fcppt.intrusive

Description

Intrusive list implementation.

Intrusive lists

An intrusive list is a list that does not actually own elements. Instead, when an element is constructed it gets the list it is going to be part of as a parameter. As long as the element is alive, it is part of the list. Such a list can be used to track elements whose lifetime is managed elsewhere. For example, fcppt.signal uses this technique to know which functions it has to call.

A type T can be inserted into an fcppt::intrusive::list<T> if it derives from fcppt::intrusive::base<T>. The implementation of fcppt::intrusive::base owns a pair of pointers that represent a list node. When such an object is destroyed or moved from, it automatically unlinks itself from the list.

Here is an example: First, we declare the list type we are going to use:

class element;
 
using element_list = fcppt::intrusive::list<element>;

Then, we define the element type, deriving from the base class and adding a constructor that takes a list as an argument:

class element : public fcppt::intrusive::base<element>
{
  FCPPT_NONCOPYABLE(element);
 
public:
  element(fcppt::reference<element_list> const _list, int const _value)
      : fcppt::intrusive::base<element>{_list.get()}, value_{_value}
  {
  }
 
  element(element &&) noexcept = default;
 
  element &operator=(element &&) noexcept = default;
 
  ~element() = default;
 
  [[nodiscard]] int value() const { return value_; }
 
private:
  int value_;
};

Here is a small example of how a list can be used:

  element_list list{};
 
  element e1{fcppt::make_ref(list), 5};
 
  {
    element const e2{fcppt::make_ref(list), 10};
 
    // Prints 5, 10
    for (element const &e : list)
    {
      std::cout << e.value() << ' ';
    }
  }
 
  std::cout << '\n';
 
  // Prints 5
  for (element const &e : list)
  {
    std::cout << e.value() << ' ';
  }
 

Classes
class	fcppt::intrusive::base< Type >
	The base class of an element. More...
class	fcppt::intrusive::iterator< Type >
	The iterator type of an intrusive list. More...
class	fcppt::intrusive::list< Type >
	An intrusive list. More...