FLAC::File::save() has several bugs.

Question

(Related to #612)

FLAC::File::save() may write duplicate ID3v2 tags any number of times. For example:

  void testSaveTags()
  {
    ScopedFileCopy copy("no-tags", ".flac");

    FLAC::File f(copy.fileName().c_str());
    f.ID3v2Tag(true)->setTitle("0123456789");
    f.save();
    f.save();

    // ID3v2 tag has been written twice, and overwritten by metadata blocks.
    // As a result, FLAC stream header has gone.
  }

I already found a way to fix it. But it may interfere with #557, so I will fix it after it will be merged.

该提问来源于开源项目：taglib/taglib

Answer 1

Gosh! It can never update an exiting ID3v2 tag.

  void testSaveTags()
  {
    ScopedFileCopy copy("no-tags", ".flac");

    {
      FLAC::File f(copy.fileName().c_str());
      f.ID3v2Tag(true)->setTitle("0123456789");
      f.save();
    }

    {
      FLAC::File f(copy.fileName().c_str());
      f.ID3v2Tag()->setTitle("ABCDEFGHIJ");
      f.save();
    }

    {
      FLAC::File f(copy.fileName().c_str());
      CPPUNIT_ASSERT_EQUAL(String("ABCDEFGHIJ"), f.ID3v2Tag()->title());

      // Failed. Title is still "0123456789".
    }
  }

due to this check always true.

  if(d->ID3v2Location < d->flacStart)
    debug("FLAC::File::save() -- This can't be right -- an ID3v2 tag after the "
          "start of the FLAC bytestream?  Not writing the ID3v2 tag.");

Maybe, it demonstrates how few people use an ID3v2 with a FLAC file.