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name : sql_list.h
 #ifndef INCLUDES_MYSQL_SQL_LIST_H
#define INCLUDES_MYSQL_SQL_LIST_H
/* Copyright (c) 2000, 2012, Oracle and/or its affiliates.
   Copyright (c) 2019, MariaDB Corporation.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */

#ifdef USE_PRAGMA_INTERFACE
#pragma interface			/* gcc class implementation */
#endif

#include "sql_alloc.h"
#include <iterator>

/**
  Simple intrusive linked list.

  @remark Similar in nature to base_list, but intrusive. It keeps a
          a pointer to the first element in the list and a indirect
          reference to the last element.
*/

template <typename T>
class SQL_I_List :public Sql_alloc
{
public:
  uint elements;
  /** The first element in the list. */
  T *first;
  /** A reference to the next element in the list. */
  T **next;

  SQL_I_List() { empty(); }

  SQL_I_List(const SQL_I_List &tmp) : Sql_alloc()
  {
    elements= tmp.elements;
    first= tmp.first;
    next= elements ? tmp.next : &first;
  }

  SQL_I_List& operator=(const SQL_I_List &tmp)
  {
    elements= tmp.elements;
    first= tmp.first;
    next= elements ? tmp.next : &first;;
    return *this;
  }

  inline void empty()
  {
    elements= 0;
    first= NULL;
    next= &first;
  }

  inline void link_in_list(T *element, T **next_ptr)
  {
    elements++;
    (*next)= element;
    next= next_ptr;
    *next= NULL;
  }

  inline void save_and_clear(SQL_I_List<T> *save)
  {
    *save= *this;
    empty();
  }

  inline void push_front(SQL_I_List<T> *save)
  {
    /* link current list last */
    *save->next= first;
    first= save->first;
    elements+= save->elements;
  }

  inline void push_back(SQL_I_List<T> *save)
  {
    if (save->first)
    {
      *next= save->first;
      next= save->next;
      elements+= save->elements;
    }
  }
};


/*
  Basic single linked list
  Used for item and item_buffs.
  All list ends with a pointer to the 'end_of_list' element, which
  data pointer is a null pointer and the next pointer points to itself.
  This makes it very fast to traverse lists as we don't have to
  test for a specialend condition for list that can't contain a null
  pointer.
*/


/**
  list_node - a node of a single-linked list.
  @note We never call a destructor for instances of this class.
*/

struct list_node :public Sql_alloc
{
  list_node *next;
  void *info;
  list_node(const void *info_par, list_node *next_par)
    :next(next_par), info(const_cast<void *>(info_par))
  {}
  list_node()					/* For end_of_list */
  {
    info= 0;
    next= this;
  }
};

typedef bool List_eq(void *a, void *b);

extern MYSQL_PLUGIN_IMPORT list_node end_of_list;

class base_list :public Sql_alloc
{
protected:
  list_node *first,**last;

public:
  uint elements;

  bool operator==(const base_list &rhs) const
  {
    return
      elements == rhs.elements &&
      first == rhs.first &&
      last == rhs.last;
  }
  base_list& operator=(const base_list &rhs)
  {
    elements= rhs.elements;
    first= rhs.first;
    last= elements ? rhs.last : &first;
    return *this;
  }

  inline void empty() { elements=0; first= &end_of_list; last=&first;}
  inline base_list() { empty(); }
  /**
    This is a shallow copy constructor that implicitly passes the ownership
    from the source list to the new instance. The old instance is not
    updated, so both objects end up sharing the same nodes. If one of
    the instances then adds or removes a node, the other becomes out of
    sync ('last' pointer), while still operational. Some old code uses and
    relies on this behaviour. This logic is quite tricky: please do not use
    it in any new code.
  */
  inline base_list(const base_list &tmp) :Sql_alloc()
  {
    *this= tmp;
  }
  /**
    Construct a deep copy of the argument in memory root mem_root.
    The elements themselves are copied by pointer. If you also
    need to copy elements by value, you should employ
    list_copy_and_replace_each_value after creating a copy.
  */
  bool copy(const base_list *rhs, MEM_ROOT *mem_root);
  base_list(const base_list &rhs, MEM_ROOT *mem_root) { copy(&rhs, mem_root); }
  inline base_list(bool) {}
  inline bool push_back(void *info)
  {
    if (((*last)=new list_node(info, &end_of_list)))
    {
      last= &(*last)->next;
      elements++;
      return 0;
    }
    return 1;
  }
  inline bool push_back(void *info, MEM_ROOT *mem_root)
  {
    if (((*last)=new (mem_root) list_node(info, &end_of_list)))
    {
      last= &(*last)->next;
      elements++;
      return 0;
    }
    return 1;
  }
  bool push_front_impl(list_node *node)
  {
    if (node)
    {
      if (last == &first)
        last= &node->next;
      first=node;
      elements++;
      return 0;
    }
    return 1;
  }
  inline bool push_front(void *info)
  { return push_front_impl(new list_node(info, first)); }
  inline bool push_front(void *info, MEM_ROOT *mem_root)
  { return push_front_impl(new (mem_root) list_node(info,first)); }
  void remove(list_node **prev)
  {
    list_node *node=(*prev)->next;
    if (!--elements)
      last= &first;
    else if (last == &(*prev)->next)
      last= prev;
    delete *prev;
    *prev=node;
  }
  inline void append(base_list *list)
  {
    if (!list->is_empty())
    {
      if (is_empty())
      {
        *this= *list;
        return;
      }
      *last= list->first;
      last= list->last;
      elements+= list->elements;
    }
  }
  inline void *pop(void)
  {
    if (first == &end_of_list) return 0;
    list_node *tmp=first;
    first=first->next;
    if (!--elements)
      last= &first;
    return tmp->info;
  }

