file.h

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/***************************************************************************
 * include/stxxl/bits/io/file.h
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2002 Roman Dementiev <[email protected]>
 * Copyright (C) 2008, 2010 Andreas Beckmann <[email protected]>
 * Copyright (C) 2008, 2009 Johannes Singler <[email protected]>
 * Copyright (C) 2013 Timo Bingmann <[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_FILE_HEADER
#define STXXL_IO_FILE_HEADER

#include <stxxl/bits/config.h>

#if defined (__linux__)
 #define STXXL_CHECK_BLOCK_ALIGNING
#endif

#include <cassert>
#include <ostream>
#include <string>

#include <stxxl/bits/common/exceptions.h>
#include <stxxl/bits/common/mutex.h>
#include <stxxl/bits/common/types.h>
#include <stxxl/bits/io/request.h>
#include <stxxl/bits/io/request_interface.h>
#include <stxxl/bits/libstxxl.h>
#include <stxxl/bits/namespace.h>
#include <stxxl/bits/noncopyable.h>
#include <stxxl/bits/unused.h>
#include <stxxl/bits/verbose.h>


STXXL_BEGIN_NAMESPACE

//! \addtogroup iolayer
//! \{

class completion_handler;

//! Defines interface of file.
//!
//! It is a base class for different implementations that might
//! base on various file systems or even remote storage interfaces
class file : private noncopyable
{
 mutex request_ref_cnt_mutex;
 int request_ref_cnt;

protected:
 //! Initializes file object.
 //! \remark Called in implementations of file
 file() : request_ref_cnt(0) { }

public:
 //! the offset of a request, also the size of the file
 typedef request::offset_type offset_type;
 //! the size of a request
 typedef request::size_type size_type;

 //! Definition of acceptable file open modes.
 //!
 //! Various open modes in a file system must be
 //! converted to this set of acceptable modes
 enum open_mode
 {
 RDONLY = 1, //!< only reading of the file is allowed
 WRONLY = 2, //!< only writing of the file is allowed
 RDWR = 4, //!< read and write of the file are allowed
 CREAT = 8, //!< in case file does not exist no error occurs and file is newly created
 DIRECT = 16, //!< I/Os proceed bypassing file system buffers, i.e. unbuffered I/O.
 //!< Tries to open with appropriate flags, if fails print warning and open normally.
 TRUNC = 32, //!< once file is opened its length becomes zero
 SYNC = 64, //!< open the file with O_SYNC | O_DSYNC | O_RSYNC flags set
 NO_LOCK = 128, //!< do not aquire an exclusive lock by default
 REQUIRE_DIRECT = 256 //!< implies DIRECT, fail if opening with DIRECT flag does not work.
 };

 static const int DEFAULT_QUEUE = -1;
 static const int NO_QUEUE = -2;
 static const int NO_ALLOCATOR = -1;

 //! Schedules an asynchronous read request to the file.
 //! \param buffer pointer to memory buffer to read into
 //! \param pos file position to start read from
 //! \param bytes number of bytes to transfer
 //! \param on_cmpl I/O completion handler
 //! \return \c request_ptr request object, which can be used to track the status of the operation
 virtual request_ptr aread(void* buffer, offset_type pos, size_type bytes,
 const completion_handler& on_cmpl) = 0;

 //! Schedules an asynchronous write request to the file.
 //! \param buffer pointer to memory buffer to write from
 //! \param pos starting file position to write
 //! \param bytes number of bytes to transfer
 //! \param on_cmpl I/O completion handler
 //! \return \c request_ptr request object, which can be used to track the status of the operation
 virtual request_ptr awrite(void* buffer, offset_type pos, size_type bytes,
 const completion_handler& on_cmpl) = 0;

 virtual void serve(const request* req) throw (io_error) = 0;

 void add_request_ref()
 {
 scoped_mutex_lock Lock(request_ref_cnt_mutex);
 ++request_ref_cnt;
 }

 void delete_request_ref()
 {
 scoped_mutex_lock Lock(request_ref_cnt_mutex);
 assert(request_ref_cnt > 0);
 --request_ref_cnt;
 }

 int get_request_nref()
 {
 scoped_mutex_lock Lock(request_ref_cnt_mutex);
 return request_ref_cnt;
 }

 //! Changes the size of the file.
 //! \param newsize new file size
 virtual void set_size(offset_type newsize) = 0;

 //! Returns size of the file.
 //! \return file size in bytes
 virtual offset_type size() = 0;

 //! Returns the identifier of the file's queue.
 //! \remark Files allocated on the same physical device usually share the same queue
 //! \return queue number
 virtual int get_queue_id() const = 0;

 //! Returns the file's allocator.
 //! \return allocator number
 virtual int get_allocator_id() const = 0;

 virtual int get_physical_device_id() const
 {
 return get_queue_id();
 }

 //! Locks file for reading and writing (acquires a lock in the file system).
 virtual void lock() = 0;

 //! Discard a region of the file (mark it unused).
 //! Some specialized file types may need to know freed regions
 virtual void discard(offset_type offset, offset_type size)
 {
 STXXL_UNUSED(offset);
 STXXL_UNUSED(size);
 }

 virtual void export_files(offset_type offset, offset_type length, std::string prefix)
 {
 STXXL_UNUSED(offset);
 STXXL_UNUSED(length);
 STXXL_UNUSED(prefix);
 }

 //! close and remove file
 virtual void close_remove() { }

 virtual ~file()
 {
 int nr = get_request_nref();
 if (nr != 0)
 STXXL_ERRMSG("stxxl::file is being deleted while there are still " << nr << " (unfinished) requests referencing it");
 }

 //! Identifies the type of I/O implementation.
 //! \return pointer to null terminated string of characters, containing the name of I/O implementation
 virtual const char * io_type() const
 {
 return "none";
 }

public:
 //! \name Static Functions for Platform Abstraction
 //! \{

 //! unlink path from filesystem
 static int unlink(const char* path);

 //! truncate a path to given length. Use this only if you dont have a
 //! fileio-specific object, which provides truncate().
 static int truncate(const char* path, external_size_type length);

 //! \}
};

//! \defgroup fileimpl File I/O Implementations
//! Implementations of \c stxxl::file and \c stxxl::request
//! for various file access methods
//! \{
//! \}

//! \}

STXXL_END_NAMESPACE

#endif // !STXXL_IO_FILE_HEADER
// vim: et:ts=4:sw=4