| /* Copyright (C) 2009-2021 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 |