vc_CONTAINING_RECORD使用

#include <Windows.h>
#include <stdio.h>
struct tagCONTAINING_RECORD
{
    int a;
    char b;
    int c;
    int d;
};
// 使用 CONTAINING_RECORD
void test(char* cb)
{
    tagCONTAINING_RECORD *t = CONTAINING_RECORD(cb, tagCONTAINING_RECORD, b);
    printf("test中a:%d b:%c c:%d d:%d
", t->a, t->b, t->c, t->d);
    t->a = 10;
}
// 详解
//这是如何做到的呢?我们来看看CONTAINING_RECORD的表达式:
//((type *)( (PCHAR)(address) - (ULONG_PTR)(&((type *)0)->field)))
//我们看最后一部分(&((type *)0)->field)将0空指针转成type取地址在本例
//就是将空指针转成ABCD*然后指向b这个变量然后在取地址,这个操作的作用就是
//假设ABCD开始在0x000000内存位置上分配内存在此基础上求b的内存地址,说白了
//就是求得b的内存结构体对齐偏移量,OK求得b的地址我们转成ULONG_PTR类型,然后用实际
//b的内存地址减去b的结构体偏移量求得结构体首地址。

void detail(char* cb)
{
    printf("详解
");
    tagCONTAINING_RECORD *pT = (tagCONTAINING_RECORD*)0;
    char* pB = &pT->b;
    ULONG_PTR offset = (ULONG_PTR)pB;
    printf("b的偏移值%d
", offset);
    tagCONTAINING_RECORD *pF = (tagCONTAINING_RECORD*)(cb - offset);
    printf("detail中a:%d b:%c c:%d d:%d
", pF->a, pF->b, pF->c, pF->d);
    pF->c = 20;
}
int main()
{
    tagCONTAINING_RECORD t = { 1,'a',3,4 };
    test(&t.b);
    printf("main1中a:%d b:%c c:%d d:%d
", t.a, t.b, t.c, t.d);
    detail(&t.b);
    printf("main2中a:%d b:%c c:%d d:%d
", t.a, t.b, t.c, t.d);
    getchar();
    return 0;
}