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来源于网络，侵删
C 语言面向对象编程的最佳实践
一、前言
以STM32为例，打开网络上下载的例程或者是购买开发板自带的例程，都会发现应用层中会有stm32f10x.h或者stm32f10x_gpio.h，这些文件严格来时属于硬件层的，如果软件层出现这些文件会显得很乱。
使用过Linux的童鞋们肯定知道linux系统无法直接操作硬件层，打开linux或者rt_thread代码会发现代码中都会有device的源文件，没错，这就是驱动层。
二、实现原理
原理就是将硬件操作的接口全都放到驱动链表上，在驱动层实现device的open、read、write等操作。当然这样做也有弊端，就是驱动find的时候需要遍历一遍驱动链表，这样会增加代码运行时间。
三、代码实现
国际惯例，写代码先写头文件。rt_thread中使用的是双向链表，为了简单在这我只用单向链表。有兴趣的可以自行研究rt_thread
头文件接口:
本次只实现如下接口，device_open 和device_close等剩下的接口可以自行研究。这样就可以在应用层中只调用如下接口可实现：
/*
驱动注册
*/
int cola_device_register(cola_device_t *dev);/*
驱动查找
*/
cola_device_t *cola_device_find(const char *name);/*
驱动读
*/
int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size);/*
驱动写
*/
int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size);/*
驱动控制
*/
int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg);;头文件cola_device.h：
#ifndef _COLA_DEVICE_H_
#define _COLA_DEVICE_H_enum LED_state
{LED_OFF,LED_ON,LED_TOGGLE,
};typedef struct cola_device cola_device_t;
struct cola_device_ops
{
int (*init) (cola_device_t *dev);
int (*open) (cola_device_t *dev, int oflag);
int (*close) (cola_device_t *dev);
int (*read) (cola_device_t *dev, int pos, void *buffer, int size);
int (*write) (cola_device_t *dev, int pos, const void *buffer, int size);
int (*control)(cola_device_t *dev, int cmd, void *args);
};struct cola_device
{
const char * name;
struct cola_device_ops *dops;
struct cola_device *next;
};/*
驱动注册
*/
int cola_device_register(cola_device_t *dev);/*
驱动查找
*/
cola_device_t *cola_device_find(const char *name);/*
驱动读
*/
int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size);/*
驱动写
*/
int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size);/*
驱动控制
*/
int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg);#endif源文件cola_device.c：
#include "cola_device.h"
#include <string.h>
#include <stdbool.h>struct cola_device *device_list = NULL;/*
查找任务是否存在
*/
static bool cola_device_is_exists( cola_device_t *dev )
{
cola_device_t* cur = device_list;
while( cur != NULL ){
if( strcmp(cur->name,dev->name)==0){ return true;} cur = cur->next; } return false;
}static int device_list_inster(cola_device_t *dev)
{
cola_device_t *cur = device_list;if(NULL == device_list){device_list = dev;dev->next = NULL;}
else{
while(NULL != cur->next){cur = cur->next;}cur->next = dev;dev->next = NULL;}
return 1;
}/*
驱动注册
*/
int cola_device_register(cola_device_t *dev)
{
if((NULL == dev) || (cola_device_is_exists(dev))){
return 0;}
if((NULL == dev->name) || (NULL == dev->dops)){
return 0;}
return device_list_inster(dev);
}/*
驱动查找
*/
cola_device_t *cola_device_find(const char *name)
{
cola_device_t* cur = device_list;
while( cur != NULL ){
if( strcmp(cur->name,name)==0){
return cur;}cur = cur->next;}
return NULL;
}/*
驱动读
*/
int cola_device_read(cola_device_t *dev, int pos, void *buffer, int size)
{
if(dev){
if(dev->dops->read){
return dev->dops->read(dev, pos, buffer, size);}}
return 0;
}/*
驱动写
*/
int cola_device_write(cola_device_t *dev, int pos, const void *buffer, int size)
{
if(dev){
if(dev->dops->write){
return dev->dops->write(dev, pos, buffer, size);}}
return 0;
}/*
驱动控制
*/
int cola_device_ctrl(cola_device_t *dev, int cmd, void *arg)
{
if(dev){
if(dev->dops->control){
return dev->dops->control(dev, cmd, arg);}}
return 0;
}硬件注册方式：以LED为例，初始化接口void led_register(void)，需要在初始化中调用。
#include "stm32f0xx.h"
#include "led.h"
#include "cola_device.h"
#define PORT_GREEN_LED GPIOC
#define PIN_GREENLED GPIO_Pin_13 /* LED亮、灭、变化 */
#define LED_GREEN_OFF (PORT_GREEN_LED->BSRR = PIN_GREENLED)
#define LED_GREEN_ON (PORT_GREEN_LED->BRR = PIN_GREENLED)
#define LED_GREEN_TOGGLE (PORT_GREEN_LED->ODR ^= PIN_GREENLED)static cola_device_t led_dev;static void led_gpio_init(void)
{GPIO_InitTypeDef GPIO_InitStructure;RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);GPIO_InitStructure.GPIO_Pin = PIN_GREENLED; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; GPIO_Init(PORT_GREEN_LED, &GPIO_InitStructure);LED_GREEN_OFF;
}static int led_ctrl(cola_device_t *dev, int cmd, void *args)
{
if(LED_TOGGLE == cmd){LED_GREEN_TOGGLE;}
else {}
return 1;
}static struct cola_device_ops ops =
{.control = led_ctrl,
};void led_register(void)
{led_gpio_init();led_dev.dops = &ops;led_dev.name = "led";cola_device_register(&led_dev);
}应用层app代码:
#include <string.h>
#include "app.h"
#include "config.h"
#include "cola_device.h"
#include "cola_os.h"static task_t timer_500ms;
static cola_device_t *app_led_dev;//led每500ms状态改变一次
static void timer_500ms_cb(uint32_t event)
{cola_device_ctrl(app_led_dev,LED_TOGGLE,0);
}void app_init(void)
{app_led_dev = cola_device_find("led");assert(app_led_dev);cola_timer_create(&timer_500ms,timer_500ms_cb);cola_timer_start(&timer_500ms,TIMER_ALWAYS,500);
}这样 app.c 文件中就不需要调用 led.h 头文件了，rtt 就是这样实现的。
四、总结
这样就可以实现软硬件分层了，是不是非常好用！
五、代码下载链接
https://gitee.com/schuck/cola_os
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