Class CMMFPtrBuffer

class CMMFPtrBuffer : public CMMFDataBuffer;

Description

This class is a wrapper class intended to provide support for shared I/O buffers under EKA2 This class, unlike other data buffers does not own memory - rather it contains a pointer to already allocated memory The purpose of this class is that components such as codecs can use CMMFDataBuffers transparently without having to be concerned with whether the buffer is a standard buffer or memory residing in shared I/O

Users of this class need to be very careful when using buffers of this type. It cannot be assumed that a buffer of this type can be written/read by any process other than the current one - example - handing CMMFPtrBuffer to the file server may not work since the file server's process may not have access to write data buffer.

Derivation

• CBase - Base class for all classes to be instantiated on the heap

• CMMFBuffer - Abstract representation of a buffer to contain multimedia data

• CMMFDataBuffer - This class is an abstract class for databuffers that can be presented in the form of a descriptor

• CMMFPtrBuffer - This class is a wrapper class intended to provide support for shared I/O buffers under EKA2 This class, unlike other data buffers does not own memory - rather it contains a pointer to already allocated memory The purpose of this class is that components such as codecs can use CMMFDataBuffers transparently without having to be concerned with whether the buffer is a standard buffer or memory residing in shared I/O

Members

Defined in CMMFPtrBuffer:
BufferSize(), Data(), Data(), NewL(), NewL(), SetPosition(), SetPtr(), SetRequestSizeL(), SetStatus(), ~CMMFPtrBuffer()

Inherited from CBase:
Delete(), Extension_(), operator new()

Inherited from CMMFBuffer:
FrameNumber(), IsFileServerSafe(), IsSupportedDataBuffer(), LastBuffer(), NextFrame(), Position(), RequestSize(), SetFrameNumber(), SetLastBuffer(), SetTimeToPlay(), Status(), TimeToPlay(), Type(), iFrameNumber, iLastBuffer, iPosition, iRequestSize, iStatus, iTimeToPlay, iType

static IMPORT_C CMMFPtrBuffer *NewL();

Description

Function to instantiate a CMMFPtrBuffer. This NewL creates an unititalised CMMFPtrBuffer.

Return value

CMMFPtrBuffer * A pointer to a new CMMFPtrBuffer.

static IMPORT_C CMMFPtrBuffer *NewL(const TPtr8 &aPtr);

Description

Function to instantiate a CMMFPtrBuffer. This NewL creates a CMMFPtrBuffer which owns a TPtr8.

Parameters

const TPtr8 &aPtr A reference to a TPtr containing the CMMFPtrBuffer data.

Return value

CMMFPtrBuffer * A pointer to a new CMMFPtrBuffer.

IMPORT_C ~CMMFPtrBuffer();

Description

Destructor.

Destructor does no deletion, as this buffer class does not own the memory.

IMPORT_C void SetPtr(const TPtr8 &aPtr);

Description

Takes a TPtr8 to pre-allocated memory.

Parameters

const TPtr8 &aPtr The pointer refernce.

virtual TDes8 &Data();

Description

Returns a descriptor to the data contained in the CMMFPtrBuffer.

Return value

TDes8 & A reference to a TPtr containing the CMMFPtrBuffer data.

virtual const TDesC8 &Data() const;

Description

Returns a descriptor to the data contained in the CMMFPtrBuffer.

Return value

const TDesC8 & A const reference to a TPtr containing the CMMFPtrBuffer data.

virtual void SetStatus(TBufferStatus aStatus);

Description

Overriden method to set the status. Resets the data size to 0 when the buffer becomes available.

Parameters

TBufferStatus aStatus The buffer status. See enum TBufferStatus.

virtual void SetRequestSizeL(TInt aSize);

Description

Sets the request size.

This method is used in cases where a component (eg. a data source) may not be able or be desirable to write to the entire max length of the buffer (eg. variable bit rate codecs). In this case, the SetRequestSizeL() can be set which can be read by the RequestSize() function in the component so that it knows to only write data upto the requested size and not fill the buffer up to its maximum length.

Parameters

TInt aSize The request size.

virtual TUint BufferSize() const;

Description

Returns the actual data size (ie. not the max length) of the data contained in the CMMFPtrBuffer.

Return value

TUint The size in bytes of the data contained in the CMMFPtrBuffer.

virtual void SetPosition(TUint aPosition);

Description

Sets the position.

This function is used by components (eg. codecs) which read data from a buffer and wish to store a read position marker for further reads.

Note: The position cannot exceed the size of the actual data not the maximum length.

Parameters

TUint aPosition The position.