版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/qq_22520215/article/details/79028089
在初始化数据时,尤其结构体里的数组,新手就设个i,然后来个for循环一个一个初始化为0,memset()函数就是简化了这个步骤,因为上面这个步骤你可能搞错数组长度,废话不多说,下面教你如何编写memset()及最基本常用的方法!
一、函数分析
void memset(void *src, unsigned char ch, unsigned char len)
{
char *psrc = (char *)src;
if(src == NULL) return;
while(len--)
{
*psrc = ch;
psrc++;
}
}
1、void *src
我们在传入数据时,因为数据长度有8位,16位,32位,为了可以统一赋值,我们就取8位作为赋值的单位,这样16位我们赋值2次,32位赋值4次就可以了;所以在不知道传入的数据时什么类型的情况下,我们用void *src 来接收不同的数据;
2、char *psrc = (char *)src
将传入数据的首地址强制装换为char*类型即长度为8位的指针,因为一个8位地址对应一个8位数据;
3、len
那传入的数据可以分为多少个8位呢?这里我们用sizeof()函数计算,长度=sizeof(数据名)/sizeof(unsigned char),这样可以避免自己数错;
二、函数实战(这里只做0的赋值)
1、unsigned char类型数组清0实例
#include <stdio.h>
int main()
{
unsigned char i;
unsigned char arr[]= {"我是"};
printf("原数据\n");
for(i=0;i<(sizeof(arr)/sizeof(unsigned char));i++)
{
printf(" =%x= ",arr[i]);
}
memset(arr,0,sizeof(arr)/sizeof(unsigned char));
printf("\n");
printf("处理后数据\n");
for(i=0;i<(sizeof(arr)/sizeof(unsigned char));i++)
{
printf(" =%x= ",arr[i]);
}
return 0;
}
结果为:
原数据
=e6= =88= =91= =e6= =98= =af= =0=
处理后数据
=0= =0= =0= =0= =0= =0= =0=
2、unsigned int类型数组清0实例
#include <stdio.h>
int main()
{
unsigned char i;
unsigned int arr[]= {0x12,0x23,0x45,0x56,0xab,0xdf};
printf("原数据\n");
for(i=0;i<(sizeof(arr)/sizeof(unsigned int));i++)
{
printf(" =%x= ",arr[i]);
}
memset(arr,0,sizeof(arr)/sizeof(unsigned char));
printf("\n");
printf("处理后数据\n");
for(i=0;i<(sizeof(arr)/sizeof(unsigned int));i++)
{
printf(" =%x= ",arr[i]);
}
return 0;
}
结果为:
原数据
=12= =23= =45= =56= =ab= =df=
处理后数据
=0= =0= =0= =0= =0= =0=
3、typedef struct类型清0实例
#include <stdio.h>
typedef struct
{
unsigned int a[3];
unsigned char b[2];
}Example;
int main()
{
unsigned char i;
Example Struct_Arr;
Struct_Arr.a[0] = 0x12;
Struct_Arr.a[1] = 0xa34;
Struct_Arr.a[2] = 0x1234;
Struct_Arr.b[0] = 0xab;
Struct_Arr.b[1] = 0xcd;
printf("原数据 a\n");
for(i=0;i<(sizeof(Struct_Arr.a)/sizeof(unsigned int));i++)
{
printf(" =%x= ",Struct_Arr.a[i]);
}
printf("\n");
printf("原数据 b\n");
for(i=0;i<(sizeof(Struct_Arr.b)/sizeof(unsigned char));i++)
{
printf(" =%x= ",Struct_Arr.b[i]);
}
memset(&Struct_Arr,0,sizeof(Struct_Arr)/sizeof(unsigned char));
printf("\n");
printf("处理后a数据\n");
for(i=0;i<(sizeof(Struct_Arr.a)/sizeof(unsigned int));i++)
{
printf(" =%x= ",Struct_Arr.a[i]);
}
printf("\n");
printf("处理后b数据\n");
for(i=0;i<(sizeof(Struct_Arr.b)/sizeof(unsigned char));i++)
{
printf(" =%x= ",Struct_Arr.b[i]);
}
return 0;
}
结果为:
原数据 a
=12= =a34= =1234=
原数据 b
=ab= =cd=
处理后a数据
=0= =0= =0=
处理后b数据
=0= =0=
以上就是很简单的快速清0操作,最后一个在嵌入式初始化数据很常用!!!