1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/os/persistentdata/persistentstorage/dbms/sdbms/Sd_DriveSpace.h Fri Jun 15 03:10:57 2012 +0200
1.3 @@ -0,0 +1,156 @@
1.4 +// Copyright (c) 2004-2009 Nokia Corporation and/or its subsidiary(-ies).
1.5 +// All rights reserved.
1.6 +// This component and the accompanying materials are made available
1.7 +// under the terms of "Eclipse Public License v1.0"
1.8 +// which accompanies this distribution, and is available
1.9 +// at the URL "http://www.eclipse.org/legal/epl-v10.html".
1.10 +//
1.11 +// Initial Contributors:
1.12 +// Nokia Corporation - initial contribution.
1.13 +//
1.14 +// Contributors:
1.15 +//
1.16 +// Description:
1.17 +// Reserving/Accessing/Releasing drive space - CDriveSpace, RDriveSpaceCol, CDbsSessDriveSpace
1.18 +// classes declarations
1.19 +//
1.20 +//
1.21 +
1.22 +#ifndef __SD_DRIVESPACE_H__
1.23 +#define __SD_DRIVESPACE_H__
1.24 +
1.25 +#include <f32file.h>
1.26 +
1.27 +//Forward declarations
1.28 +class RDriveSpaceCol;
1.29 +class CDbsSessDriveSpace;
1.30 +class CDbsServer;
1.31 +
1.32 +/**
1.33 +This class describes an object, which is responsible for handling
1.34 +"reserve/get access/release" requests for a particular drive.
1.35 +Since the drive is shared between many DBMS sessions and there is only one RFs instance,
1.36 +the current solution is that CDriveSpace objects reserve some predefined amount of disk space
1.37 +at the time of their creation and then the access to the reserved disk space is reference counted.
1.38 +There is one obvious disadvantage of this solution: if a bad application "forgets" to release
1.39 +the access to the reserved disk space, it may be used by the DBMS file session and at the moment,
1.40 +when some client will really need it to complete its "delete" transaction, it may happen that
1.41 +there is no reserved disk space at all, because it is already used. But I don't think there
1.42 +is an acceptable solution for this case, if there is only one shared file session.
1.43 +The class shall not be used directly, that's the reason its constructor and NewLC() are private.
1.44 +The class functionality shall be used by the controlling collection object - RDriveSpaceCol.
1.45 +@internalComponent
1.46 +*/
1.47 +NONSHARABLE_CLASS(CDriveSpace) : public CBase
1.48 + {
1.49 + friend class RDriveSpaceCol;
1.50 +
1.51 +public:
1.52 + inline TDriveNumber Drive() const;
1.53 + void GrantAccessL();
1.54 + void ReleaseAccess();
1.55 +
1.56 +private:
1.57 + static CDriveSpace* NewLC(RFs& aFs, TDriveNumber aDrive);
1.58 + CDriveSpace(RFs& aFs, TDriveNumber aDrive);
1.59 + virtual ~CDriveSpace();
1.60 + void ConstructL();
1.61 +
1.62 +private:
1.63 + RFs& iFs; //File session reference
1.64 + TDriveNumber iDrive; //Drive number
1.65 + TInt iGrantAccessRefCnt;//"Get access" requests count
1.66 +
1.67 + };
1.68 +
1.69 +/**
1.70 +@return The drive number, where the CDriveSpace object handles the reservation requests
1.71 +*/
1.72 +inline TDriveNumber CDriveSpace::Drive() const
1.73 + {
1.74 + return iDrive;
1.75 + }
1.76 +
1.77 +/**
1.78 +This class describes a collection of CDriveSpace objects. Each CDriveSpace object in the
1.79 +collection is responsible for handling "reserve/get access/release" requests for a particular
1.80 +drive.
1.81 +Only one instace of RDriveSpaceCol class should be created and used in the DBMS server.
1.82 +An object of this class shall be created by the DBMS server, but the DBMS server is alloved only
1.83 +to close (destroy) it at the end. RDriveSpaceCol collection shall be used by CDbsSessDriveSpace
1.84 +instances, which shall be created/used/destroyed by the DBMS sessions.
