expects a struct list_head*. However, I can't think of a
way to achieve interoperability in the opposite direction.

For example, I have an existing function (to be precise, a callback that I
pass to legacy C code), that accepts a struct list_head* that is expected
to contain a list of elements of a certain type. I want some way to "wrap"
this raw pointer in a type-safe intrusive list type that I use as naturally
as a boost::intrusive::list (iteration, modification, etc.). I see no way
to achieve this.

The way I see it, what I need is a boost::intrusive::list_ptr, a container
that doesn't actually own the list head, but rather, points to a list head
stored elsewhere. It would have the same interface as a list, allowing me
to push_back, clear, etc., but behaves as a pointer when it comes to moves
and copies. Additionally, there should also be a
boost::intrusive::const_list_ptr, which will not allow me to modify the
list, but still allows iteration and other non-modifying operations.

Unless, of course, there are already existing mechanisms to achieve this.
If anyone has any ideas, please let me know.

Thanks.