1 sensrvchannel.h

     1 /*

     2 * Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies). 

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

     5 * under the terms of the License "Symbian Foundation License v1.0" to Symbian Foundation members and "Symbian Foundation End User License Agreement v1.0" to non-members

     6 * which accompanies this distribution, and is available

     7 * at the URL "http://www.symbianfoundation.org/legal/licencesv10.html".

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description:  Sensor channel class definition

    15 *

    16 */

    17 

    18 

    19 #ifndef SENSRVCHANNEL_H

    20 #define SENSRVCHANNEL_H

    21 

    22 #include <e32base.h>

    23 #include <sensrvtypes.h>

    24 #include <sensrvchannelconditionset.h>

    25 #include <sensrvchannelinfo.h>

    26 

    27 

    28 class MSensrvPropertyListener;

    29 class MSensrvDataListener;

    30 class MSensrvChannelConditionListener;

    31 class CSensrvChannelCondition;

    32 class CSensrvChannelListener;

    33 

    34 

    35 /**

    36 * The CSensrvChannel class provides an API that allows clients to open, control, configure, 

    37 * receive data and receive notifications from a sensor channel.

    38 * 

    39 * When instantiating CSensrvChannel an instance of TSensrvChannelInfo returned by

    40 * CSensrvChannelFinder::FindChannelsL() must be used. This ensures that internal data used

    41 * in identifying the chosen channel is passed back to Sensor Services in its entirety

    42 * therefore ensuring correct operation. Not using the instance returned by

    43 * CSensrvChannelFinder::FindChannelsL() will result in undefined behaviour.

    44 * 

    45 * On instantiation of this class a session connection to the Sensor Server is made. The Sensor

    46 * server is a transient server and is started, if not already running, when a session connection

    47 * is made. The sensor server is shutdown when a device-configured timeout period expires after

    48 * the last session connection has been dropped. The Sensor Server will not shutdown if there is

    49 * a session connection to it.

    50 * 

    51 * The instance of TSensrvChannelInfo returned by CSensrvChannelFinder::FindChannelsL()

    52 * contains a channel Id which is only valid for the lifetime of the sensor server. If a client

    53 * requires that this id remains unchanged then the client must ensure that an instance of either

    54 * CSensrvChannelFinder or CSensrvChannel remains instantiated. This keeps a session connection with

    55 * the server open which prevents the sensor server from shutting down.

    56 * 

    57 * After creating an instance of this class a client would typically:

    58 * 1. Check the configuration of the channel using GetPropertyL() or GetAllPropertuies().

    59 * 2. Change the configuration where necessary using SetPropertiesL()

    60 * 3. If SetPropertiesL() failed, because of higher priority clients of this same channel or higher

    61 * priority clients of impacted channels on the same sensor, listen for notifications indicating

    62 * when it is able to set properties using SetPropertyListenerl().

    63 * 4. Listen for property changes using SetPropertyListenerl(). This notifies the client of property

    64 * changes made by other clients of this same channel.

    65 * 5. Listen for data and retrieve data on the channel using StartDataListeningL() and GetData().

    66 * 6. Set trigger conditions for a 1 off notification when the condition is met using AddConditionL()

    67 * and SetConditionListeningL(). 

    68 * 

    69 * Its possible that there may be more than 1 client using the same sensor channel on the device. Each

    70 * of these clients will have created their own instance of CSensrvChannel and can attempt to configure

    71 * the sensor using the SetPropertyL() operation. To manage any contention between clients wishing to

    72 * change the configuration of the sensor a concept of Client Priorities is employed. This means that a

    73 * device creator assigns a pre-determined priority to a client. If a client has not been assigned a

    74 * priority then it is assumed it has the lowest priority.

    75 * 

    76 * When the SetPropertyL() operation is called the sensor server checks to see if the client has the

    77 * highest Client Priority of all clients using that channel or using an impacted channel on the same

    78 * sensor. If it has the property is set and all other clients of the channel are notified of the property

    79 * change. If it has not the SetPropertyL() operation fails with KErrAccessDenied. If clients have

    80 * the same priority then property setting is done on a first come first served basis.

    81 * 

    82 * If a client is unable to set a property because of higher priority clients then the client should

    83 * implement the MSensrvPropertyListener::SetPropertySuccessIndicationChanged() callback so that they can

    84 * be notified when they are able to set properties.

    85 * 

    86 * All client applications should be designed in such a way so that they are able to handle the situation

    87 * where they are unable to configure a channel using the SetPropertyL() operation.

