intrusive_links.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2016 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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******************************************************************************/
 
#ifndef ETL_INTRUSIVE_LINKS_INCLUDED
#define ETL_INTRUSIVE_LINKS_INCLUDED
 
#include "platform.h"
#include "algorithm.h"
#include "error_handler.h"
#include "exception.h"
#include "nullptr.h"
#include "type_traits.h"
#include "utility.h"
 
#include <stddef.h>
 
//*****************************************************************************
// Note:
// The link functions work slightly differently to the STL 'insert' convention
// in that the second link parameter will be inserted after the first.
// i.e.
// If the list contains '1', '2', '3', '4' and "link_splice '2','5'" is invoked
// the resulting list will contain '1', '2', '5', '3', '4' This is to maintain
// consistency between forward and bidirectional links and also is intuitive.
//*****************************************************************************
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  class link_exception : public etl::exception
  {
  public:
 
    link_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class not_unlinked_exception : public etl::link_exception
  {
  public:
 
    not_unlinked_exception(string_type file_name_, numeric_type line_number_)
      : link_exception(ETL_ERROR_TEXT("link:still linked", ETL_INTRUSIVE_LINKS_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  template <size_t ID_>
  struct forward_link
  {
    enum
    {
      ID = ID_,
    };
 
    //***********************************
    ETL_CONSTEXPR forward_link()
      : etl_next(ETL_NULLPTR)
    {
    }
 
    //***********************************
    ETL_CONSTEXPR forward_link(forward_link* p_next)
      : etl_next(p_next)
    {
    }
 
    //***********************************
    ETL_CONSTEXPR forward_link(const forward_link& other)
      : etl_next(other.etl_next)
    {
    }
 
    //***********************************
    ETL_CONSTEXPR14 forward_link& operator=(const forward_link& other)
    {
      etl_next = other.etl_next;
 
      return *this;
    }
 
    //***********************************
    void clear()
    {
      etl_next = ETL_NULLPTR;
    }
 
    //***********************************
    ETL_NODISCARD
    bool is_linked() const
    {
      return etl_next != ETL_NULLPTR;
    }
 
    //***********************************
    ETL_NODISCARD
    bool has_next() const
    {
      return etl_next != ETL_NULLPTR;
    }
 
    //***********************************
    void set_next(forward_link* n)
    {
      etl_next = n;
    }
 
    //***********************************
    void set_next(forward_link& n)
    {
      etl_next = &n;
    }
 
    //***********************************
    ETL_NODISCARD
    forward_link* get_next() const
    {
      return etl_next;
    }
 
    forward_link* etl_next;
  };
 
  //***********************************
  template <typename TLink>
  struct is_forward_link
  {
    static ETL_CONSTANT bool value = etl::is_same<TLink, etl::forward_link<TLink::ID> >::value;
  };
 
  //***********************************
#if ETL_USING_CPP17
  template <typename TLink>
  inline constexpr bool is_forward_link_v = etl::is_forward_link<TLink>::value;
#endif
 
  //***************************************************************************
  // link
  //***************************************************************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link(TLink& lhs, TLink& rhs)
  {
    lhs.etl_next = &rhs;
  }
 
  //***********************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link(TLink* lhs, TLink* rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      lhs->etl_next = rhs;
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link(TLink& lhs, TLink* rhs)
  {
    lhs.etl_next = rhs;
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link(TLink* lhs, TLink& rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      lhs->etl_next = &rhs;
    }
  }
 
  //***************************************************************************
  // link_splice
  //***************************************************************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_splice(TLink& lhs, TLink& rhs)
  {
    rhs.etl_next = lhs.etl_next;
    lhs.etl_next = &rhs;
  }
 
