memmove,memcpy,mecset在库函数都是有的,可以直接使用,需要引用头文件
#include<memory.h>
#include<string.h>
void * memcpy ( void * destination, const void * source, size_t num );
void * memset ( void * ptr, int value, size_t num );
void * memmove ( void * destination, const void * source, size_t num );
num都是字节大小!
它们的格式都是
1.memcpy的实现
#include<stdio.h>
#include<assert.h>
#include<stdlib.h>
#include<memory.h>
void* my_memmove(void* arr1, void* arr2, int size) {
assert(arr1);//防止为空指针
assert(arr2);
void* ret = arr1;
while (size--) {
*(char*)arr1 = *(char*)arr2;
arr1 = (char*)arr1 + 1;
arr2 = (char*)arr2 + 1;
}
return ret;
}
int main() {
int arr1[20];
int arr2[20];
scanf("%s%s", arr1, arr2);
printf("%s", my_memmove(arr1, arr2, 20));//20为字节大小
return 0;
}
2.memmove的实现
#include<stdio.h>
#include<assert.h>
#include<stdlib.h>
#include<memory.h>
void* my_memmove(void* arr1, void* arr2, int size) {
assert(arr1);
assert(arr2);
void* ret = arr1;
if (ret <= arr2)
{
while (size--) {
*(char*)arr1 = *(char*)arr2;
arr1 = (char*)arr1 + 1;
arr2 = (char*)arr2 + 1;
}
}
else {
void* src = (char*)arr2 + size - 1;
void* des = (char*)arr1 + size - 1;
while (size--) {
*(char*)des = *(char*)src;
des = (char*)des - 1;
src = (char*)src - 1;
}
}
return ret;
}
int main() {
char arr1[20];
char arr2[20];
scanf("%s%s", arr1, arr2);
printf("%s", my_memmove(arr1, arr2, 8));
return 0;
}
3.memset的实现
#include<stdio.h>
#include<assert.h>
#include<stdlib.h>
#include<memory.h>
void* my_memset(void* arr1, int x, int size) {
assert(arr1);
int i = 0;
char* ret =(char*)arr1;
while (size--) {
ret[i++] = x;
}
return ret;
}
int main() {
char arr1[20];
scanf("%s", arr1);
puts(my_memset(arr1,'1', 8));
return 0;
}