The main class in the ID3v2 implementation. More...

#include <id3v2tag.h>

Inheritance diagram for TagLib::ID3v2::Tag:
Collaboration diagram for TagLib::ID3v2::Tag:

Public Member Functions

 Tag ()
 Tag (File *file, long tagOffset, const FrameFactory *factory=FrameFactory::instance())
virtual ~Tag ()
virtual String title () const
virtual String artist () const
virtual String album () const
virtual String comment () const
virtual String genre () const
virtual uint year () const
virtual uint track () const
virtual void setTitle (const String &s)
virtual void setArtist (const String &s)
virtual void setAlbum (const String &s)
virtual void setComment (const String &s)
virtual void setGenre (const String &s)
virtual void setYear (uint i)
virtual void setTrack (uint i)
virtual bool isEmpty () const
Headerheader () const
ExtendedHeaderextendedHeader () const
Footerfooter () const
const FrameListMapframeListMap () const
const FrameListframeList () const
const FrameListframeList (const ByteVector &frameID) const
void addFrame (Frame *frame)
void removeFrame (Frame *frame, bool del=true)
void removeFrames (const ByteVector &id)
PropertyMap properties () const
void removeUnsupportedProperties (const StringList &properties)
PropertyMap setProperties (const PropertyMap &)
ByteVector render () const
ByteVector render (int version) const

Static Public Member Functions

static Latin1StringHandler const * latin1StringHandler ()
static void setLatin1StringHandler (const Latin1StringHandler *handler)
- Static Public Member Functions inherited from TagLib::Tag
static void duplicate (const Tag *source, Tag *target, bool overwrite=true)

Protected Member Functions

void read ()
void parse (const ByteVector &data)
void setTextFrame (const ByteVector &id, const String &value)
void downgradeFrames (FrameList *existingFrames, FrameList *newFrames) const

Detailed Description

The main class in the ID3v2 implementation.

This is the main class in the ID3v2 implementation. It serves two functions. This first, as is obvious from the public API, is to provide a container for the other ID3v2 related classes. In addition, through the read() and parse() protected methods, it provides the most basic level of parsing. In these methods the ID3v2 tag is extracted from the file and split into data components.

ID3v2 tags have several parts, TagLib attempts to provide an interface for them all. header(), footer() and extendedHeader() corespond to those data structures in the ID3v2 standard and the APIs for the classes that they return attempt to reflect this.

Also ID3v2 tags are built up from a list of frames, which are in turn have a header and a list of fields. TagLib provides two ways of accessing the list of frames that are in a given ID3v2 tag. The first is simply via the frameList() method. This is just a list of pointers to the frames. The second is a map from the frame type – i.e. "COMM" for comments – and a list of frames of that type. (In some cases ID3v2 allows for multiple frames of the same type, hence this being a map to a list rather than just a map to an individual frame.)

More information on the structure of frames can be found in the ID3v2::Frame class.

read() and parse() pass binary data to the other ID3v2 class structures, they do not handle parsing of flags or fields, for instace. Those are handled by similar functions within those classes.

Note
All pointers to data structures within the tag will become invalid when the tag is destroyed.
Warning
Dealing with the nasty details of ID3v2 is not for the faint of heart and should not be done without much meditation on the spec. It's rather long, but if you're planning on messing with this class and others that deal with the details of ID3v2 (rather than the nice, safe, abstract TagLib::Tag and friends), it's worth your time to familiarize yourself with said spec (which is distrubuted with the TagLib sources). TagLib tries to do most of the work, but with a little luck, you can still convince it to generate invalid ID3v2 tags. The APIs for ID3v2 assume a working knowledge of ID3v2 structure. You're been warned.

Constructor & Destructor Documentation

TagLib::ID3v2::Tag::Tag ( )

Constructs an empty ID3v2 tag.

Note
You must create at least one frame for this tag to be valid.

Reimplemented from TagLib::Tag.

TagLib::ID3v2::Tag::Tag ( File file,
long  tagOffset,
const FrameFactory factory = FrameFactory::instance() 
)

Constructs an ID3v2 tag read from file starting at tagOffset. factory specifies which FrameFactory will be used for the construction of new frames.

Note
You should be able to ignore the factory parameter in almost all situations. You would want to specify your own FrameFactory subclass in the case that you are extending TagLib to support additional frame types, which would be incorperated into your factory.
See Also
FrameFactory
virtual TagLib::ID3v2::Tag::~Tag ( )
virtual

Destroys this Tag instance.

Reimplemented from TagLib::Tag.

Member Function Documentation

void TagLib::ID3v2::Tag::addFrame ( Frame frame)

Add a frame to the tag. At this point the tag takes ownership of the frame and will handle freeing its memory.

