A very small (<~200 NLOC), generic FSM implementation in C++.
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README.md

microfsm

A very small (<~200 nloc), generic FSM implementation in C++

microFSM

Requirements

  • A C++11 compiler.
  • Maybe meson, for building tests, etc.

Features

  • Any (less-than comparable) type as a state type.
  • Any callable as a transition function.
  • Enforces valid end states at run-time.
  • The FSM design is non-deterministic.

Usage


enum state { START, MIDDLE, END };

// Create an instance specifying:
// - potential argument types for the progress and transition
//   functions
// - a start state
// - one or more end states
microfsm<state, arg_type1, ...> fsm{ START, { END }};

// Add transition functions:
// - from a start state
// - with possible end states
fsm.add_transition(START,
    [](state, arg_type1) -> state {
      // Depending on argument, return MIDDLE or END
    },
    { MIDDLE, END }
);

// Progress from the current state, passing any specified
// arguments.
arg_type1 arg1;
fsm.progress(arg1, ...);

// Read the FSM state or meta state:
auto res = fsm.meta_state(); // one of RUNNING, ENDED, ERRORED
auto s = fsm.current_state(); // one of START, MIDDLE, END
auto e = fsm.error(); // if res == ERRORED

Logging (v0.2.5+)

If you want to know what the FSM does, and especially for logging exceptions that might occur in transition functions, add a log function. Log functions take a message string.

fsm.set_log_function([](std::string const & msg) -> void
    {
      std::cerr << msg << std::endl;
    });

License

Licensed under MIT +no-false-attribs License