sl@0: // Copyright (c) 1996-2009 Nokia Corporation and/or its subsidiary(-ies).
sl@0: // All rights reserved.
sl@0: // This component and the accompanying materials are made available
sl@0: // under the terms of the License "Eclipse Public License v1.0"
sl@0: // which accompanies this distribution, and is available
sl@0: // at the URL "http://www.eclipse.org/legal/epl-v10.html".
sl@0: //
sl@0: // Initial Contributors:
sl@0: // Nokia Corporation - initial contribution.
sl@0: //
sl@0: // Contributors:
sl@0: //
sl@0: // Description:
sl@0: // f32\sfat\sl_disk.cpp
sl@0: // 
sl@0: //
sl@0: 
sl@0: //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
sl@0: //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
sl@0: //!!
sl@0: //!! WARNING!! DO NOT edit this file !! '\sfat' component is obsolete and is not being used. '\sfat32'replaces it
sl@0: //!!
sl@0: //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
sl@0: //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
sl@0: 
sl@0: #include "sl_disk.h"
sl@0: #include "sl_cache.h"
sl@0: #include "sl_dir_cache.h"
sl@0: 
sl@0: /**
sl@0: @file
sl@0: */
sl@0: 
sl@0: 
sl@0: //################################################################################################################################
sl@0: //#     CRawDisk implementation
sl@0: //################################################################################################################################
sl@0: 
sl@0: 
sl@0: /**
sl@0:     Factory function. Constructs objects of the classes derived from CRawDisk.
sl@0:     
sl@0:     @param  aOwner      reference to the onwning FAT Mount class
sl@0:     @param  aLocDrvCaps local drive capabilities from the media driver
sl@0:     @return pointer to the constructed object. May be NULL on error.
sl@0: */
sl@0: CRawDisk* CRawDisk::NewL(CFatMountCB& aOwner, const TLocalDriveCaps& aLocDrvCaps)
sl@0: {
sl@0:     __PRINT1(_L("CRawDisk::NewL() drv:%d"), aOwner.DriveNumber());
sl@0: 
sl@0:     if(aLocDrvCaps.iMediaAtt & KMediaAttVariableSize)
sl@0:     {//-- this is the RAM drive "attribute"
sl@0:         ASSERT((aLocDrvCaps.iDriveAtt & (KDriveAttInternal|KDriveAttLocal)) && aLocDrvCaps.iType == EMediaRam);
sl@0:         if(!aLocDrvCaps.iBaseAddress)
sl@0:         {
sl@0:             ASSERT(0);
sl@0:             return NULL;
sl@0:         }
sl@0: 
sl@0:         return CRamDisk::NewL(aOwner);
sl@0:     }
sl@0: 
sl@0:     //-- create CAtaDisk by default
sl@0:     return CAtaDisk::NewL(aOwner);
sl@0: }
sl@0: 
sl@0: 
sl@0: CRawDisk::CRawDisk(CFatMountCB& aOwner)
sl@0:     {
sl@0:     iFatMount = &aOwner;
sl@0:     }
sl@0: 
sl@0: /**
sl@0:     Default implementation. Initialises and re-initialises the object.
sl@0: */
sl@0: void CRawDisk::InitializeL()
sl@0:     {
sl@0:     ASSERT(iFatMount);
sl@0:     }
sl@0: 
sl@0: 
sl@0: TInt CRawDisk::GetLastErrorInfo(TDes8& /*aErrorInfo*/) const
sl@0:     {
sl@0:     return KErrNotSupported;
sl@0:     }
sl@0: 
sl@0: //################################################################################################################################
sl@0: //##    CAtaDisk class implementation
sl@0: //################################################################################################################################
sl@0: 
sl@0: CAtaDisk::CAtaDisk(CFatMountCB& aFatMount)
sl@0:          :CRawDisk(aFatMount), iDrive(aFatMount.DriveInterface())
sl@0:     {
sl@0:     }
sl@0: 
sl@0: CAtaDisk::~CAtaDisk()
sl@0:     {
sl@0:     delete ipDirCache;
sl@0:     delete iUidCache;
sl@0:     
sl@0:     }
sl@0: 
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     CAtaDisk factory method.
