程序架構(gòu)重要性

很多人尤其是初學(xué)者在寫代碼的時候往往都是想一點寫一點，最開始沒有一個整體的規(guī)劃，導(dǎo)致后面代碼越寫越亂，bug不斷。 最終代碼跑起來看似沒有問題(有可能也真的沒有問題)，但是要加一個功能的時候會浪費大量的時間，甚至導(dǎo)致整個代碼的崩潰。 所以，在一個項目開始的時候多花一些時間在代碼的架構(gòu)設(shè)計上是十分有必要的。代碼架構(gòu)確定好了之后你會發(fā)現(xiàn)敲代碼的時候會特別快，并且在后期調(diào)試的時候也不會像無頭蒼蠅一樣胡亂找問題。當(dāng)然，調(diào)試也是一門技術(shù)。 在學(xué)習(xí)實時操作系統(tǒng)的過程中，發(fā)現(xiàn)實時操作系統(tǒng)框架與個人的業(yè)務(wù)代碼之間的耦合性就非常低，都是只需要將業(yè)務(wù)代碼通過一定的接口函數(shù)注冊好后就交給操作系統(tǒng)托管了，十分方便。 但是操作系統(tǒng)的調(diào)度過于復(fù)雜，這里就使用操作系統(tǒng)的思維方式來重構(gòu)這個時間片輪詢框架。實現(xiàn)該框架的完全解耦，用戶只需要包含頭文件，并且在使用過程中不需要改動已經(jīng)寫好的庫文件。

Demo

首先來個demo，該demo是使用電腦開兩個線程：一個線程模擬單片機的定時器中斷產(chǎn)生時間片輪詢個時鐘，另一個線程則模擬主函數(shù)中一直運行的時間片輪詢調(diào)度程序。

#include 
#include 
#include 
#include "timeslice.h"


// 創(chuàng)建5個任務(wù)對象
TimesilceTaskObj task_1, task_2, task_3, task_4, task_5;


// 具體的任務(wù)函數(shù)
void task1_hdl()
{
    printf(">> task 1 is running ...
");
}


void task2_hdl()
{
    printf(">> task 2 is running ...
");
}


void task3_hdl()
{
    printf(">> task 3 is running ...
");
}


void task4_hdl()
{
    printf(">> task 4 is running ...
");
}


void task5_hdl()
{
    printf(">> task 5 is running ...
");
}


// 初始化任務(wù)對象，并且將任務(wù)添加到時間片輪詢調(diào)度中
void task_init()
{
    timeslice_task_init(&task_1, task1_hdl, 1, 10);
    timeslice_task_init(&task_2, task2_hdl, 2, 20);
    timeslice_task_init(&task_3, task3_hdl, 3, 30);
    timeslice_task_init(&task_4, task4_hdl, 4, 40);
    timeslice_task_init(&task_5, task5_hdl, 5, 50);
    timeslice_task_add(&task_1);
    timeslice_task_add(&task_2);
    timeslice_task_add(&task_3);
    timeslice_task_add(&task_4);
    timeslice_task_add(&task_5);
}




// 開兩個線程模擬在單片機上的運行過程
void timeslice_exec_thread()
{
    while (true)
    {
        timeslice_exec();
    }
}


void timeslice_tick_thread()
{
    while (true)
    {
        timeslice_tick();
        Sleep(10);
    }
}


int main()
{
    task_init();


    printf(">> task num: %d
", timeslice_get_task_num());
    printf(">> task len: %d
", timeslice_get_task_timeslice_len(&task_3));


    timeslice_task_del(&task_2);
    printf(">> delet task 2
");
    printf(">> task 2 is exist: %d
", timeslice_task_isexist(&task_2));


    printf(">> task num: %d
", timeslice_get_task_num());


    timeslice_task_del(&task_5);
    printf(">> delet task 5
");


    printf(">> task num: %d
", timeslice_get_task_num());


    printf(">> task 3 is exist: %d
", timeslice_task_isexist(&task_3));
    timeslice_task_add(&task_2);
    printf(">> add task 2
");
    printf(">> task 2 is exist: %d
", timeslice_task_isexist(&task_2));


    timeslice_task_add(&task_5);
    printf(">> add task 5
");


    printf(">> task num: %d
", timeslice_get_task_num());


    printf("

========timeslice running===========
");


    std::thread thread_1(timeslice_exec_thread);
    std::thread thread_2(timeslice_tick_thread);


    thread_1.join();
    thread_2.join();




    return 0;
}

時間片輪詢架構(gòu)

其實該部分主要使用了面向?qū)ο蟮乃季S，使用結(jié)構(gòu)體作為對象，并使用結(jié)構(gòu)體指針作為參數(shù)傳遞，這樣作可以節(jié)省資源，并且有著極高的運行效率。 其中最難的部分是侵入式鏈表的使用，這種鏈表在一些操作系統(tǒng)內(nèi)核中使用十分廣泛，這里是參考RT-Thread實時操作系統(tǒng)中的侵入式鏈表實現(xiàn)。 h文件：

