class input_filter :in_obj_channel -> io_obj_channel ->
in_obj_channel
input_filter
filters the data read from it through the
io_obj_channel
(usually a pipe
after the data have been
retrieved from the passed in_obj_channel
.
An input_filter
object never generates Buffer_underrun
exceptions.
However, if the passed in_obj_channel
or io_obj_channel
raises such
an exception, the exception will fall through the calling chain.
If the filter is closed, the io_obj_channel
will be closed, too,
but not the source in_obj_channel
(so you can still read further
data from it).