innobase/include/ut0lst.h

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/** @file include/ut0lst.h
 List utilities

 Created 9/10/1995 Heikki Tuuri
 Rewritten by Sunny Bains Dec 2011.
 ***********************************************************************/

#ifndef ut0lst_h
#define ut0lst_h

/* Do not include univ.i because univ.i includes this. */

#include "ut0dbg.h"

/* This module implements the two-way linear list. Note that a single
list node may belong to two or more lists, but is only on one list
at a time. */

/** The two way list node.
 @tparam Type the list node type name */
template <typename Type>
struct ut_list_node {
  Type *prev; /*!< pointer to the previous
              node, NULL if start of list */
  Type *next; /*!< pointer to next node,
              NULL if end of list */

  void reverse() {
    Type *tmp = prev;
    prev = next;
    next = tmp;
  }
};

/** Macro used for legacy reasons */
#define UT_LIST_NODE_T(t) ut_list_node<t>

/** The two-way list base node. The base node contains pointers to both ends
 of the list and a count of nodes in the list (excluding the base node
 from the count). We also store a pointer to the member field so that it
 doesn't have to be specified when doing list operations.
 @tparam Type the type of the list element
 @tparam NodePtr field member pointer that points to the list node */
template <typename Type, typename NodePtr>
struct ut_list_base {
  typedef Type elem_type;
  typedef NodePtr node_ptr;
  typedef ut_list_node<Type> node_type;

  ulint count{0};            /*!< count of nodes in list */
  elem_type *start{nullptr}; /*!< pointer to list start,
                             NULL if empty */
  elem_type *end{nullptr};   /*!< pointer to list end,
                             NULL if empty */
  node_ptr node{nullptr};    /*!< Pointer to member field
                             that is used as a link node */
#ifdef UNIV_DEBUG
  ulint init{0}; /*!< UT_LIST_INITIALISED if
                 the list was initialised with
                 UT_LIST_INIT() */
#endif           /* UNIV_DEBUG */

  void reverse() {
    Type *tmp = start;
    start = end;
    end = tmp;
  }
};

#define UT_LIST_BASE_NODE_T(t) ut_list_base<t, ut_list_node<t> t::*>

#ifdef UNIV_DEBUG
#define UT_LIST_INITIALISED 0xCAFE
#define UT_LIST_INITIALISE(b) (b).init = UT_LIST_INITIALISED
#define UT_LIST_IS_INITIALISED(b) ut_a(((b).init == UT_LIST_INITIALISED))
#else
#define UT_LIST_INITIALISE(b)
#define UT_LIST_IS_INITIALISED(b)
#endif /* UNIV_DEBUG */

/** Note: This is really the list constructor. We should be able to use
 placement new here.
 Initializes the base node of a two-way list.
 @param b the list base node
 @param pmf point to member field that will be used as the link node */
#define UT_LIST_INIT(b, pmf) \
  {                          \
    (b).count = 0;           \
    (b).start = 0;           \
    (b).end = 0;             \
    (b).node = pmf;          \
    UT_LIST_INITIALISE(b);   \
  }

/** Functor for accessing the embedded node within a list element. This is
required because some lists can have the node emebedded inside a nested
struct/union. See lock0priv.h (table locks) for an example. It provides a
specialised functor to grant access to the list node. */
template <typename Type>
struct GenericGetNode {
  typedef ut_list_node<Type> node_type;

  GenericGetNode(node_type Type::*node) : m_node(node) {}

  node_type &operator()(Type &elem) { return (elem.*m_node); }

  node_type Type::*m_node;
};

/** Adds the node as the first element in a two-way linked list.
 @param list the base node (not a pointer to it)
 @param elem the element to add */
template <typename List>
void ut_list_prepend(List &list, typename List::elem_type *elem) {
  typename List::node_type &elem_node = elem->*list.node;

  UT_LIST_IS_INITIALISED(list);

  elem_node.prev = nullptr;
  elem_node.next = list.start;

  if (list.start != nullptr) {
    typename List::node_type &base_node = list.start->*list.node;

    ut_ad(list.start != elem);

    base_node.prev = elem;
  }

  list.start = elem;

  if (list.end == nullptr) {
    list.end = elem;
  }

  ++list.count;
}

/** Adds the node as the first element in a two-way linked list.
 @param LIST the base node (not a pointer to it)
 @param ELEM the element to add */
#define UT_LIST_ADD_FIRST(LIST, ELEM) ut_list_prepend(LIST, ELEM)

