Hi List,
On several occasions I have needed (and build) a parser that reads a
binary piece of data with custom structure. For example (bogus one):
BE
+---------+---------+-------------+-------------+------+--------+
| Version | Command | Instruction | Data Length | Data | Filler |
+---------+---------+-------------+-------------+------+--------+
Version: 6 bits
Command: 4 bits
Instruction: 5 bits
Data Length: 5 bits
Data: 0-31 bits
Filler: filling 0 bits to make the packet dividable by 8
what I usually do is read the packet in binary mode, convert the output
to a concatenated 'binary string'(i.e. '0101011000110') and then use
slice indeces to get the right data portions.
Depending on what I need to do with these portions I convert them to
whatever is handy (usually an integer).
This works out fine for me. Most of the time I also put the ASCII art
diagram of this 'protocol' as a comment in the code, making it more
readable/understandable.
Though there are a couple of things that bothers me with my approach:
- This seems such a general problem that I think that there must be
already a general pythonic solution.
- Using a string for binary representation takes at least 8 times more
memory for the packet than strictly necessary.
- Seems to need a lot of prep work before doing the actual parsing.
Any suggestion is greatly appreciated.
--
MPH
http://blog.dcuktec.com
'If consumed, best digested with added seasoning to own preference.'
--
http://mail.python.org/mailman/listinfo/python-list
