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c语言面向对象之封装c面向对象之继承Linux源码分析之多态 一、封装
封装的本质就是将数据和方法集中到一个对象中#xff0c;c或者java使用的是class来实现。c语言中可以使用struct来实现同样的功能。比如下面的程序#xff1a;
struct student
{int…本文参考
c语言面向对象之封装c面向对象之继承Linux源码分析之多态 一、封装
封装的本质就是将数据和方法集中到一个对象中c或者java使用的是class来实现。c语言中可以使用struct来实现同样的功能。比如下面的程序
struct student
{int age;char *name;void (*read)(char *);
};void read_book(char *book)
{printf(book is :%s, book);
}int main(void)
{struct student s1;s1.age 10;s1.name strdup(xiaoming);s1.read read_book;printf(name: %s age: %d\n, s1.name, s1.age);s1.read(math);free(s1.name)return 0;
}二、继承
继承可以让子类使用父类的资源减少重复。父类可以是将子类的共同点抽象出来提升代码层次。 如何使用c来实现同样的效果首先肯定还是需要struct来构建父类和子类同时如果要达到is a的效果从内存空间来看也就意味着父类占据了子类内存地址的最开始位置。所以我们可以按照下面的方式来构造继承。
struct parent
{void (*func1)(void);
};struct child
{struct parent pt;void (*func2)(void);
};void test(struct parent *p)
{p-func1();
}int main()
{struct child cd;test((struct parent *)cd);
}三、多态
多态就是在程序运行时父类指针可以根据具体的子类对象来执行不同的函数行为。c中一般通过虚函数来实现。c实现多态主要是通过结构体和函数指针。
#include stdio.h // 定义基类
struct Shape
{ void (*draw)(struct Shape*);
};// 定义派生类
struct Circle
{ struct Shape shape; int radius;
};struct Rectangle
{ struct Shape shape; int width; int height;
};void drawCircle(struct Shape *shape)
{ printf(Drawing a circle...\n);struct Circle *circle (struct Circle *)shape;printf(Circle radius is %d\n, circle-radius);
}void drawRectangle(struct Shape *shape)
{ printf(Drawing a rectangle...\n);struct Rectangle *rectangle (struct Rectangle *)shape;printf(Rectangle width is %d\n, rectangle-width);printf(Rectangle height is %d\n, rectangle-height);
}int main()
{ struct Circle circle;circle.shape.draw drawCircle;circle.radius 10;struct Rectangle rectangle; rectangle.shape.draw drawRectangle;rectangle.width 10;rectangle.height 20;struct Shape *shape;shape (struct Shape *)circle;shape-draw(shape);shape (struct Shape *)rectangle;shape-draw(shape);return 0;
}在Linux内核中数量最多的就是驱动程序代码因为硬件设备是多种多样的每种设备都会有对应的驱动程序。Linux对上层的接口都是统一和抽象的要保证相同的接口最终能够对应到特定的硬件设备这就需要使用多态的技巧。
include/linux/i2c.h
这个结构体定义了不少函数指针就是实现多态的关键struct i2c_driver {unsigned int class;/* Standard driver model interfaces */int (*probe)(struct i2c_client *, const struct i2c_device_id *);int (*remove)(struct i2c_client *);/* New driver model interface to aid the seamless removal of the* current probe()s, more commonly unused than used second parameter.*/int (*probe_new)(struct i2c_client *);/* driver model interfaces that dont relate to enumeration */void (*shutdown)(struct i2c_client *);/* Alert callback, for example for the SMBus alert protocol.* The format and meaning of the data value depends on the protocol.* For the SMBus alert protocol, there is a single bit of data passed* as the alert responses low bit (event flag).* For the SMBus Host Notify protocol, the data corresponds to the* 16-bit payload data reported by the slave device acting as master.*/void (*alert)(struct i2c_client *, enum i2c_alert_protocol protocol,unsigned int data);/* a ioctl like command that can be used to perform specific functions* with the device.*/int (*command)(struct i2c_client *client, unsigned int cmd, void *arg);struct device_driver driver;const struct i2c_device_id *id_table;/* Device detection callback for automatic device creation */int (*detect)(struct i2c_client *, struct i2c_board_info *);const unsigned short *address_list;struct list_head clients;bool disable_i2c_core_irq_mapping;
};
drivers/i2c/i2c-slave-eeprom.c