/** Adds the node as the last element in a two-way linked list.
 @param list list
 @param elem the element to add
 @param get_node to get the list node for that element */
template <typename List, typename Functor>
void ut_list_append(List &list, typename List::elem_type *elem,
                    Functor get_node) {
  typename List::node_type &node = get_node(*elem);

  UT_LIST_IS_INITIALISED(list);

  node.next = nullptr;
  node.prev = list.end;

  if (list.end != nullptr) {
    typename List::node_type &base_node = get_node(*list.end);

    ut_ad(list.end != elem);

    base_node.next = elem;
  }

  list.end = elem;

  if (list.start == nullptr) {
    list.start = elem;
  }

  ++list.count;
}

/** Adds the node as the last element in a two-way linked list.
 @param list list
 @param elem the element to add */
template <typename List>
void ut_list_append(List &list, typename List::elem_type *elem) {
  ut_list_append(list, elem,
                 GenericGetNode<typename List::elem_type>(list.node));
}

/** Adds the node as the last element in a two-way linked list.
 @param LIST list base node (not a pointer to it)
 @param ELEM the element to add */
#define UT_LIST_ADD_LAST(LIST, ELEM) ut_list_append(LIST, ELEM)

/** Inserts a ELEM2 after ELEM1 in a list.
 @param list the base node
 @param elem1 node after which ELEM2 is inserted
 @param elem2 node being inserted after ELEM1 */
template <typename List>
void ut_list_insert(List &list, typename List::elem_type *elem1,
                    typename List::elem_type *elem2) {
  ut_ad(elem1 != elem2);
  UT_LIST_IS_INITIALISED(list);

  typename List::node_type &elem1_node = elem1->*list.node;
  typename List::node_type &elem2_node = elem2->*list.node;

  elem2_node.prev = elem1;
  elem2_node.next = elem1_node.next;

  if (elem1_node.next != nullptr) {
    typename List::node_type &next_node = elem1_node.next->*list.node;

    next_node.prev = elem2;
  }

  elem1_node.next = elem2;

  if (list.end == elem1) {
    list.end = elem2;
  }

  ++list.count;
}

/** Inserts a ELEM2 after ELEM1 in a list.
 @param LIST list base node (not a pointer to it)
 @param ELEM1 node after which ELEM2 is inserted
 @param ELEM2 node being inserted after ELEM1 */
#define UT_LIST_INSERT_AFTER(LIST, ELEM1, ELEM2) \
  ut_list_insert(LIST, ELEM1, ELEM2)

/** Removes a node from a two-way linked list.
 @param list the base node (not a pointer to it)
 @param node member node within list element that is to be removed
 @param get_node functor to get the list node from elem */
template <typename List, typename Functor>
void ut_list_remove(List &list, typename List::node_type &node,
                    Functor get_node) {
  ut_a(list.count > 0);
  UT_LIST_IS_INITIALISED(list);

  if (node.next != nullptr) {
    typename List::node_type &next_node = get_node(*node.next);

    next_node.prev = node.prev;
  } else {
    list.end = node.prev;
  }

  if (node.prev != nullptr) {
    typename List::node_type &prev_node = get_node(*node.prev);

    prev_node.next = node.next;
  } else {
    list.start = node.next;
  }

  node.next = nullptr;
  node.prev = nullptr;

  --list.count;
}

/** Removes a node from a two-way linked list.
 @param list the base node (not a pointer to it)
 @param elem element to be removed from the list
 @param get_node functor to get the list node from elem */
template <typename List, typename Functor>
void ut_list_remove(List &list, typename List::elem_type *elem,
                    Functor get_node) {
  ut_list_remove(list, get_node(*elem), get_node);
}

/** Removes a node from a two-way linked list.
 @param list the base node (not a pointer to it)
 @param elem element to be removed from the list */
template <typename List>
void ut_list_remove(List &list, typename List::elem_type *elem) {
  ut_list_remove(list, elem->*list.node,
                 GenericGetNode<typename List::elem_type>(list.node));
}

