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Improve FrameFactory subclassing

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Change the ID3v2 frame factory so it is possible to subclass it for
implementing own frames.  Additionally it splits up the createFrame()
method to make its usage in subclasses a bit more easy.
This commit is contained in:
Max-F-Helm 2022-03-03 21:29:05 +01:00 committed by Urs Fleisch
parent c54c924333
commit 271bd05afa
2 changed files with 50 additions and 10 deletions
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35
taglib/mpeg/id3v2/id3v2framefactory.cpp
View File

@ -116,9 +116,9 @@ FrameFactory *FrameFactory::instance()
return &factory;
}
Frame *FrameFactory::createFrame(const ByteVector &origData, const Header *tagHeader) const
std::pair<Frame::Header *, bool> FrameFactory::prepareFrameHeader(
ByteVector &data, const Header *tagHeader) const
{
ByteVector data = origData;
unsigned int version = tagHeader->majorVersion();
auto header = new Frame::Header(data, version);
ByteVector frameID = header->frameID();
@ -131,7 +131,7 @@ Frame *FrameFactory::createFrame(const ByteVector &origData, const Header *tagHe
header->frameSize() > data.size())
{
delete header;
return nullptr;
return {nullptr, false};
}
#ifndef NO_ITUNES_HACKS
@ -148,7 +148,7 @@ Frame *FrameFactory::createFrame(const ByteVector &origData, const Header *tagHe
for(auto it = frameID.cbegin(); it != frameID.cend(); it++) {
if( (*it < 'A' || *it > 'Z') && (*it < '0' || *it > '9') ) {
delete header;
return nullptr;
return {nullptr, false};
}
}
@ -165,24 +165,39 @@ Frame *FrameFactory::createFrame(const ByteVector &origData, const Header *tagHe
if(!zlib::isAvailable() && header->compression()) {
debug("Compressed frames are currently not supported.");
return new UnknownFrame(data, header);
return {header, false};
}
if(header->encryption()) {
debug("Encrypted frames are currently not supported.");
return new UnknownFrame(data, header);
return {header, false};
}
if(!updateFrame(header)) {
header->setTagAlterPreservation(true);
return new UnknownFrame(data, header);
return {header, false};
}
// updateFrame() might have updated the frame ID.
return {header, true};
}
frameID = header->frameID();
Frame *FrameFactory::createFrame(const ByteVector &origData,
const Header *tagHeader) const
{
ByteVector data = origData;
auto [header, ok] = prepareFrameHeader(data, tagHeader);
if(!ok) {
// check if frame is valid and return as UnknownFrame
return header ? new UnknownFrame(data, header) : nullptr;
}
return createFrame(data, header, tagHeader);
}
// This is where things get necissarily nasty. Here we determine which
Frame *FrameFactory::createFrame(const ByteVector &data, Frame::Header *header,
const Header *tagHeader) const {
ByteVector frameID = header->frameID();
// This is where things get necessarily nasty. Here we determine which
// Frame subclass (or if none is found simply an Frame) based
// on the frame ID. Since there are a lot of possibilities, that means
// a lot of if blocks.

25
taglib/mpeg/id3v2/id3v2framefactory.h
View File

@ -127,6 +127,31 @@ namespace TagLib {
*/
virtual bool updateFrame(Frame::Header *header) const;
/*!
* Creates and prepares the frame header for createFrame().
*
* \param data data of the frame (might be modified)
* \param tagHeader the tag header
* \param header reference to frame header pointer, will be set to
* nullptr if the frame is invalid
* \return {header, ok}: header is a created frame header or nullptr
* if the frame is invalid; ok is true if the frame is supported.
*/
std::pair<Frame::Header *, bool> prepareFrameHeader(
ByteVector &data, const Header *tagHeader) const;
/*!
* Create a frame based on \a data. \a header should be a valid frame
* header and \a tagHeader a valid ID3v2::Header instance.
*
* This method is called by the public overloaded method
* createFrame(const ByteVector &, const Header *) after creating
* \a header from verified \a data using prepareFrameHeader(), so
* this method is provided to be reimplemented in derived classes.
*/
virtual Frame *createFrame(const ByteVector &data, Frame::Header *header,
const Header *tagHeader) const;
private:
FrameFactory(const FrameFactory &) = delete;
FrameFactory &operator=(const FrameFactory &) = delete;