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/*
Scan Tailor - Interactive post-processing tool for scanned pages.
Copyright (C) 2007-2008 Joseph Artsimovich <joseph_a@mail.ru>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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, see <http://www.gnu.org/licenses/>.
*/
#ifndef ATOMICFILEOVERWRITER_H_
#define ATOMICFILEOVERWRITER_H_
#include "NonCopyable.h"
#include <memory>
class QString;
class QIODevice;
class QTemporaryFile;
/**
* \brief Overwrites files by writing to a temporary file and then replacing
* the target file with it.
*
* Because renaming across volumes doesn't work, we create a temporary file
* in the same directory as the target file.
*/
class AtomicFileOverwriter
{
DECLARE_NON_COPYABLE(AtomicFileOverwriter)
public:
AtomicFileOverwriter();
/**
* \brief Destroys the object and calls abort() if necessary.
*/
~AtomicFileOverwriter();
/**
* \brief Start writing to a temporary file.
*
* \returns A temporary file as QIODevice, or null of temporary file
* could not be opened. In latter case, calling abort()
* is not necessary.
*
* If a file is already being written, it calles abort() and then
* proceeds as usual.
*/
QIODevice* startWriting(QString const& file_path);
/**
* \brief Replaces the target file with the temporary one.
*
* If replacing failed, false is returned and the temporary file
* is removed.
*/
bool commit();
/**
* \brief Removes the temporary file without touching the target one.
*/
void abort();
private:
std::auto_ptr<QTemporaryFile> m_ptrTempFile;
};
#endif