    88 * 

    89 * For example:

    90 * Should application features be disabled or should the application shutdown in such conditions?

    91 * Should features be disabled under certain channel configurations?

    92 * 

    93 * This object is closed when deleted either by a call to operator delete or by the cleanup stack. No special

    94 * cleanup code is necessary to close the object before deletion.

    95 *

    96 * @see CSensrvChannelFinder

    97 * @lib sensrvclient.lib

    98 * @since S60 5.0

    99 */

   100 

   101 NONSHARABLE_CLASS( CSensrvChannel ): public CBase

   102     {

   103     public:

   104     /**

   105     * Two-phased constructor.

   106     *

   107     * The Sensor Server uses aChannelInfo to identify the channel in the server that the returned object

   108     * represents.

   109     *

   110     * @since S60 5.0

   111     * @param  aChannelInfo The information that determines which channel object is created. This must

   112     *         be an object returned by CSensrvChannelFinder::FindChannelsL().

   113     * @return Pointer to created CSensorChannel object

   114     * @leave  KErrNoMemory

   115     * @leave  One of the system-wide error codes

   116     */  

   117     IMPORT_C static CSensrvChannel* NewL

   118             ( const TSensrvChannelInfo& aChannelInfo );

   119 

   120     /**

   121     * Two-phased constructor.      

   122     * 

   123     * The Sensor Server uses aChannelInfo to identify the channel in the server that the returned object

   124     * represents.

   125     * 

   126     * @since S60 5.0

   127     * @param  aChannelInfo The information that determines which channel object is created. This must

   128     *         be an object returned by CSensrvChannelFinder::FindChannelsL().

   129     * @return Pointer to created CSensorChannel object that is placed on the cleanup stack.      

   130     * @leave  KErrNoMemory

   131     * @leave  One of the system-wide error codes

   132     */  

   133     IMPORT_C static CSensrvChannel* NewLC

   134             ( const TSensrvChannelInfo& aChannelInfo );

   135   

   136     public:

   137     /**

   138     * Initializes and opens the channel. After the channel is opened, the client can set and get channel

   139     * properties, add channel conditions and listen for sensor data.

   140     * 

   141     * @since S60 5.0

   142     * @leave  KErrAlreadyExists if channel is already open

   143     * @leave  One of the system-wide error codes

   144     */

   145     virtual void OpenChannelL() = 0;

   146 

   147     /**

   148     * Closes the channel. 

   149     * 

   150     * This object is closed when deleted either by a call to operator delete or by the cleanup stack. No special

   151     * cleanup code is necessary to close the object before deletion.

   152     * 

   153     * @since S60 5.0

   154     * @return KErrNone if channel closing is successful, or one of the system-wide error codes

   155     */  

   156     virtual TInt CloseChannel() = 0;

   157     

   158     /**

   159     * Retrieves a channel information object related to this channel.

   160     *     

   161     * @since S60 5.0

   162     * @return Reference to the channel information object

   163     */  

   164     virtual const TSensrvChannelInfo& GetChannelInfo() const = 0;

   165 

   166     /**

   167     * Starts channel data listening on the channel.

   168     * 

   169     * To use this operation clients must provide an object that inherits from MSensrvDataListener.  

   170     * 

   171     * When new data is available to be read, the client is notified by the

   172     * MSensrvDataListener::DataReceived() callback. On receiving this notificaton the client should

   173     * retrieve the data using the GetData() operation.

   174     * 

   175     * Note that if a client is listening for both data and conditions on the channel then the lower

   176     * desired count and buffering period provided in either start listening operation arguments will be

   177     * used for both listeners. When either listener is stopped neither the desired count nor the

   178     * buffering period shall be changed.

   179     * 

   180     * For the best performance, always use the highest desired count and maximum count as the use case

   181     * allows. This will reduce the overhead caused by a high volume of IPC context switches. However,

   182     * be aware that higher counts need to reserve more memory.

   183     * 

   184     * @since S60 5.0

   185     * @param  aDataListener Data listener for the channel. Must be valid until data listening is stopped. 

   186     * @param  aDesiredCount Desired receiving buffer size defined as a count of the channel data objects.

   187     *         The maximum value is determined by sensor server internal channel buffer size, and minimum

   188     *         value is one. Any value outside these limits is interpreted as maximum possible value.

   189     *         The actual count of channel data objects received may be smaller than aDesiredCount, if a

   190     *         non-zero buffering period has been specified.

   191     *         The actual count of channel data objects received may larger, if aMaximumCount is bigger

   192     *         than aDesiredCount.

