Subj : Re: implementation of finite state machine
To   : comp.programming
From : Thad Smith
Date : Thu Oct 06 2005 12:03 pm

pete wrote:
> 
> Roman Mashak wrote:
> >
> > Hello, Dave!
> > You wrote  on Thu, 06 Oct 2005 10:11:59 +0100:
> >
> >  ??>> Could you please point me to some resource, describing sample
> >  ??>> implementation of FSM in C language, just to better catch
> >  ??>> idea. TIA. With best regards, Roman Mashak.  E-mail: mrv@tusur.ru
> >
> > >What approaches have you tried so far?
> >
> > Due to my understandanding of FSM,
> > I used 'if-elseif-else' chain. Might me
> > there are other ways and more efficient methods?
> 
> Use an array of function pointers.
> The index into the array, is the state.
> The state is updated either as the return value of the function call
> or the address of the state object can be passed as an argument.

Another common technique is a switch statement, with a case for each
state.  The case logic evaluates input criteria to determine when to
change state.

Another technique is table driven, based on small number of input
variables.  Index into the array based on input values to choose the
next state.

In both techniques you can use either a particular transition or
particular state to choose an action routine (or block of code) to
perform based on either the transition or the current state.

Thad

.