include/stxxl/bits/io/fileperblock_file.h

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/***************************************************************************
 *  include/stxxl/bits/io/fileperblock_file.h
 *
 *  Part of the STXXL. See http://stxxl.sourceforge.net
 *
 *  Copyright (C) 2008, 2009 Johannes Singler <singler@ira.uka.de>
 *
 *  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_FILEPERBLOCK_FILE_HEADER
#define STXXL_FILEPERBLOCK_FILE_HEADER

#include <string>
#include <stxxl/bits/io/disk_queued_file.h>


__STXXL_BEGIN_NAMESPACE

//! \addtogroup fileimpl
//! \{

//! \brief Implementation of file based on other files, dynamically allocate one file per block.
//! Allows for dynamic disk space consumption.
template <class base_file_type>
class fileperblock_file : public disk_queued_file
{
private:
    std::string filename_prefix;
    int mode;
    unsigned_type current_size;
    bool lock_file_created;
    base_file_type lock_file;

protected:
    //! \brief Constructs a file name for a given block.
    std::string filename_for_block(unsigned_type offset);

public:
    //! \brief constructs file object
    //! \param filename_prefix  filename prefix, numbering will be appended to it
    //! \param mode open mode, see \c file::open_modes
    //! \param disk disk(file) identifier
    fileperblock_file(
        const std::string & filename_prefix,
        int mode,
        int queue_id = DEFAULT_QUEUE,
        int allocator_id = NO_ALLOCATOR);

    virtual ~fileperblock_file();

    virtual void serve(const request * req) throw (io_error);

    //! \brief Changes the size of the file
    //! \param new_size value of the new file size
    virtual void set_size(offset_type new_size) { current_size = new_size; }

    //! \brief Returns size of the file
    //! \return file size in length
    virtual offset_type size() { return current_size; }

    virtual void lock();

    //! \brief Frees the specified region.
    //! Actually deletes the corresponding file if the whole thing is deleted.
    virtual void discard(offset_type offset, offset_type length);

    //! Rename the file corresponding to the offset such that it is out of reach for deleting.
    virtual void export_files(offset_type offset, offset_type length, std::string filename);

    const char * io_type() const;
};

//! \}

__STXXL_END_NAMESPACE

#endif // !STXXL_FILEPERBLOCK_FILE_HEADER