董的博客 ? C语言实现封装、继承和多态

//内存管理类new.h

#ifndef NEW_H

#define NEW_H

void * new (const void * class, ...);

void delete (void * item);

void draw (const void * self);

#endif

//内存管理类的C文件：new.c

#include “new.h”

#include “base.h”

void * new (const void * _base, ...)

{

const struct Base * base = _base;

void * p = calloc(1, base->size);

assert(p);

* (const struct Base **) p = base;

if (base ->ctor)

{

va_list ap;

va_start(ap, _base);

p = base ->ctor(p, &ap);

va_end(ap);

}

return p;

}

void delete (void * self)

{

const struct Base ** cp = self;

if (self && * cp && (* cp) —> dtor)

self = (* cp) —>dtor(self);

free(self);

}

void draw (const void * self)

{

const struct Base * const * cp = self;

assert(self &&* cp && (* cp)->draw);

(* cp) ->draw(self);

}

//基类：base.h

#ifndef BASE_H

#define BASE_H

struct Base

{

size_t size; //类所占空间

void * (* ctor) (void * self, va_list * app); //构造函数

void * (* dtor) (void * self); //析构函数

void (* draw) (const void * self); //作图

};

#endif

//Point头文件(对外提供的接口)：point.h

#ifndef   POINT_H

#define  POINT_H

extern const void * Point;                /* 使用方法：new (Point, x, y); */

#endif

//Point内部头文件(外面看不到)：point.r

#ifndef POINT_R

#define POINT_R

struct Point

{

const void * base; //继承，基类指针，放在第一个位置，const是防止修改

int x, y;        //坐标

};

#endif

//Point的C文件：point.c

#include “point.h”

#include “new.h”

#include “point.h”

#include “point.r”

static void * Point_ctor (void * _self, va_list * app)

{

struct Point * self = _self;

self ->x = va_arg(* app, int);

self ->y = va_arg(* app, int);

return self;

}

static void Point_draw (const void * _self)

{

const struct Point * self = _self;

printf(“draw (%d,%d)”, self -> x, self -> y);

}

static const struct Base _Point = {

sizeof(struct Point), Point_ctor, 0, Point_draw

};

const void * Point = & _Point;

//测试程序：main.c

#include “point.h”

#include “new.h”

int main (int argc, char ** argv)

{

void * p = new(Point, 1, 2);

draw(p);

delete(p);

}