  /*
    Remove from this list elements that are contained in the passed list. 
    We assume that the passed list is a tail of this list (that is, the whole 
    list_node* elements are shared).
  */
  inline void disjoin(const base_list *list)
  {
    list_node **prev= &first;
    list_node *node= first;
    list_node *list_first= list->first;
    elements=0;
    while (node != &end_of_list && node != list_first)
    {
      prev= &node->next;
      node= node->next;
      elements++;
      if (node == &end_of_list)
        return;
    }
    *prev= &end_of_list;
    last= prev;
  }
  inline void prepend(base_list *list)
  {
    if (!list->is_empty())
    {
      if (is_empty())
        last= list->last;
      *list->last= first;
      first= list->first;
      elements+= list->elements;
    }
  }
  /**
    Swap two lists.
  */
  inline void swap(base_list &rhs)
  {
    list_node **rhs_last=rhs.last;
    swap_variables(list_node *, first, rhs.first);
    swap_variables(uint, elements, rhs.elements);
    rhs.last= last == &first ? &rhs.first : last;
    last = rhs_last == &rhs.first ? &first : rhs_last;
  }

  inline list_node* last_node() { return *last; }
  inline list_node* first_node() { return first;}
  inline void *head() { return first->info; }
  inline void **head_ref() { return first != &end_of_list ? &first->info : 0; }
  inline bool is_empty() { return first == &end_of_list ; }
  inline list_node *last_ref() { return &end_of_list; }
  inline bool add_unique(void *info, List_eq *eq)
  {
    list_node *node= first;
    for (;
         node != &end_of_list && (!(*eq)(node->info, info));
         node= node->next) ;
    if (node == &end_of_list)
      return push_back(info);
    return 1;
  }
  friend class base_list_iterator;
  friend class error_list;
  friend class error_list_iterator;

  /*
    Return N-th element in the list, or NULL if the list has
    less than N elements.
  */
  void *elem(uint n)
  {
    list_node *node= first;
    void *data= NULL;
    for (uint i= 0; i <= n; i++)
    {
      if (node == &end_of_list)
      {
        data= NULL;
        break;
      }
      data= node->info;
      node= node->next;
    }
    return data;
  }

#ifdef LIST_EXTRA_DEBUG
  /*
    Check list invariants and print results into trace. Invariants are:
      - (*last) points to end_of_list
      - There are no NULLs in the list.
      - base_list::elements is the number of elements in the list.

    SYNOPSIS
      check_list()
        name  Name to print to trace file

    RETURN 
      1  The list is Ok.
      0  List invariants are not met.
  */

  bool check_list(const char *name)
  {
    base_list *list= this;
    list_node *node= first;
    uint cnt= 0;

    while (node->next != &end_of_list)
    {
      if (!node->info)
      {
        DBUG_PRINT("list_invariants",("%s: error: NULL element in the list", 
                                      name));
        return FALSE;
      }
      node= node->next;
      cnt++;
    }
    if (last != &(node->next))
    {
      DBUG_PRINT("list_invariants", ("%s: error: wrong last pointer", name));
      return FALSE;
    }
    if (cnt+1 != elements)
    {
      DBUG_PRINT("list_invariants", ("%s: error: wrong element count", name));
      return FALSE;
    }
    DBUG_PRINT("list_invariants", ("%s: list is ok", name));
    return TRUE;
  }
#endif // LIST_EXTRA_DEBUG

