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Keyfile.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
 *
 *==========================================================================
*/


#ifndef _LEMUR_KEYFILE_H
#define _LEMUR_KEYFILE_H

class Keyfile {
public:
  Keyfile() : _handleSize(0), _handle(NULL) {
  }

  void put( const char* key, const void* value, int valueSize );

  void put( int key, const void* value, int valueSize );

  bool get( const char* key, void* value, int& actualSize, int maxSize ) const;

  bool get( const char* key, char** value, int& actualSize ) const;

  bool get( int key, void* value, int& actualSize, int maxSize ) const;

  bool get( int key, char** value, int& actualSize ) const;

  // redundant with getNext... combine.
  bool next( char* key, int& keyLength, char* value, int& valueLength );
  bool next( int& key, char* value, int& valueLength );

  bool previous( char* key, int& keyLength, char* value, int& valueLength );
  bool previous( int& key, char* value, int& valueLength );

  int getSize( const char* key ) const;

  int getSize( int key ) const;

  void remove( const char* key );

  void remove( int key );

  void open( const std::string& filename, int cacheSize = 1024 * 1024, bool readOnly = false);

  void open( const char* filename, int cacheSize = 1024 * 1024, bool readOnly = false );

  void openRead( const std::string& filename, int cacheSize = 1024 * 1024 );

  void create( const std::string& filename, int cacheSize = 1024 * 1024 );

  void create( const char* filename, int cacheSize = 1024 * 1024 );

  void close();

  void setFirst();

  bool getNext( int& key, void* value, int& actualSize, int maxSize ) const;

  bool getNext( char* key, int maxKeySize, void* value, 
                int& actualSize, int maxSize ) const;

  bool getNext( char* key, int& actKeySize, int maxKeySize, void* value, 
                int& actualSize, int maxSize ) const;

  enum {
    MAX_KEY_LENGTH = 512
  };
  
private:
  char* _handle; // file control block of the keyfile
  int _handleSize; // sizeof _handle buffer

  void _buildHandle( int cacheSize );
  void _createKey( char* keyBuf, int number ) const;
  int _decodeKey( char* keyBuf ) const;
};

#endif // _LEMUR_KEYFILE_H

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