memcpy的实现.

[cpp] view plaincopy
#include <iostream>
#include <string.h>
using namespace std;

void *mymemcpy(void *des,const void * src , int size)
{
char *d = (char*)des;
char *s = (char*)src;
if(d < s)
while(size–)
*d++ = *s++;
else
{
d += size-1;
s += size-1;
while(size–)
*d– = *s–;
/*
d += size;
s += size;
while(size–)
*–d = *–s;
*/
}
return d;
}

int main()
{
cout << “Hello world!” << endl;
char src[] = “abcdefg”;
char *des = (char*)malloc(strlen(src)); //包括’\0′
mymemcpy((void *)des,(void *)src,3);
cout<<src<<endl;
cout<<des<<endl;
return 0;
}