protected:
  void after(const void *info, list_node *node)
  {
    list_node *new_node=new list_node(info,node->next);
    node->next=new_node;
    elements++;
    if (last == &(node->next))
      last= &new_node->next;
  }
};


class base_list_iterator
{
protected:
  base_list *list;
  list_node **el,**prev,*current;
  void sublist(base_list &ls, uint elm)
  {
    ls.first= *el;
    ls.last= list->last;
    ls.elements= elm;
  }
public:
  base_list_iterator() 
    :list(0), el(0), prev(0), current(0)
  {}

  base_list_iterator(base_list &list_par) 
  { init(list_par); }

  inline void init(base_list &list_par)
  {
    list= &list_par;
    el= &list_par.first;
    prev= 0;
    current= 0;
  }

  inline void *next(void)
  {
    prev=el;
    current= *el;
    el= &current->next;
    return current->info;
  }
  /* Get what calling next() would return, without moving the iterator */
  inline void *peek()
  {
    return (*el)->info;
  }
  inline void *next_fast(void)
  {
    list_node *tmp;
    tmp= *el;
    el= &tmp->next;
    return tmp->info;
  }
  inline void rewind(void)
  {
    el= &list->first;
  }
  inline void *replace(const void *element)
  {						// Return old element
    void *tmp=current->info;
    DBUG_ASSERT(current->info != 0);
    current->info= const_cast<void *>(element);
    return tmp;
  }
  void *replace(base_list &new_list)
  {
    void *ret_value=current->info;
    if (!new_list.is_empty())
    {
      *new_list.last=current->next;
      current->info=new_list.first->info;
      current->next=new_list.first->next;
      if ((list->last == &current->next) && (new_list.elements > 1))
	list->last= new_list.last;
      list->elements+=new_list.elements-1;
    }
    return ret_value;				// return old element
  }
  inline void remove(void)			// Remove current
  {
    list->remove(prev);
    el=prev;
    current=0;					// Safeguard
  }
  void after(const void *element)		// Insert element after current
  {
    list->after(element,current);
    current=current->next;
    el= &current->next;
  }
  inline void **ref(void)			// Get reference pointer
  {
    return &current->info;
  }
  inline bool is_last(void)
  {
    return el == &list->last_ref()->next;
  }
  inline bool at_end()
  {
    return current == &end_of_list;
  }
  friend class error_list_iterator;
};

template <class T> class List :public base_list
{
public:
  inline List() :base_list() {}
  inline List(const List<T> &tmp, MEM_ROOT *mem_root) :
    base_list(tmp, mem_root) {}
  inline bool push_back(T *a) { return base_list::push_back(a); }
  inline bool push_back(T *a, MEM_ROOT *mem_root)
  { return base_list::push_back((void*) a, mem_root); }
  inline bool push_front(T *a) { return base_list::push_front(a); }
  inline bool push_front(T *a, MEM_ROOT *mem_root)
  { return base_list::push_front((void*) a, mem_root); }
  inline T* head() {return (T*) base_list::head(); }
  inline T** head_ref() {return (T**) base_list::head_ref(); }
  inline T* pop()  {return (T*) base_list::pop(); }
  inline void append(List<T> *list) { base_list::append(list); }
  inline void prepend(List<T> *list) { base_list::prepend(list); }
  inline void disjoin(List<T> *list) { base_list::disjoin(list); }
  inline bool add_unique(T *a, bool (*eq)(T *a, T *b))
  { return base_list::add_unique(a, (List_eq *)eq); }
  inline bool copy(const List<T> *list, MEM_ROOT *root)
  { return base_list::copy(list, root); }
  void delete_elements(void)
  {
    list_node *element,*next;
    for (element=first; element != &end_of_list; element=next)
    {
      next=element->next;
      delete (T*) element->info;
    }
    empty();
  }
  T *elem(uint n) { return (T*) base_list::elem(n); }
  // Create a new list with one element
  static List<T> *make(MEM_ROOT *mem_root, T *first)
  {
    List<T> *res= new (mem_root) List<T>;
    return res == NULL || res->push_back(first, mem_root) ? NULL : res;
  }

  class Iterator;
  using value_type= T;
  using iterator= Iterator;

  iterator begin() const { return iterator(first); }
  iterator end() const { return iterator(); }

  class Iterator
  {
  public:
    using iterator_category= std::forward_iterator_tag;
    using value_type= T;
    using difference_type= std::ptrdiff_t;
    using pointer= T *;
    using reference= T &;

