Class RFileBuf

RFileBuf

Support

Supported from 5.0

Description

A stream buffer hosted by a file.

Instances of this class are used by file based persistent stores, i.e. CFileStore type objects. An RFileBuf object is associated with a file and the file is said to be attached to the stream buffer.

An RFileBuf object is also used by RFileReadStream and RFileWriteStream objects to provide buffered file I/O.

The stream buffer has intermediate buffering capabilities.

When used as the basis for a file store, it hosts multiple streams through the TStreamExchange and RShareBuf classes

Derivation

MStreamBuf A stream buffer that provides a generic I/O interface for streamed data RFileBuf A stream buffer hosted by a file TStreamBuf Adds buffering capabilities to a stream buffer

Defined in RFileBuf:
Reset(), Attach(), Close(), Create(), Detach(), File(), Open(), RFileBuf(), Reattach(), Replace(), Reset(), SetSizeL(), Temp()

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

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

See also:

• CFileStore
• RFileReadStream
• RFileWriteStream

RFileBuf();

Description

Constructs the object with a default intermediate buffer size.

The size of the intermediate buffer is the value of the constant KDefaultFileBufSize.

RFileBuf(TInt aSize);

Description

Constructs the object with the specified intermediate buffer size.

Parameters

TInt aSize The size of the intermediate buffer.

Notes:

• If the intermediate buffer size is zero, then the class provides an MStreamBuf interface to unbuffered file I/O.

void Reset();

Description

Frees the intermediate buffer.

If there is any read data in the intermediate buffer, then the function reverts the read position within the stream.

Notes:

• The intermediate buffer must not contain any outstanding write data, otherwise the function raises a STORE-File 6 panic.

void Reset(TInt aSize);

Description

Frees the intermediate buffer and changes the size of any future intermediate buffer to the specified value.

Parameters

TInt aSize The size of any future intermediate buffer.

Notes:

• The intermediate buffer must not contain any outstanding write data, otherwise the function raises a STORE-File 6 panic.

void SetSizeL(TInt aSize);
    

Description

Changes the size of the file attached to this buffer to the specified value.

Writes any outstanding data from the intermediate buffer to the stream hosted by the file. Any data in the intermediate buffer that would lie beyond the end of the truncated file, is not written.

Parameters

TInt aSize The new size of the file.

void Attach(RFile& aFile,TInt aPos=0);

Description

Attaches the specified file to this stream buffer.

The function also re-sets the intermediate buffer's read and write marks to the beginning of the intermediate buffer and sets the read and write stream positions to the specified offset within the file.

Parameters

RFile& aFile The file to be attached. TInt aPos The offset within the file to which the read and write stream positions are set. By default this is zero.

See also:

• Detach()
• Reattach()

void Detach();

Description

Detaches the file from this stream buffer.

The intermediate buffer's read and write marks are not changed, and the stream positions are not changed. This means that the contents of the file should not change while it is detached.

See also:

• Attach()
• Reattach()

void Reattach(RFile& aFile);

Description

Re-attaches the specified file to this stream buffer.

The intermediate buffer's read and write marks are not changed, and the stream positions are not changed.

The file should be the one that was detached using the Detach() function.

Parameters

RFile& aFile The file to be re-attached.

See also:

• Attach()
• Detach()

TInt Open(RFs& aFs,const TDesC& aName,TUint aFileMode);

Description

Opens the specified file and attaches it to this stream buffer.

Parameters

RFs& aFs Handle to a file server session through which the file is opened. const TDesC& aName The name of the file to be opened. TUint aFileMode The mode in which the file is to be accessed. The mode is defined by the TFileMode type.

Return value

TInt KErrNone, if successful, otherwise one of the other system wide error codes.

Notes:

• If the file cannot be opened, then it is not attached to this stream buffer.

See also:

• Attach()
• TFileMode
• RFile

TInt Create(RFs& aFs,const TDesC& aName,TUint aFileMode);

Description

Creates a file with the specified name and attaches it to this stream buffer.

The file must not already exist.

Parameters

RFs& aFs Handle to a file server session through which the file is created. const TDesC& aName The name of the file to be created. TUint aFileMode The mode in which the file is to be accessed. The mode is defined by the TFileMode type.

Return value

TInt KErrNone, if successful, otherwise one of the other system wide error codes.

Notes:

• If the file cannot be created and opened, then it is not attached to this stream buffer.

See also:

• Attach()
• TFileMode
• RFile

TInt Replace(RFs& aFs,const TDesC& aName,TUint aFileMode);

Description

Replaces the file with the specified name and attaches it to this stream buffer.

If there is an existing file with the same name, then this function overwrites it. If the file does not already exist, it is created.

Parameters

RFs& aFs Handle to a file server session through which the file is replaced. const TDesC& aName The name of the file to be replaced. TUint aFileMode The mode in which the file is to be accessed. The mode is defined by the TFileMode type.

Return value

TInt KErrNone, if successful, otherwise one of the other system wide error codes.

Notes:

• If the file cannot be replaced, then it is not attached to this stream buffer.

See also:

• Attach()
• TFileMode
• RFile

TInt Temp(RFs& aFs,const TDesC& aPath,TFileName& aName,TUint aFileMode);

Description

Creates and opens a temporary file with a unique name and attaches it to this stream buffer.

Parameters

RFs& aFs Handle to a file server session through which the file is created. const TDesC& aPath The directory in which the file is created. const TDesC& aName On return, contains the full path and file name of the file. The filename is guaranteed to be unique within the specified directory. TUint aFileMode The mode in which the file is to be accessed. The mode is defined by the TFileMode type.

See also:

• Attach()
• TFileMode
• RFile

RFile& File() const;

Description

Gets a reference to the file attached to this stream buffer.

Return value

RFile& The file attached to this stream buffer.

void Close();

Description

Writes any outstanding data from the intermediate buffer before freeing the intermediate buffer and closing the attached file.

RFileBuf(TCapture<RFileBuf> aCapture);

Description

This is internal and is not intended for use.

Parameters

TCapture<RFileBuf> aCapture No description.