memcpy即内存复制，程序如下

void *my_memcopy(void *dst,const void *src,size_t count){	char *pdst = (char*)dst;	char *psrc = (char*)src;		if(pdst == NULL || psrc == NULL)	{		return NULL;	}	if(pdst > psrc && pdst < psrc + count)//防止内存复制重叠，所以从后向前复制	{		pdst = pdst + count + 1;		psrc = psrc + count + 1;		while(count != 0)		{			*pdst = *psrc;			psrc--;			pdst--;			count--;		}	}	else	{		size_t i = 0;		for(i = 0;i < count;i++)		{			*pdst = *psrc;			psrc++;			pdst++;		}	}	return dst;}复制代码