Class RShareBuf

class RShareBuf : public MStreamBuf;

Description

A shared stream buffer.

This class is part of the framework used by CFileStore that allows multiple stream buffers to concurrently access the single hosting file buffer, an RFileBuf object.

Each shared stream buffer maintains its own read and write positions.

Read and write operations to RShareBuf are directed through separate TStreamMark objects, one for read and one for write. The TStreamMark objects re-direct read/write operations through a TStreamExchange object to the RFileBuf object, which handles the actual file read and write operations.

This stream buffer can also be accessed through RShareReadStream and RShareWriteStream objects.

Derivation

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

• RShareBuf - A shared stream buffer.

Members

Defined in RShareBuf:

• DoReadL(MStreamInput &,TStreamTransfer)Reads data from the stream into the specified data sink.
• DoReadL(TAny *,TInt)
• DoReadL(TDes8 &,TInt,TRequestStatus &)Reads data from the stream buffer into the specified descriptor.
• DoRelease()Frees resources before abandoning the stream buffer.
• DoSeekL(TMark,TStreamLocation,TInt)
• DoWriteL(MStreamOutput &,TStreamTransfer)
• DoWriteL(const TAny *,TInt)
• DoWriteL(const TDesC8 &,TInt,TRequestStatus &)Writes data from the specified descriptor into this stream buffer.
• Open(TStreamExchange &,TInt)Prepares the shared stream buffer for streaming.
• Open(TStreamExchange &,TStreamPos,TInt)Prepares the shared stream buffer for streaming.
• RShareBuf()Constructs an empty shared stream buffer object.

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...

See also:

• RFileBufA stream buffer hosted by a file. ...
• RShareReadStream...
• RShareWriteStream...

IMPORT_C RShareBuf();

Description

Constructs an empty shared stream buffer object.

Call one of the RShareBuf::Open(TStreamExchange &,TStreamPos,TInt) functions to prepare the stream.

IMPORT_C void Open(TStreamExchange &aHost, TStreamPos aPos, TInt aMode=ERead|EWrite);

Description

Prepares the shared stream buffer for streaming.

The function sets the read mark and/or the write mark to the specified position within the host stream.

Parameters

TStreamExchange &aHost The object that manages shared streaming. TStreamPos aPos The position within the host stream. TInt aMode The streaming mode. This can be read and/or write, as indicated by the ERead and EWrite bits.

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...

inline void Open(TStreamExchange &aHost, TInt aMode=ERead|EWrite);

Description

Prepares the shared stream buffer for streaming.

The function sets the read mark and/or the write mark to the beginning of the host stream.

Parameters

TStreamExchange &aHost The object that manages shared streaming. TInt aMode The streaming mode. This can be read and/or write, as indicated by the ERead and EWrite bits.

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 void DoRelease();

Description

Frees resources before abandoning the stream buffer.

It is called by MStreamBuf::Release().

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

See also:

• MStreamBuf::Release()Frees resources before abandoning the stream buffer.

protected: IMPORT_C virtual TInt DoReadL(TAny *aPtr, TInt aMaxLength);

Description

Parameters

TAny *aPtr TInt aMaxLength

Return value

TInt

protected: IMPORT_C virtual TInt DoReadL(TDes8 &aDes, TInt aMaxLength, TRequestStatus &aStatus);

Description

Reads data from the stream buffer into the specified descriptor.

This function is called by MStreamBuf::ReadL(TDes8 &,TInt,TRequestStatus &).

This implementation deals with the request synchronously, and completes the request with KErrNone. Other implementations may choose to deal with this in a true asynchronous manner.

In addition, the read operation itself uses the RShareBuf::DoReadL(TAny *,TInt) variant.

Parameters

TDes8 &aDes The target descriptor for the data read from the stream buffer. On return, the length of the descriptor is set to the number of bytes read from the stream buffer. TInt aMaxLength The maximum number of bytes to be read. This value must not be greater than the maximum length of the descriptor, otherwise the function raises a STORE-Stream 2 panic. TRequestStatus &aStatus The request status that indicates the completion status of this asynchronous request.

Return value

TInt The maximum number of bytes to be read, as used in this request. This implementation uses, and returns, the value supplied in aMaxLength. Other implementations may choose to use a different value.

See also:

• MStreamBuf::ReadL(TAny *,TInt)Reads data from the stream buffer into the specified memory location.

protected: IMPORT_C virtual TStreamTransfer DoReadL(MStreamInput &anInput, TStreamTransfer aTransfer);

Description

Reads data from the stream into the specified data sink.

It is called by MStreamBuf::ReadL(MStreamInput &,TStreamTransfer).

This implementation calls the sink's ReadFromL() function, which performs the read (transfer) operation.

This implementation of RShareBuf::DoReadL(TAny *,TInt) is called for streams that do not have buffering capabilities, and that are derived directly from this class.

Parameters

MStreamInput &anInput The target data sink. TStreamTransfer aTransfer A stream transfer object defining the amount of data available to be read.

Return value

TStreamTransfer A stream transfer object defining the amount of data that was not consumed.

See also:

• MStreamInput::ReadFromL(MStreamBuf &,TStreamTransfer)Reads data from the specified stream into this stream input object.

protected: IMPORT_C virtual void DoWriteL(const TAny *aPtr, TInt aLength);

Description

Parameters

const TAny *aPtr TInt aLength

protected: IMPORT_C virtual TInt DoWriteL(const TDesC8 &aDes, TInt aMaxLength, TRequestStatus &aStatus);

Description

Writes data from the specified descriptor into this stream buffer.

This function is called by MStreamBuf::WriteL(const TDesC8 &,TInt,TRequestStatus &).

This implementation deals with the request synchronously, and completes the request with KErrNone. Other implementations may choose to deal with this in a true asynchronous manner.

In addition, the write operation itself uses the DoWriteL(TAny*,TInt) variant.

Parameters

const TDesC8 &aDes The source descriptor for the data to be written into the stream buffer. TInt aMaxLength The number of bytes to be written. This value must not be greater than the maximum length of the descriptor, otherwise the function raises a STORE-Stream 6 panic. TRequestStatus &aStatus The request status that indicates the completion status of this asynchronous request.

Return value

TInt The maximum number of bytes to be written, as used in this request. This implementation uses, and returns, the value supplied in aMaxLength. Other implementations may choose to use a different value.

See also:

• MStreamBuf::WriteL(const TAny *,TInt)Writes data from the specified memory location into the stream buffer.

protected: IMPORT_C virtual TStreamTransfer DoWriteL(MStreamOutput &anOutput, TStreamTransfer aTransfer);

Description

Parameters

MStreamOutput &anOutput TStreamTransfer aTransfer

Return value

TStreamTransfer

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

Description

Parameters

MStreamBuf::TMark aMark TStreamLocation aLocation TInt anOffset

Return value

TStreamPos