指針間接賦值，指針賦值

指針間接賦值，指針賦值

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

/*間接賦值成立的三個條件：

條件一：//定義一個實參　　//定義一個形參

條件二：//建立關聯：把實參取地址傳給形參

條件三：//形參間接去修改實參的值

*/

/*

　　用n級指針形參，去間接的修改n-1級指針（實參）的值。

*/

/*間接賦值的場景

//1 2 3 這3個條件 寫在有一個函數
//12 寫在一塊 3 單獨寫在另外一個函數裡面 =====>函數調用
//1 23寫在一塊

void main()

{

　　

char from[128];
char to[128] = {0};
char *p1 = from;
char *p2 = to;

strcpy(from, "1122233133332fafdsafas");

while (*p1 != '\0')
{
*p2 = *p1;
p2 ++;
p1++;
}

printf("to:%s \n", to);

　

}

*/


int getMem3(char **myp1, int *mylen1, char **myp2, int *mylen2)
{
int ret = 0;
char *tmp1, *tmp2;
tmp1 = (char*)malloc(100);
strcpy(tmp1, "1234456789");
*mylen1 = strlen(tmp1);    //1級指針
*myp1 = tmp1;    //2級指針的間接賦值


tmp2 = (char*)malloc(200);
strcpy(tmp2, "abcdefghigklmn");
*mylen2 = strlen(tmp2);//1級指針
*myp2 = tmp2;//2級指針的間接賦值
return ret;
}

int main()
{
char *p1 = NULL;
char *p2 = NULL;
int len1 = 0;
int len2 = 0;
int ret = getMem3(&p1,&len1,&p2,&len2);
if (ret !=0){
printf("func getMem3 %d",ret);
return ret;
}
printf("p1:%s\n", p1);
printf("p2:%s\n", p2);
if (p1 != NULL)
{
free(p1);
p1 = NULL;
}
if (p2 != NULL)
{
free(p2);
p2 = NULL;
}
system("pause");
return 0;
}