20191001（12）RT-Thread 时钟管理 源码解读（1）创建部分

目的

1. 了解创建和初始化源码

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正文

根据阅读线程源码的经验，我直接开始阅读最核心的函数 _rt_timer_init()

/**
 * timer structure
 */
struct rt_timer
{
    struct rt_object parent;                            /**< inherit from rt_object */

    rt_list_t        row[RT_TIMER_SKIP_LIST_LEVEL];

    void (*timeout_func)(void *parameter);              /**< timeout function */
    void            *parameter;                         /**< timeout function's parameter */

    rt_tick_t        init_tick;                         /**< timer timeout tick */
    rt_tick_t        timeout_tick;                      /**< timeout tick */
};
typedef struct rt_timer *rt_timer_t;

static void _rt_timer_init(rt_timer_t timer, //静态定时器对象句柄 
                           void (*timeout)(void *parameter), //超时回调函数
                           void      *parameter,//传入参数
                           rt_tick_t  time,//超时时间
                           rt_uint8_t flag)//定时器创建时的参数，支持的值包括单次定时、周期定时、 硬件定时器、软件定时器（可以用 “或” 关系取多个值）
{
    int i;

    /* set flag */
    timer->parent.flag  = flag;

    /* set deactivated */
    timer->parent.flag &= ~RT_TIMER_FLAG_ACTIVATED;

    timer->timeout_func = timeout;
    timer->parameter    = parameter;

    timer->timeout_tick = 0;
    timer->init_tick    = time;

    /* initialize timer list */
    for (i = 0; i < RT_TIMER_SKIP_LIST_LEVEL; i++)
    {
        rt_list_init(&(timer->row[i])); //见
    }
}

/**
 * @brief initialize a list
 *
 * @param l list to be initialized
 */
rt_inline void rt_list_init(rt_list_t *l)
{
    l->next = l->prev = l;
}

总体看来这部内容就是对于 rt_timer 数据结构进行赋值操作，总体操作与线程部分一致不做细致讲解

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初始化函数和创建函数

//function: rt_timer_create() 
/**
 * This function will create a timer
 *
 * @param name the name of timer
 * @param timeout the timeout function
 * @param parameter the parameter of timeout function
 * @param time the tick of timer
 * @param flag the flag of timer
 *
 * @return the created timer object
 */
rt_timer_t rt_timer_create(const char *name, //定时器名字
                           void (*timeout)(void *parameter),
                           void       *parameter,
                           rt_tick_t   time,
                           rt_uint8_t  flag)
{
    struct rt_timer *timer;

    /* allocate a object */
    //由系统分配一个定时器对象
    timer = (struct rt_timer *)rt_object_allocate(RT_Object_Class_Timer, name);
    if (timer == RT_NULL)
    {
        return RT_NULL;
    }

    _rt_timer_init(timer, timeout, parameter, time, flag);

    return timer;
}

//rt_timer_init()
/**
 * This function will initialize a timer, normally this function is used to
 * initialize a static timer object.
 *
 * @param timer the static timer object
 * @param name the name of timer
 * @param timeout the timeout function
 * @param parameter the parameter of timeout function
 * @param time the tick of timer
 * @param flag the flag of timer
 */
void rt_timer_init(rt_timer_t  timer, //定时器对象的句柄（指针）
                   const char *name,
                   void (*timeout)(void *parameter),
                   void       *parameter,
                   rt_tick_t   time,
                   rt_uint8_t  flag)
{
    /* timer check */
    RT_ASSERT(timer != RT_NULL);

    /* timer object initialization */
    rt_object_init((rt_object_t)timer, RT_Object_Class_Timer, name);

    _rt_timer_init(timer, timeout, parameter, time, flag);
}