Patent attributes
Methods and apparatus, including computer programs, implementing a technique for creating and using marked foreign data blocks. In general, in one aspect, the technique includes receiving a host data file and a foreign data block. The host data file has a host data file format that is a native file format for a host application. The foreign data block is not native to the host data file format. The technique includes determining characteristics of the foreign data block and generating information describing the characteristics of the foreign data block, including information marking the beginning and end of the foreign data block and further including an identifier designed to be distinguishable from all other data in the host data file. The technique includes embedding the information and the foreign data block as a foreign data block packet in the host data file.