ktorrent/libktorrent/util/mmapfile.h

/***************************************************************************
 *   Copyright (C) 2005 by Joris Guisson                                   *
 *   joris.guisson@gmail.com                                               *
 *                                                                         *
 *   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 2 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, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.             *
 ***************************************************************************/
#ifndef BTMMAPFILE_H
#define BTMMAPFILE_H


#include <qstring.h>
#include <util/constants.h>

namespace bt
{

	/**
	 * @author Joris Guisson
	 * @brief Memory mapped file
	 *
	 * This class allows to access memory mapped files. It's pretty similar to
	 * File.
	 * TODO: make sure large files work (not really needed for the blocklist)
	*/
	class MMapFile
	{
	public:
		MMapFile();
		virtual ~MMapFile();

		enum Mode
		{
			READ,WRITE, RW
		};
		/**
		 * Open the file. If mode is write and the file doesn't exist, it will
		 * be created.
		 * @param file Filename
		 * @param mode Mode (READ, WRITE or RW)
		 * @return true upon succes
		 */
		bool open(const QString & file,Mode mode);
		
		/**
		 * Open the file. If mode is write and the file doesn't exist, it will
		 * be created.
		 * @param file Filename
		 * @param mode Mode (READ, WRITE or RW)
		 * @param size Size of the memory mapping (the file will be enlarged to this value)
		 * @return true upon succes
		 */
		bool open(const QString & file,Mode mode,Uint64 size);
		
		/**
		 * Close the file. Undoes the memory mapping.
		 */
		void close();
		
		/**
		 * Flush the file.
		 */
		void flush();
		
		/**
		 * Write a bunch of data.
		 * @param buf The data
		 * @param size Size of the data
		 * @return The number of bytes written
		 */
		Uint32 write(const void* buf,Uint32 size);
		
		/**
		 * Read a bunch of data
		 * @param buf The buffer to store the data
		 * @param size Size of the buffer
		 * @return The number of bytes read
		 */
		Uint32 read(void* buf,Uint32 size);

		enum SeekPos
		{
			BEGIN,
			END,
			CURRENT
		};
		
		/**
		 * Seek in the file.
		 * @param from Position to seek from
		 * @param num Number of bytes to move
		 * @return New position
		 */
		Uint64 seek(SeekPos from,Int64 num);

		/// Check to see if we are at the end of the file.
		bool eof() const;

		/// Get the current position in the file.
		Uint64 tell() const;

		/// Get the error string.
		QString errorString() const;
		
		/// Get the file size
		Uint64 getSize() const;

		
		/**
		 * Get a pointer to the mmapped region of data.
		 * @param off Offset into buffer, if invalid 0 will be returned
		 * @return Pointer to a location in the mmapped region
		 */
		Uint8* getData(Uint64 off);
		
		/// Gets the data pointer
		void* getDataPointer() { return data; }
	private:
		void growFile(Uint64 new_size);

	private:
		int fd;
		Uint8* data;
		Uint64 size;	// size of mmapping
		Uint64 file_size; // size of file
		Uint64 ptr; 
		QString filename;
		Mode mode;
	};

}


#endif