list_basics.h

/*
 * (c) 2011 Alexander Warg <warg@os.inf.tu-dresden.de>
 *     economic rights: Technische Universität Dresden (Germany)
 *
 * License: see LICENSE.spdx (in this directory or the directories above)
 */
 
#pragma once
 
namespace cxx { namespace Bits {
 
template< typename T >
class List_iterator_end_ptr
{
private:
  template< typename U > friend class Basic_list;
  static void * const _end;
};
 
template< typename T >
void * const List_iterator_end_ptr<T>::_end = nullptr;
 
template< typename VALUE_T, typename TYPE >
struct Basic_list_policy
{
  typedef VALUE_T *Value_type;
  typedef VALUE_T const *Const_value_type;
  typedef TYPE **Type;
  typedef TYPE *Const_type;
  typedef TYPE *Head_type;
  typedef TYPE Item_type;
 
  static Type next(Type c) { return &(*c)->_n; }
  static Const_type next(Const_type c) { return c->_n; }
};

template< typename POLICY >
class Basic_list
{
  Basic_list(Basic_list const &) = delete;
  void operator = (Basic_list const &) = delete;
 
public:
  typedef typename POLICY::Value_type Value_type;
  typedef typename POLICY::Const_value_type Const_value_type;
 
  class Iterator
  {
  private:
    typedef typename POLICY::Type Internal_type;
 
  public:
    typedef typename POLICY::Value_type value_type;
    typedef typename POLICY::Value_type Value_type;
 
    Value_type operator * () const { return static_cast<Value_type>(*_c); }
    Value_type operator -> () const { return static_cast<Value_type>(*_c); }
    Iterator operator ++ () { _c = POLICY::next(_c); return *this; }
 
    friend bool operator == (Iterator const &lhs, Iterator const &rhs)
    { return *lhs._c == *rhs._c; }
    friend bool operator != (Iterator const &lhs, Iterator const &rhs)
    { return *lhs._c != *rhs._c; }
 
    Iterator() : _c(__end()) {}
 
  private:
    friend class Basic_list;
    static Internal_type __end()
    {
      union X { Internal_type l; void * const *v; } z;
      z.v = &Bits::List_iterator_end_ptr<void>::_end;
      return z.l;
    }
 
    explicit Iterator(Internal_type i) : _c(i) {}
 
    Internal_type _c;
  };
 
  class Const_iterator
  {
  private:
    typedef typename POLICY::Const_type Internal_type;
 
  public:
    typedef typename POLICY::Value_type value_type;
    typedef typename POLICY::Value_type Value_type;
 
    Value_type operator * () const { return static_cast<Value_type>(_c); }
    Value_type operator -> () const { return static_cast<Value_type>(_c); }
    Const_iterator operator ++ () { _c = POLICY::next(_c); return *this; }
 
    friend bool operator == (Const_iterator const &lhs, Const_iterator const &rhs)
    { return lhs._c == rhs._c; }
    friend bool operator != (Const_iterator const &lhs, Const_iterator const &rhs)
    { return lhs._c != rhs._c; }
 
    Const_iterator() {}
    Const_iterator(Iterator const &o) : _c(*o) {}
 
  private:
    friend class Basic_list;
 
    explicit Const_iterator(Internal_type i) : _c(i) {}
 
    Internal_type _c;
  };
 
  // BSS allocation
  explicit Basic_list(bool) {}
  constexpr Basic_list() : _f(nullptr) {}
 
  Basic_list(Basic_list &&o) : _f(o._f)
  {
    o.clear();
  }
 
  Basic_list &operator = (Basic_list &&o) &
  {
    if (&o != this)
      {
        _f = o._f;
        o.clear();
      }
 
    return *this;
  }

  bool empty() const { return !_f; }
  Value_type front() const { return static_cast<Value_type>(_f); }

  void clear() { _f = nullptr; }

  Iterator begin() { return Iterator(&_f); }
  Const_iterator begin() const { return Const_iterator(_f); }
  static Const_iterator iter(Const_value_type c) { return Const_iterator(c); }
  Const_iterator end() const { return Const_iterator(nullptr); }
  Iterator end() { return Iterator(); }
 
protected:
  static typename POLICY::Type __get_internal(Iterator const &i) { return i._c; }
  static Iterator __iter(typename POLICY::Type c) { return Iterator(c); }

  typename POLICY::Head_type _f;
};
 
}}