tag_parse.cpp

本人收集整理的一份c/c++跨平台网络库

  ifstream file;
  if (ID3E_NoError != openReadableFile(this->GetFileName(), file))
  {
    // log this...
    return;
  }
  ID3_IFStreamReader ifsr(file);
  ParseReader(ifsr);
  file.close();
}

//used for streaming media
void ID3_TagImpl::ParseReader(ID3_Reader &reader)
{
  size_t mp3_core_size;
  size_t bytes_till_sync;

  io::WindowedReader wr(reader);
  wr.setBeg(wr.getCur());

  _file_tags.clear();
  _file_size = reader.getEnd();

  ID3_Reader::pos_type beg  = wr.getBeg();
  ID3_Reader::pos_type cur  = wr.getCur();
  ID3_Reader::pos_type end  = wr.getEnd();

  ID3_Reader::pos_type last = cur;

  if (_tags_to_parse.test(ID3TT_ID3V2))
  {
    do
    {
      last = cur;
      // Parse tags at the beginning of the file first...
      if (id3::v2::parse(*this, wr))
      {
        _file_tags.add(ID3TT_ID3V2);
      }
      cur  = wr.getCur();
      wr.setBeg(cur);
    } while (!wr.atEnd() && cur > last);
  }
  // add silly padding outside the tag to _prepended_bytes
  if (!wr.atEnd() && wr.peekChar() == '\0')
  {
    ID3D_NOTICE( "ID3_TagImpl::ParseReader(): found padding outside tag" );
    do
    {
      last = cur;
      cur = wr.getCur() + 1;
      wr.setBeg(cur);
      wr.setCur(cur);
    } while (!wr.atEnd() &&  cur > last && wr.peekChar() == '\0');
  }
  if (!wr.atEnd() && _file_size - (cur - beg) > 4 && wr.peekChar() == 255)
  { //unfortunatly, this is necessary for finding an invalid padding
    wr.setCur(cur + 1); //cur is known by peekChar
    if (wr.readChar() == '\0' && wr.readChar() == '\0' && wr.peekChar() == '\0')
    { //three empty bytes found, enough for me, this is stupid padding
      cur += 3; //those are now allready read in (excluding the peekChar, since it will be added by do{})
      do
      {
        last = cur;
        cur = wr.getCur() + 1;
        wr.setBeg(cur);
        wr.setCur(cur);
      } while (!wr.atEnd() &&  cur > last && wr.peekChar() == '\0');
    }
    else
      wr.setCur(cur);
  }
  _prepended_bytes = cur - beg;
  // go looking for the first sync byte to add to bytes_till_sync
  // by not adding it to _prepended_bytes, we preserve this 'unknown' data
  // The routine's only effect is helping the lib to find things as bitrate etc.
  beg  = wr.getBeg();
  if (!wr.atEnd() && wr.peekChar() != 0xFF) //no sync byte, so, either this is not followed by a mp3 file or it's a fLaC file, or an encapsulating format, better check it
  {
    ID3D_NOTICE( "ID3_TagImpl::ParseReader(): Didn't find mp3 sync byte" );
    if ((_file_size - (cur - beg)) >= 4)
    { //there is room to search for some kind of ID
      unsigned char buf[5];
      wr.readChars(buf, 4);
      buf[4] = '\0';
      // check for RIFF (an encapsulating format) ID
      if (strncmp((char*)buf, "RIFF", 4) == 0 || strncmp((char*)buf, "RIFX", 4) == 0)
      {
        // next 4 bytes are RIFF size, skip them
        cur = wr.getCur() + 4;
        wr.setCur(cur);
        // loop until first possible sync byte
        if (!wr.atEnd() && wr.peekChar() != 0xFF)
        {
          do
          {
            last = cur;
            cur = wr.getCur() + 1;
            wr.setCur(cur);
          } while (!wr.atEnd() &&  cur > last && wr.peekChar() != 0xFF);
        }
      }
      else if (strncmp((char*)buf, "fLaC", 4) == 0)
      { //a FLAC file, no need looking for a sync byte
        beg = cur;
      }
      else
      { //since we set the cursor 4 bytes ahead for looking for RIFF, RIFX or fLaC, better set it back
        // but peekChar allready checked the first one, so we add one
        cur = cur + 1;
        wr.setCur(cur);
        //go looking for a sync byte
        if (!wr.atEnd() && wr.peekChar() != 0xFF) //no sync byte, we have an unknown byte
        {
          do
          {
            last = cur;
            cur = wr.getCur() + 1;
            wr.setCur(cur);
          } while (!wr.atEnd() &&  cur > last && wr.peekChar() != 0xFF);
        }
      }
    } //if ((_file_size - (cur - beg)) >= 4)
    else
    { //remaining size is smaller than 4 bytes, can't be useful, but leave it for now
      beg = cur;
      //file.close();
      //return;
    }
  }
  bytes_till_sync = cur - beg;

