动态使用结构数据大小

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

/********************************************

Function : Actual use the size of struct

is less than declared size.

using memcpy()

********************************************/

int main()

{

struct aStr

{

int a;

double b;

char c;

};

struct Data

{

struct aStr aBuyStr[20] ;

struct aStr aSellStr[20] ;

char temp ;

int p ;

};

struct ActualData

{

struct aStr aBuyStr[5] ;

struct aStr aSellStr[5] ;

char temp ;

int p ;

};

int num = 0 ;

char caBuffer[1000] ;

struct Data sData ;

struct Data *pData ;

struct ActualData *pActualData ;

pData = &sData ;

memset(pData,NULL,sizeof(struct Data));

memset(caBuffer,NULL,1000);

printf("Pls input the num of struct :/n");

scanf("%d",&num);

for(int i=0;i<20;i++)

{

pData->aBuyStr[i].a = i;

pData->aBuyStr[i].b = i+1;

pData->aBuyStr[i].c = 'B';

pData->aSellStr[i].a = i+10;

pData->aSellStr[i].b = i+11;

pData->aSellStr[i].c = 'S';

pData->temp = 'd';

pData->p = i+2;

}

memcpy(caBuffer,pData,num*sizeof(struct aStr));

memcpy(caBuffer+num*(sizeof(struct aStr)),pData,20*sizeof(struct aStr));

memcpy(caBuffer+10*(sizeof(struct aStr)),pData,40*sizeof(struct aStr));

pActualData = (struct ActualData *)caBuffer ;

return 0;

}