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218 lines
5.4 KiB
C
218 lines
5.4 KiB
C
/* A splay-tree datatype.
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Copyright (C) 1998-2015 Free Software Foundation, Inc.
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Contributed by Mark Mitchell (mark@markmitchell.com).
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This file is part of the GNU Offloading and Multi Processing Library
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(libgomp).
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Libgomp is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* The splay tree code copied from include/splay-tree.h and adjusted,
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so that all the data lives directly in splay_tree_node_s structure
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and no extra allocations are needed. */
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/* For an easily readable description of splay-trees, see:
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Lewis, Harry R. and Denenberg, Larry. Data Structures and Their
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Algorithms. Harper-Collins, Inc. 1991.
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The major feature of splay trees is that all basic tree operations
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are amortized O(log n) time for a tree with n nodes. */
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#include "libgomp.h"
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#include "splay-tree.h"
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extern int splay_compare (splay_tree_key, splay_tree_key);
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/* Rotate the edge joining the left child N with its parent P. PP is the
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grandparents' pointer to P. */
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static inline void
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rotate_left (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
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{
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splay_tree_node tmp;
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tmp = n->right;
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n->right = p;
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p->left = tmp;
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*pp = n;
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}
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/* Rotate the edge joining the right child N with its parent P. PP is the
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grandparents' pointer to P. */
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static inline void
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rotate_right (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
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{
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splay_tree_node tmp;
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tmp = n->left;
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n->left = p;
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p->right = tmp;
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*pp = n;
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}
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/* Bottom up splay of KEY. */
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static void
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splay_tree_splay (splay_tree sp, splay_tree_key key)
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{
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if (sp->root == NULL)
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return;
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do {
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int cmp1, cmp2;
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splay_tree_node n, c;
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n = sp->root;
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cmp1 = splay_compare (key, &n->key);
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/* Found. */
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if (cmp1 == 0)
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return;
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/* Left or right? If no child, then we're done. */
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if (cmp1 < 0)
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c = n->left;
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else
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c = n->right;
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if (!c)
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return;
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/* Next one left or right? If found or no child, we're done
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after one rotation. */
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cmp2 = splay_compare (key, &c->key);
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if (cmp2 == 0
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|| (cmp2 < 0 && !c->left)
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|| (cmp2 > 0 && !c->right))
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{
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if (cmp1 < 0)
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rotate_left (&sp->root, n, c);
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else
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rotate_right (&sp->root, n, c);
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return;
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}
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/* Now we have the four cases of double-rotation. */
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if (cmp1 < 0 && cmp2 < 0)
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{
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rotate_left (&n->left, c, c->left);
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rotate_left (&sp->root, n, n->left);
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}
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else if (cmp1 > 0 && cmp2 > 0)
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{
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rotate_right (&n->right, c, c->right);
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rotate_right (&sp->root, n, n->right);
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}
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else if (cmp1 < 0 && cmp2 > 0)
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{
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rotate_right (&n->left, c, c->right);
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rotate_left (&sp->root, n, n->left);
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}
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else if (cmp1 > 0 && cmp2 < 0)
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{
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rotate_left (&n->right, c, c->left);
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rotate_right (&sp->root, n, n->right);
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}
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} while (1);
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}
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/* Insert a new NODE into SP. The NODE shouldn't exist in the tree. */
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attribute_hidden void
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splay_tree_insert (splay_tree sp, splay_tree_node node)
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{
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int comparison = 0;
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splay_tree_splay (sp, &node->key);
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if (sp->root)
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comparison = splay_compare (&sp->root->key, &node->key);
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if (sp->root && comparison == 0)
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gomp_fatal ("Duplicate node");
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else
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{
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/* Insert it at the root. */
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if (sp->root == NULL)
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node->left = node->right = NULL;
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else if (comparison < 0)
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{
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node->left = sp->root;
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node->right = node->left->right;
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node->left->right = NULL;
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}
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else
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{
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node->right = sp->root;
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node->left = node->right->left;
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node->right->left = NULL;
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}
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sp->root = node;
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}
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}
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/* Remove node with KEY from SP. It is not an error if it did not exist. */
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attribute_hidden void
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splay_tree_remove (splay_tree sp, splay_tree_key key)
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{
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splay_tree_splay (sp, key);
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if (sp->root && splay_compare (&sp->root->key, key) == 0)
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{
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splay_tree_node left, right;
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left = sp->root->left;
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right = sp->root->right;
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/* One of the children is now the root. Doesn't matter much
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which, so long as we preserve the properties of the tree. */
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if (left)
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{
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sp->root = left;
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/* If there was a right child as well, hang it off the
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right-most leaf of the left child. */
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if (right)
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{
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while (left->right)
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left = left->right;
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left->right = right;
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}
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}
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else
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sp->root = right;
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}
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}
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/* Lookup KEY in SP, returning NODE if present, and NULL
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otherwise. */
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attribute_hidden splay_tree_key
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splay_tree_lookup (splay_tree sp, splay_tree_key key)
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{
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splay_tree_splay (sp, key);
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if (sp->root && splay_compare (&sp->root->key, key) == 0)
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return &sp->root->key;
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else
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return NULL;
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}
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