sl@0:     
sl@0:     @param  aFatMount reference to the owner.
sl@0:     @return pointer to the constructed object.
sl@0: */
sl@0: CAtaDisk* CAtaDisk::NewL(CFatMountCB& aFatMount)
sl@0:     {
sl@0:     __PRINT1(_L("CAtaDisk::NewL() drv:%d"), aFatMount.DriveNumber());
sl@0: 
sl@0:     CAtaDisk* pSelf = new (ELeave) CAtaDisk(aFatMount);
sl@0:     
sl@0:     CleanupStack::PushL(pSelf);
sl@0:     
sl@0:     pSelf->ConstructL();
sl@0:     pSelf->InitializeL();
sl@0:     
sl@0:     CleanupStack::Pop();
sl@0: 
sl@0:     return pSelf;
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /** 2nd stage constructor */
sl@0: void CAtaDisk::ConstructL()
sl@0:     {
sl@0:     //===========================  create data WT cache that is primarily used for caching exacutable modules' UIDs
sl@0:     const TUint32 KUidCachePageSzLog2 = 9; //-- 512 bytes in page 
sl@0:     const TUint32 KUidCachePages = 64;     //-- 64 pages; total cache size is 32K 
sl@0: 
sl@0:     iUidCache = CMediaWTCache::NewL(iDrive, KUidCachePages, KUidCachePageSzLog2);
sl@0: 
sl@0: 
sl@0:     //=========================== create directory cache
sl@0:     
sl@0:     //-- Get dir. cache parameters from config. They may be set in estart.txt for a specified drive.
sl@0:     const TUint32 KDirCacheSize = iFatMount->FatConfig().DirCacheSize(); //- Total directory cache size, bytes.
sl@0:     const TUint32 KMaxDirCachePageSzLog2 = iFatMount->FatConfig().DirCacheMaxPageSizeLog2(); //- Log2 of the Max. dir. cache page.
sl@0: 
sl@0:     __PRINT2(_L("CAtaDisk::ConstructL() Dir Cache config:%d,%d"),KDirCacheSize,KMaxDirCachePageSzLog2);
sl@0: 
sl@0:     ASSERT(KDirCacheSize >= K1KiloByte && KDirCacheSize <= K1MegaByte);
sl@0:     ASSERT((KMaxDirCachePageSzLog2 >= KDefSectorSzLog2) && (Pow2(KMaxDirCachePageSzLog2) <= KDirCacheSize));
sl@0: 
sl@0:     //-- calculate the size and number of pages for the dir. cache. 
sl@0:     //-- if the mount's cluster size is less than max. page size from config, the page size will be cluster size.
sl@0:     //-- otherwise it will be the value from config. I.e  the minimal page size is cluster size; the maximal page size is taken from config.
sl@0:     //-- The number of pages depends on total cache size and page size.
sl@0:     const TUint clustSizeLog2 = iFatMount->ClusterSizeLog2(); //-- current FAT cluster size Log2
sl@0:     const TUint32 pageSzLog2 = (clustSizeLog2 <= KMaxDirCachePageSzLog2) ? clustSizeLog2 : KMaxDirCachePageSzLog2;
sl@0:     const TUint32 numPages = KDirCacheSize / (Pow2(pageSzLog2));
sl@0: 
sl@0:     ASSERT(!ipDirCache);
sl@0: 
sl@0: #ifdef USE_DP_DIR_CACHE
sl@0: 
sl@0:     //=========================== create Demand Paging type of the directory cache
sl@0: 
sl@0:     // initialize cache memory manager as all file systems have mounted by now
sl@0:     if(CCacheMemoryManagerFactory::CacheMemoryManager())
sl@0:         {
sl@0:         // Note: the configuration data of min and max cache size are aligned with the memory size it
sl@0:         //  occupies in kernel as we are using demand paging subsystem for dynamic cache size support. 
