原创 国嵌mp3播放器应用程序

*************************************************
Function name: main
Parameter    : void
Description  : 主函数
Return   : int
Argument     : void
Autor & date : ada 09.12.07
**************************************************/
int main(void)
{
 int buttons_fd;
 int key_value;
 struct song *head;
 /*打开设备文件*/
 buttons_fd = open("/dev/buttons", 0);

 if (buttons_fd < 0)
 {
  perror("open device buttons");
  exit(1);
 }

  /*创建播放列表*/
 head = creat_song_list();
 printf("===================================OPTION=======================================\n\n\n\n");
 printf("        K1:START/PAUSE     K2:STOP   K3:NEXT      K4:PRIOR\n\n\n\n");
 printf("================================================================================\n");

   /*共享内存：用于存放子进程ID，播放列表位置*/
   //5表示5页，1页地址空间表示4096字节(4KByte),5页也就是20KByte
 if((shmid = shmget(IPC_PRIVATE,5,PERM))== -1)
  exit(1);
 
 //void *shmat(int shmid, const void *shmaddr, int shm***)
 //添加共享内存映射到自己进程地址空间，用于操作使用
 p_addr = shmat(shmid,0,0);
 
 //void *memset(void *s, int c, size_t n);
 memset(p_addr,'\0',1024);

 while(1)
 {
  fd_set rds;
  int ret;

  FD_ZERO(&rds);
  FD_SET(buttons_fd, &rds);

  /*监听获取键值*/
  ret = select(buttons_fd + 1, &rds, NULL, NULL, NULL);
  if (ret < 0)
  {
   perror("select");
   exit(1);
  }
  if (ret == 0)
   printf("Timeout.\n");
  else if (FD_ISSET(buttons_fd, &rds))
  {
   int ret = read(buttons_fd, &key_value, sizeof key_value);
   if (ret != sizeof key_value)
   {
    if (errno != EAGAIN)
     perror("read buttons\n");
    continue;
   }
   else
   {
    printf("buttons_value: %d\n", key_value+1);

    
    /*首次播放，必须是按键1*/
    if(first_key)
    {
     switch(key_value)
     { 
      case 0:
       startplay(&pid,head);
       first_key=0;
       break;
      case 1:
      case 2:
      case 3:
       printf("=======================PRESS K1 TO START PLAY===================\n");
       break;
         default:
       printf("=======================PRESS K1 TO START PLAY===================\n");
       break;
     } //end switch
    }//end if(first_key)
    /*若不是首次播放，则根据不同键值处理*/
    else if(!first_key)
    {
        switch(key_value)
     {
      case 0:
       //printf("play_flag:%d\n",play_flag);
       if(play_flag)
        my_pause(gradchild);
       else
        conti_play(gradchild);
       break;
      case 1:
       my_stop(gradchild);
       break;
      case 2:
       next(gradchild);
       break;
      case 3:
       prev(gradchild);
       break;
     } //end switch
     }//end if(!first_key)

   }
    
  }
 }

 close(buttons_fd);
 
 return 0;
}