[ragel-users] Best practice: using ragel for bit-based state machines on microcontroller?

[Adrian Thurston]

Sorry, I meant *getkey* directive. Uh oh, I'm getting the keywords of my 
own language wrong. That's embarrassing!

-Adrian

Adrian Thurston wrote:
> Ah, you can process at the bit level. See attached code. You'll probably 
> want to scrutinize the generated and compiled code to see if it's good 
> enough for your needs. One thing to note about using the getchar 
> directive is that the expression can be evaluated more than once per 
> value of p and if the compiler doesn't optimize that duplicate work away 
> then your code won't be optimal.
> 
> By the way, I'm not sure if I just figured this out now, or if somebody 
> told me about this technique a while back and I forgot. (Bob maybe?)
> 
> -Adrian
> 
> Jan Sporbeck wrote:
>> Hello there!
>>
>> I'd like to use ragel to design the state machine for a microcontroller
>> project (avr atmega8535) written in C.
>>
>> I think I understand how to use it for streams of char, int, etc. But
>> what's the best practice to use for bit based decisions?
>>
>> I could use union..struct to pack all bits in one datatype and process
>> that. But I doubt that'll yield a performant implementation.
>>
>> I read messages on this list that ragel is used for uC projects, but no
>> details how.
>>
>> So any hints or example code to get me started is appreciated.
>>
>> Thanks in advance,
>> /Jan.
>>
>>
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> 
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