sl@0:         //  Therefore, they are refered as 'Mem Size' in following calculation.
sl@0:         //  However, 'Data Size' refers to the logical size of a page, i.e. the actual data size each page
sl@0:         //  contains.
sl@0:         // The constraints we have to consider when setting up the dynamic cache:
sl@0:         //  1. each page's data size is aligned with cluster size, unless cluster size is bigger than
sl@0:         //      the default maximum page size allowed (typically 32 KB).
sl@0:         //  2. if page's data size is smaller than segment size (typically 4 KB), i.e. the unit size of 
sl@0:         //      demand paging subsystem's page management, we will still use up the whole segment for
sl@0:         //      that page.
sl@0:         //  3. the default min and max cache's memory size is pre-defined in  fat_config.cpp file.
sl@0:         //      (see KDef_DynamicDirCacheMin & KDef_DynamicDirCacheMax).
sl@0: 
sl@0:         // calculate page data size (logical view of page size)
sl@0:         const TUint32 DefMaxCachePageLog2 = iFatMount->FatConfig().DynamicDirCacheMaxPageSizeLog2();
sl@0:         const TUint32 PageDataSizeLog2 = clustSizeLog2 < DefMaxCachePageLog2 ? clustSizeLog2 : DefMaxCachePageLog2;
sl@0:         
sl@0:         // calculate page number, based on memory size we have reserved
sl@0:         const TUint32 SegmentSizeLog2 = CCacheMemoryManagerFactory::CacheMemoryManager()->SegmentSizeInBytesLog2();
sl@0:         const TUint32 PageMemSizeLog2 = PageDataSizeLog2 < SegmentSizeLog2 ? SegmentSizeLog2 : PageDataSizeLog2;
sl@0:         TUint32 CacheSizeMinInPages = iFatMount->FatConfig().DynamicDirCacheSizeMin() >> PageMemSizeLog2;
sl@0:         TUint32 CacheSizeMaxInPages = iFatMount->FatConfig().DynamicDirCacheSizeMax() >> PageMemSizeLog2;
sl@0: 
sl@0:         // cache memory client is connected via name 
sl@0:         TBuf<0x20> clientName = _L("CACHE_MEM_CLIENT:");
sl@0:         clientName.Append('A'+iFatMount->DriveNumber());
sl@0: 
sl@0:         TRAPD(err, ipDirCache = CDynamicDirCache::NewL(iDrive, CacheSizeMinInPages, CacheSizeMaxInPages, PageDataSizeLog2, clientName));
sl@0:         if (err == KErrNone)
sl@0:             {
sl@0:             __PRINT4(_L("CDynamicDirCache::NewL(drv:%C, minPageNum:%u, maxPageNum:%u, pageDataSize:%u)\n"), 'A'+iFatMount->DriveNumber(), CacheSizeMinInPages, CacheSizeMaxInPages, 1<<PageDataSizeLog2);
sl@0:             return;
sl@0:             }
sl@0:         }
sl@0: #endif // USE_DP_DIR_CACHE
sl@0: 
sl@0:     //=========================== create legacy type of the directory cache
sl@0:     ASSERT(!ipDirCache);
sl@0: 
sl@0:     ipDirCache = CMediaWTCache::NewL(iDrive, numPages, pageSzLog2);
sl@0:     __PRINT3(_L("CDirCache::NewL(drive: %C, NumPages=%d, PageSize=%u)"), 'A'+iFatMount->DriveNumber(), numPages, 1<<pageSzLog2);
sl@0:     
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     Initialises and re-initialises the object.
sl@0: */
sl@0: void CAtaDisk::InitializeL()
sl@0: {
sl@0:     CRawDisk::InitializeL();
sl@0:     
sl@0:     //-- there is a little issue here. after formatting FAT mounts's cluster size can change.
sl@0:     //-- dir. cache page size depends on the cluster size. This method doesn't change the dir. cache page size.
