Initialising a Parser Plug-in

This tutorial describes how to initialise a parser plug-in.

Purpose

The purpose of this tutorial is to show you how to use the metadata client utility to initialise a parser plug-in.

Required Background

The Metadata Utility Library Overview introduces the metadata client utility.

Introduction

Client applications must initialise a parser before it can be used to read metadata. The client initialises the parser plug-in by passing either a filename (including path), file handler or buffer (containing unique header data and metadata). The InitializeParserL() method is used to do this. InitializeParserL() is responsible for deciding which parser plug-in should be used to provide support for a particular format.

Parser plug-ins provide information in their ECOM resource file. This information allows MUF (and ultimately the client application) to determine:

The formats the parser plug-in can parse
The MIME types applicable to the format
The file extensions that identify files that can be handled by the format
Any segments of header data that can be matched against the multimedia data to check that the data could be handled using this format.
The UID of the parser plug-in implementation.

Using InitializeParserL()

The following tasks will be covered in this tutorial:

Initialise a parser plug-in

Basic Procedure

The high level steps to initialise a parser plug-in are shown here:

Create a new metadata utility object.
Initialise a parser plug-in using one of the following overloads of InitializeParserL():
- Initialise with input file
```
IMPORT_C void InitializeParserL(const TDesC& aFileName);
```
  Call CMetaDataClientUtility::InitializeParserL() and set aFileName to an input file name including path. MUF resolves the parser plug-in using the input file extension and initialises the parser plug-in with the input file name.
- Initialise with file handler
```
IMPORT_C void InitializeParserL(RFile& aFile);
```
  Call CMetaDataClientUtility::InitializeParserL() and set aFile to an input file handler. MUF reads the file extension, resolves the parser plug-in with the input file extension and initialises the parser plug-in with the input file name.
- Initialise with DRM protected file
```
IMPORT_C void InitializeParserL(const TMMSource& aDRMSource);
```
  Call CMetaDataClientUtility::InitializeParserL() and set aDRMSource to a protected file source. MUF resolves the parser plug-in with the MIME type and initialises the parser plug-in with ContentAccess::CData.
- Initialise with data buffer
```
IMPORT_C void InitializeParserL(const TDesC8& aDescriptor);
```
  Call CMetaDataClientUtility::InitializeParserL() and set aDescriptor to a source buffer. Note that the source buffer contains unique header data and metadata. MUF resolves the parser plug-in with the unique header data and initialises the parser plug-in with the source buffer.
- Initialise parser directly
```
IMPORT_C void InitializeParserL(const TUid aParserUid,const TDesC& aFileName);
```
  If the client application resolves the parser from the supported formats, then the application can pass the UID of the parser and an input file name. Call CMetaDataClientUtility::InitializeParserL() and set aParserUid to the UID of the parser and aFileName to the input file name (including full path). MUF directly sets the file name on the requested parser.
  
  Note: ECOM plug-ins have several associated UIDs. The one identifying the plug-in is the implementation UID.

Examples

Initialise with input file

_LIT(KTestMp3File, "c:\\mm\\muf\\testfiles\\aagaya.mp3");
const TPtrC fileName(KTestMp3File);

CMetaDataClientUtility* utility = CMetaDataClientUtility::NewL(EAllPlugIns);
CleanupStack::PushL(utility);

utility->InitializeParserL(fileName);
:
CleanupStack::PopAndDestroy();

Initialise with file handler

_LIT(KTestMp3File, "c:\\mm\\muf\\testfiles\\aagaya.mp3");
const TPtrC fileName(KTestMp3File);
CMetaDataClientUtility* utility = CMetaDataClientUtility::NewL(EAllPlugIns);
CleanupStack::PushL(utility);
RFile file;
RFs fs;
User::LeaveIfError(fs.Connect());
User::LeaveIfError(file.Open(fs, fileName, EFileShareReadersOnly));
utility->InitializeParserL(file);
:
CleanupStack::PopAndDestroy();
file.Close();
fs.Close();

Initialise with DRM protected file

TPtrC proFileName;
CMetaDataClientUtility* utility = CMetaDataClientUtility::NewL(EAllPlugIns);
CleanupStack::PushL(utility);

utility->InitializeParserL(TMMFileSource(proFileName, KRightsPlayerUniqueId001, ContentAccess::EPlay));
:
CleanupStack::PopAndDestroy();

Initialise with data buffer

_LIT(KTestMp3File, "c:\\mm\\muf\\testfiles\\aagaya.mp3");
const TPtrC fileName(KTestMp3File);
CMetaDataClientUtility* utility = CMetaDataClientUtility::NewL(EAllPlugIns);
CleanupStack::PushL(utility);
RFile file;
RFs fs;
TInt headerSize = set to header size;
User::LeaveIfError(fs.Connect());
User::LeaveIfError(file.Open(fs, fileName, EFileRead));
HBufC8* fileData = HBufC8::NewL(headerSize);
TPtr8 buf = fileData->Des();
file.Read(buf, headerSize);
utility->InitializeParserL(*fileData);
:
CleanupStack::PopAndDestroy(2);
file.Close();
fs.Close();

Initialise parser directly

CMetaDataClientUtility* utility = CMetaDataClientUtility::NewL(EAllPlugIns);
CleanupStack::PushL(utility);
TUid uid;
//Get the uid from supported formats

utility->InitializeParserL(uid, fileName);
:
CleanupStack::PopAndDestroy();

Initialising a Parser Plug-in

Purpose

Using InitializeParserL()

Examples

See Also