May be some more explanation is necessary: I'm reading (non-blocking) to a socket where a process running on another machine sends logging stuff to me. Sometimes I get many single characters sometimes I get large blocks. I don't know when I will receive the next package. A user can give me a regular expression I have to watch for and a timeout value. If I can match I return immediately if not I return after given timeout with an error.
Using expressions like "ABC" works quite fast and don't cause any problems with the timeout but not expressions like "AB.*Z". They only work as long as I get a few characters wihtin a few packages but not with thousands of them.
If I check the received string length and cut it after e.g. it gets larger than 20 characters I have no timeout problems any more and eth. works fine.