// Copyright (c) 1996-2009 Nokia Corporation and/or its subsidiary(-ies).

// All rights reserved.

// This component and the accompanying materials are made available

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

// which accompanies this distribution, and is available

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

//

// Initial Contributors:

// Nokia Corporation - initial contribution.

//

// Contributors:

//

// Description:

// f32\sfat32\inc\sl_cache.h

// 

//

/**

 @file

 @internalTechnology

*/

#ifndef SL_CACHE_H

#define SL_CACHE_H

//---------------------------------------------------------------------------------------------------------------------------------

//-- dedicated FAT directory cache related stuff

//---------------------------------------------------------------------------------------------------------------------------------

/** 

    An abstract interface to the media Write-Through cache

*/

class MWTCacheInterface

    {

public:

	/** Enums for control functions. See Control() */

	enum TControl

	    {

	    EDisableCache = 0, 	///< disable/enable cache, can be used for debug purposes

	    EDumpCache = 1, 	///< print full cache content, can be used for debug purposes

	    ECacheInfo = 2, 	///< print cache info, can be used for debug purposes

	    };

        virtual ~MWTCacheInterface() {}

        /** the same meaning and parameters as in CRawDisk::ReadL */

        virtual void    ReadL(TInt64 aPos, TInt aLength, TDes8& aDes)=0;

        /** the same meaning and parameters as in CRawDisk::WriteL */

        virtual void    WriteL(TInt64 aPos,const TDesC8& aDes)=0;

        /** Invalidates whole directory cache*/

        virtual void    InvalidateCache(void)=0;

        /** invalidate a single cache page if the aPos is cached*/

        virtual void    InvalidateCachePage(TUint64 aPos)=0;

        /**

        Finds out if the media position "aPosToSearch" is in the cache and returns cache page information in this case.

        @param  aPosToSearch    linear media position to lookup in the cache

        @return 0 if aPosToSearch isn't cached, otherwise  cache page size in bytes (see also aCachedPosStart).

        */

        /**

        @return size of the cache in bytes. Can be 0.

        */

        virtual TUint32 CacheSizeInBytes() const = 0;

        /**

        Make the page indexed by aPos the MRU page in the cache.

        Assumes cache evicts pages according to LRU algorithm.

        */

        virtual void MakePageMRU(TInt64 aPos) = 0;

        /**

        @return log2 number of the size of the cache in bytes.

        */

        virtual TUint32 PageSizeInBytesLog2() const = 0;

        /**

        Control method.

          @param  aFunction   control function

          @param  aParam1     just arbitrary parameter 

          @param  aParam2     just arbitrary parameter 

          @return Standard error code.

        */

        virtual TInt Control(TUint32 aFunction, TUint32 aParam1, TAny* aParam2)=0;

        /**

        Set cache base position at aBasePos

        @param  aBasePos  base position of the cache pages. Affects pages alignment.

        */

        virtual void SetCacheBasePos(TInt64 aBasePos)=0;

    };

//---------------------------------------------------------------------------------------------------------------------------------

/**

This class represents the media Write-Through cache page

*/

class CWTCachePage

    {

public:   

        static CWTCachePage* NewL(TUint32 aPageSizeLog2);

        ~CWTCachePage();

        inline TBool   PosCached(TInt64 aPos) const;

        inline TUint32 PosInCachePage(TInt64 aPos) const; 

        inline TUint8* PtrInCachePage(TInt64 aPos) const; 

        inline TUint32 PageSize() const;

protected:

        CWTCachePage();

        CWTCachePage(const CWTCachePage&);

        CWTCachePage& operator=(const CWTCachePage&);

public:

        TInt32  iValid;     ///< 0 if the page doesn't contain valid data

        TInt64  iStartPos;  ///< cache page base media position

        RBuf8   iData;      ///< page Data

    };

//---------------------------------------------------------------------------------------------------------------------------------

/**

    Media Write-through cache.

*/

class CMediaWTCache : public CBase, public MWTCacheInterface

    {

public:

        ~CMediaWTCache();

        //-- overloads from the base class

        void    ReadL (TInt64 aPos,TInt aLength,TDes8& aDes);

        void    WriteL(TInt64 aPos,const TDesC8& aDes);

        void    InvalidateCache(void);

        void    InvalidateCachePage(TUint64 aPos);

        TUint32 CacheSizeInBytes()  const;

        void 	MakePageMRU(TInt64 aPos);

        TUint32 PageSizeInBytesLog2()	const;

        TInt    Control(TUint32 aFunction, TUint32 aParam1, TAny* aParam2);

        inline void SetCacheBasePos(TInt64 aBasePos);

        //--

protected:

        CMediaWTCache();

        CMediaWTCache(TDriveInterface& aDrive);

        inline TInt64  CalcPageStartPos(TInt64 aPos) const;

        inline TUint32 PageSize() const;

        void MakePageLRU(TInt aPageNo);

        TInt    FindPageByPos(TInt64 aPos) const;

        TUint32 GrabPage() const;

        TUint32 GrabReadPageL(TInt64 aPos);

        TUint32 FindOrGrabReadPageL(TInt64 aPos);

protected:

        TDriveInterface& iDrive;        ///< reference to the driver for media access

        mutable TBool       iAllPagesValid;///< ETrue if all cache pages have valid data

        TInt64              iCacheBasePos; ///< Cache pages base position, used to align them at cluster size

        RPointerArray<CWTCachePage> iPages; ///< array of pointers to the cache pages. Used for organising LRU list

        TUint32             iCacheDisabled :1; ///< if not 0 the cache is disabled totally and all reads and writes go via TDriveInterface directly

    };

#include"sl_cache.inl"

#endif //SL_CACHE_H