/*

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

 * All rights reserved.

 * This component and the accompanying materials are made available

 * under the terms of "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:  Sensor channel class definition

 *

 */

 #ifndef SENSRVCHANNEL_H

 #define SENSRVCHANNEL_H

 #include <e32base.h>

 #include <sensrvtypes.h>

 #include <sensrvchannelconditionset.h>

 #include <sensrvchannelinfo.h>

 class MSensrvPropertyListener;

 class MSensrvDataListener;

 class MSensrvChannelConditionListener;

 class CSensrvChannelCondition;

 class CSensrvChannelListener;

 /**

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

 * receive data and receive notifications from a sensor channel.

 * 

 * When instantiating CSensrvChannel an instance of TSensrvChannelInfo returned by

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

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

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

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

 * 

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

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

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

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

 * a session connection to it.

 * 

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

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

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

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

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

 * 

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

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

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

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

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

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

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

 * changes made by other clients of this same channel.

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

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

 * and SetConditionListeningL(). 

 * 

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

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

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

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

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

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

 * 

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

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

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

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

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

 * 

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

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

 * be notified when they are able to set properties.

 * 

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

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

 * 

 * For example:

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

 * Should features be disabled under certain channel configurations?

 * 

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

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

 *

 * @see CSensrvChannelFinder

 * @lib sensrvclient.lib

 * @since S60 5.0

 */

 NONSHARABLE_CLASS( CSensrvChannel ): public CBase

     {

     public:

     /**

     * Two-phased constructor.

     *

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

     * represents.

     *

     * @since S60 5.0

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

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

     * @return Pointer to created CSensorChannel object

     * @leave  KErrNoMemory

     * @leave  One of the system-wide error codes

     */  

     IMPORT_C static CSensrvChannel* NewL

             ( const TSensrvChannelInfo& aChannelInfo );

     /**

     * Two-phased constructor.      

     * 

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

     * represents.

     * 

     * @since S60 5.0

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

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

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

     * @leave  KErrNoMemory

     * @leave  One of the system-wide error codes

     */  

     IMPORT_C static CSensrvChannel* NewLC

             ( const TSensrvChannelInfo& aChannelInfo );

     public:

     /**

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

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

     * 

     * @since S60 5.0

     * @leave  KErrAlreadyExists if channel is already open

     * @leave  One of the system-wide error codes

     */

     virtual void OpenChannelL() = 0;

     /**

     * Closes the channel. 

     * 

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

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

     * 

     * @since S60 5.0

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

     */  

     virtual TInt CloseChannel() = 0;

     /**

     * Retrieves a channel information object related to this channel.

     *     

     * @since S60 5.0

     * @return Reference to the channel information object

     */  

     virtual const TSensrvChannelInfo& GetChannelInfo() const = 0;

     /**

     * Starts channel data listening on the channel.

     * 

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

     * 

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

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

     * retrieve the data using the GetData() operation.

     * 

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

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

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

     * buffering period shall be changed.

     * 

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

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

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

     * 

     * @since S60 5.0

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

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

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

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

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

     *         non-zero buffering period has been specified.

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

     *         than aDesiredCount.

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

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

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

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

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

     *         value.

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

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

     *         context switches and data loss.

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

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

     *         available when the client is notified.

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

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

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

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

     *         desired count is otherwise too expensive performance-wise.

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

     * @leave  KErrNotFound if the channel is not open

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

     * @leave  One of the system-wide error codes

     */  

     virtual void StartDataListeningL( MSensrvDataListener* aDataListener, 

                                       const TInt aDesiredCount, 

                                       const TInt aMaximumCount,

                                       const TInt aBufferingPeriod ) = 0;

     /**

     * Stop channel data listening. 

     * 

     * @since S60 5.0

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

     */  

     virtual TInt StopDataListening() = 0;

     /**

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

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

     * contained in aData. 

     * 

     * Example:

     *     

     * How to retrieve data using TPckg

     * 

     * @code

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

 		* {

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

 		* 	{

 		* 	TSensrvAccelerometerAxisData XYZData;

 	  *       TPckg<TSensrvAccelerometerAxisData> XYZPackage( XYZData );

 	  *       aChannel.GetData( XYZPackage );

 		* 	}

 		* }

     * @endcode

     *  

     * @since S60 5.0

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

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

     *         the package types and data supported by a channel.

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

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

     */  

     virtual TInt GetData( TDes8& aData ) = 0;

     /**

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

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

     * description for further information.

