Biegral Blog

      库函数memcpy的原型是这样的：void *memcpy(void *dest, const void *src, size_t n); 下面，我们也来写个内存复制函数吧，主要是为了深入了解指针的应用，顺便熟悉一下assert的应用，程序如下：

#include <iostream>
#include <cassert>
using namespace std;

void myMemCpy(void *dst, void *src, int n) // 注意dst和src的习惯顺序
{
	assert(NULL != dst && NULL != src && n >= 0);  // 分号别搞掉了
	char *to = (char *)dst;   // 类型转换不可少
	char *from = (char *)src; // 类型转换不可少
	while(n--)
	{
		*to++ = *from++;
	}
}

int main()
{
	int a = 100;
	int *pa = &a;
	int b = 20;
	int *pb = &b;

	myMemCpy(pb, pa, sizeof(int));
	cout << b << endl;

	char str1[] = "hello,world!";
	char str2[] = "cplusplus";
	myMemCpy(str1, str2, strlen(str2));
	cout << str1 << endl;
    
	myMemCpy(str1, str2, sizeof(str2));
	cout << str1 << endl;

	cout << endl;

	char str3[] = "hello!";
	char str4[] = "cplusplus";
	myMemCpy(str3, str4, strlen(str4));
	cout << str3 << endl; // 很有可能是乱码
    
	myMemCpy(str3, str4, sizeof(str4));
	cout << str3 << endl;

	return 0;
}

100
cplusplusld!
cplusplus


cplusplusplusplus
cplusplus