tree.cc

// RB tree utilities implementation -*- C++ -*-

// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library 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; either version 2, or (at your option)
// any later version.

// This library 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 library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 */

#include <bits/stl_tree.h>

namespace std
{
  _Rb_tree_node_base*
  _Rb_tree_increment(_Rb_tree_node_base* __x)
  {
    if (__x->_M_right != 0) 
      {
        __x = __x->_M_right;
        while (__x->_M_left != 0)
          __x = __x->_M_left;
      }
    else 
      {
        _Rb_tree_node_base* __y = __x->_M_parent;
        while (__x == __y->_M_right) 
          {
            __x = __y;
            __y = __y->_M_parent;
          }
        if (__x->_M_right != __y)
          __x = __y;
      }
    return __x;
  }

  const _Rb_tree_node_base*
  _Rb_tree_increment(const _Rb_tree_node_base* __x)
  {
    return _Rb_tree_increment(const_cast<_Rb_tree_node_base*>(__x));
  }

  _Rb_tree_node_base*
  _Rb_tree_decrement(_Rb_tree_node_base* __x)
  {
    if (__x->_M_color == _S_red 
        && __x->_M_parent->_M_parent == __x)
      __x = __x->_M_right;
    else if (__x->_M_left != 0) 
      {
        _Rb_tree_node_base* __y = __x->_M_left;
        while (__y->_M_right != 0)
          __y = __y->_M_right;
        __x = __y;
      }
    else 
      {
        _Rb_tree_node_base* __y = __x->_M_parent;
        while (__x == __y->_M_left) 
          {
            __x = __y;
            __y = __y->_M_parent;
          }
        __x = __y;
      }
    return __x;
  }

  const _Rb_tree_node_base*
  _Rb_tree_decrement(const _Rb_tree_node_base* __x)
  {
    return _Rb_tree_decrement(const_cast<_Rb_tree_node_base*>(__x));
  }

  void 
  _Rb_tree_rotate_left(_Rb_tree_node_base* const __x, 
               _Rb_tree_node_base*& __root)
  {
    _Rb_tree_node_base* const __y = __x->_M_right;

    __x->_M_right = __y->_M_left;
    if (__y->_M_left !=0)
      __y->_M_left->_M_parent = __x;
    __y->_M_parent = __x->_M_parent;
    
    if (__x == __root)
      __root = __y;
    else if (__x == __x->_M_parent->_M_left)
      __x->_M_parent->_M_left = __y;
    else
      __x->_M_parent->_M_right = __y;
    __y->_M_left = __x;
    __x->_M_parent = __y;
  }

  void 
  _Rb_tree_rotate_right(_Rb_tree_node_base* const __x, 
            _Rb_tree_node_base*& __root)
  {
    _Rb_tree_node_base* const __y = __x->_M_left;

    __x->_M_left = __y->_M_right;
    if (__y->_M_right != 0)
      __y->_M_right->_M_parent = __x;
    __y->_M_parent = __x->_M_parent;

    if (__x == __root)
      __root = __y;
    else if (__x == __x->_M_parent->_M_right)
      __x->_M_parent->_M_right = __y;
    else
      __x->_M_parent->_M_left = __y;
    __y->_M_right = __x;
    __x->_M_parent = __y;
  }

  void 
  _Rb_tree_insert_and_rebalance(const bool          __insert_left,
                                _Rb_tree_node_base* __x,
                                _Rb_tree_node_base* __p,
                                _Rb_tree_node_base& __header)
  {
    _Rb_tree_node_base *& __root = __header._M_parent;

    // Initialize fields in new node to insert.
    __x->_M_parent = __p;
    __x->_M_left = 0;
    __x->_M_right = 0;
    __x->_M_color = _S_red;