sl@0:     //-- At present it is done in CFatMountCB::InitializeL() that deletes this object and then reconstructs it again.
sl@0: 
sl@0:     //-- invalidate directory cache here
sl@0:     ipDirCache->InvalidateCache();
sl@0:     
sl@0:     TInt64  cacheBasePos;
sl@0:     
sl@0:     if(iFatMount->FatType() == EFat32)
sl@0:         {
sl@0:         //-- this is FAT32, all directories including Root are files and aligned to the cluster heap boundary
sl@0:         //-- set dir. cache base position to the cluster heap boundary
sl@0:         const TUint32 offsetMask = (1 << iFatMount->ClusterSizeLog2() )-1;
sl@0:         cacheBasePos = (iFatMount->ClusterBasePosition() & offsetMask);
sl@0:         }
sl@0:     else
sl@0:         {
sl@0:         //-- this is FAT12/16. Root directory is a separate volume object and has no alignment.
sl@0:         //-- set cache base position to its beginning.
sl@0:         cacheBasePos = iFatMount->StartOfRootDirInBytes();
sl@0:         }
sl@0: 
sl@0:     ipDirCache->SetCacheBasePos(cacheBasePos);
sl@0:     
sl@0: }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     Read data from the media through LRU data cache cache. 
sl@0: 
sl@0:     @param  aPos        absolute media position
sl@0:     @param  aLength     how many bytes to read
sl@0:     @param  aDes        data descriptor
sl@0: 
sl@0:     @leave on error
sl@0: */
sl@0: void CAtaDisk::ReadCachedL(TInt64 aPos,TInt aLength,TDes8& aDes) const
sl@0:     {
sl@0:     __PRINT3(_L("CAtaDisk::ReadL() pos:%u:%u, len:%u"), I64HIGH(aPos), I64LOW(aPos), aLength);
sl@0:     iUidCache->ReadL(aPos, aLength, aDes);
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     Write data to the media through LRU data cache
sl@0: 
sl@0:     @param  aPos        absolute media position
sl@0:     @param  aDes        data descriptor
sl@0: 
sl@0:     @leave on error
sl@0: */
sl@0: void CAtaDisk::WriteCachedL(TInt64 aPos, const TDesC8& aDes)
sl@0:     {
sl@0:     __PRINT3(_L("CAtaDisk::WriteL() pos:%u:%u, len:%u"), I64HIGH(aPos), I64LOW(aPos), aDes.Size());
sl@0:     iUidCache->WriteL(aPos, aDes);
sl@0:     }
sl@0: 
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     Read data from the media directly without any caches.
sl@0:     Mostly used by file IO
sl@0: 
sl@0:     @param  aPos        absolute media position
sl@0:     @param  aLength     how many bytes to read
sl@0:     @param  aTrg        Pointer to the data descriptor, i.e. (const TAny*)(&TDes8)
sl@0:     @param  aMessage    Refrence to server message from request
sl@0:     @param  anOffset    Offset into read data to write
sl@0: 
sl@0:     @leave on error
sl@0: */
sl@0: void CAtaDisk::ReadL(TInt64 aPos,TInt aLength,const TAny* aTrg,const RMessagePtr2 &aMessage,TInt anOffset) const
sl@0:     {
sl@0: 
sl@0:     __PRINT4(_L("CAtaDisk::ReadL() pos:%u:%u, len:%u, offset:%u"), I64HIGH(aPos), I64LOW(aPos), aLength, anOffset);
sl@0:     User::LeaveIfError(iDrive.ReadNonCritical(aPos,aLength,aTrg,aMessage,anOffset));
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     Write data to the media directly without any cached.
sl@0:     Mostly used by file IO
sl@0: 
sl@0:     This method shall invalidate some data caches to keep them in synch with the media.