    Iterator(list_node *p= &end_of_list) : node{p} {}

    Iterator &operator++()
    {
      DBUG_ASSERT(node != &end_of_list);

      node= node->next;
      return *this;
    }

    Iterator operator++(int)
    {
      Iterator tmp(*this);
      operator++();
      return tmp;
    }

    T &operator*() { return *static_cast<T *>(node->info); }
    T *operator->() { return static_cast<T *>(node->info); }

    bool operator==(const typename List<T>::iterator &rhs)
    {
      return node == rhs.node;
    }

    bool operator!=(const typename List<T>::iterator &rhs)
    {
      return node != rhs.node;
    }

  private:
    list_node *node{&end_of_list};
  };
};


template <class T> class List_iterator :public base_list_iterator
{
public:
  List_iterator(List<T> &a) : base_list_iterator(a) {}
  List_iterator() : base_list_iterator() {}
  inline void init(List<T> &a) { base_list_iterator::init(a); }
  inline T* operator++(int) { return (T*) base_list_iterator::next(); }
  inline T* peek() { return (T*) base_list_iterator::peek(); }
  inline T *replace(T *a)   { return (T*) base_list_iterator::replace(a); }
  inline T *replace(List<T> &a) { return (T*) base_list_iterator::replace(a); }
  inline void rewind(void)  { base_list_iterator::rewind(); }
  inline void remove()      { base_list_iterator::remove(); }
  inline void after(T *a)   { base_list_iterator::after(a); }
  inline T** ref(void)	    { return (T**) base_list_iterator::ref(); }
};


template <class T> class List_iterator_fast :public base_list_iterator
{
protected:
  inline T *replace(T *)   { return (T*) 0; }
  inline T *replace(List<T> &) { return (T*) 0; }
  inline void remove(void)  {}
  inline void after(T *)    {}
  inline T** ref(void)	    { return (T**) 0; }

public:
  inline List_iterator_fast(List<T> &a) : base_list_iterator(a) {}
  inline List_iterator_fast() : base_list_iterator() {}
  inline void init(List<T> &a) { base_list_iterator::init(a); }
  inline T* operator++(int) { return (T*) base_list_iterator::next_fast(); }
  inline void rewind(void)  { base_list_iterator::rewind(); }
  void sublist(List<T> &list_arg, uint el_arg)
  {
    base_list_iterator::sublist(list_arg, el_arg);
  }
};


/*
  Bubble sort algorithm for List<T>.
  This sort function is supposed to be used only for very short list.
  Currently it is used for the lists of Item_equal objects and
  for some lists in the table elimination algorithms. In both
  cases the sorted lists are very short.
*/

template <class T> 
inline void bubble_sort(List<T> *list_to_sort,
                        int (*sort_func)(T *a, T *b, void *arg), void *arg)
{
  bool swap;
  T **ref1= 0;
  T **ref2= 0;
  List_iterator<T> it(*list_to_sort);
  do
  {
    T **last_ref= ref1;
    T *item1= it++;
    ref1= it.ref();
    T *item2;

    swap= FALSE;
    while ((item2= it++) && (ref2= it.ref()) != last_ref)
    {
      if (sort_func(item1, item2, arg) > 0)
      {
        *ref1= item2;
        *ref2= item1;
        swap= TRUE;
      }
      else
        item1= item2;
      ref1= ref2;
    }
    it.rewind();
  } while (swap);
}


/*
  A simple intrusive list which automaticly removes element from list
  on delete (for THD element)
*/

struct ilink
{
  struct ilink **prev,*next;
  static void *operator new(size_t size) throw ()
  {
    return (void*)my_malloc(PSI_INSTRUMENT_ME,
                            (uint)size, MYF(MY_WME | MY_FAE | ME_FATAL));
  }
  static void operator delete(void* ptr_arg, size_t)
  {
     my_free(ptr_arg);
  }

  inline ilink()
  {
    prev=0; next=0;
  }
  inline void unlink()
  {
    /* Extra tests because element doesn't have to be linked */
    if (prev) *prev= next;
    if (next) next->prev=prev;
    prev=0 ; next=0;
  }
  inline void assert_linked()
  {
    DBUG_ASSERT(prev != 0 && next != 0);
  }
  inline void assert_not_linked()
  {
    DBUG_ASSERT(prev == 0 && next == 0);
  }
  virtual ~ilink() { unlink(); }		/*lint -e1740 */
};


/* Needed to be able to have an I_List of char* strings in mysqld.cc. */

class i_string: public ilink
{
public:
  const char* ptr;
  i_string():ptr(0) { }
  i_string(const char* s) : ptr(s) {}
};