    // Insert.
    // Make new node child of parent and maintain root, leftmost and
    // rightmost nodes.
    // N.B. First node is always inserted left.
    if (__insert_left)
      {
        __p->_M_left = __x; // also makes leftmost = __x when __p == &__header

        if (__p == &__header)
        {
            __header._M_parent = __x;
            __header._M_right = __x;
        }
        else if (__p == __header._M_left)
          __header._M_left = __x; // maintain leftmost pointing to min node
      }
    else
      {
        __p->_M_right = __x;

        if (__p == __header._M_right)
          __header._M_right = __x; // maintain rightmost pointing to max node
      }
    // Rebalance.
    while (__x != __root 
       && __x->_M_parent->_M_color == _S_red) 
      {
    _Rb_tree_node_base* const __xpp = __x->_M_parent->_M_parent;

    if (__x->_M_parent == __xpp->_M_left) 
      {
        _Rb_tree_node_base* const __y = __xpp->_M_right;
        if (__y && __y->_M_color == _S_red) 
          {
        __x->_M_parent->_M_color = _S_black;
        __y->_M_color = _S_black;
        __xpp->_M_color = _S_red;
        __x = __xpp;
          }
        else 
          {
        if (__x == __x->_M_parent->_M_right) 
          {
            __x = __x->_M_parent;
            _Rb_tree_rotate_left(__x, __root);
          }
        __x->_M_parent->_M_color = _S_black;
        __xpp->_M_color = _S_red;
        _Rb_tree_rotate_right(__xpp, __root);
          }
      }
    else 
      {
        _Rb_tree_node_base* const __y = __xpp->_M_left;
        if (__y && __y->_M_color == _S_red) 
          {
        __x->_M_parent->_M_color = _S_black;
        __y->_M_color = _S_black;
        __xpp->_M_color = _S_red;
        __x = __xpp;
          }
        else 
          {
        if (__x == __x->_M_parent->_M_left) 
          {
            __x = __x->_M_parent;
            _Rb_tree_rotate_right(__x, __root);
          }
        __x->_M_parent->_M_color = _S_black;
        __xpp->_M_color = _S_red;
        _Rb_tree_rotate_left(__xpp, __root);
          }
      }
      }
    __root->_M_color = _S_black;
  }

  _Rb_tree_node_base*
  _Rb_tree_rebalance_for_erase(_Rb_tree_node_base* const __z, 
                   _Rb_tree_node_base& __header)
  {
    _Rb_tree_node_base *& __root = __header._M_parent;
    _Rb_tree_node_base *& __leftmost = __header._M_left;
    _Rb_tree_node_base *& __rightmost = __header._M_right;
    _Rb_tree_node_base* __y = __z;
    _Rb_tree_node_base* __x = 0;
    _Rb_tree_node_base* __x_parent = 0;

