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/* A splay-tree datatype.

   Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.

   Contributed by Mark Mitchell (mark@markmitchell.com).

This file is part of GNU CC.

GNU CC 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.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to

the Free Software Foundation, 51 Franklin Street - Fifth Floor,

Boston, MA 02110-1301, USA.  */

/* For an easily readable description of splay-trees, see:

     Lewis, Harry R. and Denenberg, Larry.  Data Structures and Their

     Algorithms.  Harper-Collins, Inc.  1991.  */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#include <stdio.h>

#include "libiberty.h"

#include "splay-tree.h"

static void splay_tree_delete_helper (splay_tree, splay_tree_node);

static inline void rotate_left (splay_tree_node *,

                                splay_tree_node, splay_tree_node);

static inline void rotate_right (splay_tree_node *,

                                splay_tree_node, splay_tree_node);

static void splay_tree_splay (splay_tree, splay_tree_key);

static int splay_tree_foreach_helper (splay_tree, splay_tree_node,

                                      splay_tree_foreach_fn, void*);

/* Deallocate NODE (a member of SP), and all its sub-trees.  */

static void

splay_tree_delete_helper (splay_tree sp, splay_tree_node node)

{

  splay_tree_node pending = 0;

  splay_tree_node active = 0;

  if (!node)

    return;

#define KDEL(x)  if (sp->delete_key) (*sp->delete_key)(x);

#define VDEL(x)  if (sp->delete_value) (*sp->delete_value)(x);

  KDEL (node->key);

  VDEL (node->value);

  /* We use the "key" field to hold the "next" pointer.  */

  node->key = (splay_tree_key)pending;

  pending = (splay_tree_node)node;

  /* Now, keep processing the pending list until there aren't any

     more.  This is a little more complicated than just recursing, but

     it doesn't toast the stack for large trees.  */

  while (pending)

    {

      active = pending;

      pending = 0;

      while (active)

        {

          splay_tree_node temp;

          /* active points to a node which has its key and value

             deallocated, we just need to process left and right.  */

          if (active->left)

            {

              KDEL (active->left->key);

              VDEL (active->left->value);

              active->left->key = (splay_tree_key)pending;

              pending = (splay_tree_node)(active->left);

            }

          if (active->right)

            {

              KDEL (active->right->key);

              VDEL (active->right->value);

              active->right->key = (splay_tree_key)pending;

              pending = (splay_tree_node)(active->right);

            }

          temp = active;

          active = (splay_tree_node)(temp->key);

          (*sp->deallocate) ((char*) temp, sp->allocate_data);

        }

    }

#undef KDEL

#undef VDEL

}

/* Rotate the edge joining the left child N with its parent P.  PP is the

   grandparents' pointer to P.  */

static inline void

rotate_left (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)

{

  splay_tree_node tmp;

  tmp = n->right;

  n->right = p;

  p->left = tmp;

  *pp = n;

}

/* Rotate the edge joining the right child N with its parent P.  PP is the

   grandparents' pointer to P.  */

static inline void

rotate_right (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)

{

  splay_tree_node tmp;

  tmp = n->left;

  n->left = p;

  p->right = tmp;

  *pp = n;

}

/* Bottom up splay of key.  */

static void

splay_tree_splay (splay_tree sp, splay_tree_key key)

{

  if (sp->root == 0)

    return;

  do {

    int cmp1, cmp2;

    splay_tree_node n, c;

    n = sp->root;

    cmp1 = (*sp->comp) (key, n->key);

    /* Found.  */

    if (cmp1 == 0)

      return;

    /* Left or right?  If no child, then we're done.  */

    if (cmp1 < 0)

      c = n->left;

    else

      c = n->right;

    if (!c)

      return;

    /* Next one left or right?  If found or no child, we're done

       after one rotation.  */

    cmp2 = (*sp->comp) (key, c->key);

    if (cmp2 == 0

        || (cmp2 < 0 && !c->left)

        || (cmp2 > 0 && !c->right))

      {

        if (cmp1 < 0)

          rotate_left (&sp->root, n, c);

        else

          rotate_right (&sp->root, n, c);

        return;

      }

    /* Now we have the four cases of double-rotation.  */

    if (cmp1 < 0 && cmp2 < 0)

      {

        rotate_left (&n->left, c, c->left);

        rotate_left (&sp->root, n, n->left);

      }

    else if (cmp1 > 0 && cmp2 > 0)

      {

        rotate_right (&n->right, c, c->right);

        rotate_right (&sp->root, n, n->right);

