File.hpp

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/*==========================================================================
 * Copyright (c) 2003 University of Massachusetts.  All Rights Reserved.
 *
 * Use of the Lemur Toolkit for Language Modeling and Information Retrieval
 * is subject to the terms of the software license set forth in the LICENSE
 * file included with this software, and also available at
 * http://www.lemurproject.org/license.html
 *
 *==========================================================================
 */


//
// File.hpp
//
// 1 December 2003 - tds
//

#ifndef LEMUR_FILE_HPP
#define LEMUR_FILE_HPP

#include <vector>
#include <sstream>
#include <fstream>
#include <assert.h>
#include "lemur-platform.h"
#include "lemur-compat.hpp"
namespace lemur
{
  namespace file
  {
    

    class File {
    public:
      typedef INT64 offset_type;
      typedef FILE_OFFSET library_offset_type;

    private:
      struct FileSegment {
        std::fstream stream;
        offset_type start;
        offset_type end;

        bool contains( offset_type position ) {
          return start <= position && end > position;
        }

        bool before( offset_type position ) {
          return end <= position;
        }
      };

      std::string _fileName;
      std::vector<FileSegment*> _segments;

      FileSegment* _readSegment;
      FileSegment* _writeSegment;
      offset_type _readPosition; // seekg, read
      offset_type _writePosition; // seekp, write
      offset_type _readCount;
      bool _readPointerValid;
      bool _writePointerValid;
      int _mode;
      int _state;

      static std::string segmentName( const std::string& fileName, int segment );
      void _appendSegment();

      offset_type _absolutePosition( offset_type relativePosition,
                                     offset_type currentPosition,
                                     std::fstream::seekdir direction ) const;
      FileSegment* _segmentForPosition( offset_type absolutePosition, FileSegment* guess );
      void _validateReadPointer();
      void _validateWritePointer();

    public:
      File();
      ~File();
      void open( const std::string& fileName, int mode );
      void close();
      void read( void* buffer, offset_type count );
      void write( const void* buffer, offset_type count );
      void seekg( offset_type relativePosition, std::fstream::seekdir direction );
      void seekp( offset_type relativePosition, std::fstream::seekdir direction ) ;
      offset_type tellg();
      offset_type tellp();
      offset_type gcount();

      // only does eof right now
      int rdstate();
      offset_type size() const;
      void unlink();

      static void unlink( const std::string& fileName );
      static void rename( const std::string& oldName, const std::string& newName );
    };
  }
}

#endif // LEMUR_FILE_HPP

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