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-- GHDL Run Time (GRT) - binary balanced tree.
-- Copyright (C) 2002, 2003, 2004, 2005 Tristan Gingold
--
-- GHDL 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 2, or (at your option) any later
-- version.
--
-- GHDL 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.
--
-- You should have received a copy of the GNU General Public License
-- along with GCC; see the file COPYING. If not, write to the Free
-- Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-- 02111-1307, USA.
with Grt.Types; use Grt.Types;
package Grt.Avls is
-- Implementation of a binary balanced tree.
-- This package is very generic, and provides only the algorithm.
-- The user must provide the storage of the tree.
-- The basic types of this implementation ares:
-- * AVL_Value: the value stored in the tree. This is an integer on 32
-- bits. However, they may either really represent integers or an index
-- into another table. To compare two values, a user function is always
-- provided.
-- * AVL_Nid: a node id or an index into the tree.
-- * AVL_Node: a node, indexed by AVL_Nid.
-- * AVL_Tree: an array of AVL_Node, indexed by AVL_Nid. This represents
-- the tree. The root of the tree is always AVL_Root, which is the
-- first element of the array.
--
-- As a choice, this package never allocate nodes. So, to insert a value
-- in the tree, the user must allocate an (empty) node, set the value of
-- the node and try to insert this node into the tree. If the value is
-- already in the tree, Get_Node will returns the node id which contains
-- the value. Otherwise, Get_Node returns the node just created by the
-- user.
-- The value in an AVL tree.
-- This is fixed.
type AVL_Value is new Ghdl_I32;
-- An AVL node id.
type AVL_Nid is new Ghdl_I32;
AVL_Nil : constant AVL_Nid := 0;
AVL_Root : constant AVL_Nid := 1;
type AVL_Node is record
Val : AVL_Value;
Left : AVL_Nid;
Right : AVL_Nid;
Height : Ghdl_I32;
end record;
type AVL_Tree is array (AVL_Nid range <>) of AVL_Node;
-- Compare two values.
-- Returns < 0 if L < R, 0 if L = R, > 0 if L > R.
type AVL_Compare_Func is access function (L, R : AVL_Value) return Integer;
-- Try to insert node N into TREE.
-- Returns either N or the node id of a node containing already the value.
procedure Get_Node (Tree : in out AVL_Tree;
Cmp : AVL_Compare_Func;
N : AVL_Nid;
Res : out AVL_Nid);
function Find_Node (Tree : AVL_Tree;
Cmp : AVL_Compare_Func;
Val : AVL_Value) return AVL_Nid;
end Grt.Avls;
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