/*
	Copyright (C) 2005 Kazuya Ujihara. All rights reserved.

	This software is provided 'as-is', without any express or implied
	warranty.  In no event will the authors be held liable for any damages
	arising from the use of this software.

	Permission is granted to anyone to use this software for any purpose,
	including commercial applications, and to alter it and redistribute it
	freely, subject to the following restrictions:

	1. The origin of this software must not be misrepresented; you must not
		claim that you wrote the original software. If you use this software
		in a product, an acknowledgment in the product documentation would be
		appreciated but is not required.
	2. Altered source versions must be plainly marked as such, and must not be
		misrepresented as being the original software.
	3. This notice may not be removed or altered from any source distribution.

	Kazuya Ujihara <http://www.ujihara.jp/>
 */

package java.lang;

import System.LocalDataStoreSlot;

public class InheritableThreadLocal extends ThreadLocal
{
	private static final Object NOT_INIT = new Object();
	private Thread rootThread;
	private Object rootValue;

	public InheritableThreadLocal()
	{
		super();
		rootThread = Thread.currentThread();
		rootValue = NOT_INIT;
	}

	private boolean isRoot()
	{
		return Thread.currentThread().equals(rootThread);
	}

	private Object getRootValue()
	{
		if (rootValue == NOT_INIT)
			rootValue = super.get();
		return rootValue;
	}

	private void setRootValue(Object value)
	{
		this.rootValue = value;
	}

	public synchronized Object get()
	{
		if (!isRoot())
		{
			Object o = System.Threading.Thread.GetData(slot);
			if (o == null)
			{
				o = childValue(getRootValue());
				System.Threading.Thread.SetData(slot, o);
			}
		}
		return super.get();
	}

	public synchronized void set(Object value)
	{
		if (value == null)
			value = NULL;
		System.Threading.Thread.SetData(slot, value);
		if (isRoot())
			setRootValue(value);
	}

	protected Object childValue(Object parentValue)
	{
		return parentValue;
	}
}