有限状态机—— FSM(finite-state machine)

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我是靠谱客的博主喜悦飞鸟，最近开发中收集的这篇文章主要介绍有限状态机—— FSM(finite-state machine)，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

//有限状态机 finite-state machine

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#define TTY1 "/dev/tty11"
#define TTY2 "/dev/tty12"
#define BUFSIZE 1024

enum
{
STATE_R=1,
STATE_W,
STATE_Ex,
STATE_T //finil state
};

struct fsa_st
{
int state;
int sfd,dfd;
char buf[BUFSIZE];
int len,pos;
char *errstr;
};

static void fsa_driver(struct fsa_st *fsa)
{
int ret;

switch(fsa->state)
{
  case STATE_R:
   fsa->len = read(fsa->sfd,fsa->buf,BUFSIZE);
   if(fsa->len == 0)
    fsa->state = STATE_T;
   else if(fsa->len < 0)
    {
     if(errno == EAGAIN)
      fsa->state = STATE_R;
     else
     {
      fsa->state = STATE_Ex;
      fsa->errstr = "read()";
     }
    }
    else
    {
     fsa->pos = 0;
     fsa->state = STATE_W;
    }
   break;

  case STATE_W:
   ret = write(fsa->dfd,fsa->buf+fsa->pos,fsa->len);
   if(ret < 0)
   {
    if(errno == EAGAIN)
     fsa->state = STATE_W;
    else
    {
     fsa->errstr = "write()";
     fsa->state = STATE_Ex;
    }

   }
   else
   {
    fsa->pos += ret;
    fsa->len -= ret;
    if(fsa->len == 0)
     fsa->state = STATE_R;
    else
     fsa->state = STATE_W;
   }
   break;

  case STATE_Ex:
   perror(fsa->errstr);
   fsa->state = STATE_T;
   break;

case STATE_T:/*do nothing*/
break;

  default:
   abort();
   break;
}

}

static void relay(int fd1,int fd2)
{
int fd1_save,fd2_save;
struct fsa_st fsa12,fsa21;

fd1_save = fcntl(fd1,F_GETFL);
fcntl(fd1,F_SETFL,fd1_save|O_NONBLOCK);
fd2_save = fcntl(fd2,F_GETFL);
fcntl(fd2,F_SETFL,fd2_save|O_NONBLOCK);

fsa12.state = STATE_R;
fsa12.sfd = fd1;
fsa12.dfd = fd2;

fsa21.state = STATE_R;
fsa21.sfd = fd2;
fsa21.dfd = fd1;

while(fsa12.state != STATE_T || fsa21.state != STATE_T) //cann't is finil state
{
fsa_driver(&fsa12);
fsa_driver(&fsa21);
}
// recover
fcntl(fd1,F_SETFL,fd1_save);
fcntl(fd2,F_SETFL,fd2_save);

}

int main()
{
int fd1,fd2;

fd1 = open(TTY1,O_RDWR);
if(fd1 < 0)
{
perror("open()");
exit(1);
}
write(fd1,"TTY1n",5);

fd2 = open(TTY2,O_RDWR|O_NONBLOCK);
    if(fd2 < 0)
    {
        perror("open()");
        exit(1);
    }
write(fd2,"TTY2n",5);

relay(fd1,fd2);

close(fd1);
close(fd2);

exit(0);
}