completion_handler.h

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/***************************************************************************
 * include/stxxl/bits/io/completion_handler.h
 *
 * Loki-style completion handler (functors)
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2003 Roman Dementiev <[email protected]>
 * Copyright (C) 2008 Andreas Beckmann <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#ifndef STXXL_IO_COMPLETION_HANDLER_HEADER
#define STXXL_IO_COMPLETION_HANDLER_HEADER

#include <stxxl/bits/namespace.h>
#include <stxxl/bits/compat/unique_ptr.h>
#include <cstdlib>

STXXL_BEGIN_NAMESPACE

class request;

class completion_handler_impl
{
public:
 virtual void operator () (request*) = 0;
 virtual completion_handler_impl * clone() const = 0;
 virtual ~completion_handler_impl() { }
};

template <typename HandlerType>
class completion_handler1 : public completion_handler_impl
{
private:
 HandlerType m_handler;

public:
 completion_handler1(const HandlerType& handler)
 : m_handler(handler)
 { }
 completion_handler1 * clone() const
 {
 return new completion_handler1(*this);
 }
 void operator () (request* req)
 {
 m_handler(req);
 }
};

//! Completion handler class (Loki-style).
//!
//! In some situations one needs to execute some actions after completion of an
//! I/O request. In these cases one can use an I/O completion handler - a
//! function object that can be passed as a parameter to asynchronous I/O calls
//! \c stxxl::file::aread and \c stxxl::file::awrite .
class completion_handler
{
 compat_unique_ptr<completion_handler_impl>::result m_ptr;

public:
 //! Construct default, no operation completion handler.
 completion_handler()
 : m_ptr(static_cast<completion_handler_impl*>(NULL))
 { }

 //! Copy constructor.
 completion_handler(const completion_handler& obj)
 : m_ptr(obj.m_ptr.get() ? obj.m_ptr.get()->clone() : NULL)
 { }

 //! Construct a completion handler which calls some function.
 template <typename HandlerType>
 completion_handler(const HandlerType& handler)
 : m_ptr(new completion_handler1<HandlerType>(handler))
 { }

 //! Assignment operator
 completion_handler& operator = (const completion_handler& obj)
 {
 m_ptr.reset(obj.m_ptr.get() ? obj.m_ptr.get()->clone() : NULL);
 return *this;
 }

 //! Call the enclosed completion handler.
 void operator () (request* req)
 {
 if (m_ptr.get())
 (* m_ptr)(req);
 }
};

STXXL_END_NAMESPACE

#endif // !STXXL_IO_COMPLETION_HANDLER_HEADER
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