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