Re: finite state machine/automaton framework?
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On 03.09.2004, at 19:54, Matthew Dillon wrote:
> :hey,
> :
> :considering that operating systems in general (and dfly in special)
> :have lots of finite state machines in source - most of them hidden as
> :evil if/else constructs of which the authors supposedly never heard
> :about FSM before.
> :Is it a good or bad idea to have a (simple) FSM framework available
> :which can be used by different parts of the operating system? If yes,
> :do such frameworks already exist?
> :
> :Just a thought because of the need to implement a i8254 PIT
> emulation...
> Well, I don't think it's really applicable to what the kernel
> has to do in most cases. For example, emulating an 8254 with an
> FSM
> would basically require emulating the 8254's logic, which would
> take
> megabytes through a generic FSM module, even one designed for logic
> emulation. But it would only a few kilobytes if you 'faked' it in
> C
> (emulated the 8254 at a functional level rather then at a logic
> level).
I was thinking of a system that generates C code out of a formal
description. This way the code wouldn't differ much from the hand
written one, but it would definitely be better to maintain (compare
yacc).
for example:
state_idle:
if:
written_byte & WHATEVER_BITMASK
newstate:
state_program_oneshot
output:
this_var = that_var;
run_foo();
etc
cheers
simon
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