2022-10-27 18:55:19 +00:00
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/* Copyright (C) 2009-2022 Free Software Foundation, Inc.
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2012-03-27 23:13:14 +00:00
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU Transactional Memory Library (libitm).
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Libitm 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 of the License, or
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(at your option) any later version.
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Libitm 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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// Implements an AA tree (http://en.wikipedia.org/wiki/AA_tree) with an
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// integer key, and data attached to the node via flexible array member.
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#include "libitm_i.h"
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namespace GTM HIDDEN {
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// The code for rebalancing the tree is greatly simplified by never
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// having to check for null pointers. Instead, leaf node links point
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// to this node, NIL, which points to itself.
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const aa_node_base aa_node_base::s_nil(0);
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// Remove left horizontal links. Swap the pointers of horizontal left links.
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aa_node_base *
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aa_node_base::skew ()
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{
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aa_node_base *l = this->link(L);
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if (this->m_level != 0 && l->m_level == this->m_level)
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{
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this->set_link(L, l->link(R));
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l->set_link(R, this);
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return l;
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}
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return this;
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}
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// Remove consecutive horizontal links. Take the middle node,
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// elevate it, and return it.
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aa_node_base *
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aa_node_base::split ()
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{
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aa_node_base *r = this->link(R);
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if (this->m_level != 0 && r->link(R)->m_level == this->m_level)
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{
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this->set_link(R, r->link(L));
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r->set_link(L, this);
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r->m_level += 1;
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return r;
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}
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return this;
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}
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// Decrease the level of THIS to be one more than the level of its children.
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void
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aa_node_base::decrease_level ()
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{
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aa_node_base *l = this->link(L);
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aa_node_base *r = this->link(R);
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level_type llev = l->m_level;
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level_type rlev = r->m_level;
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level_type should_be = (llev < rlev ? llev : rlev) + 1;
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if (should_be < this->m_level)
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{
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this->m_level = should_be;
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if (should_be < rlev)
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r->m_level = should_be;
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}
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}
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// Find and return the node in the tree with key K.
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template<typename KEY>
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typename aa_tree_key<KEY>::node_ptr
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aa_tree_key<KEY>::find(KEY k) const
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{
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node_ptr t = m_tree;
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if (t != 0)
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do
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{
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if (t->key == k)
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return t;
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t = t->link(k > t->key);
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}
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while (!t->is_nil());
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return 0;
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}
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// Insert N into T and rebalance. Return the new balanced tree.
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template<typename KEY>
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typename aa_tree_key<KEY>::node_ptr
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aa_tree_key<KEY>::insert_1 (node_ptr t, node_ptr n)
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{
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bool dir = n->key > t->key;
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node_ptr c = t->link(dir);
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// Insert the node, recursively.
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if (c->is_nil())
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c = n;
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else
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c = insert_1 (c, n);
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t->set_link(dir, c);
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// Rebalance the tree, as needed.
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t = t->skew();
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t = t->split();
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return t;
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}
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template<typename KEY>
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void
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aa_tree_key<KEY>::insert(node_ptr n)
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{
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if (m_tree == 0)
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m_tree = n;
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else
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m_tree = insert_1 (m_tree, n);
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}
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// Delete K from T and rebalance. Return the new balanced tree.
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template<typename KEY>
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typename aa_tree_key<KEY>::node_ptr
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aa_tree_key<KEY>::erase_1 (node_ptr t, KEY k, node_ptr *pfree)
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{
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node_ptr r;
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bool dir;
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// If this is the node we're looking for, delete it. Else recurse.
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if (k == t->key)
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{
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node_ptr l, sub, end;
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l = t->link(node::L);
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r = t->link(node::R);
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if (pfree)
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*pfree = t;
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// If this is a leaf node, simply remove the node. Otherwise,
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// we have to find either a predecessor or a successor node to
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// replace this one.
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if (l->is_nil())
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{
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if (r->is_nil())
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return r;
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sub = r, dir = node::L;
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}
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else
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sub = l, dir = node::R;
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// Find the successor or predecessor.
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for (end = sub; !end->link(dir)->is_nil(); end = end->link(dir))
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continue;
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// Remove it (but don't free) from the subtree.
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sub = erase_1 (sub, end->key, 0);
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// Replace T with the successor we just extracted.
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end->set_link(!dir, sub);
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t = end;
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}
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else
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{
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dir = k > t->key;
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t->set_link(dir, erase_1 (t->link(dir), k, pfree));
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}
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// Rebalance the tree.
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t->decrease_level();
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t = t->skew();
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r = t->link(node::R)->skew();
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t->set_link(node::R, r);
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r->set_link(node::R, r->link(node::R)->skew());
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t = t->split ();
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t->set_link(node::R, t->link(node::R)->split());
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return t;
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}
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template<typename KEY>
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typename aa_tree_key<KEY>::node_ptr
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aa_tree_key<KEY>::erase (KEY k)
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{
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node_ptr t = m_tree;
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if (t == 0)
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return 0;
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node_ptr do_free = 0;
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t = erase_1 (t, k, &do_free);
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if (t->is_nil())
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t = 0;
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m_tree = t;
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return do_free;
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}
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// Instantiate key classes.
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template class aa_tree_key<uintptr_t>;
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} // namespace GTM
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