  cur = wr.setCur(end);
  if (_file_size > _prepended_bytes)
  {
    do
    {
      last = cur;
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): beg = " << wr.getBeg() );
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): cur = " << wr.getCur() );
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): end = " << wr.getEnd() );
      // ...then the tags at the end
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): musicmatch? cur = " << wr.getCur() );
      if (_tags_to_parse.test(ID3TT_MUSICMATCH) && mm::parse(*this, wr))
      {
        ID3D_NOTICE( "ID3_TagImpl::ParseReader(): musicmatch! cur = " << wr.getCur() );
        _file_tags.add(ID3TT_MUSICMATCH);
        wr.setEnd(wr.getCur());
      }
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): lyr3v1? cur = " << wr.getCur() );
      if (_tags_to_parse.test(ID3TT_LYRICS3) && lyr3::v1::parse(*this, wr))
      {
        ID3D_NOTICE( "ID3_TagImpl::ParseReader(): lyr3v1! cur = " << wr.getCur() );
        _file_tags.add(ID3TT_LYRICS3);
        wr.setEnd(wr.getCur());
      }
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): lyr3v2? cur = " << wr.getCur() );
      if (_tags_to_parse.test(ID3TT_LYRICS3V2) && lyr3::v2::parse(*this, wr))
      {
        ID3D_NOTICE( "ID3_TagImpl::ParseReader(): lyr3v2! cur = " << wr.getCur() );
        _file_tags.add(ID3TT_LYRICS3V2);
        cur = wr.getCur();
        wr.setCur(wr.getEnd());//set to end to seek id3v1 tag
        //check for id3v1 tag and set End accordingly
        ID3D_NOTICE( "ID3_TagImpl::ParseReader(): id3v1? cur = " << wr.getCur() );
        if (_tags_to_parse.test(ID3TT_ID3V1) && id3::v1::parse(*this, wr))
        {
          ID3D_NOTICE( "ID3_TagImpl::ParseReader(): id3v1! cur = " << wr.getCur() );
          _file_tags.add(ID3TT_ID3V1);
        }
        wr.setCur(cur);
        wr.setEnd(cur);
      }
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): id3v1? cur = " << wr.getCur() );
      if (_tags_to_parse.test(ID3TT_ID3V1) && id3::v1::parse(*this, wr))
      {
        ID3D_NOTICE( "ID3_TagImpl::ParseReader(): id3v1! cur = " << wr.getCur() );
        wr.setEnd(wr.getCur());
        _file_tags.add(ID3TT_ID3V1);
      }
      cur = wr.getCur();
    } while (cur != last);
    _appended_bytes = end - cur;

    // Now get the mp3 header
    mp3_core_size = (_file_size - _appended_bytes) - (_prepended_bytes + bytes_till_sync);
    if (mp3_core_size >= 4)
    { //it has at least the size for a mp3 header (a mp3 header is 4 bytes)
      wr.setBeg(_prepended_bytes + bytes_till_sync);
      wr.setCur(_prepended_bytes + bytes_till_sync);
      wr.setEnd(_file_size - _appended_bytes);

      _mp3_info = new Mp3Info;
      ID3D_NOTICE( "ID3_TagImpl::ParseReader(): mp3header? cur = " << wr.getCur() );

      if (_mp3_info->Parse(wr, mp3_core_size))
      {
        ID3D_NOTICE( "ID3_TagImpl::ParseReader(): mp3header! cur = " << wr.getCur() );
      }
      else
      {
        delete _mp3_info;
        _mp3_info = NULL;
      }
    }
  }
  else
    this->SetPadding(false); //no need to pad an empty file
}