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TItem Class Reference

class TItem

HID item class A HID report descriptor is comprised of a sequence of "items" that provide information about the device. Items consist of a header and zero or more bytes of data. The header contains the item type (main/global/local), an item "tag" (subtype) and the item size. Items can be "short" (containing a maximum of 4 bytes of data) or "long" (a maximum of 255 bytes of data).

A TItem represents a single HID report descriptor item. It is constructed from an eight bit non-modifiable (Symbian-) descriptor, which is assumed to contain report (HID-) descriptor data.

generichid.lib

Since: S60 v5.0

Public Member Functions
	TItem (const TDesC8 &)
TUint32	Data ()
TInt	DataSize ()
TBool	IsGlobal ()
TBool	IsLocal ()
TBool	IsLong ()
TBool	IsMain ()
TInt	ItemSize ()
TInt32	SignedData ()
TInt	Tag ()
TItemType	Type ()
TUint8	operator[] ( TInt )

Public Member Enumerations
enum	TItemType { EMain = 0, EGlobal = 1, ELocal = 2, EReserved = 3 }

Private Attributes
TInt	iDataOffset
TPtrC8	iRawData
TInt	iSize
TInt	iTag
TItemType	iType

Constructor & Destructor Documentation

TItem(const TDesC8 &)

TItem

(

const TDesC8 &

aRawData

)

The constructor takes a an eight bit non-modifiable (Symbian-) descriptor containing report (HID-) descriptor data. The item tag, type, data size and offset are calculated here.

Since: S60 v5.0

Parameters

const TDesC8 & aRawData

The raw item data, represented as a Symbian descriptor. The item data is assumed to be at the beginning of the descriptor. The size of the TDesC8 may be greater than the size of the item, as the item size will be calculated from the raw HID descriptor data. Of course, the TDesC8 should be at least as long as the raw item data.

Member Functions Documentation

Data()

TUint32

Data

(

)

const

Data() returns the data associated with the item, represented as a 32-bit unsigned integer. This is only meaningful if the data length is less than 4 bytes.

Since: S60 v5.0

DataSize()

TInt

DataSize

(

)

const

DataSize() returns the size of the item data in bytes. This is the total item size minus the size of any header information. (A short item header is a single byte, a long item header is three bytes long.)

Since: S60 v5.0

IsGlobal()

TBool

IsGlobal

(

)

const

Check if item is global

Since: S60 v5.0

IsLocal()

TBool

IsLocal

(

)

const

Check if item is local

Since: S60 v5.0

IsLong()

TBool

IsLong

(

)

const

Check if item is global

Since: S60 v5.0

IsMain()

TBool

IsMain

(

)

const

Check if item is main

Since: S60 v5.0

ItemSize()

TInt

ItemSize

(

)

const

ItemSize() returns the total size of this item, including the header data.

Since: S60 v5.0

SignedData()

TInt32

SignedData

(

)

const

SignedData() returns the data associated with the item, represented as a 32-bit signed integer. This is only meaningful if the data length is less than 4 bytes.

Since: S60 v5.0

Tag()

TInt

Tag

(

)

const

Tag() returns the tag (subtype) value for this item.

Since: S60 v5.0

Type()

TItemType

Type

(

)

const

Type() returns the item type (e.g. "global").

Since: S60 v5.0

operator[](TInt)

TUint8

operator[]

(

TInt

aIndex

)

const

Returns the byte at the given offset within the item data block.

Since: S60 v5.0

Parameters

TInt aIndex

The index within the data block for the current tag.

Member Enumerations Documentation

Enum TItemType

The possible item types: main, global or local. Item type is a two-bit field -- the 11b value is reserved for "long items", which are only used for vendor-specific commands.