Package com.db4o.internal

Source Code of com.db4o.internal.TreeReader

/* Copyright (C) 2004 - 2006  db4objects Inc.  http://www.db4o.com

This file is part of the db4o open source object database.

db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.

db4o 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 this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
package com.db4o.internal;

import com.db4o.foundation.Tree;


/**
* @exclude
*/
public final class TreeReader 
{
  private final Readable i_template;
  private final Buffer i_bytes;
  private int i_current = 0;
  private int i_levels = 0;
  private int i_size;
  private boolean i_orderOnRead;
 
  public TreeReader(Buffer a_bytes, Readable a_template) {
    this(a_bytes, a_template, false);
  }
 
  public TreeReader(Buffer a_bytes, Readable a_template, boolean a_orderOnRead) {
    i_template = a_template;
    i_bytes = a_bytes;
    i_orderOnRead = a_orderOnRead;
  }
 
  public Tree read() {
      return read(i_bytes.readInt());
  }
 
  public Tree read(int a_size){
      i_size = a_size;
    if(i_size > 0){
      if(i_orderOnRead){
        Tree tree = null;
        for (int i = 0; i < i_size; i++) {
            tree = Tree.add(tree, (Tree)i_template.read(i_bytes));
                }
                return tree;
      }
      while ((1 << i_levels) < (i_size + 1)){
        i_levels ++;
      }
      return linkUp(null, i_levels);
    }
    return null;
  }
 
  private final Tree linkUp(Tree a_preceding, int a_level){
    Tree node = (Tree)i_template.read(i_bytes);
    i_current++;
    node._preceding = a_preceding;
    node._subsequent = linkDown(a_level + 1);
    node.calculateSize();
    if(i_current < i_size){
      return linkUp(node, a_level - 1);
    }
    return node;

  }

  private final Tree linkDown(int a_level){
    if(i_current < i_size){
      i_current++;
      if(a_level < i_levels) {
        Tree preceding = linkDown(a_level + 1);
        Tree node = (Tree)i_template.read(i_bytes);
        node._preceding = preceding;
        node._subsequent = linkDown(a_level + 1);
        node.calculateSize();
        return node;
      }
      return (Tree)i_template.read(i_bytes);
    }
    return null;
  }
}
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