1.85 +@see CDriveSpace
1.86 +@internalComponent
1.87 +*/
1.88 +class RDriveSpaceCol
1.89 + {
1.90 + friend class CDbsServer;
1.91 + friend class CDbsSessDriveSpace;
1.92 +
1.93 +private:
1.94 + RDriveSpaceCol(RFs& aFs);
1.95 + void Close();
1.96 + CDriveSpace* Find(TDriveNumber aDrive);
1.97 + CDriveSpace* CreateAddL(TDriveNumber aDrive);
1.98 +
1.99 +private:
1.100 + RFs& iFs; //File session reference
1.101 + RPointerArray<CDriveSpace> iDriveSpaceCol; //Collection of CDriveSpace objects: one per drive
1.102 +
1.103 + };
1.104 +
1.105 +/**
1.106 +This structure describes an object, which handles all disk space related requests per
1.107 +DBMS session instance.
1.108 +Using it, the DBMS session can control the access to the reserved drive space for a
1.109 +particular drive(s).
1.110 +Although it seems a good idea to save some binary code space and use directly CDriveSpace and
1.111 +RDriveSpaceCol classes - no, it is not that good.
1.112 +If you use directly CDriveSpace and RDriveSpaceCol, you have to control that every "Reserve"
1.113 +call is matched by a "Free" call and every "Get/GrantAcces" call is matched by a "ReleaseAccess"
1.114 +call. Also you have to take care about checking that the appropriate CDriveSpace object has
1.115 +been created already or if not - you have to create and add it to the RDriveSpaceCol colelction.
1.116 +All that is done in CDbsSessDriveSpace class.
1.117 +@internalComponent
1.118 +*/
1.119 +NONSHARABLE_CLASS(CDbsSessDriveSpace) : public CBase
1.120 + {
1.121 +private:
1.122 + /**
1.123 + This structure describes the state of the disk space reservation requests, related to a
1.124 + particular drive. It holds an information like: drive number, was the disk space
1.125 + already reserved?, was an access to it already granted?
1.126 + Using the TDriveSpaceRq objects, the caller can ensure that every "Reserve" call is
1.127 + matched by a "Free" call, every "GetAccess" call is matched by a "ReleaseAccess" call.
1.128 + @internalComponent
1.129 + */
1.130 + struct TDriveSpaceRq
1.131 + {
1.132 + TDriveSpaceRq(CDriveSpace& aDriveSpace);
1.133 + CDriveSpace& iDriveSpace; //This object will handle the reservation requests
1.134 + TUint8 iReserved: 1; //If non-zero then the space was already reserved
1.135 + TUint8 iAccessGranted: 1; //If non-zero then an access to the space was already granted
1.136 + };
1.137 +
1.138 +public:
1.139 + static CDbsSessDriveSpace* NewL(RDriveSpaceCol& aDriveSpaceCol);
1.140 + virtual ~CDbsSessDriveSpace();
1.141 +
1.142 + void ReserveL(TDriveNumber aDrive);
1.143 + void Free(TDriveNumber aDrive);
1.144 + void GrantAccessL(TDriveNumber aDrive);
1.145 + void ReleaseAccess(TDriveNumber aDrive);
1.146 +
1.147 +private:
1.148 + CDbsSessDriveSpace(RDriveSpaceCol& aDriveSpaceCol);
1.149 + TDriveSpaceRq* Find(TDriveNumber aDrive);
1.150 + TDriveSpaceRq& CreateAddL(TDriveNumber aDrive);
1.151 + TDriveSpaceRq& GetL(TDriveNumber aDrive);
1.152 +
1.153 +private:
1.154 + RDriveSpaceCol& iDriveSpaceCol;//Reference to the RDriveSpaceCol colelction.
1.155 + RArray<TDriveSpaceRq> iDriveSpaceRqCol;//Collection of TDriveSpaceRq objects: one per drive
1.156 +
1.157 + };
1.158 +
1.159 +#endif//__SD_DRIVESPACE_H__