/** Removes a node from a two-way linked list.
 @param LIST the base node (not a pointer to it)
 @param ELEM node to be removed from the list */
#define UT_LIST_REMOVE(LIST, ELEM) ut_list_remove(LIST, ELEM)

/** Gets the next node in a two-way list.
 @param NAME list name
 @param N pointer to a node
 @return the successor of N in NAME, or NULL */
#define UT_LIST_GET_NEXT(NAME, N) (((N)->NAME).next)

/** Gets the previous node in a two-way list.
 @param NAME list name
 @param N pointer to a node
 @return the predecessor of N in NAME, or NULL */
#define UT_LIST_GET_PREV(NAME, N) (((N)->NAME).prev)

/** Alternative macro to get the number of nodes in a two-way list, i.e.,
 its length.
 @param BASE the base node (not a pointer to it).
 @return the number of nodes in the list */
#define UT_LIST_GET_LEN(BASE) (BASE).count

/** Gets the first node in a two-way list.
 @param BASE the base node (not a pointer to it)
 @return first node, or NULL if the list is empty */
#define UT_LIST_GET_FIRST(BASE) (BASE).start

/** Gets the last node in a two-way list.
 @param BASE the base node (not a pointer to it)
 @return last node, or NULL if the list is empty */
#define UT_LIST_GET_LAST(BASE) (BASE).end

struct NullValidate {
  void operator()(const void *elem) {}
};

/** Iterate over all the elements and call the functor for each element.
 @param[in]	list	base node (not a pointer to it)
 @param[in,out]	functor	Functor that is called for each element in the list */
template <typename List, class Functor>
void ut_list_map(const List &list, Functor &functor) {
  ulint count = 0;

  UT_LIST_IS_INITIALISED(list);

  for (typename List::elem_type *elem = list.start; elem != nullptr;
       elem = (elem->*list.node).next, ++count) {
    functor(elem);
  }

  ut_a(count == list.count);
}

template <typename List>
void ut_list_reverse(List &list) {
  UT_LIST_IS_INITIALISED(list);

  for (typename List::elem_type *elem = list.start; elem != nullptr;
       elem = (elem->*list.node).prev) {
    (elem->*list.node).reverse();
  }

  list.reverse();
}

#define UT_LIST_REVERSE(LIST) ut_list_reverse(LIST)

/** Checks the consistency of a two-way list.
 @param[in]		list base node (not a pointer to it)
 @param[in,out]		functor Functor that is called for each element in
 the list */
template <typename List, class Functor>
void ut_list_validate(const List &list, Functor &functor) {
  ut_list_map(list, functor);

  /* Validate the list backwards. */
  ulint count = 0;

  for (typename List::elem_type *elem = list.end; elem != nullptr;
       elem = (elem->*list.node).prev) {
    ++count;
  }

  ut_a(count == list.count);
}

/** Check the consistency of a two-way list.
@param[in] LIST base node reference */
#define UT_LIST_CHECK(LIST)        \
  do {                             \
    NullValidate nullV;            \
    ut_list_validate(LIST, nullV); \
  } while (0)

/** Move the given element to the beginning of the list.
@param[in,out]	list	the list object
@param[in]	elem	the element of the list which will be moved
                        to the beginning of the list. */
template <typename List>
void ut_list_move_to_front(List &list, typename List::elem_type *elem) {
  ut_ad(ut_list_exists(list, elem));

  if (UT_LIST_GET_FIRST(list) != elem) {
    ut_list_remove(list, elem);
    ut_list_prepend(list, elem);
  }
}

#ifdef UNIV_DEBUG
/** Check if the given element exists in the list.
@param[in,out]	list	the list object
@param[in]	elem	the element of the list which will be checked */
template <typename List>
bool ut_list_exists(List &list, typename List::elem_type *elem) {
  typename List::elem_type *e1;

  for (e1 = UT_LIST_GET_FIRST(list); e1 != nullptr;
       e1 = (e1->*list.node).next) {
    if (elem == e1) {
      return (true);
    }
  }
  return (false);
}
#endif

#define UT_LIST_MOVE_TO_FRONT(LIST, ELEM) ut_list_move_to_front(LIST, ELEM)

#endif /* ut0lst.h */