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(), DoReadL(), DoReadL(), DoRelease(), DoSeekL(), DoWriteL(), DoWriteL(), DoWriteL(), Open(), Open(), RShareBuf()

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

See also:

• TStreamMark
• TStreamExchange
• RFileBuf
• RShareReadStream
• RShareWriteStream

IMPORT_C RShareBuf();

Description

Constructs an empty shared stream buffer object.

Call one of the Open() 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::TRead
• MStreamBuf::TWrite

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::TRead
• MStreamBuf::TWrite

protected: virtual IMPORT_C void DoRelease();

Description

Frees resources before abandoning the stream buffer.

It is called by Release().

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

See also:

• MStreamBuf::Release()

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

Description

Parameters

TAny *aPtr TInt aMaxLength

Return value

TInt

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

Description

Reads data from the stream buffer into the specified descriptor.

This function is called by 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 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()

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

Description

Reads data from the stream into the specified data sink.

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

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

This implementation of DoReadL() 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()

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

Description

Parameters

const TAny *aPtr TInt aLength

protected: virtual IMPORT_C 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 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()

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

Description

Parameters

MStreamOutput &anOutput TStreamTransfer aTransfer

Return value

TStreamTransfer

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

Description

Parameters

TMark aMark TStreamLocation aLocation TInt anOffset

Return value

TStreamPos