   193     *         If the sensor supplies data sporadically, and the clients requires every data object then

   194     *         aDesiredCount should be set to one to ensure that no data objects are missed. 

   195     * @param  aMaximumCount Maximum receiving buffer size defined as a count of the channel data object.

   196     *         The Maximum value is determined by sensor server internal channel buffer size, and minimum

   197     *         value is aDesiredCount. Any value outside these limits is interpreted as maximum possible

   198     *         value.

   199     *         It is recommended that whenever aDesiredCount needs to be low and sensor has relatively high

   200     *         data rate, aMaximumCount is set to significantly higher than aDesiredCount to reduce IPC

   201     *         context switches and data loss.

   202     * @param  aBufferingPeriod Specifies the maximum time in milliseconds that sensor server waits before

   203     *         notifying the client that new data is available. It is possible that no new data is will be

   204     *         available when the client is notified.

   205     *         Zero timeout means that only desired and maximum counts are used in getting data.

   206     *         Using a buffering period results in lot of unnecessary IPC context switches if a sensor

   207     *         channel supplies data sporadically. It is therefore recommended that a buffering period is

   208     *         used only when it is absolutely vital to have data at specific intervals and using a low

   209     *         desired count is otherwise too expensive performance-wise.

   210     * @leave  KErrArgument if aDataListener is NULL, or if a negative argument is supplied

   211     * @leave  KErrNotFound if the channel is not open

   212     * @leave  KErrAlreadyExists if data listening has already started on the channel

   213     * @leave  One of the system-wide error codes

   214     */  

   215     virtual void StartDataListeningL( MSensrvDataListener* aDataListener, 

   216                                       const TInt aDesiredCount, 

   217                                       const TInt aMaximumCount,

   218                                       const TInt aBufferingPeriod ) = 0;

   219 

   220     /**

   221     * Stop channel data listening. 

   222     * 

   223     * @since S60 5.0

   224     * @return KErrNone if stopping successful or one of the system-wide error codes

   225     */  

   226     virtual TInt StopDataListening() = 0;

   227 

   228     /**

   229     * Get data items when the client is notified by the MSensrvDataListener::DataReceived() callback

   230     * that new data is ready to be retrieved. The callback also indicates the number of data items

   231     * contained in aData. 

   232     * 

   233     * Example:

   234     *     

   235     * How to retrieve data using TPckg

   236     * 

   237     * @code

   238 	  * void DataReceived(CSensrvChannel& aChannel, TInt aCount, TInt aDataLost )

   239 		* {

   240     * if(aChannel.GetChannelInfo().iChannelType == KSensrvChannelTypeIdAccelerometerXYZAxisData)

   241 		* 	{

   242 		* 	TSensrvAccelerometerAxisData XYZData;

   243 	  *       TPckg<TSensrvAccelerometerAxisData> XYZPackage( XYZData );

   244 	  *       aChannel.GetData( XYZPackage );

   245 		* 	}

   246 		* }

   247     * @endcode

   248     *  

   249     * @since S60 5.0

   250     * @param  aData Reference to descriptor that contains the data. Typically this is a package buffer

   251     *         defined for data type of this channel. See channel specific data headers for details of

   252     *         the package types and data supported by a channel.

   253     * @return KErrNotFound if data buffer is empty, KErrOverflow if aData is wrong size for data

   254     *         item, or one of the system-wide error codes

   255     */  

   256     virtual TInt GetData( TDes8& aData ) = 0;

   257  

   258     /**

   259     * Sets a property value for this channel. To manage any contention between multiple clients wishing

   260     * to change the configuration of the sensor a concept of Client Priorities is employed. See class

   261     * description for further information.

   262     * 

   263     * The sensor plugin may police setting of properties by verifying that the client making the request

   264     * has the necessary capabilities. If the client does not then it will return with KErrAccessDenied.

   265     * @since S60 5.0

   266     * @param  aProperty Identifies the property that is to be set and its new value. Only the Property Id,

   267     *         Item Index and Property Value should be filled in. All other fields in TSensrvProperty are

   268     *         ignored.

   269     * @return KErrNotFound if channel is not open or if the property does not exist, KErrAccessDenied

   270     *         if there are other clients for this channel or impacted channel on the same sensor with a

   271     *         higher Client Priority, KErrAccessDenied if the client does not have the required

   272     *         capabilities or one of the system-wide error codes

   273     */  

   274     virtual TInt SetProperty(  const TSensrvProperty& aProperty ) = 0;

   275       

   276     /**

   277     * Gets a channel property value for this channel.

