1 // Copyright (c) 2004-2009 Nokia Corporation and/or its subsidiary(-ies).

     2 // All rights reserved.

     3 // This component and the accompanying materials are made available

     4 // under the terms of "Eclipse Public License v1.0"

     5 // which accompanies this distribution, and is available

     6 // at the URL "http://www.eclipse.org/legal/epl-v10.html".

     7 //

     8 // Initial Contributors:

     9 // Nokia Corporation - initial contribution.

    10 //

    11 // Contributors:

    12 //

    13 // Description:

    14 //

    15 

    16 #ifndef __T_RNDUTILS_H__

    17 #define __T_RNDUTILS_H__

    18 

    19 

    20 #include "T_UTILS.H"

    21 #include "t_utils2.h"

    22 

    23 const TInt KDigramNumberOfNonLetters =  3;	// space, -, null

    24 const TInt KDigramNumberOfLetters =  26 ;

    25 const TInt KDigramNumberOfChars =  KDigramNumberOfLetters*2+ KDigramNumberOfNonLetters;

    26 

    27 /** Used to create randomly generated words using n-grams found in the specified data file.

    28 	Using n-grams lead to much more realistic words and thus makes it obvious a descriptor

    29 	is data and not noise.

    30 	This implementation only supports digrams */

    31 	

    32 class CWordNgrams : public CBase, public MRandomWordGenerator

    33 	{

    34 	public:

    35 		HBufC* WordLC();

    36 		

    37 	protected: 

    38 		

    39 		TBool AddLetter(TDes& aWord);

    40 		void ConstructL(const TDesC& aFilename, TInt aNgramSize = 2, TBool aUseNarrowChar = ETrue);

    41 		virtual TChar NextLetter(const TDesC& aWord) = 0;

    42 		virtual void SetNgram(const TDesC8& aNgram, TUint aNumber) = 0;

    43 		virtual void SetNgram(const TDesC16& aNgram, TUint aNumber) = 0;

    44 

    45 	};

    46 	

    47 

    48 /** Implementation of CWordNgrams which uses digram frequencies (letter pairs)

    49 	to generate random words */

    50 class CWordDigrams : public CWordNgrams

    51 	{

    52 	public:

    53 		static CWordDigrams* NewLC(const TDesC& aFilename, TInt64& aRandSeed );

    54 		virtual ~CWordDigrams();

    55 		

    56 	protected: 

    57 		void ConstructL(const TDesC& aFilename);

    58 		void SetNgram(const TDesC8& aNgram, TUint aNumber);

    59 		void SetNgram(const TDesC16& aNgram, TUint aNumber); // empty function

    60 		TChar NextLetter(const TDesC& aWord);

    61 

    62 	private:

    63 		CWordDigrams(TInt64& aRandSeed);

    64 		static TInt Index(const TChar c);

    65 		static TChar Char(TInt i);

    66 		

    67 	private:

    68 		TInt64& iRandSeed;

    69 		TUint8 iDigrams[KDigramNumberOfChars][KDigramNumberOfChars];

    70 		TUint16 iSizes[KDigramNumberOfChars];

    71 	};

    72 

    73 

    74 

    75 #endif