/*

* 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