   278     * 

   279     * @since S60 5.0

   280     * @param  aPropertyId Id of the property that is to be retrieved

   281     * @param  aItemIndex The Item Index of the property to be retrieved. This is mapped to a specific item

   282     *         in channel data structure. See channel specific data headers.

   283     * @param  aProperty Reference for a property object where property data is to be copied

   284     * @leave  KErrNotFound if channel is not open

   285     * @leave  KErrNotFound if property does not exist

   286     * @leave  KErrArgument if a negative argument is supplied

   287     * @leave  One of the system-wide error codes

   288     * */

   289     virtual void GetPropertyL( const TSensrvPropertyId aPropertyId, 

   290                                const TInt aItemIndex,

   291                                TSensrvProperty& aProperty ) = 0;

   292                                

   293     /**

   294     * Get a channel property value for this channel

   295     * 

   296     * @since S60 5.0

   297     * @param  aPropertyId Id of the property that is to be retrieved

   298     * @param  aItemIndex Item Index of the property to be retrieved. This is mapped to a specific item

   299     *         in channel data structure. See channel specific data headers.

   300     * @param  aArrayIndex Array index of the property to be retrieved when the property is part of a

   301     *         property array.

   302     * @param  aProperty Reference for a property object where property data is to be copied

   303     * @leave  KErrNotFound if channel is not open

   304     * @leave  KErrNotFound if property does not exist

   305     * @leave  KErrArgument if a negative argument is supplied

   306     * @leave  One of the system-wide error codes

   307     */  

   308     virtual void GetPropertyL( const TSensrvPropertyId aPropertyId, 

   309                                const TInt aItemIndex,

   310                                const TInt aArrayIndex,

   311                                TSensrvProperty& aProperty ) = 0;

   312 

   313     /**

   314     * Get all properties for this channel

   315     * 

   316     * @since S60 5.0

   317     * @param  aChannelPropertyList Reference for a property list where all property data is to be

   318     *         copied. Any existing data in the list will be lost.

   319     * @leave  KErrNotFound if channel is not open

   320     * @leave  One of the system-wide error codes

   321     */  

   322     virtual void GetAllPropertiesL

   323             ( RSensrvPropertyList& aChannelPropertyList ) = 0;

   324             

   325     /**

   326     * Get all channel properties having the supplied Property Id. This is used when the property

   327     * is an array property.    

   328     * 

   329     * @since S60 5.0

   330     * @param  aPropertyId Id of the property to be retrieved

   331     * @param  aChannelPropertyList Reference for a property list where all property data is to be

   332     *         copied. Any existing data in the list will be lost.

   333     * @leave  KErrNotFound if channel is not open

   334     * @leave  KErrNotFound if property does not exist

   335     * @leave  One of the system-wide error codes

   336     */  

   337     virtual void GetAllPropertiesL

   338             ( const TSensrvPropertyId aPropertyId, 

   339               RSensrvPropertyList& aChannelPropertyList ) = 0;

   340 

   341     /**

   342     * Start property listening on this channel.

   343     * 

   344     * To use this operation clients must provide an object that inherits from MSensrvPropertyListener.

   345     *     

   346     * The client can use the property listener to get notifications when properties are changed and

   347     * to get a notification when the client is able/unable to set properties because of higher priority

   348     * clients have opened/closed the same sensor channel.

   349     * 

   350     * If the client itself changes a property value, no notification is received for that property by

   351     * the client. If another client changes a property on this channel or another channel that impacts

   352     * this channel a notification will be received by the client.

   353     * 

   354     * Some sensors support a number of channels with each channel having some common properties.

   355     * Therefore changing a common property may result in notifications on a number of other channels

   356     * supported by the sensor.

   357     * 

   358     * @since S60 5.0

   359     * @param  aChannelPropertyListener Pointer to channel property listener callback instance. The

   360     *         channel property listener must be valid until the CSensrvChannel object is destroyed or

   361     *         listening has been stopped. Listening can be stopped using a NULL parameter.

   362     * @leave  KErrAlreadyExists if channel property listener has already been set

   363     * @leave  KErrNotFound if channel is not open

   364     * @leave  One of the system-wide error codes

   365     */  

   366     virtual void SetPropertyListenerL

   367                   ( MSensrvPropertyListener* aChannelPropertyListener ) = 0;

   368  

   369     /**

   370     * Add a channel ConditionSet to the channel.

   371     * 

   372     * Channel ConditionSet's are used for channel condition listening and at least 1 ConditionSet must

   373     * be added before listening can begin.

