本文的目的是基于C语言实现简单高效的状态机。例子是倒计时bomb。Bomb有两种状态，一种是设置状态，一种是倒计时。一旦开始计时，要想回到设置状态必须要调整code的值等于bomb预设的密码值，否则无法进行状态转换。倒计时到0就BOMB了啦。基于这个例子来实现状态机。状态机实现框架包括以下几个部分：
1. 状态
enum BombStates {
SETTING_STATE,//设置
TIMING_STATE//倒计时
};
2. 触发状态转换的信号事件，用键盘模拟
enum BombSignals {
UP_SIG, //按u
DOWN_SIG,//按d
ARM_SIG,//按a，状态转换键
TICK_SIG//0.1秒发出一个倒计时事件
};
3. 信号事件的数据结构
typedef struct EventTag {
uint16_t sig; // BombSignals的赋值
/* 可以添加其他属性到这里 */
} Event;
此外，还要定义信号事件附带的参数：
typedef struct TickEvtTag {
Event super; //继承Event
uint8_t fine_time; //毫秒值，为0时代表倒计1秒
} TickEvt;
4. 状态全局变量
typedef struct Bomb1Tag {
uint8_t state; // BombStates状态赋值
uint8_t timeout; //当前倒计时间，为0游戏结束
uint8_t code; //用于调整数值，等于defuse密码才能转换状态
uint8_t defuse; //解除bomb的密码，需要预设
} Bomb1;
5. 状态初始化
#define INIT_TIMEOUT 10
#define TRAN(target_) (me->state = (uint8_t)(target_))
void Bomb1_ctor(Bomb1 *me, uint8_t defuse){
me->defuse = defuse;
}
void Bomb1_init(Bomb1 *me) {
me->timeout = INIT_TIMEOUT;
TRAN(SETTING_STATE);
}
6. 状态转换
void Bomb1_dispatch(Bomb1 *me, Event const*e) {
switch (me->state) {
case SETTING_STATE: {
switch (e->sig) {
case UP_SIG: {
if (me->timeout < 60){
++me->timeout;
BSP_display(me->timeout);
}
break;
}
case DOWN_SIG: {
if (me->timeout > 1){
--me->timeout;
BSP_display(me->timeout);
}
break;
}
case ARM_SIG: {
me->code = 0;
TRAN(TIMING_STATE); /* transition to "timing"*/
break;
}
}
break;
}
case TIMING_STATE: {
switch (e->sig) {
case UP_SIG: {
me->code <<= 1;
me->code |= 1;
BSP_display(me->code);
break;
}
case DOWN_SIG: {
me->code <<= 1;
BSP_display(me->code);
break;
}
case ARM_SIG: {
if (me->code ==me->defuse) {
TRAN(SETTING_STATE); /*transition to "setting" */
}
break;
}
case TICK_SIG: {
if (((TickEvt const*)e)->fine_time == 0) {
--me->timeout;
BSP_display(me->timeout);
if (me->timeout ==0) {
BSP_boom(); /* destroy the bomb */
}
}
break;
}
}
break;
}
}
}
7. 测试代码，用VC6.0
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <dos.h>
#include<windows.h>
static Bomb1 l_bomb; /* time bomb FSM*/
void main() {
Bomb1_ctor(&l_bomb, 0x0D); /* the secret defuse code, 1101 binary */
printf("Time Bomb (Nested switch)\n"
"Press 'u' for UP event\n"
"Press 'd' for DOWNevent\n"
"Press 'a' for ARM event\n"
"Press <Esc> to quit.\n");
Bomb1_init(&l_bomb); /* take the initialtransition */
for (;;) { /* event loop */
static TickEvt tick_evt = { TICK_SIG, 0};
Sleep(100); /* 100ms delay */
if (++tick_evt.fine_time == 10) {
tick_evt.fine_time = 0;
}
printf("T(%1d)%c", tick_evt.fine_time,
(tick_evt.fine_time == 0)? '\n' : ' ');
Bomb1_dispatch(&l_bomb, (Event *)&tick_evt); /* dispatch tickevent */
if (kbhit()) {
static Event const up_evt = {UP_SIG };
static Event const down_evt = { DOWN_SIG };
static Event const arm_evt = {ARM_SIG };
Event const *e = (Event *)0;
switch (getch()) {
case 'u': { /* UP event*/
printf("\nUP : ");
e = &up_evt; /* generate the UP event */
break;
}
case 'd': { /* DOWNevent */
printf("\nDOWN: ");
e = &down_evt; /* generate the DOWN event */
break;
}
case 'a': { /* ARMevent */
printf("\nARM : ");
e = &arm_evt; /* generate the ARM event */
break;
}
case '\33': { /*<Esc> key */
printf("\nESC : Bye!Bye!");
exit(0);
break;
}
}
if (e != (Event *)0) { /* keyboard event available? */
Bomb1_dispatch(&l_bomb,e); /* dispatch the event */
}
}
}
}
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