软件定时器这个程序谁能给我讲一下如何实现的

fanhuayishi · 发表于 2018-8-15 09:51:57

软件定时器这个程序谁能给我讲一下如何实现的，用的是链表指针，实现了一个定时器转多路定时器的功能，但是代码看不太懂，有没有大神给解析一下。这是.c文件

[mw_shl_code=c,true]
#include "multi_timer.h"

//timer handle list head.
static struct Timer* head_handle = NULL;

//Timer ticks
static uint32_t _timer_ticks = 0;

/**
  * @brief  Initializes the timer struct handle.
  * @param  handle: the timer handle strcut.
  * @param  timeout_cb: timeout callback.
  * @param  repeat: repeat interval time.
  * @retval None
  */
void timer_init(struct Timer* handle, void(*timeout_cb)(), uint32_t timeout, uint32_t repeat)
{
// memset(handle, sizeof(struct Timer), 0);
handle->timeout_cb = timeout_cb;
handle->timeout = _timer_ticks + timeout;
handle->repeat = repeat;
}

/**
  * @brief  Start the timer work, add the handle into work list.
  * @param  btn: target handle strcut.
  * @retval 0: succeed. -1: already exist.
  */
int timer_start(struct Timer* handle)
{
struct Timer* target = head_handle;//这里是把头，也就是刚才的那个数，赋值给这里新定义的目标。
while(target) {
if(target == handle) return -1; //already exist.
target = target->next;
}
handle->next = head_handle;
head_handle = handle;
return 0;
}
//
/**
  * @brief  Stop the timer work, remove the handle off work list.
  * @param  handle: target handle strcut.
  * @retval None
  */
void timer_stop(struct Timer* handle)
{
struct Timer** curr;
for(curr = &head_handle; *curr; ) {
struct Timer* entry = *curr;
if (entry == handle) {
*curr = entry->next;
// free(entry);
} else
curr = &entry->next;
}
}

/**
  * @brief  main loop.
  * @param  None.
  * @retval None
  */
void timer_loop()
{
struct Timer* target;
for(target=head_handle; target; target=target->next) {
if(_timer_ticks >= target->timeout) {
if(target->repeat == 0) {
timer_stop(target);
} else {
target->timeout = _timer_ticks + target->repeat;
}
target->timeout_cb();
}
}
}

/**
  * @brief  background ticks, timer repeat invoking interval 1ms.
  * @param  None.
  * @retval None.
  */
void timer_ticks()
{
_timer_ticks++;
}

[/mw_shl_code]

这是.h文件
[mw_shl_code=c,true]/*
* Copyright (c) 2016 Zibin Zheng <znbin@qq.com>
* All rights reserved
*/

#ifndef _MULTI_TIMER_H_
#define _MULTI_TIMER_H_

#include "stdint.h"

typedef struct Timer {
uint32_t timeout;
uint32_t repeat;
void (*timeout_cb)(void);
struct Timer* next;
}Timer;

#ifdef __cplusplus
extern "C" {
#endif

void timer_init(struct Timer* handle, void(*timeout_cb)(), uint32_t timeout, uint32_t repeat);
int  timer_start(struct Timer* handle);
void timer_stop(struct Timer* handle);
void timer_ticks(void);
void timer_loop(void);

#ifdef __cplusplus
}
#endif

#endif
[/mw_shl_code]

然后主函数

[mw_shl_code=applescript,true]#include "multi_timer.h"

struct Timer timer1;
struct Timer timer2;

void timer1_callback()
{
printf("timer1 timeout!\r\n");
}

void timer2_callback()
{
printf("timer2 timeout!\r\n");
}

int main()
{
timer_init(&timer1, timer1_callback, 1000, 1000); //1s loop
timer_start(&timer1);

timer_init(&timer2, timer2_callback, 50, 0); //50ms delay
timer_start(&timer2);

while(1) {

      timer_loop();
}
}

void HAL_SYSTICK_Callback(void)
{
timer_ticks(); //1ms ticks
}[/mw_shl_code]