I built a grammar to tackle these sorts of problems when I had trouble writing formal grammar notations for my binary data format. It's even got a syntax highlighter.
So far it's been able to describe 90% of what's out there. Some examples:
- 802.3 layer 2 Ethernet: https://github.com/kstenerud/dogma/blob/master/v1/examples/8...
- Microsoft ICO format: https://github.com/kstenerud/dogma/blob/master/v1/examples/i...
- Android Dex v39: https://github.com/kstenerud/dogma/blob/master/v1/examples/d...
- IPv4: https://github.com/kstenerud/dogma/blob/master/v1/examples/i...
- DNS query: https://github.com/kstenerud/dogma/blob/master/v1/examples/d...
- Microsoft Minidump: https://github.com/kstenerud/dogma/blob/master/v1/examples/m...
- Concise Binary Encoding: https://github.com/kstenerud/concise-encoding/blob/master/cb...
- Concise Text Encoding: https://github.com/kstenerud/concise-encoding/blob/master/ct...