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>


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 handler_type>
class completion_handler1 : public completion_handler_impl
{
private:
 handler_type handler_;

public:
 completion_handler1(const handler_type& handler__) : handler_(handler__) { }
 completion_handler1 * clone() const
 {
 return new completion_handler1(*this);
 }
 void operator () (request* req)
 {
 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 sp_impl_;

public:
 completion_handler() :
 sp_impl_(static_cast<completion_handler_impl*>(0))
 { }

 completion_handler(const completion_handler& obj) :
 sp_impl_(obj.sp_impl_.get()->clone())
 { }

 template <typename handler_type>
 completion_handler(const handler_type& handler__) :
 sp_impl_(new completion_handler1<handler_type>(handler__))
 { }

 completion_handler& operator = (const completion_handler& obj)
 {
 sp_impl_.reset(obj.sp_impl_.get()->clone());
 return *this;
 }
 void operator () (request* req)
 {
 (* sp_impl_)(req);
 }
};

//! Default completion handler class.

struct default_completion_handler
{
 //! An operator that does nothing.
 void operator () (request*) { }
};

STXXL_END_NAMESPACE

#endif // !STXXL_IO_COMPLETION_HANDLER_HEADER
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