[bitwize]

kentonv introduced the term 'parsing' into the discussion, not me. Originally I wasn't talking about parsing as such, just being explicit about the byte-offset, length, and ordering of any piece of data you fetch or store by doing (ptr[n] << 24) | (ptr[n+1] << 16) | (ptr[n+2] << 8) | ptr[n+3], or the corresponding write operation, if you're working with a chunk of data that came from, or is destined for, a file or the network. And if for whatever reason you want or need to work with structs, don't try to alias them onto the disk or network-bound bits. FSMs don't even come into it. It's just a matter of being a little more careful than mmap()ing into a C struct and hoping for the best.