写入Vorbis注释元数据（标签）使用libFLAC++

Question

如何写Vorbis注释的元数据，即标签（例如“TITLE”），使用libFLAC现有FLAC文件++（http://flac.sourceforge.net）现有FLAC文件？

例如：

const char* fileName = "/path/to/file.flac"; 

// read tags from the file 
FLAC::Metadata::VorbisComment vorbisComment; 
FLAC::Metadata::get_tags(fileName, vorbisComment); 

// make some changes 
vorbisComment.append_comment("TITLE", "This is title"); 

// write changes back to the file ... 
// :-(there is no API for that, i.e. something like this: 
// FLAC::Metadata::write_tags(fileName, vorbisComment); 

Answer 1

我已经分析了metaflac源代码（如建议），这里是该问题的解决方案：

#include <FLAC++/metadata.h> 

const char* fileName = "/path/to/file.flac"; 

// read a file using FLAC::Metadata::Chain class 
FLAC::Metadata::Chain chain; 
if (!chain.read(fileName)) { 
    // error handling 
    throw ...; 
} 

// now, find vorbis comment block and make changes in it 
{ 
    FLAC::Metadata::Iterator iterator; 
    iterator.init(chain); 

    // find vorbis comment block 
    FLAC::Metadata::VorbisComment* vcBlock = 0; 
    do { 
     FLAC::Metadata::Prototype* block = iterator.get_block(); 
     if (block->get_type() == FLAC__METADATA_TYPE_VORBIS_COMMENT) { 
      vcBlock = (FLAC::Metadata::VorbisComment*) block; 
      break; 
     } 
    } while (iterator.next()); 

    // if not found, create a new one 
    if (vcBlock == 0) { 
     // create a new block 
     vcBlock = new FLAC::Metadata::VorbisComment(); 

     // move iterator to the end 
     while (iterator.next()) { 
     } 

     // insert a new block at the end 
     if (!iterator.insert_block_after(vcBlock)) { 
      delete vcBlock; 
      // error handling 
      throw ...; 
     } 
    } 

    // now, you can make any number of changes to the vorbis comment block, 
    // for example you can append TITLE comment: 
    vcBlock->append_comment(
     FLAC::Metadata::VorbisComment::Entry("TITLE", "This is title")); 
} 

// write changes back to the file 
if (!chain.write()) { 
    // error handling 
    throw ...; 
}