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 MStreamBuf::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(TMark,TStreamLocation,TInt)
• DoSynchL()Synchronises the stream buffer with the stream, leaving if any error occurs.
• OverflowL()Empties the intermediate buffer and resets the start and end points of the write...
• Set(TDes8 &,TInt)Sets up the stream to use the specified descriptor.
• TDesBuf()Constructs an empty object.
• UnderflowL(TInt)Re-fills the intermediate buffer and resets the start and end points of the read...

Inherited from MStreamBuf:

• Close()Closes the stream buffer.
• ERead
• EWrite
• PushL()Puts a cleanup item for this object onto the cleanup stack.
• Read(TDes8 &,TInt,TRequestStatus &)Reads data, asynchronously, from the stream buffer into the specified descriptor...
• Read(TDes8 &,TRequestStatus &)Reads data, asynchronously, from the stream buffer into the specified descriptor...
• ReadL(MStreamInput &)Reads data from the stream buffer into the specified data sink.
• ReadL(MStreamInput &,TInt)Reads data from the stream buffer into the specified data sink.
• ReadL(MStreamInput &,TStreamTransfer)Reads data from the stream buffer into the specified data sink.
• ReadL(TAny *,TInt)Reads data from the stream buffer into the specified memory location.
• ReadL(TDes8 &,TInt,TRequestStatus &)Reads data, asynchronously, from the stream buffer into the specified descriptor...
• ReadL(TDes8 &,TRequestStatus &)Reads data, asynchronously, from the stream buffer into the specified descriptor...
• Release()Frees resources before abandoning the stream buffer.
• SeekL(TMark,TStreamLocation,TInt)Moves the position of the read mark or the write mark in the stream.
• SeekL(TMark,TStreamPos)Moves the position of the read or write mark in the stream.
• SeekL(TRead,TInt)Moves the position of the read mark in the stream by the specified offset.
• SeekL(TRead,TStreamLocation,TInt)Moves the position of the read mark in the stream.
• SeekL(TWrite,TInt)Moves the position of the write mark in the stream by the specified offset.
• SeekL(TWrite,TStreamLocation,TInt)Moves the position of the write mark in the stream.
• SizeL()constGets the size of the stream.
• Synch()Synchronises the stream buffer with the stream, returning any error.
• SynchL()Synchronises the stream buffer with the stream, leaving if any error occurs.
• TMarkUsed to identify the type of mark in a stream.
• TReadIndicates that an operation applies to the read mark in a stream or to the read ...
• TWriteIndicates that an operation applies to the write mark in a stream or to the writ...
• TellL(TRead)constGets the position of the read mark within the stream.
• TellL(TWrite)constGets the position of the write mark within the stream.
• Write(const TDesC8 &,TInt,TRequestStatus &)
• Write(const TDesC8 &,TRequestStatus &)Writes data, asynchronously, from the specified descriptor into the stream buffe...
• WriteL(MStreamOutput &)Writes data into the stream buffer from the specified data source.
• WriteL(MStreamOutput &,TInt)Writes data into the stream buffer from the specified data source.
• WriteL(MStreamOutput &,TStreamTransfer)Writes data into the stream buffer from the specified data source.
• WriteL(const TAny *,TInt)Writes data from the specified memory location into the stream buffer.
• WriteL(const TDesC8 &,TInt,TRequestStatus &)Writes data, asynchronously, from the specified descriptor into the stream buffe...
• WriteL(const TDesC8 &,TRequestStatus &)Writes data, asynchronously, from the specified descriptor into the stream buffe...

Inherited from TStreamBuf:

• Avail(TArea)constGets the number of bytes available in the read or write area within the intermed...
• Avail(TRead)constGets the number of bytes available in the read area within the intermediate buff...
• Avail(TWrite)constGets the number of bytes available in the write area within the intermediate buf...
• DoReadL(MStreamInput &,TStreamTransfer)Reads data from the intermediate buffer and, if necessary, any remaining data fr...
• DoReadL(TAny *,TInt)Reads data from the intermediate buffer into the specified memory location.
• DoWriteL(MStreamOutput &,TStreamTransfer)
• DoWriteL(const TAny *,TInt)Writes data from the specified memory location into the intermediate buffer.
• End(TArea)constGets the current end point of the read or write area within the intermediate buf...
• End(TRead)constGets the current end point of the read area within the intermediate buffer.
• End(TWrite)constGets the current end point of the write area within the intermediate buffer.
• Ptr(TArea)constGets the current start point of the read or write area within the intermediate b...
• Ptr(TRead)constGets the current start point of the read area within the intermediate buffer.
• Ptr(TWrite)constGets the current start point of the write area within the intermediate buffer.
• SetBuf(TArea,TUint8 *,TUint8 *)Sets the start and end points of the read and/or the write area within the inter...
• SetBuf(TRead,TUint8 *,TUint8 *)Sets the start and end points of the read area within the intermediate buffer.
• SetBuf(TWrite,TUint8 *,TUint8 *)Sets the start and end points of the write area within the intermediate buffer.
• SetEnd(TArea,TUint8 *)
• SetEnd(TRead,TUint8 *)
• SetEnd(TWrite,TUint8 *)
• SetPtr(TArea,TUint8 *)Sets the start point of the read and/or the write area within the intermediate b...
• SetPtr(TRead,TUint8 *)Sets the start point of the write area within the intermediate buffer.
• SetPtr(TWrite,TUint8 *)Sets the start point of the write area within the intermediate buffer.
• TAreaUsed to identify the type of area within an intermediate buffer.

See also:

• RWriteStream::CommitL()Ensures that any buffered data is written to the stream. Once committed, it is n...
• MStreamBuf::SynchL()Synchronises the stream buffer with the stream, leaving if any error occurs.

IMPORT_C TDesBuf();

Description

Constructs an empty object.

Call TDesBuf::Set(TDes8 &,TInt) 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:

• MStreamBuf::TReadIndicates that an operation applies to the read mark in a stream or to the read ...
• MStreamBuf::TWriteIndicates that an operation applies to the write mark in a stream or to the writ...

protected: IMPORT_C virtual 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: IMPORT_C virtual 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: IMPORT_C virtual 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 MStreamBuf::SynchL().

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

See also:

• MStreamBuf::SynchL()Synchronises the stream buffer with the stream, leaving if any error occurs.

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

Description

Parameters

MStreamBuf::TMark aMark TStreamLocation aLocation TInt anOffset

Return value

TStreamPos