#ifndef _TIMESLICE_H
#define _TIMESLICE_H


#include "./list.h"


typedef enum {
    TASK_STOP,
    TASK_RUN
} IsTaskRun;


typedef struct timesilce
{
    unsigned int id;
    void (*task_hdl)(void);
    IsTaskRun is_run;
    unsigned int timer;
    unsigned int timeslice_len;
    ListObj timeslice_task_list;
} TimesilceTaskObj;


void timeslice_exec(void);
void timeslice_tick(void);
void timeslice_task_init(TimesilceTaskObj* obj, void (*task_hdl)(void), unsigned int id, unsigned int timeslice_len);
void timeslice_task_add(TimesilceTaskObj* obj);
void timeslice_task_del(TimesilceTaskObj* obj);
unsigned int timeslice_get_task_timeslice_len(TimesilceTaskObj* obj);
unsigned int timeslice_get_task_num(void);
unsigned char timeslice_task_isexist(TimesilceTaskObj* obj);


#endif

#include "./timeslice.h"


static LIST_HEAD(timeslice_task_list);


void timeslice_exec()
{
    ListObj* node;
    TimesilceTaskObj* task;


    list_for_each(node, ×lice_task_list)
    {
           
        task = list_entry(node, TimesilceTaskObj, timeslice_task_list);
        if (task->is_run == TASK_RUN)
        {
            task->task_hdl();
            task->is_run = TASK_STOP;
        }
    }
}


void timeslice_tick()
{
    ListObj* node;
    TimesilceTaskObj* task;


    list_for_each(node, ×lice_task_list)
    {
        task = list_entry(node, TimesilceTaskObj, timeslice_task_list);
        if (task->timer != 0)
        {
            task->timer--;
            if (task->timer == 0)
            {
                task->is_run = TASK_RUN;
                task->timer = task->timeslice_len;
            }
        }
    }
}


unsigned int timeslice_get_task_num()
{
    return list_len(×lice_task_list);
}


void timeslice_task_init(TimesilceTaskObj* obj, void (*task_hdl)(void), unsigned int id, unsigned int timeslice_len)
{
    obj->id = id;
    obj->is_run = TASK_STOP;
    obj->task_hdl = task_hdl;
    obj->timer = timeslice_len;
    obj->timeslice_len = timeslice_len;
}


void timeslice_task_add(TimesilceTaskObj* obj)
{
    list_insert_before(×lice_task_list, &obj->timeslice_task_list);
}


void timeslice_task_del(TimesilceTaskObj* obj)
{
    if (timeslice_task_isexist(obj))
        list_remove(&obj->timeslice_task_list);
    else
        return;
}




unsigned char timeslice_task_isexist(TimesilceTaskObj* obj)
{
    unsigned char isexist = 0;
    ListObj* node;
    TimesilceTaskObj* task;


    list_for_each(node, ×lice_task_list)
    {
        task = list_entry(node, TimesilceTaskObj, timeslice_task_list);
        if (obj->id == task->id)
            isexist = 1;
    }


    return isexist;
}


unsigned int timeslice_get_task_timeslice_len(TimesilceTaskObj* obj)
{
    return obj->timeslice_len;
}

底層侵入式雙向鏈表

該鏈表是linux內(nèi)核中使用十分廣泛，也十分經(jīng)典，其原理具體可以參考文章： https://www.cnblogs.com/skywang12345/p/3562146.html h文件：

#ifndef _LIST_H
#define _LIST_H


#define offset_of(type, member)             (unsigned long) &((type*)0)->member
#define container_of(ptr, type, member)     ((type *)((char *)(ptr) - offset_of(type, member)))


typedef struct list_structure
{
    struct list_structure* next;
    struct list_structure* prev;
} ListObj;


#define LIST_HEAD_INIT(name)    {&(name), &(name)}
#define LIST_HEAD(name)         ListObj name = LIST_HEAD_INIT(name)


void list_init(ListObj* list);
void list_insert_after(ListObj* list, ListObj* node);
void list_insert_before(ListObj* list, ListObj* node);
void list_remove(ListObj* node);
int list_isempty(const ListObj* list);
unsigned int list_len(const ListObj* list);


#define list_entry(node, type, member) 
    container_of(node, type, member)


#define list_for_each(pos, head) 
    for (pos = (head)->next; pos != (head); pos = pos->next)


#define list_for_each_safe(pos, n, head) 
  for (pos = (head)->next, n = pos->next; pos != (head); 
    pos = n, n = pos->next)


#endif

#include "list.h"


void list_init(ListObj* list)
{
    list->next = list->prev = list;
}


void list_insert_after(ListObj* list, ListObj* node)
{
    list->next->prev = node;
    node->next = list->next;


    list->next = node;
    node->prev = list;
}


void list_insert_before(ListObj* list, ListObj* node)
{
    list->prev->next = node;
    node->prev = list->prev;


    list->prev = node;
    node->next = list;
}


void list_remove(ListObj* node)
{
    node->next->prev = node->prev;
    node->prev->next = node->next;


    node->next = node->prev = node;
}


int list_isempty(const ListObj* list)
{
    return list->next == list;
}


unsigned int list_len(const ListObj* list)
{
    unsigned int len = 0;
    const ListObj* p = list;
    while (p->next != list)
    {
        p = p->next;
        len++;
    }


    return len;
}

審核編輯：黃飛