      }

    else if (cmp1 < 0 && cmp2 > 0)

      {

        rotate_right (&n->left, c, c->right);

        rotate_left (&sp->root, n, n->left);

      }

    else if (cmp1 > 0 && cmp2 < 0)

      {

        rotate_left (&n->right, c, c->left);

        rotate_right (&sp->root, n, n->right);

      }

  } while (1);

}

/* Call FN, passing it the DATA, for every node below NODE, all of

   which are from SP, following an in-order traversal.  If FN every

   returns a non-zero value, the iteration ceases immediately, and the

   value is returned.  Otherwise, this function returns 0.  */

static int

splay_tree_foreach_helper (splay_tree sp, splay_tree_node node,

                           splay_tree_foreach_fn fn, void *data)

{

  int val;

  if (!node)

    return 0;

  val = splay_tree_foreach_helper (sp, node->left, fn, data);

  if (val)

    return val;

  val = (*fn)(node, data);

  if (val)

    return val;

  return splay_tree_foreach_helper (sp, node->right, fn, data);

}

/* An allocator and deallocator based on xmalloc.  */

static void *

splay_tree_xmalloc_allocate (int size, void *data ATTRIBUTE_UNUSED)

{

  return (void *) xmalloc (size);

}

static void

splay_tree_xmalloc_deallocate (void *object, void *data ATTRIBUTE_UNUSED)

{

  free (object);

}

/* Allocate a new splay tree, using COMPARE_FN to compare nodes,

   DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate

   values.  Use xmalloc to allocate the splay tree structure, and any

   nodes added.  */

splay_tree

splay_tree_new (splay_tree_compare_fn compare_fn,

                splay_tree_delete_key_fn delete_key_fn,

                splay_tree_delete_value_fn delete_value_fn)

{

  return (splay_tree_new_with_allocator

          (compare_fn, delete_key_fn, delete_value_fn,

           splay_tree_xmalloc_allocate, splay_tree_xmalloc_deallocate, 0));

}

/* Allocate a new splay tree, using COMPARE_FN to compare nodes,

   DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate

   values.  */

splay_tree

splay_tree_new_with_allocator (splay_tree_compare_fn compare_fn,

                               splay_tree_delete_key_fn delete_key_fn,

                               splay_tree_delete_value_fn delete_value_fn,

                               splay_tree_allocate_fn allocate_fn,

                               splay_tree_deallocate_fn deallocate_fn,

                               void *allocate_data)

{

  splay_tree sp = (splay_tree) (*allocate_fn) (sizeof (struct splay_tree_s),

                                               allocate_data);

  sp->root = 0;

  sp->comp = compare_fn;

  sp->delete_key = delete_key_fn;

  sp->delete_value = delete_value_fn;

  sp->allocate = allocate_fn;

  sp->deallocate = deallocate_fn;

  sp->allocate_data = allocate_data;

  return sp;

}

/* Deallocate SP.  */

void

splay_tree_delete (splay_tree sp)

{

  splay_tree_delete_helper (sp, sp->root);

  (*sp->deallocate) ((char*) sp, sp->allocate_data);

}

/* Insert a new node (associating KEY with DATA) into SP.  If a

   previous node with the indicated KEY exists, its data is replaced

   with the new value.  Returns the new node.  */

splay_tree_node

splay_tree_insert (splay_tree sp, splay_tree_key key, splay_tree_value value)

{

  int comparison = 0;

  splay_tree_splay (sp, key);

  if (sp->root)

    comparison = (*sp->comp)(sp->root->key, key);

  if (sp->root && comparison == 0)

    {

      /* If the root of the tree already has the indicated KEY, just

         replace the value with VALUE.  */

      if (sp->delete_value)

        (*sp->delete_value)(sp->root->value);

      sp->root->value = value;

    }

  else

    {

      /* Create a new node, and insert it at the root.  */

      splay_tree_node node;

      node = ((splay_tree_node)

              (*sp->allocate) (sizeof (struct splay_tree_node_s),

                               sp->allocate_data));

      node->key = key;

      node->value = value;

      if (!sp->root)

        node->left = node->right = 0;

      else if (comparison < 0)

        {

          node->left = sp->root;

          node->right = node->left->right;

          node->left->right = 0;

        }

      else

        {

          node->right = sp->root;

          node->left = node->right->left;

          node->right->left = 0;

        }

      sp->root = node;

    }

  return sp->root;

