Class TDesBuf

class TDesBuf : public TStreamBuf;

Description

A stream buffer that uses a descriptor for its implementation.

A stream of this type is used by RDesWriteStream and RDesReadStream objects. It also has intermediate buffering capabilities.

This is a seekable stream buffer.

When used in write mode, the length of the descriptor is only updated when the stream buffer's SynchL() function is called, i.e. as a result of a call to RWriteStream::CommitL().

Derivation

• MStreamBuf - A stream buffer that provides a generic I/O interface for streamed data

• TStreamBuf - Adds buffering capabilities to a stream buffer

• TDesBuf - A stream buffer that uses a descriptor for its implementation

Members

Defined in TDesBuf:
DoSeekL(), DoSynchL(), OverflowL(), Set(), TDesBuf(), UnderflowL()

Inherited from MStreamBuf:
Close(), DoRelease(), ERead, EWrite, PushL(), Read(), ReadL(), Release(), SeekL(), SizeL(), Synch(), SynchL(), TMark, TRead, TWrite, TellL(), Write(), WriteL()

Inherited from TStreamBuf:
Avail(), DoReadL(), DoWriteL(), End(), Ptr(), SetBuf(), SetEnd(), SetPtr(), TArea

See also:

• RDesWriteStream
• RDesReadStream
• RWriteStream::CommitL()
• MStreamBuf::SynchL()

IMPORT_C TDesBuf();

Description

Constructs an empty object.

Call Set() before using the object.

IMPORT_C void Set(TDes8 &aDes, TInt aMode=ERead|EWrite);

Description

Sets up the stream to use the specified descriptor.

Parameters

TDes8 &aDes The descriptor that hosts the stream and that also acts as the intermediate buffer. TInt aMode The mode in which the buffer is to be used. It can be used in either or both read and write modes, represented by ERead and EWrite.

See also:

• TDes8
• MStreamBuf::TRead
• MStreamBuf::TWrite

protected: virtual IMPORT_C TInt UnderflowL(TInt aMaxLength);

Description

Re-fills the intermediate buffer and resets the start and end points of the read area.

The implementation of this function depends on the way the stream itself is implemented. For example, the in-memory streams have simple implementations.

Parameters

TInt aMaxLength The maximum amount of data required for the intermediate buffer.

Return value

TInt The amount of data available in the intermediate buffer.

protected: virtual IMPORT_C void OverflowL();

Description

Empties the intermediate buffer and resets the start and end points of the write area.

The implementation of this function depends on the way the stream itself is implemented. For example, the in-memory streams have simple implementations.

protected: virtual IMPORT_C void DoSynchL();

Description

Synchronises the stream buffer with the stream, leaving if any error occurs.

In effect, this ensures that buffered data is delivered to the stream.

It is called by SynchL().

This implementation is empty, but classes derived from MStreamBuf can provide their own implementation, if necessary.

See also:

• MStreamBuf::SynchL()

protected: virtual IMPORT_C TStreamPos DoSeekL(TMark aMark, TStreamLocation aLocation, TInt anOffset);

Description

Parameters

TMark aMark TStreamLocation aLocation TInt anOffset

Return value

TStreamPos