一个CD播放器的例子：

cdplayer.h

#ifndef _CDPLAYER_H_

#define _CDPLAYER_H_

#ifdef __cplusplus

extern "C" {

#endif

typedef enum {

    EV_STOP,

    EV_PLAY_PAUSE

}EventCode;

void initialize();

void OnEvent(EventCode ec);

static void startPlayer();

static void pausePlayer();

static void resumePlayer();

static void stopPlayer();

#ifdef __cplusplus

}

#endif

#endif

 

 

cdplayer.c

#include <stdbool.h>

#include <stdio.h>

#include "cdplayer.h"

bool playflg;

bool pauseflag;

void initialize() {

    playflg = false;

    pauseflag = false;

}

void OnEvent(EventCode ec){

    switch(ec){

        case EV_STOP:

            if(playflg == true || pauseflag == true)

                stopPlayer();

            break;

        case EV_PLAY_PAUSE:

            if(playflg == true)

                pausePlayer();

            else if(pauseflag == true)

                resumePlayer();

            else

                startPlayer();

            break;

        default:

            break;

    }

}

static void startPlayer(){

    playflg = true;

    pauseflag = false;

    //do something to start player   

    printf("start\n");

}

static void pausePlayer(){

    playflg = false;

    pauseflag = true;

    //do something to pause player  

    printf("pause\n"); 

}

static void resumePlayer(){

    playflg = true;

    pauseflag = false;

    //do something to resume player

    printf("resume\n");   

}

static void stopPlayer(){

    playflg = false;

    pauseflag = false;

    //do something to stop player

    printf("stop\n");   

}

 cdplayer_test.c

#include "cdplayer.h" int main(int argc, char const *argv[]{
    initialize();
    OnEvent(EV_PLAY_PAUSE);
    OnEvent(EV_PLAY_PAUSE);
    OnEvent(EV_PLAY_PAUSE);
    OnEvent(EV_STOP);
    return 0;
}  

代码好写，不好阅读（两个状态变量来表现三种状态），不好扩展。