  //***********************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_splice(TLink* lhs, TLink* rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      if (rhs != ETL_NULLPTR)
      {
        rhs->etl_next = lhs->etl_next;
      }
 
      lhs->etl_next = rhs;
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_splice(TLink& lhs, TLink* rhs)
  {
    if (rhs != ETL_NULLPTR)
    {
      rhs->etl_next = lhs.etl_next;
    }
 
    lhs.etl_next = rhs;
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_splice(TLink* lhs, TLink& rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      rhs.etl_next  = lhs->etl_next;
      lhs->etl_next = &rhs;
    }
  }
 
  //***********************************
  // Reference, Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_splice(TLink& lhs, TLink& first, TLink& last)
  {
    last.etl_next = lhs.etl_next;
    lhs.etl_next  = &first;
  }
 
  //***********************************
  // Pointer, Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_splice(TLink* lhs, TLink& first, TLink& last)
  {
    if (lhs != ETL_NULLPTR)
    {
      last.etl_next = lhs->etl_next;
      lhs->etl_next = &first;
    }
    else
    {
      last.etl_next = ETL_NULLPTR;
    }
  }
 
  //***************************************************************************
  // unlink_after
  //***************************************************************************
  // Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type unlink_after(TLink& node)
  {
    if (node.etl_next != ETL_NULLPTR)
    {
      TLink* unlinked_node = node.etl_next;
      node.etl_next        = unlinked_node->etl_next;
      unlinked_node->clear();
      return unlinked_node;
    }
 
    return node.etl_next;
  }
 
  //***********************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type unlink_after(TLink& before, TLink& last)
  {
    TLink* first = before.etl_next;
 
    if (&before != &last)
    {
      before.etl_next = last.etl_next;
      last.clear();
    }
 
    return first;
  }
 
  // Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, bool>::type is_linked(TLink& node)
  {
    return node.is_linked();
  }
 
  // Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, bool>::type is_linked(TLink* node)
  {
    return node->is_linked();
  }
 
  //***************************************************************************
  // link_clear
  //***************************************************************************
  // Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_clear(TLink& start)
  {
    start.etl_next = ETL_NULLPTR;
  }
 
  //***********************************
  // Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_clear(TLink* start)
  {
    if (start != ETL_NULLPTR)
    {
      etl::link_clear(*start);
    }
  }
 
  //***************************************************************************
  // link_clear range
  //***************************************************************************
  // Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_clear_range(TLink& start)
  {
    TLink* current = &start;
 
    while (current != ETL_NULLPTR)
    {
      TLink* next = current->etl_next;
      current->clear();
      current = next;
    }
  }
 
  //***********************************
  // Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type link_clear_range(TLink* start)
  {
    if (start != ETL_NULLPTR)
    {
      etl::link_clear_range(*start);
    }
  }
 
#if ETL_USING_CPP17
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type create_linked_list(TLink& first, TLinks&... links)
  {
    TLink* current = &first;
    ((current->etl_next = &links, current = &links), ...);
 
    return current;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type create_linked_list(TLink* first, TLinks*... links)
  {
    if (first != ETL_NULLPTR)
    {
      return create_linked_list(*first, (*links)...);
    }
    else
    {
      return nullptr;
    }
  }
#elif ETL_USING_CPP11
  //***************************************************************************
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type create_linked_list(TLink& first)
  {
    return &first;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type create_linked_list(TLink& first, TLink& next, TLinks&... links)
  {
    first.etl_next = &next;
    return create_linked_list(next, static_cast<TLink&>(links)...);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type create_linked_list(TLink* first)
  {
    if (first != ETL_NULLPTR)
    {
      return create_linked_list(*first);
    }
    else
    {
      return ETL_NULLPTR;
    }
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, TLink*>::type create_linked_list(TLink* first, TLink* next, TLinks*... links)
  {
    if (first != ETL_NULLPTR)
    {
      return create_linked_list(*first, *next, static_cast<TLink&>(*links)...);
    }
    else
    {
      return ETL_NULLPTR;
    }
  }
#endif
 
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type detach_linked_list(TLink& first)
  {
    link_clear_range(first);
  }
 
