Several users of the signal API used custom convenience classes to
invoke signal-handling functions on the reception of incoming signals.
The 'Signal_dispatcher' pattern turned out to be particularly useful. To
avoid the duplication of this code across the code base, this patch
adds the interface to 'base/signal.h'.
Furthermore, the patch changes the 'Signal::num()' return type from int
to unsigned because negative numbers are meaningless here.
Fixes#511
There are certain programms which check if an fd is open by calling
fcntl(fd, F_GETFL, ...). So to keep them happy we return true if
such an request was done to our terminal fd's.
It does not suffice to constrain the amount of returned data with chunk
size of the transport buffer because the client may have specified an
even smaller value. For example, libreadline reads single characters
from the terminal and expects a single character in return. A different
amount is interpreted as EOF.