sl@0: 
sl@0:     @param aPos     Media position in bytes
sl@0:     @param aLength  Length in bytes of write
sl@0:     @param aTrg     Pointer to the data descriptor, i.e. (const TAny*)(&TDes8)
sl@0:     @param aMessage Refrence to server message from request, contains data
sl@0:     @param anOffset Offset into write data to use in write
sl@0: 
sl@0:     @leave on error
sl@0: */
sl@0: void CAtaDisk::WriteL(TInt64 aPos,TInt aLength,const TAny* aSrc,const RMessagePtr2 &aMessage,TInt anOffset)
sl@0:     {
sl@0:     __PRINT4(_L("CAtaDisk::WriteL() pos:%u:%u, len:%u, offset:%u"), I64HIGH(aPos), I64LOW(aPos), aLength, anOffset);
sl@0: 
sl@0:     //-- write data to the media directly
sl@0:     User::LeaveIfError(iDrive.WriteNonCritical(aPos,aLength,aSrc,aMessage,anOffset));
sl@0: 
sl@0:     //-- we need to invalidate UID cache page that corresponds to aPos (if any). This is UID caching specific. UID is stored in the first few bytes of 
sl@0:     //-- the executable module and therefore belongs to one cache page only.
sl@0:     //-- If someone writes to the beginning of the exe module file, corresponding UID cache page will be invalidated and re-read from the media later
sl@0:     iUidCache->InvalidateCachePage(aPos); 
sl@0: 
sl@0:     //-- invalidate affected(if any) part of the FAT cache in the case if someone used to write data to FAT area, which usually do not happen 
sl@0:     iFatMount->FAT().InvalidateCacheL(aPos,aLength);
sl@0: 
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /** Get information for last disk error */
sl@0: TInt CAtaDisk::GetLastErrorInfo(TDes8& aErrorInfo) const
sl@0:     {
sl@0:     return iDrive.GetLastErrorInfo(aErrorInfo);
sl@0:     }
sl@0: 
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: /** Invalidate whole UID cache */
sl@0: void CAtaDisk::InvalidateUidCache()
sl@0: {
sl@0:     ASSERT(iUidCache);
sl@0:     iUidCache->InvalidateCache();
sl@0: }
sl@0: 
sl@0: /** 
sl@0:     Invalidate the UID cache page that has aPos cached.
sl@0:     This method doesn't pay attention to the length of the block being invalidated because
sl@0:     UID lives in the very beginning of the exe module and always fits into a single page
sl@0: */
sl@0: void CAtaDisk::InvalidateUidCachePage(TUint64 aPos)
sl@0: {
sl@0:     ASSERT(iUidCache);
sl@0:     iUidCache->InvalidateCachePage(aPos);
sl@0: }
sl@0: 
sl@0: 
sl@0: //################################################################################################################################
sl@0: //##    CRamDisk class implementation
sl@0: //################################################################################################################################
sl@0: 
sl@0: 
sl@0: /**
sl@0:     CRamDisk factory method.
sl@0:     
sl@0:     @param  aFatMount reference to the owner.
sl@0:     @return pointer to the constructed object.
sl@0: */
sl@0: CRamDisk* CRamDisk::NewL(CFatMountCB& aFatMount)
sl@0:     {
sl@0:     __PRINT1(_L("CRamDisk::NewL() drv:%d"), aFatMount.DriveNumber());
sl@0:     CRamDisk* pSelf = new(ELeave)CRamDisk(aFatMount);
sl@0: 
sl@0:     CleanupStack::PushL(pSelf);
sl@0:   
sl@0:     pSelf->InitializeL();
sl@0:     
sl@0:     CleanupStack::Pop();
sl@0: 
sl@0:     return pSelf;
sl@0:     }
sl@0: 
sl@0: CRamDisk::CRamDisk(CFatMountCB& aFatMount)
sl@0:          :CRawDisk(aFatMount)
sl@0:     {
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: 
sl@0: /**
sl@0:     Initialises and re-initialises the object.