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_forward_link<TLink>::value, void>::type detach_linked_list(TLink* first)
  {
    if (first != ETL_NULLPTR)
    {
      detach_linked_list(*first);
    }
  }
 
  //***************************************************************************
  //***************************************************************************
  template <size_t ID_>
  struct bidirectional_link
  {
    enum
    {
      ID = ID_,
    };
 
    //***********************************
    ETL_CONSTEXPR bidirectional_link()
      : etl_previous(ETL_NULLPTR)
      , etl_next(ETL_NULLPTR)
    {
    }
 
    //***********************************
    ETL_CONSTEXPR bidirectional_link(bidirectional_link* p_previous, bidirectional_link* p_next)
      : etl_previous(p_previous)
      , etl_next(p_next)
    {
    }
 
    //***********************************
    ETL_CONSTEXPR bidirectional_link(const bidirectional_link& other)
      : etl_previous(other.etl_previous)
      , etl_next(other.etl_next)
    {
    }
 
    //***********************************
    ETL_CONSTEXPR14 bidirectional_link& operator=(const bidirectional_link& other)
    {
      etl_previous = other.etl_previous;
      etl_next     = other.etl_next;
 
      return *this;
    }
 
    //***********************************
    void clear()
    {
      etl_previous = ETL_NULLPTR;
      etl_next     = ETL_NULLPTR;
    }
 
    //***********************************
    ETL_NODISCARD
    bool is_linked() const
    {
      return (etl_previous != ETL_NULLPTR) || (etl_next != ETL_NULLPTR);
    }
 
    //***********************************
    ETL_NODISCARD
    bool has_next() const
    {
      return etl_next != ETL_NULLPTR;
    }
 
    //***********************************
    ETL_NODISCARD
    bool has_previous() const
    {
      return etl_previous != ETL_NULLPTR;
    }
 
    //***********************************
    void set_next(bidirectional_link* n)
    {
      etl_next = n;
    }
 
    //***********************************
    void set_next(bidirectional_link& n)
    {
      etl_next = &n;
    }
 
    //***********************************
    ETL_NODISCARD
    bidirectional_link* get_next() const
    {
      return etl_next;
    }
 
    //***********************************
    void set_previous(bidirectional_link* n)
    {
      etl_previous = n;
    }
 
    //***********************************
    void set_previous(bidirectional_link& n)
    {
      etl_previous = &n;
    }
 
    //***********************************
    ETL_NODISCARD
    bidirectional_link* get_previous() const
    {
      return etl_previous;
    }
 
    //***********************************
    void reverse()
    {
      using ETL_OR_STD::swap; // Allow ADL
      swap(etl_previous, etl_next);
    }
 
    //***********************************
    void unlink()
    {
      // Connect the previous link with the next.
      if (etl_previous != ETL_NULLPTR)
      {
        etl_previous->etl_next = etl_next;
      }
 
      // Connect the next link with the previous.
      if (etl_next != ETL_NULLPTR)
      {
        etl_next->etl_previous = etl_previous;
      }
 
      clear();
    }
 
    bidirectional_link* etl_previous;
    bidirectional_link* etl_next;
  };
 
  //***********************************
  template <typename TLink>
  struct is_bidirectional_link
  {
    static ETL_CONSTANT bool value = etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value;
  };
 
  //***********************************
#if ETL_USING_CPP17
  template <typename TLink>
  inline constexpr bool is_bidirectional_link_v = etl::is_bidirectional_link<TLink>::value;
#endif
 
  //***************************************************************************
  // link
  //***************************************************************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link(TLink& lhs, TLink& rhs)
  {
    lhs.etl_next     = &rhs;
    rhs.etl_previous = &lhs;
  }
 
