Boost C++ Libraries - Intrusive doubly linked list: list

Intrusive doubly linked list: list

list hooks
list container
Example

list is a doubly linked list. The memory overhead it imposes is 2 pointers per node. An empty, non constant-time size list also has the size of 2 pointers. list has many more constant-time operations than slist and provides a bidirectional iterator. It is recommended to use list instead of slist if the size overhead is acceptable:

list hooks

Like the rest of Boost.Intrusive containers, list has two hook types:

template <class ...Options>
class list_base_hook;

list_base_hook: the user class derives publicly from list_base_hook to make it list-compatible.

template <class ...Options>
class list_member_hook;

list_member_hook: the user class contains a public list_member_hook to make it list-compatible.

list_base_hook and list_member_hook receive the same options explained in the section How to use Boost.Intrusive:

tag<class Tag> (for base hooks only): This argument serves as a tag, so you can derive from more than one list hook. Default: tag<default_tag>.
link_mode<link_mode_type LinkMode>: The linking policy. Default: link_mode<safe_link>.
void_pointer<class VoidPointer>: The pointer type to be used internally in the hook and propagated to the container. Default: void_pointer<void*>.

list container

template <class T, class ...Options>
class list;

list receives the same options explained in the section How to use Boost.Intrusive:

base_hook<class Hook> / member_hook<class T, class Hook, Hook T::* PtrToMember> / value_traits<class ValueTraits>: To specify the hook type or value traits used to configure the container. (To learn about value traits go to the section Containers with custom ValueTraits.)
constant_time_size<bool Enabled>: To activate the constant-time size() operation. Default: constant_time_size<true>
size_type<bool Enabled>: To specify the type that will be used to store the size of the container. Default: size_type<std::size_t>

Example

Now let's see a small example using both hooks:

#include <boost/intrusive/list.hpp>
#include <vector>

using namespace boost::intrusive;

class MyClass : public list_base_hook<>   //This is a derivation hook
{
   int int_;

   public:
   //This is a member hook
   list_member_hook<> member_hook_;

   MyClass(int i)
      :  int_(i)
   {}
};

//Define a list that will store MyClass using the public base hook
typedef list<MyClass>   BaseList;

//Define a list that will store MyClass using the public member hook
typedef list< MyClass
            , member_hook< MyClass, list_member_hook<>, &MyClass::member_hook_> 
            > MemberList;

int main()
{
   typedef std::vector<MyClass>::iterator VectIt;
   typedef std::vector<MyClass>::reverse_iterator VectRit;

   //Create several MyClass objects, each one with a different value
   std::vector<MyClass> values;
   for(int i = 0; i < 100; ++i)  values.push_back(MyClass(i));

   BaseList baselist;
   MemberList memberlist;

   //Now insert them in the reverse order in the base hook list
   for(VectIt it(values.begin()), itend(values.end()); it != itend; ++it)
      baselist.push_front(*it);

   //Now insert them in the same order as in vector in the member hook list
   for(VectIt it(values.begin()), itend(values.end()); it != itend; ++it)
      memberlist.push_back(*it);

   //Now test lists
   {
      BaseList::reverse_iterator rbit(baselist.rbegin()), rbitend(baselist.rend());
      MemberList::iterator mit(memberlist.begin()), mitend(memberlist.end());
      VectIt  it(values.begin()), itend(values.end());

      //Test the objects inserted in the base hook list
      for(; it != itend; ++it, ++rbit)
         if(&*rbit != &*it)   return 1;

      //Test the objects inserted in the member hook list
      for(it = values.begin(); it != itend; ++it, ++mit)
         if(&*mit != &*it)    return 1;
   }

   return 0;
}