/* needed for linked list of two strings for replicate-rewrite-db */
class i_string_pair: public ilink
{
public:
  const char* key;
  const char* val;
  i_string_pair():key(0),val(0) { }
  i_string_pair(const char* key_arg, const char* val_arg) : 
    key(key_arg),val(val_arg) {}
};


template <class T> class I_List_iterator;


class base_ilist
{
  struct ilink *first;
  struct ilink last;
public:
  inline void empty() { first= &last; last.prev= &first; }
  base_ilist() { empty(); }
  inline bool is_empty() {  return first == &last; }
  // Returns true if p is the last "real" object in the list,
  // i.e. p->next points to the sentinel.
  inline bool is_last(ilink *p) { return p->next == NULL || p->next == &last; }
  inline void append(ilink *a)
  {
    first->prev= &a->next;
    a->next=first; a->prev= &first; first=a;
  }
  inline void push_back(ilink *a)
  {
    *last.prev= a;
    a->next= &last;
    a->prev= last.prev;
    last.prev= &a->next;
  }
  inline struct ilink *get()
  {
    struct ilink *first_link=first;
    if (first_link == &last)
      return 0;
    first_link->unlink();			// Unlink from list
    return first_link;
  }
  inline struct ilink *head()
  {
    return (first != &last) ? first : 0;
  }

  /**
    Moves list elements to new owner, and empties current owner (i.e. this).

    @param[in,out]  new_owner  The new owner of the list elements.
                               Should be empty in input.
  */

  void move_elements_to(base_ilist *new_owner)
  {
    DBUG_ASSERT(new_owner->is_empty());
    new_owner->first= first;
    new_owner->last= last;
    empty();
  }

  friend class base_ilist_iterator;
 private:
  /*
    We don't want to allow copying of this class, as that would give us
    two list heads containing the same elements.
    So we declare, but don't define copy CTOR and assignment operator.
  */
  base_ilist(const base_ilist&);
  void operator=(const base_ilist&);
};


class base_ilist_iterator
{
  base_ilist *list;
  struct ilink **el;
protected:
  struct ilink *current;
public:
  base_ilist_iterator(base_ilist &list_par) :list(&list_par),
    el(&list_par.first),current(0) {}
  void *next(void)
  {
    /* This is coded to allow push_back() while iterating */
    current= *el;
    if (current == &list->last) return 0;
    el= &current->next;
    return current;
  }
  /* Unlink element returned by last next() call */
  inline void unlink(void)
  {
    struct ilink **tmp= current->prev;
    current->unlink();
    el= tmp;
  }
};


template <class T>
class I_List :private base_ilist
{
public:
  I_List() :base_ilist()	{}
  inline bool is_last(T *p)     { return base_ilist::is_last(p); }
  inline void empty()		{ base_ilist::empty(); }
  inline bool is_empty()        { return base_ilist::is_empty(); } 
  inline void append(T* a)	{ base_ilist::append(a); }
  inline void push_back(T* a)	{ base_ilist::push_back(a); }
  inline T* get()		{ return (T*) base_ilist::get(); }
  inline T* head()		{ return (T*) base_ilist::head(); }
  inline void move_elements_to(I_List<T>* new_owner) {
    base_ilist::move_elements_to(new_owner);
  }
#ifndef _lint
  friend class I_List_iterator<T>;
#endif
};


template <class T> class I_List_iterator :public base_ilist_iterator
{
public:
  I_List_iterator(I_List<T> &a) : base_ilist_iterator(a) {}
  inline T* operator++(int) { return (T*) base_ilist_iterator::next(); }
  /* Remove element returned by last next() call */
  inline void remove(void)
  {
    unlink();
    delete (T*) current;
    current= 0;                                 // Safety
  }
};

/**
  Make a deep copy of each list element.

  @note A template function and not a template method of class List
  is employed because of explicit template instantiation:
  in server code there are explicit instantiations of List<T> and
  an explicit instantiation of a template requires that any method
  of the instantiated class used in the template can be resolved.
  Evidently not all template arguments have clone() method with
  the right signature.

  @return You must query the error state in THD for out-of-memory
  situation after calling this function.
*/

template <typename T>
inline
void
list_copy_and_replace_each_value(List<T> &list, MEM_ROOT *mem_root)
{
  /* Make a deep copy of each element */
  List_iterator<T> it(list);
  T *el;
  while ((el= it++))
    it.replace(el->clone(mem_root));
}

void free_list(I_List <i_string_pair> *list);
void free_list(I_List <i_string> *list);

#endif // INCLUDES_MYSQL_SQL_LIST_H
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