class input_channel :?onclose:unit -> unit -> Pervasives.in_channel ->in_obj_channel
in_channel, which must be open.
The method pos_in reflects the real position in the channel as
returned by Pervasives.pos_in. This works for both seekable and
non-seekable channels.
The method close_in also closes the underlying in_channel.
The function onclose is called after the in_channel has been closed.
