有限状态机在C语言编程中的各种应用

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1. 使用case的有限状态机

//使用switch/case或者if/else实现的基于状态机(FSM)的密码锁//只有正确输入密码 2479 才能解锁 #include <stdio.h>  #include <stdlib.h>  #include <string.h>   typedef enum{   STATE0 = 0,   STATE1,   STATE2,  STATE3,   STATE4,  }STATE;  int main()   {   char ch; STATE current_state = STATE0;    while(1){   printf("In put password:");   while((ch = getchar()) != '\n'){   if((ch < '0') || (ch > '9')){   printf("Input num,ok?/n");   break;   }   switch(current_state){   case STATE0:   if(ch == '2')   current_state = STATE1;   break;   case STATE1:   if(ch == '4')   current_state = STATE2;   break;   case STATE2:   if(ch == '7')   current_state = STATE3;   break;   case STATE3:   if(ch == '9')   current_state = STATE4;   break;   default:   current_state = STATE0;   break;   }   }   //end inner while if(current_state == STATE4){   printf("Correct, lock is open!\n");   current_state =   STATE0;}else{printf("Wrong, locked!\n");   current_state =   STATE0;}break;}   return 0;   } //代码摘自http://blog.csdn.net/qp120291570/article/details/8634582

2. 使用函数指针的有限状态机的应用

//使用函数指针实现的基于状态机(FSM)的密码锁//只有正确输入密码 2479 才能解锁 #include <stdio.h>  //这个秘密锁的密码是xxxx2479,就是说最后4位是2479,前面若干为为0~9里的数字,也可没有 #include <stdlib.h>  #include <string.h>   //定义锁事件处理函数的函数指针类型typedef void (*lock_func_temp)(char c);typedef lock_func_temp (*lock_func)(char c);lock_func state;//函数声明队列 //列出来,交叉引用才不会报错 lock_func init_state(char ch);lock_func state1(char ch);lock_func state2(char ch);lock_func state3(char ch);lock_func state4(char ch);//初始状态 lock_func init_state(char ch){    if ((ch < '0') || (ch > '9'))        return NULL;    else    return state1(ch); //这里还必须得有参数,不然就会漏处理一个字符 }//状态1 lock_func state1(char ch){if (ch == '2'){return state2;} else {return init_state;}}//状态2 lock_func state2(char ch){if (ch == '4'){return state3;} else {return init_state;}}//状态3 lock_func state3(char ch){if (ch == '7'){return state4;} else {return init_state;}}//状态4 lock_func state4(char ch){if (ch == '9'){printf("Correct, lock is open!\n"); return NULL;} else {return init_state;}}//结束状态是NULL//就是通过 return NULL;表达的结束状态.  //状态转换在这里 void lock_handle (void){char ch;state = init_state;while (state){ch = getchar();state = (*state)(ch);}}  int main()   {     lock_handle();}

3.基于状态矩阵的FSM应用

参考:http://www.cookiebear.info/archives/557