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/* A splay-tree datatype.
Copyright (C) 1998-2015 Free Software Foundation, Inc.
Contributed by Mark Mitchell (mark@markmitchell.com).
This file is part of the GNU OpenMP Library (libgomp).
Libgomp 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 3, or (at your option)
any later version.
Libgomp 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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* The splay tree code copied from include/splay-tree.h and adjusted,
so that all the data lives directly in splay_tree_node_s structure
and no extra allocations are needed.
Files including this header should before including it add:
typedef struct splay_tree_node_s *splay_tree_node;
typedef struct splay_tree_s *splay_tree;
typedef struct splay_tree_key_s *splay_tree_key;
define splay_tree_key_s structure, and define
splay_compare inline function. */
/* For an easily readable description of splay-trees, see:
Lewis, Harry R. and Denenberg, Larry. Data Structures and Their
Algorithms. Harper-Collins, Inc. 1991.
The major feature of splay trees is that all basic tree operations
are amortized O(log n) time for a tree with n nodes. */
/* The nodes in the splay tree. */
struct splay_tree_node_s {
struct splay_tree_key_s key;
/* The left and right children, respectively. */
splay_tree_node left;
splay_tree_node right;
};
/* The splay tree. */
struct splay_tree_s {
splay_tree_node root;
};
/* 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 == NULL)
return;
do {
int cmp1, cmp2;
splay_tree_node n, c;
n = sp->root;
cmp1 = splay_compare (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 = splay_compare (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);
}
/* Insert a new NODE into SP. The NODE shouldn't exist in the tree. */
static void
splay_tree_insert (splay_tree sp, splay_tree_node node)
{
int comparison = 0;
splay_tree_splay (sp, &node->key);
if (sp->root)
comparison = splay_compare (&sp->root->key, &node->key);
if (sp->root && comparison == 0)
abort ();
else
{
/* Insert it at the root. */
if (sp->root == NULL)
node->left = node->right = NULL;
else if (comparison < 0)
{
node->left = sp->root;
node->right = node->left->right;
node->left->right = NULL;
}
else
{
node->right = sp->root;
node->left = node->right->left;
node->right->left = NULL;
}
sp->root = node;
}
}
/* Remove node with KEY from SP. It is not an error if it did not exist. */
static void
splay_tree_remove (splay_tree sp, splay_tree_key key)
{
splay_tree_splay (sp, key);
if (sp->root && splay_compare (&sp->root->key, key) == 0)
{
splay_tree_node left, right;
left = sp->root->left;
right = sp->root->right;
/* 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 NODE if present, and NULL
otherwise. */
static splay_tree_key
splay_tree_lookup (splay_tree sp, splay_tree_key key)
{
splay_tree_splay (sp, key);
if (sp->root && splay_compare (&sp->root->key, key) == 0)
return &sp->root->key;
else
return NULL;
}
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