threadlocal.h

This software aims to create an applet and panel tools to manage a wireless interface card, such as

//
// ThreadLocal.h
//
// $Id: //poco/Main/Foundation/include/Foundation/ThreadLocal.h#5 $
//
// Definition of the ThreadLocal template and related classes.
//
// Copyright (c) 2004, Guenter Obiltschnig/Applied Informatics.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
//
// 3. Redistributions in any form must be accompanied by information on
//    how to obtain complete source code for this software and any
//    accompanying software that uses this software.  The source code
//    must either be included in the distribution or be available for no
//    more than the cost of distribution plus a nominal fee, and must be
//    freely redistributable under reasonable conditions.  For an
//    executable file, complete source code means the source code for all
//    modules it contains.  It does not include source code for modules or
//    files that typically accompany the major components of the operating
//    system on which the executable file runs.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//


#ifndef Foundation_ThreadLocal_INCLUDED
#define Foundation_ThreadLocal_INCLUDED


#ifndef Foundation_Foundation_INCLUDED
#include "Foundation/Foundation.h"
#endif
#ifndef STD_MAP_INCLUDED
#include <map>
#define STD_MAP_INCLUDED
#endif


Foundation_BEGIN


class Foundation_API TLSAbstractSlot
	/// This is the base class for all objects
	/// that the ThreadLocalStorage class manages.
{
public:
	TLSAbstractSlot();
	virtual ~TLSAbstractSlot();
};


template <class C>
class TLSSlot: public TLSAbstractSlot
	/// The Slot template wraps another class
	/// so that it can be stored in a ThreadLocalStorage
	/// object. This class is used internally, and you
	/// must not create instances of it yourself.
{
public:
	TLSSlot()
	{
	}
	
	~TLSSlot()
	{
	}
	
	C& value()
	{
		return _value;
	}
	
private:
	TLSSlot(const TLSSlot&);
	TLSSlot& operator = (const TLSSlot&);

	C _value;
};


class Foundation_API ThreadLocalStorage
	/// This class manages the local storage for each thread.
	/// Never use this class directly, always use the
	/// ThreadLocal template for managing thread local storage.
{
public:
	ThreadLocalStorage();
		/// Creates the TLS.
		
	~ThreadLocalStorage();
		/// Deletes the TLS.

	TLSAbstractSlot*& get(const void* key);
		/// Returns the slot for the given key.
		
	static ThreadLocalStorage& current();
		/// Returns the TLS object for the current thread
		/// (which may also be the main thread).
		
	static void clear();
		/// Clears the current thread's TLS object.
		/// Does nothing in the main thread.
	
private:
	typedef std::map<const void*, TLSAbstractSlot*> TLSMap;
	
	TLSMap _map;

	friend class Thread;
};


template <class C>
class ThreadLocal
	/// This template is used to declare type safe thread
	/// local variables. It can basically be used like
	/// a smart pointer class with the special feature
	/// that it references a different object
	/// in every thread. The underlying object will
	/// be created when it is referenced for the first
	/// time.
	/// See the NestedDiagnosticContext class for an
	/// example how to use this template.
	/// Every thread only has access to its own
	/// thread local data. There is no way for a thread
	/// to access another thread's local data.
{
	typedef TLSSlot<C> Slot;

public:
	ThreadLocal()
	{
	}
	
	~ThreadLocal()
	{
	}
	
	C* operator -> ()
	{
		return &get();
	}
	
	C& operator * ()
		/// "Dereferences" the smart pointer and returns a reference
		/// to the underlying data object. The reference can be used
		/// to modify the object.
	{
		return get();
	}

	C& get()
		/// Returns a reference to the underlying data object.
		/// The reference can be used to modify the object.
	{
		TLSAbstractSlot*& p = ThreadLocalStorage::current().get(this);
		if (!p) p = new Slot;
		return static_cast<Slot*>(p)->value();
	}
	
private:
	ThreadLocal(const ThreadLocal&);
	ThreadLocal& operator = (const ThreadLocal&);
};


Foundation_END


#endif // Foundation_ThreadLocal_INCLUDED