Note
Using this method will invalidate any pointers on the list returned by frameList()
virtual String TagLib::ID3v2::Tag::album ( ) const
virtual

Returns the album name; if no album name is present in the tag String::null will be returned.

Implements TagLib::Tag.

virtual String TagLib::ID3v2::Tag::artist ( ) const
virtual

Returns the artist name; if no artist name is present in the tag String::null will be returned.

Implements TagLib::Tag.

virtual String TagLib::ID3v2::Tag::comment ( ) const
virtual

Returns the track comment; if no comment is present in the tag String::null will be returned.

Implements TagLib::Tag.

void TagLib::ID3v2::Tag::downgradeFrames ( FrameList existingFrames,
FrameList newFrames 
) const
protected
ExtendedHeader* TagLib::ID3v2::Tag::extendedHeader ( ) const

Returns a pointer to the tag's extended header or null if there is no extended header.

Footer* TagLib::ID3v2::Tag::footer ( ) const

Returns a pointer to the tag's footer or null if there is no footer.

const FrameList& TagLib::ID3v2::Tag::frameList ( ) const

Returns a reference to the frame list. This is an FrameList of all of the frames in the tag in the order that they were parsed.

This can be useful if for example you want iterate over the tag's frames in the order that they occur in the tag.

Warning
You should not modify this data structure directly, instead use addFrame() and removeFrame().
const FrameList& TagLib::ID3v2::Tag::frameList ( const ByteVector frameID) const

Returns the frame list for frames with the id frameID or an empty list if there are no frames of that type. This is just a convenience and is equivalent to:

frameListMap()[frameID];
See Also
frameListMap()
const FrameListMap& TagLib::ID3v2::Tag::frameListMap ( ) const

Returns a reference to the frame list map. This is an FrameListMap of all of the frames in the tag.

This is the most convenient structure for accessing the tag's frames. Many frame types allow multiple instances of the same frame type so this is a map of lists. In most cases however there will only be a single frame of a certain type.

Let's say for instance that you wanted to access the frame for total beats per minute – the TBPM frame.

TagLib::MPEG::File f("foo.mp3");
// Check to make sure that it has an ID3v2 tag
if(f.ID3v2Tag()) {
// Get the list of frames for a specific frame type
TagLib::ID3v2::FrameList l = f.ID3v2Tag()->frameListMap()["TBPM"];
if(!l.isEmpty())
std::cout << l.front()->toString() << std::endl;
}
Warning
You should not modify this data structure directly, instead use addFrame() and removeFrame().
See Also
frameList()
virtual String TagLib::ID3v2::Tag::genre ( ) const
virtual

Returns the genre name; if no genre is present in the tag String::null will be returned.

Implements TagLib::Tag.

Header* TagLib::ID3v2::Tag::header ( ) const

Returns a pointer to the tag's header.

virtual bool TagLib::ID3v2::Tag::isEmpty ( ) const
virtual

Returns true if the tag does not contain any data. This should be reimplemented in subclasses that provide more than the basic tagging abilities in this class.

Reimplemented from TagLib::Tag.

static Latin1StringHandler const* TagLib::ID3v2::Tag::latin1StringHandler ( )
static

Gets the current string handler that decides how the "Latin-1" data will be converted to and from binary data.

See Also
Latin1StringHandler
void TagLib::ID3v2::Tag::parse ( const ByteVector data)
protected

This is called by read to parse the body of the tag. It determines if an extended header exists and adds frames to the FrameListMap.

PropertyMap TagLib::ID3v2::Tag::properties ( ) const

Implements the unified property interface – export function. This function does some work to translate the hard-specified ID3v2 frame types into a free-form string-to-stringlist PropertyMap:

  • if ID3v2 frame ID is known by Frame::frameIDToKey(), the returned key is used
  • if the frame ID is "TXXX" (user text frame), the description() is used as key
  • if the frame ID is "WXXX" (user url frame),
    • if the description is empty or "URL", the key "URL" is used
    • otherwise, the key "URL:<description>" is used;
  • if the frame ID is "COMM" (comments frame),
    • if the description is empty or "COMMENT", the key "COMMENT" is used
    • otherwise, the key "COMMENT:<description>" is used;
  • if the frame ID is "USLT" (unsynchronized lyrics),
    • if the description is empty or "LYRICS", the key "LYRICS" is used
    • otherwise, the key "LYRICS:<description>" is used;
  • if the frame ID is "TIPL" (involved peoples list), and if all the roles defined in the frame are known in TextIdentificationFrame::involvedPeopleMap(), then "<role>=<name>" will be contained in the returned obejct for each
  • if the frame ID is "TMCL" (musician credit list), then "PERFORMER:<instrument>=<name>" will be contained in the returned PropertyMap for each defined musician In any other case, the unsupportedData() of the returned object will contain the frame's ID and, in case of a frame ID which is allowed to appear more than once, the description, separated by a "/".