  //***********************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link(TLink* lhs, TLink* rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      lhs->etl_next = rhs;
    }
 
    if (rhs != ETL_NULLPTR)
    {
      rhs->etl_previous = lhs;
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link(TLink& lhs, TLink* rhs)
  {
    lhs.etl_next = rhs;
 
    if (rhs != ETL_NULLPTR)
    {
      rhs->etl_previous = &lhs;
    }
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link(TLink* lhs, TLink& rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      lhs->etl_next = &rhs;
    }
 
    rhs.etl_previous = lhs;
  }
 
  //***********************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_splice(TLink& lhs, TLink& rhs)
  {
    rhs.etl_next     = lhs.etl_next;
    rhs.etl_previous = &lhs;
 
    if (lhs.etl_next != ETL_NULLPTR)
    {
      lhs.etl_next->etl_previous = &rhs;
    }
 
    lhs.etl_next = &rhs;
  }
 
  //***************************************************************************
  // link_splice
  //***************************************************************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_splice(TLink* lhs, TLink* rhs)
  {
    if (rhs != ETL_NULLPTR)
    {
      if (lhs != ETL_NULLPTR)
      {
        rhs->etl_next = lhs->etl_next;
      }
 
      rhs->etl_previous = lhs;
    }
 
    if (lhs != ETL_NULLPTR)
    {
      if (lhs->etl_next != ETL_NULLPTR)
      {
        lhs->etl_next->etl_previous = rhs;
      }
 
      lhs->etl_next = rhs;
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_splice(TLink& lhs, TLink* rhs)
  {
    if (rhs != ETL_NULLPTR)
    {
      rhs->etl_next     = lhs.etl_next;
      rhs->etl_previous = &lhs;
    }
 
    if (lhs.etl_next != ETL_NULLPTR)
    {
      lhs.etl_next->etl_previous = rhs;
    }
 
    lhs.etl_next = rhs;
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_splice(TLink* lhs, TLink& rhs)
  {
    if (lhs != ETL_NULLPTR)
    {
      rhs.etl_next = lhs->etl_next;
    }
 
    rhs.etl_previous = lhs;
 
    if (lhs != ETL_NULLPTR)
    {
      if (lhs->etl_next != ETL_NULLPTR)
      {
        lhs->etl_next->etl_previous = &rhs;
      }
 
      lhs->etl_next = &rhs;
    }
  }
 
  //***********************************
  // Reference, Reference, Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_splice(TLink& lhs, TLink& first,
                                                                                                                    TLink& last)
  {
    last.etl_next      = lhs.etl_next;
    first.etl_previous = &lhs;
 
    if (last.etl_next != ETL_NULLPTR)
    {
      last.etl_next->etl_previous = &last;
    }
 
    lhs.etl_next = &first;
  }
 
  //***********************************
  // Pointer, Reference, Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_splice(TLink* lhs, TLink& first,
                                                                                                                    TLink& last)
  {
    if (lhs != ETL_NULLPTR)
    {
      last.etl_next = lhs->etl_next;
    }
    else
    {
      last.etl_next = ETL_NULLPTR;
    }
 
    first.etl_previous = lhs;
 
    if (last.etl_next != ETL_NULLPTR)
    {
      last.etl_next->etl_previous = &last;
    }
 
    if (lhs != ETL_NULLPTR)
    {
      lhs->etl_next = &first;
    }
  }
 
  //***************************************************************************
  // unlink
  //***************************************************************************
  // Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type unlink(TLink& node)
  {
    node.unlink();
  }
 
  //***********************************
  // Reference Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, TLink&>::type unlink(TLink& first, TLink& last)
  {
    if (&first == &last)
    {
      first.unlink();
    }
    else
    {
      if (last.etl_next != ETL_NULLPTR)
      {
        last.etl_next->etl_previous = first.etl_previous;
      }
 
      if (first.etl_previous != ETL_NULLPTR)
      {
        first.etl_previous->etl_next = last.etl_next;
      }
 
      first.etl_previous = ETL_NULLPTR;
      last.etl_next      = ETL_NULLPTR;
    }
 
    return first;
  }
 
  // Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, bool>::type is_linked(TLink& node)
  {
    return node.is_linked();
  }
 
  // Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, bool>::type is_linked(TLink* node)
  {
    return node->is_linked();
  }
 
  //***************************************************************************
  // link_clear_range
  //***************************************************************************
  // Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_clear_range(TLink& start)
  {
    TLink* current = &start;
 
    while (current != ETL_NULLPTR)
    {
      TLink* next = current->etl_next;
      current->clear();
      current = next;
    }
  }
 
  //***********************************
  // Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::bidirectional_link<TLink::ID> >::value, void>::type link_clear_range(TLink* start)
  {
    if (start != ETL_NULLPTR)
    {
      etl::link_clear_range(*start);
    }
  }
 
#if ETL_USING_CPP17
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, TLink*>::type create_linked_list(TLink& first, TLinks&... links)
  {
    TLink* current = &first;
    ((current->etl_next = &links, static_cast<TLink&>(links).etl_previous = current, current = &links), ...);
 
    return current;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, TLink*>::type create_linked_list(TLink* first, TLinks*... links)
  {
    TLink* current = first;
    ((current->etl_next = links, static_cast<TLink*>(links)->etl_previous = current, current = links), ...);
 
    return current;
  }
#elif ETL_USING_CPP11
  //***************************************************************************
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, TLink*>::type create_linked_list(TLink& first)
  {
    return &first;
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, TLink*>::type create_linked_list(TLink& first, TLink& next, TLinks&... links)
  {
    first.etl_next    = &next;
    next.etl_previous = &first;
 
    return create_linked_list(next, static_cast<TLink&>(links)...);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TLink, typename... TLinks>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, TLink*>::type create_linked_list(TLink* first, TLink* next, TLinks*... links)
  {
    if (first != ETL_NULLPTR)
    {
      return create_linked_list(*first, *next, static_cast<TLink&>(*links)...);
    }
    else
    {
      return ETL_NULLPTR;
    }
  }
#endif
 
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, void>::type detach_linked_list(TLink& first)
  {
    link_clear_range(first);
  }
 
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_bidirectional_link<TLink>::value, void>::type detach_linked_list(TLink* first)
  {
    if (first != ETL_NULLPTR)
    {
      detach_linked_list(*first);
    }
  }
 
  //***************************************************************************
  //***************************************************************************
  template <size_t ID_>
  struct tree_link
  {
    enum
    {
      ID = ID_,
    };
 
    //***********************************
    tree_link()
      : etl_parent(ETL_NULLPTR)
      , etl_left(ETL_NULLPTR)
      , etl_right(ETL_NULLPTR)
    {
    }
 
    //***********************************
    tree_link(tree_link* p_parent, tree_link* p_left, tree_link* p_right)
      : etl_parent(p_parent)
      , etl_left(p_left)
      , etl_right(p_right)
    {
    }
 
    //***********************************
    tree_link(const tree_link& other)
      : etl_parent(other.etl_parent)
      , etl_left(other.etl_left)
      , etl_right(other.etl_right)
    {
    }
 
    //***********************************
    tree_link& operator=(const tree_link& other)
    {
      etl_parent = other.etl_parent;
      etl_left   = other.etl_left;
      etl_right  = other.etl_right;
 
      return *this;
    }
 
    //***********************************
    void clear()
    {
      etl_parent = ETL_NULLPTR;
      etl_left   = ETL_NULLPTR;
      etl_right  = ETL_NULLPTR;
    }
 
    //***********************************
    bool is_linked() const
    {
      return (etl_parent != ETL_NULLPTR) || (etl_left != ETL_NULLPTR) || (etl_right != ETL_NULLPTR);
    }
 
    //***********************************
    ETL_NODISCARD
    bool has_parent() const
    {
      return etl_parent != ETL_NULLPTR;
    }
 
    //***********************************
    ETL_NODISCARD
    bool has_left() const
    {
      return etl_left != ETL_NULLPTR;
    }
 
