C库函数之memcpy的实现

memcpy的实现方式是当满足四字节对齐时，进行四字节的拷贝，不满足时进行单字节的拷贝。例如拷贝10个字节，循环两次拷贝四字节，在循环两次拷贝一字节。

void mem_memcpy(void* dst, const void* src, unsigned int cnt)
{
	char *d = (char*)(void *)dst;
	const char *s = src;

	while (cnt >= sizeof (int)) {
		*(int*)d = *(int*)s;
		d += sizeof (int);
		s += sizeof (int);
		cnt -= sizeof (int);
	}
	while ((cnt) > 0U){
		*d = *s;
		d += 1U;
		s += 1U;
		cnt -= 1U;
	}
}

end