实现memove

void *memmoves(void *dest, const void *src, size_t count){        char *tmp_dst = NULL;        const char *tmp_src = NULL;        if (dest <= src) {tmp_dst = dest;tmp_src = src;while (count--){*tmp_dst++ = *tmp_src++;}        } else {tmp_dst = dest;tmp_dst += count;tmp_src = src;tmp_src += count;while (count--){*--tmp_dst = *--tmp_src;}                }        return dest;}