   374     * 

   375     * When the conditions defined by the ConditionSet is met the client will be notified by the 

   376     * MSensrvChannelConditionListener::ConditionMet() callback and listening for this ConditionSet will

   377     * cease. If a client wishes to listen for this ConditionSet again it must be added again.

   378     * 

   379     * The client continues to own the ConditionSet object after a call to this function and must ensure

   380     * that it is destroyed when no longer required.

   381     * 

   382     * The client must ensure that the ConditionSet object is valid until it is no longer needed by the

   383     * Sensor Server. This is either after the condition set has been removed by the client using

   384     * RemoveConditionL() or the client has been notified that the condition has been met.

   385     * 

   386     * @since S60 5.0

   387     * @param  aChannelConditionSet The channel condition set to be added.

   388     * @leave  KErrNotFound if channel is not open

   389     * @leave  KErrNotSupported if a channel does not support conditions.

   390     * @leave  One of the system-wide error codes

   391     * @see CSensrvChannel::StartConditionListeningL()    

   392     */  

   393     virtual void AddConditionL( CSensrvChannelConditionSet& aChannelConditionSet ) = 0;

   394 

   395     /**

   396     * Remove a channel ConditionSet from the channel.

   397     * 

   398     * The same reference used to to add the Condition Set in AddConditionL(), must also be used to

   399     * remove it. 

   400     * 

   401     * The removed channel ConditionSet is no longer used for channel condition listening. 

   402     * 

   403     * The client continues to own the ConditionSet object after a call to this function and must ensure

   404     * that it is destroyed when no longer required.

   405     * 

   406     * @since S60 5.0

   407     * @param  aChannelConditionSet The channel condition set to be removed.

   408     * @leave  KErrNotFound if channel is not open

   409     * @leave  One of the system-wide error codes

   410     */  

   411     virtual void RemoveConditionL

   412                     ( CSensrvChannelConditionSet& aChannelConditionSet ) = 0;

   413 

   414     /**

   415     * Start channel condition listening.

   416     * 

   417     * To use this operation clients must provide an object that inherits from MSensrvChannelConditionListener.

   418     * 

   419     * If the conditions of an added ConditionSet is met the MSensrvChannelConditionListener::ConditionMet()

   420     * callback function will be called and listening for this ConditionSet will cease. If a client wishes

   421     * to listen for the same ConditionSet again it must be added again.

   422     * 

   423     * Note that if a client is listening for both data and conditions on the channel then the lower

   424     * desired count and buffering period provided in either start listening operation arguments will be

   425     * used for both listeners. When either listener is stopped neither the desired count nor the

   426     * buffering period shall be changed.

   427     * 

   428     * @since S60 5.0

   429     * @param  aChannelConditionListener Condition listener for the channel. Must be valid until data

   430     *         listening is stopped.

   431     * @param  aObjectCount Listening buffer size defined as a count of the channel data objects. When the

   432     *         desired object count is reached each ConditionSet is evaluated in turn. The maximum value is

   433     *         determined by sensor server internal channel buffer size, and minimum value is one. Any value

   434     *         outside these limits is interpreted as maximum possible value.

   435     * @param  aBufferingPeriod Specifies the maximum time in milliseconds that sensor server waits before

   436     *         evaluating new data.

   437     *         Zero timeout means that the sensor server only evaluates new data when the object count has been

   438     *         reached.

   439     * @leave  KErrArgument if aChannelConditionListener is NULL, or if a negative argument is supplied

   440     * @leave  KErrNotFound if the channel is not open

   441     * @leave  KErrAlreadyExists if condition listening has already started on the channel

   442     * @leave  One of the system-wide error codes  

   443     */  

   444     virtual void StartConditionListeningL

   445                     ( MSensrvChannelConditionListener* aChannelConditionListener,

   446                       const TInt aObjectCount,

   447                       const TInt aBufferingPeriod ) = 0;

   448 

   449     /**

   450     * Stop channel condition listening.

   451     * 

   452     * All remaining unmet ConditionSet's are removed and channel condition listening is stopped.

   453     * 

   454     * If the same ConditionSet's need to be used when condition listening has been restarted then they must be

   455     * re-added.

   456     * 

   457     * @since S60 5.0

   458     * @return KErrNone if condition listening is successfully stopped or one of the system-wide error codes

   459     */  

   460     virtual TInt StopConditionListening() = 0;

   461     

   462     public:

   463     /**

   464     * Default constructor. 

   465     */

   466     CSensrvChannel();

   467     };

   468 

   469 

   470 #endif //SENSRVCHANNEL_H

   471 

   472 // End of File