     * 

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

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

     * @since S60 5.0

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

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

     *         ignored.

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

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

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

     *         capabilities or one of the system-wide error codes

     */  

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

     /**

     * Gets a channel property value for this channel.

     * 

     * @since S60 5.0

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

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

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

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

     * @leave  KErrNotFound if channel is not open

     * @leave  KErrNotFound if property does not exist

     * @leave  KErrArgument if a negative argument is supplied

     * @leave  One of the system-wide error codes

     * */

     virtual void GetPropertyL( const TSensrvPropertyId aPropertyId, 

                                const TInt aItemIndex,

                                TSensrvProperty& aProperty ) = 0;

     /**

     * Get a channel property value for this channel

     * 

     * @since S60 5.0

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

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

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

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

     *         property array.

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

     * @leave  KErrNotFound if channel is not open

     * @leave  KErrNotFound if property does not exist

     * @leave  KErrArgument if a negative argument is supplied

     * @leave  One of the system-wide error codes

     */  

     virtual void GetPropertyL( const TSensrvPropertyId aPropertyId, 

                                const TInt aItemIndex,

                                const TInt aArrayIndex,

                                TSensrvProperty& aProperty ) = 0;

     /**

     * Get all properties for this channel

     * 

     * @since S60 5.0

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

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

     * @leave  KErrNotFound if channel is not open

     * @leave  One of the system-wide error codes

     */  

     virtual void GetAllPropertiesL

             ( RSensrvPropertyList& aChannelPropertyList ) = 0;

     /**

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

     * is an array property.    

     * 

     * @since S60 5.0

     * @param  aPropertyId Id of the property to be retrieved

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

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

     * @leave  KErrNotFound if channel is not open

     * @leave  KErrNotFound if property does not exist

     * @leave  One of the system-wide error codes

     */  

     virtual void GetAllPropertiesL

             ( const TSensrvPropertyId aPropertyId, 

               RSensrvPropertyList& aChannelPropertyList ) = 0;

     /**

     * Start property listening on this channel.

     * 

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

     *     

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

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

     * clients have opened/closed the same sensor channel.

     * 

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

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

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

     * 

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

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

     * supported by the sensor.

     * 

     * @since S60 5.0

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

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

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

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

     * @leave  KErrNotFound if channel is not open

     * @leave  One of the system-wide error codes

     */  

     virtual void SetPropertyListenerL

                   ( MSensrvPropertyListener* aChannelPropertyListener ) = 0;

     /**

     * Add a channel ConditionSet to the channel.

     * 

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

     * be added before listening can begin.

     * 

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

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

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

     * 

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

     * that it is destroyed when no longer required.

     * 

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

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

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

     * 

     * @since S60 5.0

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

     * @leave  KErrNotFound if channel is not open

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

     * @leave  One of the system-wide error codes

     * @see CSensrvChannel::StartConditionListeningL()    

     */  

     virtual void AddConditionL( CSensrvChannelConditionSet& aChannelConditionSet ) = 0;

     /**

     * Remove a channel ConditionSet from the channel.

     * 

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

     * remove it. 

     * 

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

     * 

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

     * that it is destroyed when no longer required.

     * 

     * @since S60 5.0

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

     * @leave  KErrNotFound if channel is not open

     * @leave  One of the system-wide error codes

     */  

     virtual void RemoveConditionL

                     ( CSensrvChannelConditionSet& aChannelConditionSet ) = 0;

     /**

     * Start channel condition listening.

     * 

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

     * 

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

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

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

     * 

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

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

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

     * buffering period shall be changed.

     * 

     * @since S60 5.0

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

     *         listening is stopped.

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

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

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

     *         outside these limits is interpreted as maximum possible value.

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

     *         evaluating new data.

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

     *         reached.

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

     * @leave  KErrNotFound if the channel is not open

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

     * @leave  One of the system-wide error codes  

     */  

     virtual void StartConditionListeningL

                     ( MSensrvChannelConditionListener* aChannelConditionListener,

                       const TInt aObjectCount,

                       const TInt aBufferingPeriod ) = 0;

     /**

     * Stop channel condition listening.

     * 

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

     * 

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

     * re-added.

     * 

     * @since S60 5.0

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

     */  

     virtual TInt StopConditionListening() = 0;

     public:

     /**

     * Default constructor. 

     */

     CSensrvChannel();

     };

 #endif //SENSRVCHANNEL_H

 // End of File