hsm.h

用于协议状态机的编程参考

/** hsm.h -- Hierarchical State Machine interface
 * M. Samek, 01/07/00
 */
#ifndef hsm_h
#define hsm_h

typedef int Event;
struct Msg {
  Event evt;
};

class Hsm;                         /* forward declaration */
typedef Msg const *(Hsm::*EvtHndlr)(Msg const *);

class State {
  State *super;                  /* pointer to superstate */
  EvtHndlr hndlr;             /* state's handler function */
  char const *name;
public:
  State(char const *name, State *super, EvtHndlr hndlr);
private:
  Msg const *onEvent(Hsm *ctx, Msg const *msg) {
    return (ctx->*hndlr)(msg);
  }
  friend class Hsm;
};

class Hsm {      /* Hierarchical State Machine base class */
  char const *name;             /* pointer to static name */
  State *curr;                           /* current state */
protected:
  State *next;  /* next state (non 0 if transition taken) */
  State top;                     /* top-most state object */
public:
  Hsm(char const *name, EvtHndlr topHndlr);       /* Ctor */
  void onStart();        /* enter and start the top state */
  void onEvent(Msg const *msg); /* "state machine engine" */
protected:
  unsigned char toLCA_(State *target);
  void exit_(unsigned char toLca);
  State *STATE_CURR() { return curr; }
  void STATE_START(State *target) {
    assert(next == 0);
    next = target;
  }
# define STATE_TRAN(target_) if (1) {\
    static unsigned char toLca_ = 0;\
    assert(next == 0);\
    if (toLca_ == 0)\
      toLca_ = toLCA_(target_);\
    exit_(toLca_);\
    next = (target_);\
  } else ((void)0)
}; 

#define START_EVT ((Event)(-1))
#define ENTRY_EVT ((Event)(-2))
#define EXIT_EVT  ((Event)(-3))

#endif /* hsm_h */