    //***********************************
    ETL_NODISCARD
    bool has_right() const
    {
      return etl_right != ETL_NULLPTR;
    }
 
    //***********************************
    void set_parent(tree_link* p)
    {
      etl_parent = p;
    }
 
    //***********************************
    void set_left(tree_link* l)
    {
      etl_left = l;
    }
 
    //***********************************
    void set_right(tree_link* r)
    {
      etl_right = r;
    }
 
    //***********************************
    void set_parent(tree_link& p)
    {
      etl_parent = &p;
    }
 
    //***********************************
    void set_left(tree_link& l)
    {
      etl_left = &l;
    }
 
    //***********************************
    void set_right(tree_link& r)
    {
      etl_right = &r;
    }
 
    //***********************************
    ETL_NODISCARD
    tree_link* get_parent() const
    {
      return etl_parent;
    }
 
    //***********************************
    ETL_NODISCARD
    tree_link* get_left() const
    {
      return etl_left;
    }
 
    //***********************************
    ETL_NODISCARD
    tree_link* get_right() const
    {
      return etl_right;
    }
 
    //***********************************
    void mirror()
    {
      using ETL_OR_STD::swap;
      swap(etl_left, etl_right);
    }
 
    tree_link* etl_parent;
    tree_link* etl_left;
    tree_link* etl_right;
  };
 
  //***********************************
  template <typename TLink>
  struct is_tree_link
  {
    static ETL_CONSTANT bool value = etl::is_same<TLink, etl::tree_link<TLink::ID> >::value;
  };
 
  //***********************************
#if ETL_USING_CPP17
  template <typename TLink>
  inline constexpr bool is_tree_link_v = etl::is_tree_link<TLink>::value;
#endif
 
  //***************************************************************************
  // link_left
  // Sets the left link.
  //***************************************************************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_left(TLink& parent, TLink& child)
  {
    parent.etl_left  = &child;
    child.etl_parent = &parent;
  }
 
  //***********************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_left(TLink* parent, TLink* child)
  {
    if (parent != ETL_NULLPTR)
    {
      parent->etl_left = child;
    }
 
    if (child != ETL_NULLPTR)
    {
      child->etl_parent = parent;
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_left(TLink& parent, TLink* child)
  {
    parent.etl_left = child;
 
    if (child != ETL_NULLPTR)
    {
      child->etl_parent = &parent;
    }
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_left(TLink* parent, TLink& child)
  {
    if (parent != ETL_NULLPTR)
    {
      parent->etl_left = &child;
    }
 
    child.etl_parent = parent;
  }
 
  //***************************************************************************
  // link_right
  // Sets the right link.
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_right(TLink& parent, TLink& child)
  {
    parent.etl_right = &child;
    child.etl_parent = &parent;
  }
 
  //***********************************
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_right(TLink* parent, TLink* child)
  {
    if (parent != ETL_NULLPTR)
    {
      parent->etl_right = child;
    }
 
    if (child != ETL_NULLPTR)
    {
      child->etl_parent = parent;
    }
  }
 
  //***********************************
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_right(TLink& parent, TLink* child)
  {
    parent.etl_right = child;
 
    if (child != ETL_NULLPTR)
    {
      child->etl_parent = &parent;
    }
  }
 
  //***********************************
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_right(TLink* parent, TLink& child)
  {
    if (parent != ETL_NULLPTR)
    {
      parent->etl_right = &child;
    }
 
    child.etl_parent = parent;
  }
 
  //***************************************************************************
  // link_rotate_left
  //***************************************************************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_left(TLink& parent, TLink& child)
  {
    TLink* grandparent = parent.etl_parent;
 
    parent.etl_right = child.etl_left;
 
    if (parent.etl_right != ETL_NULLPTR)
    {
      parent.etl_right->etl_parent = &parent;
    }
 
    child.etl_parent  = grandparent;
    parent.etl_parent = &child;
    child.etl_left    = &parent;
 
    if (grandparent != ETL_NULLPTR)
    {
      if (grandparent->etl_left == &parent)
      {
        grandparent->etl_left = &child;
      }
      else if (grandparent->etl_right == &parent)
      {
        grandparent->etl_right = &child;
      }
    }
  }
 
