Class CConverterBase

CConverterBase

Support

Supported from 6.0

Description

Polymorphic interface for converters from one data format to another.

Clients use this interface to access data converters. The implementator of a data converter derives a class from this in which to implement the appropriate conversion functionality.

The interface offers conversions between files, and between objects that support the stream interfaces, e.g. stream stores.

There are two flavours of conversion methods:

• the synchronous interfaces, ConvertL() and ConvertObjectL(), which perform the specified conversion and then return

• the asynchronous interfaces, ConvertAL() and ConvertObjectAL(), which initialise the converter object, and allow the client code to call DoConvertL() a number of times until the conversion is complete or abandoned

Derivation

CBase Base class for all classes to be instantiated on the heap CConverterBase Polymorphic interface for converters from one data format to another

Defined in CConverterBase:
CancelConvert(), Capabilities(), ConvertAL(), ConvertL(), ConvertObjectAL(), ConvertObjectL(), DoConvertL(), EConvertsExtract, EConvertsFiles, EConvertsObjects, EmbeddedObjectL(), GetEmbeddedFileName(), TCapability, Uid()

Inherited from CBase:
operator new()

virtual void ConvertAL(const TFileName& aSourceFile, const TFileName& aTargetFile, MConverterUiObserver* aObserver=NULL);

Description

Prepares for conversion in multiple steps of a file.

Clients must call this function before calling DoConvertL() one or more times to do the conversion. The function can call back the MaxSteps() function of the supplied MConverterUiObserver to tell the client the maximum number of calls to DoConvertL() that will be required.

The rest of the description describes how to implement this function.

The function should initialise the object before performing a conversion, but should not do the conversion itself. Such initialisation should include:

• storing the MConverterUiObserver pointer (if supplied), so the client can later be notified of conversion progress

• validating the integrity of the input data

• optionally, creating the appropriate application engine, either for input or output, to enable access to the data

• determining the number of steps (i.e. calls to DoConvertL()) required to perform the conversion and pass this to the client by calling MConverterUiObserver::MaxSteps()

The default implementation leaves with KErrNotSupported.

Parameters

const TFileName& aSourceFile File to convert const TFileName& aTargetFile File to which to write the converted output. The file can be overwritten if it already exists. const MConverterUiObserver* aObserver=NULL Observer of the conversion process

Leave codes

KErrNotSupported File conversion is not supported

virtual void ConvertL(const TFileName& aSourceFile, const TFileName& aTargetFile, MConverterUiObserver* aObserver=NULL);

Description

Converts a file in a single step.

The caller can supply a MConverterUiObserver to be informed of progress in the conversion.

The default implementation calls ConvertAL() to prepare the object to perform the conversion, and then calls DoConvertL() in a loop until conversion is complete.

Parameters

const TFileName& aSourceFile File to convert const TFileName& aTargetFile File to which to write the converted output const MConverterUiObserver* aObserver=NULL Optional observer of the conversion process

Leave codes

KErrNotSupported File conversion is not supported   Other system-wide error codes can be generated by the conversion process

virtual void ConvertObjectAL(RReadStream& aReadStream, RWriteStream& aWriteStream, MConverterUiObserver* aObserver=NULL);

Description

Prepares for conversion in multiple steps of a stream object.

Clients must call this function before calling DoConvertL() one or more times to do the conversion. The function can call back the MaxSteps() function of the supplied MConverterUiObserver to tell the client the maximum number of calls to DoConvertL() that will be required.

For a description of how to implement this function, see ConvertAL().

Parameters

RReadStream& aReadStream Stream from which to read the data to convert RWriteStream& aWriteStream Stream to which to write the converted data MConverterUiObserver* aObserver=NULL Optional observer of the conversion process

Leave codes

KErrNotSupported Stream object conversion is not supported

virtual void ConvertObjectL(RReadStream& aReadStream, RWriteStream& aWriteStream, MConverterUiObserver* aObserver=NULL);

Description

Converts a stream object in a single step.

The caller can supply a MConverterUiObserver to be informed of progress in the conversion.

The default implementation calls ConvertObjectAL() to prepare the object to perform the conversion, and then calls DoConvertL() in a loop until conversion is complete.

Parameters

RReadStream& aReadStream Stream from which to read the data to convert RWriteStream& aWriteStream Stream to which to write the converted data MConverterUiObserver* aObserver=NULL Optional observer of the conversion process

virtual TBool DoConvertL();

Description

Performs a step in converting the data.

The function advances a step in converting the data each time that it is called. When conversion is complete, the function returns EFalse.

Return value

TBool EFalse if conversion is complete, else ETrue

virtual void CancelConvert();

Description

Cleans up a conversion that has been prepared or is in progress.

It should free any resources and reset the converter object to an initial state.

The default is to do nothing.

virtual TInt Capabilities();

Description

Gets the converter's capabilities.

The default is to return a bitmask of all the TCapability flags.

Return value

TInt A bitmask of TCapability flags describing the capabilities.

virtual CConverterBase* EmbeddedObjectL(TDataType& aType);

Description

Gets a converter for an embedded object of the specified type.

The default is to return NULL.

Parameters

TDataType& aType Type of the embedded object

Return value

CConverterBase* Converter for the embedded object

virtual TBool GetEmbeddedFileName(TFileName& aFileName);

Description

Gets a filename embedded in the object.

Parameters

TFileName& aFileName File name found

Return value

TBool True if a filename found, false otherwise

virtual TUid Uid() =0;

Description

Gets the converter's UID.

Return value

TUid Converter's UID

TCapability

Description

Bitmask values that describe the capabilities of the converter.

EConvertsFiles The converter can convert files. EConvertsObjects The converter can convert stream objects. EConvertsExtract The converter can extract embedded objects.