C语言与设计模式 之 二

cdplayer.h

#ifndef _CDPLAYER_H_
#define _CDPLAYER_H_

#ifdef __cplusplus
extern "C" {
#endif

typedef enum {
    EV_STOP,
    EV_PLAY_PAUSE
}EventCode;

typedef enum {
    ST_IDLE,
    ST_PLAY,
    ST_PAUSE
}State;

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 <stdio.h>
#include "cdplayer.h"

State state;

void initialize() {
    state = ST_IDLE;
}

void OnEvent(EventCode ec){
    switch(ec){
        case EV_STOP:
            if(state == ST_PLAY || state == ST_PAUSE)
                stopPlayer();
            break;
        case EV_PLAY_PAUSE:
            if(state == ST_PLAY)
                pausePlayer();
            else if(state == ST_PAUSE)
                resumePlayer();
            else
                startPlayer();
            break;
        default:
            break;
    }
}

static void startPlayer(){
    state = ST_PLAY;
    //do something to start player   
    printf("start\n");
}

static void pausePlayer(){
    state = ST_PAUSE;
    //do something to pause player  
    printf("pause\n"); 
}

static void resumePlayer(){
    state = ST_PLAY;
    //do something to resume player
    printf("resume\n");   
}

static void stopPlayer(){
    state = ST_IDLE;
    //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;
}

 

相比一，代码意图更清晰了。