  //***********************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_left(TLink* parent, TLink* child)
  {
    if ((parent != ETL_NULLPTR) && (child != ETL_NULLPTR))
    {
      link_rotate_left(*parent, *child);
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_left(TLink& parent, TLink* child)
  {
    if (child != ETL_NULLPTR)
    {
      link_rotate_left(parent, *child);
    }
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_left(TLink* parent, TLink& child)
  {
    if (parent != ETL_NULLPTR)
    {
      link_rotate_left(*parent, child);
    }
  }
 
  //***************************************************************************
  // link_rotate_right
  //***************************************************************************
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_right(TLink& parent, TLink& child)
  {
    TLink* grandparent = parent.etl_parent;
 
    parent.etl_left = child.etl_right;
 
    if (parent.etl_left != ETL_NULLPTR)
    {
      parent.etl_left->etl_parent = &parent;
    }
 
    child.etl_parent  = grandparent;
    parent.etl_parent = &child;
    child.etl_right   = &parent;
 
    if (grandparent != ETL_NULLPTR)
    {
      if (grandparent->etl_left == &parent)
      {
        grandparent->etl_left = &child;
      }
      else if (grandparent->etl_right == &parent)
      {
        grandparent->etl_right = &child;
      }
    }
  }
 
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_right(TLink* parent, TLink* child)
  {
    if ((parent != ETL_NULLPTR) && (child != ETL_NULLPTR))
    {
      link_rotate_right(*parent, *child);
    }
  }
 
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_right(TLink& parent, TLink* child)
  {
    if (child != ETL_NULLPTR)
    {
      link_rotate_right(parent, *child);
    }
  }
 
  //***********************************
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate_right(TLink* parent, TLink& child)
  {
    if (parent != ETL_NULLPTR)
    {
      link_rotate_right(*parent, child);
    }
  }
 
  //***************************************************************************
  // link_rotate
  //***************************************************************************
  // Reference, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate(TLink& parent, TLink& child)
  {
    if (parent.etl_left == &child)
    {
      etl::link_rotate_right(parent, child);
    }
    else
    {
      etl::link_rotate_left(parent, child);
    }
  }
 
  //***********************************
  // Pointer, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate(TLink* parent, TLink* child)
  {
    if ((parent != ETL_NULLPTR) && (child != ETL_NULLPTR))
    {
      if (parent->etl_left == child)
      {
        etl::link_rotate_right(*parent, *child);
      }
      else
      {
        etl::link_rotate_left(*parent, *child);
      }
    }
  }
 
  //***********************************
  // Reference, Pointer
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate(TLink& parent, TLink* child)
  {
    if (child != ETL_NULLPTR)
    {
      if (parent.etl_left == child)
      {
        etl::link_rotate_right(parent, *child);
      }
      else
      {
        etl::link_rotate_left(parent, *child);
      }
    }
  }
 
  //***********************************
  // Pointer, Reference
  template <typename TLink>
  typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_rotate(TLink* parent, TLink& child)
  {
    if (parent != ETL_NULLPTR)
    {
      if (parent->etl_left == &child)
      {
        etl::link_rotate_right(*parent, child);
      }
      else
      {
        etl::link_rotate_left(*parent, child);
      }
    }
  }
 
  // Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_clear(TLink& node)
  {
    node.clear();
  }
 
  // Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type link_clear(TLink* node)
  {
    node->clear();
  }
 
  // Reference
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, bool>::type is_linked(TLink& node)
  {
    return node.is_linked();
  }
 
  // Pointer
  template <typename TLink>
  typename etl::enable_if< etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, bool>::type is_linked(TLink* node)
  {
    return node->is_linked();
  }
} // namespace etl
 
#endif