sl@0: */
sl@0: void CRamDisk::InitializeL()
sl@0: {
sl@0:     CRawDisk::InitializeL();
sl@0: 
sl@0:     //-- set the RAM disk base
sl@0:     TLocalDriveCapsV2 caps;
sl@0:     TPckg<TLocalDriveCapsV2> capsPckg(caps);
sl@0:     User::LeaveIfError(iFatMount->LocalDrive()->Caps(capsPckg));
sl@0:   
sl@0:     ASSERT(caps.iMediaAtt & KMediaAttVariableSize);
sl@0:     
sl@0:     //-- set RAM disk base
sl@0:     iRamDiskBase = caps.iBaseAddress; 
sl@0:     ASSERT(iRamDiskBase);
sl@0: }
sl@0: 
sl@0: 
sl@0: 
sl@0: /** @return the start address of the Ram Drive in low memory */
sl@0: TUint8* CRamDisk::RamDiskBase() const
sl@0:     {
sl@0:     return iRamDiskBase;
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: //
sl@0: // Read aLength of data from the disk
sl@0: //
sl@0: void CRamDisk::ReadCachedL(TInt64 aPos,TInt aLength,TDes8& aDes) const
sl@0:     {
sl@0:     
sl@0:     __PRINT3(_L("CRamDisk::ReadL Base 0x%x Pos 0x%x, Len %d"),RamDiskBase(),I64LOW(aPos),aLength);
sl@0:     __ASSERT_ALWAYS((aPos+aLength<=I64INT(iFatMount->Size())) && (aLength>=0),User::Leave(KErrCorrupt));
sl@0:     Mem::Copy((TUint8*)aDes.Ptr(),RamDiskBase()+I64LOW(aPos),aLength);
sl@0:     aDes.SetLength(aLength);
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: //
sl@0: // Write aLength of data to the disk
sl@0: //
sl@0: void CRamDisk::WriteCachedL(TInt64 aPos,const TDesC8& aDes)
sl@0:     {
sl@0: 
sl@0:     __PRINT3(_L("CRamDisk::WriteL Base 0x%x Pos 0x%x, Len %d"),RamDiskBase(),aPos,aDes.Length());
sl@0:     __ASSERT_ALWAYS(aPos+aDes.Length()<=I64INT(iFatMount->Size()),User::Leave(KErrCorrupt));
sl@0:     Mem::Copy(RamDiskBase()+I64LOW(aPos),(TUint8*)aDes.Ptr(),aDes.Length());
sl@0:     }
sl@0:     
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: //
sl@0: // Read from ramDrive into thread relative descriptor
sl@0: //
sl@0: void CRamDisk::ReadL(TInt64 aPos,TInt aLength,const TAny* /*aTrg*/,const RMessagePtr2 &aMessage,TInt anOffset) const
sl@0:     {
sl@0:     __PRINT2(_L("CRamDisk::ReadL TAny* Pos 0x%x, Len %d"),aPos,aLength);
sl@0:     __ASSERT_ALWAYS((aPos+aLength<=I64INT(iFatMount->Size())) && (aLength>=0),User::Leave(KErrCorrupt));
sl@0:     TUint8* pos=RamDiskBase()+I64LOW(aPos);
sl@0:     TPtrC8 buf(pos,aLength);
sl@0:     aMessage.WriteL(0,buf,anOffset);
sl@0:     }
sl@0: 
sl@0: //-------------------------------------------------------------------------------------
sl@0: //
sl@0: // Write from thread relative descriptor into ramDrive
sl@0: //
sl@0: void CRamDisk::WriteL(TInt64 aPos,TInt aLength,const TAny* /*aSrc*/,const RMessagePtr2 &aMessage,TInt anOffset)
sl@0:     {
sl@0:     __PRINT2(_L("CRamDisk::WriteL TAny* Pos 0x%x, Len %d"),aPos,aLength);
sl@0:     __ASSERT_ALWAYS(aPos+aLength<=I64INT(iFatMount->Size()),User::Leave(KErrCorrupt));
sl@0:     TUint8* pos=RamDiskBase()+I64LOW(aPos);
sl@0:     TPtr8 buf(pos,aLength);
sl@0:     aMessage.ReadL(0,buf,anOffset);
sl@0:     }
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