}

/* Remove KEY from SP.  It is not an error if it did not exist.  */

void

splay_tree_remove (splay_tree sp, splay_tree_key key)

{

  splay_tree_splay (sp, key);

  if (sp->root && (*sp->comp) (sp->root->key, key) == 0)

    {

      splay_tree_node left, right;

      left = sp->root->left;

      right = sp->root->right;

      /* Delete the root node itself.  */

      if (sp->delete_value)

        (*sp->delete_value) (sp->root->value);

      (*sp->deallocate) (sp->root, sp->allocate_data);

      /* One of the children is now the root.  Doesn't matter much

         which, so long as we preserve the properties of the tree.  */

      if (left)

        {

          sp->root = left;

          /* If there was a right child as well, hang it off the

             right-most leaf of the left child.  */

          if (right)

            {

              while (left->right)

                left = left->right;

              left->right = right;

            }

        }

      else

        sp->root = right;

    }

}

/* Lookup KEY in SP, returning VALUE if present, and NULL

   otherwise.  */

splay_tree_node

splay_tree_lookup (splay_tree sp, splay_tree_key key)

{

  splay_tree_splay (sp, key);

  if (sp->root && (*sp->comp)(sp->root->key, key) == 0)

    return sp->root;

  else

    return 0;

}

/* Return the node in SP with the greatest key.  */

splay_tree_node

splay_tree_max (splay_tree sp)

{

  splay_tree_node n = sp->root;

  if (!n)

    return NULL;

  while (n->right)

    n = n->right;

  return n;

}

/* Return the node in SP with the smallest key.  */

splay_tree_node

splay_tree_min (splay_tree sp)

{

  splay_tree_node n = sp->root;

  if (!n)

    return NULL;

  while (n->left)

    n = n->left;

  return n;

}

/* Return the immediate predecessor KEY, or NULL if there is no

   predecessor.  KEY need not be present in the tree.  */

splay_tree_node

splay_tree_predecessor (splay_tree sp, splay_tree_key key)

{

  int comparison;

  splay_tree_node node;

  /* If the tree is empty, there is certainly no predecessor.  */

  if (!sp->root)

    return NULL;

  /* Splay the tree around KEY.  That will leave either the KEY

     itself, its predecessor, or its successor at the root.  */

  splay_tree_splay (sp, key);

  comparison = (*sp->comp)(sp->root->key, key);

  /* If the predecessor is at the root, just return it.  */

  if (comparison < 0)

    return sp->root;

  /* Otherwise, find the rightmost element of the left subtree.  */

  node = sp->root->left;

  if (node)

    while (node->right)

      node = node->right;

  return node;

}

/* Return the immediate successor KEY, or NULL if there is no

   successor.  KEY need not be present in the tree.  */

splay_tree_node

splay_tree_successor (splay_tree sp, splay_tree_key key)

{

  int comparison;

  splay_tree_node node;

  /* If the tree is empty, there is certainly no successor.  */

  if (!sp->root)

    return NULL;

  /* Splay the tree around KEY.  That will leave either the KEY

     itself, its predecessor, or its successor at the root.  */

  splay_tree_splay (sp, key);

  comparison = (*sp->comp)(sp->root->key, key);

  /* If the successor is at the root, just return it.  */

  if (comparison > 0)

    return sp->root;

  /* Otherwise, find the leftmost element of the right subtree.  */

  node = sp->root->right;

  if (node)

    while (node->left)

      node = node->left;

  return node;

}

/* Call FN, passing it the DATA, for every node in SP, following an

   in-order traversal.  If FN every returns a non-zero value, the

   iteration ceases immediately, and the value is returned.

   Otherwise, this function returns 0.  */

int

splay_tree_foreach (splay_tree sp, splay_tree_foreach_fn fn, void *data)

{

  return splay_tree_foreach_helper (sp, sp->root, fn, data);

}

/* Splay-tree comparison function, treating the keys as ints.  */

int

splay_tree_compare_ints (splay_tree_key k1, splay_tree_key k2)

{

  if ((int) k1 < (int) k2)

    return -1;

  else if ((int) k1 > (int) k2)

    return 1;

  else

    return 0;

}

/* Splay-tree comparison function, treating the keys as pointers.  */

int

splay_tree_compare_pointers (splay_tree_key k1, splay_tree_key k2)

{

  if ((char*) k1 < (char*) k2)

    return -1;

  else if ((char*) k1 > (char*) k2)

    return 1;

  else

    return 0;

}