Reimplemented from TagLib::Tag.

void TagLib::ID3v2::Tag::read ( )
protected

Reads data from the file specified in the constructor. It does basic parsing of the data in the largest chunks. It partitions the tag into the Header, the body of the tag (which contains the ExtendedHeader and frames) and Footer.

void TagLib::ID3v2::Tag::removeFrame ( Frame frame,
bool  del = true 
)

Remove a frame from the tag. If del is true the frame's memory will be freed; if it is false, it must be deleted by the user.

Note
Using this method will invalidate any pointers on the list returned by frameList()
void TagLib::ID3v2::Tag::removeFrames ( const ByteVector id)

Remove all frames of type id from the tag and free their memory.

Note
Using this method will invalidate any pointers on the list returned by frameList()
void TagLib::ID3v2::Tag::removeUnsupportedProperties ( const StringList properties)

Removes unsupported frames given by properties. The elements of properties must be taken from properties().unsupportedData(); they are of one of the following forms:

  • a four-character frame ID, if the ID3 specification allows only one frame with that ID (thus, the frame is uniquely determined)
  • frameID + "/" + description(), when the ID is one of "TXXX", "WXXX", "COMM", or "USLT",
  • "UNKNOWN/" + frameID, for frames that could not be parsed by TagLib. In that case, all unknown frames with the given ID will be removed.

Reimplemented from TagLib::Tag.

ByteVector TagLib::ID3v2::Tag::render ( ) const

Render the tag back to binary data, suitable to be written to disk.

ByteVector TagLib::ID3v2::Tag::render ( int  version) const

Render the tag back to binary data, suitable to be written to disk.

The version parameter specifies the version of the rendered ID3v2 tag. It can be either 4 or 3.

virtual void TagLib::ID3v2::Tag::setAlbum ( const String s)
virtual

Sets the album to s. If s is String::null then this value will be cleared.

Implements TagLib::Tag.

virtual void TagLib::ID3v2::Tag::setArtist ( const String s)
virtual

Sets the artist to s. If s is String::null then this value will be cleared.

Implements TagLib::Tag.

virtual void TagLib::ID3v2::Tag::setComment ( const String s)
virtual

Sets the comment to s. If s is String::null then this value will be cleared.

Implements TagLib::Tag.

virtual void TagLib::ID3v2::Tag::setGenre ( const String s)
virtual

Sets the genre to s. If s is String::null then this value will be cleared. For tag formats that use a fixed set of genres, the appropriate value will be selected based on a string comparison. A list of available genres for those formats should be available in that type's implementation.

Implements TagLib::Tag.

static void TagLib::ID3v2::Tag::setLatin1StringHandler ( const Latin1StringHandler handler)
static

Sets the string handler that decides how the "Latin-1" data will be converted to and from binary data. If the parameter handler is null, the previous handler is released and default ISO-8859-1 handler is restored.

Note
The caller is responsible for deleting the previous handler as needed after it is released.
See Also
Latin1StringHandler
PropertyMap TagLib::ID3v2::Tag::setProperties ( const PropertyMap )

Implements the unified property interface – import function. See the comments in properties().

Reimplemented from TagLib::Tag.

void TagLib::ID3v2::Tag::setTextFrame ( const ByteVector id,
const String value 
)
protected

Sets the value of the text frame with the Frame ID id to value. If the frame does not exist, it is created.

virtual void TagLib::ID3v2::Tag::setTitle ( const String s)
virtual

Sets the title to s. If s is String::null then this value will be cleared.

Implements TagLib::Tag.

virtual void TagLib::ID3v2::Tag::setTrack ( uint  i)
virtual

Sets the track to i. If s is 0 then this value will be cleared.

Implements TagLib::Tag.

virtual void TagLib::ID3v2::Tag::setYear ( uint  i)
virtual

Sets the year to i. If s is 0 then this value will be cleared.

Implements TagLib::Tag.

virtual String TagLib::ID3v2::Tag::title ( ) const
virtual

Returns the track name; if no track name is present in the tag String::null will be returned.

Implements TagLib::Tag.

virtual uint TagLib::ID3v2::Tag::track ( ) const
virtual

Returns the track number; if there is no track number set, this will return 0.

Implements TagLib::Tag.

virtual uint TagLib::ID3v2::Tag::year ( ) const
virtual

Returns the year; if there is no year set, this will return 0.

Implements TagLib::Tag.


The documentation for this class was generated from the following file: