Threaded tee

ttee is a simple tool to copy stdin to more than one output files/pipes.
The main difference between it and the unix tee is that the unix tee
does something like this:
while (1) {
	bytes_read = read (0, buffer, sizeof buffer);
	if (bytes_read < 0 && errno == EINTR)
		continue;
	if (bytes_read <= 0)
		break;

      /* Write to all NFILES + 1 descriptors.
         Standard output is the first one.  */
	for (i = 0; i <= nfiles; i++)
		if (descriptors[i] && fwrite (buffer, bytes_read, 1, descriptors[i]) != 1)  {
			error (0, errno, "%s", files[i]);
			descriptors[i] = NULL;
			ok = false;
		}
}


which has the unfortunate side effect of combining the latency of all inputs
in a way which makes it very hard to use to record real-time data.

This was written mostly for me to be able to log the data from dvgrab which
was in the mean time piped to vlc to be streamed.

The tool uses a simple ring buffer and a thread for each task - one reader
and multiple writers. The code is very simple (although it can be simplified
a bit more) and work well enough to be used in production.

While running, it will display every few seconds some stats on it's performance.
The most interesing from user POV are the last numbers, which show for each thread
how behind it is in on writing the ring buffer.

For anything to configure, look at config.h.