    if (__y->_M_left == 0)     // __z has at most one non-null child. y == z.
      __x = __y->_M_right;     // __x might be null.
    else
      if (__y->_M_right == 0)  // __z has exactly one non-null child. y == z.
    __x = __y->_M_left;    // __x is not null.
      else 
    {
      // __z has two non-null children.  Set __y to
      __y = __y->_M_right;   //   __z's successor.  __x might be null.
      while (__y->_M_left != 0)
        __y = __y->_M_left;
      __x = __y->_M_right;
    }
    if (__y != __z) 
      {
    // relink y in place of z.  y is z's successor
    __z->_M_left->_M_parent = __y; 
    __y->_M_left = __z->_M_left;
    if (__y != __z->_M_right) 
      {
        __x_parent = __y->_M_parent;
        if (__x) __x->_M_parent = __y->_M_parent;
        __y->_M_parent->_M_left = __x;   // __y must be a child of _M_left
        __y->_M_right = __z->_M_right;
        __z->_M_right->_M_parent = __y;
      }
    else
      __x_parent = __y;  
    if (__root == __z)
      __root = __y;
    else if (__z->_M_parent->_M_left == __z)
      __z->_M_parent->_M_left = __y;
    else 
      __z->_M_parent->_M_right = __y;
    __y->_M_parent = __z->_M_parent;
    std::swap(__y->_M_color, __z->_M_color);
    __y = __z;
    // __y now points to node to be actually deleted
      }
    else 
      {                        // __y == __z
    __x_parent = __y->_M_parent;
    if (__x) 
      __x->_M_parent = __y->_M_parent;   
    if (__root == __z)
      __root = __x;
    else 
      if (__z->_M_parent->_M_left == __z)
        __z->_M_parent->_M_left = __x;
      else
        __z->_M_parent->_M_right = __x;
    if (__leftmost == __z) 
      if (__z->_M_right == 0)        // __z->_M_left must be null also
        __leftmost = __z->_M_parent;
    // makes __leftmost == _M_header if __z == __root
      else
        __leftmost = _Rb_tree_node_base::_S_minimum(__x);
    if (__rightmost == __z)  
      if (__z->_M_left == 0)         // __z->_M_right must be null also
        __rightmost = __z->_M_parent;  
    // makes __rightmost == _M_header if __z == __root
      else                      // __x == __z->_M_left
        __rightmost = _Rb_tree_node_base::_S_maximum(__x);
      }
    if (__y->_M_color != _S_red) 
      { 
    while (__x != __root && (__x == 0 || __x->_M_color == _S_black))
      if (__x == __x_parent->_M_left) 
        {
          _Rb_tree_node_base* __w = __x_parent->_M_right;
          if (__w->_M_color == _S_red) 
        {
          __w->_M_color = _S_black;
          __x_parent->_M_color = _S_red;
          _Rb_tree_rotate_left(__x_parent, __root);
          __w = __x_parent->_M_right;
        }
          if ((__w->_M_left == 0 || 
           __w->_M_left->_M_color == _S_black) &&
          (__w->_M_right == 0 || 
           __w->_M_right->_M_color == _S_black)) 
        {
          __w->_M_color = _S_red;
          __x = __x_parent;
          __x_parent = __x_parent->_M_parent;
        } 
          else 
        {
          if (__w->_M_right == 0 
              || __w->_M_right->_M_color == _S_black) 
            {
              __w->_M_left->_M_color = _S_black;
              __w->_M_color = _S_red;
              _Rb_tree_rotate_right(__w, __root);
              __w = __x_parent->_M_right;
            }
          __w->_M_color = __x_parent->_M_color;
          __x_parent->_M_color = _S_black;
          if (__w->_M_right) 
            __w->_M_right->_M_color = _S_black;
          _Rb_tree_rotate_left(__x_parent, __root);
          break;
        }
        } 
      else 
        {   
          // same as above, with _M_right <-> _M_left.
          _Rb_tree_node_base* __w = __x_parent->_M_left;
          if (__w->_M_color == _S_red) 
        {
          __w->_M_color = _S_black;
          __x_parent->_M_color = _S_red;
          _Rb_tree_rotate_right(__x_parent, __root);
          __w = __x_parent->_M_left;
        }
          if ((__w->_M_right == 0 || 
           __w->_M_right->_M_color == _S_black) &&
          (__w->_M_left == 0 || 
           __w->_M_left->_M_color == _S_black)) 
        {
          __w->_M_color = _S_red;
          __x = __x_parent;
          __x_parent = __x_parent->_M_parent;
        } 
          else 
        {
          if (__w->_M_left == 0 || __w->_M_left->_M_color == _S_black) 
            {
              __w->_M_right->_M_color = _S_black;
              __w->_M_color = _S_red;
              _Rb_tree_rotate_left(__w, __root);
              __w = __x_parent->_M_left;
            }
          __w->_M_color = __x_parent->_M_color;
          __x_parent->_M_color = _S_black;
          if (__w->_M_left) 
            __w->_M_left->_M_color = _S_black;
          _Rb_tree_rotate_right(__x_parent, __root);
          break;
        }
        }
    if (__x) __x->_M_color = _S_black;
      }
    return __y;
  }

  unsigned int
  _Rb_tree_black_count(const _Rb_tree_node_base* __node,
                       const _Rb_tree_node_base* __root)
  {
    if (__node == 0)
      return 0;
    unsigned int __sum = 0;
    do 
      {
    if (__node->_M_color == _S_black) 
      ++__sum;
    if (__node == __root) 
      break;
    __node = __node->_M_parent;
      } 
    while (1);
    return __sum;
  }
} // namespace std 

---