美女大街上尿裤子视频:有谁能帮我看看下面这段程序什么意思tv.tv_sec=1什么意思？c语言的

int read_GPS_datas(int fd, char *rcv_buf)
{
int retval;
fd_set rfds;
struct timeval tv;
int ret,pos;
tv.tv_sec = 1;
tv.tv_usec = 0;
pos = 0; // point to rceeive buf
while (1)
{
FD_ZERO(&rfds);
FD_SET(fd, &rfds);
retval = select(fd+1 , &rfds, NULL, NULL, &tv);
if (retval == -1)
{
perror("select()");
break;
}
else if (retval)
{// 判断是否受到数据
ret = read(fd, rcv_buf+pos, 2048);
pos += ret;
if (rcv_buf[pos-2] == '\r' && rcv_buf[pos-1] == '\n')
{
FD_ZERO(&rfds);
FD_SET(fd, &rfds);
retval = select(fd+1 , &rfds, NULL, NULL, &tv);
if (!retval) break;// if no datas, break
}
}
else
{
printf("No data\n");
break;
}
}
return 1;
}