A long time ago, I started working on something similar. There are some binary editors that support writing grammars. I worked on reverse engineering several binary file formats. When working on Quark Express file format, I discovered you do need two layers of grammars, as the file contains a header followed by allocated blocks, where the bocks are linked (by indices) and chains of linked blocks contain streams of data. I remember that there are also file formats, that simply have pointers to certain sections of the data contained in the file. I once implemented a memory mapped file data storage where all pointers to allocated blocks where represented by an offset from the start of the file. (I later, came up with a better idea and that is to make them relative to the location of the pointer, such that you do need to know the offset at which the memory mapped file is placed in memory. So basically, there are lots of 'pointers' in the file and you can only read the data in the file following those pointers.)

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