Add set_read_timeout/2 and set_write_timeout/2

[aarroyoc]

Add timeout option for Tcp Streams

This fixes #1083 but there are two issues:

• The error it gives when the timeout works (and the read operation fails) doesn't make any sense, but I think it requires more refactoring so I'm waiting until the new rebis-dev branch arrives. For example: caught: error(syntax_error(input_output_error),get_char/2) its what get_char/2 throws when the timeout does its job
• infinite is a special value. An atom to deactivate the timeout. However, using other atoms don't throw type_error nor domain_error (it just fails). I've added a comment but I think a new value of DomainErrorType could fit here, but other approaches might be worth discussing

Test code:

?- use_module(library(sockets)).
   true.
?- socket_server_open('0.0.0.0':9000, Socket), socket_server_accept(Socket, _, Stream, [type(text)]), set_read_timeout(Stream, 10), get_char(Stream, X).

Then telnet to port 9000 and wait ten seconds.

[UWN]

Why not as an option to write_term/2 and read_term/2? Avoid state, if possible, OTOH, not sure what you mean by read and write.

[aarroyoc]

@UWN in #1083 it was said that a separate predicate would be an option. These predicates only apply to TcpStream (reading now, maybe it's not clear from the original text).

[UWN]

Needs to be discussed.

[triska]

I think one of the most important applications for this may be phrase_from_stream/2, i.e., to apply a DCG to a network stream. Should a timeout option become available for every predicate that reads from a stream, such as read_n_chars/3 or read_line_to_chars/3 from library(charsio)?

[aarroyoc]

That would work too but I'm not sure it's worth duplicating every read/write predicate. Implementation will also be more complicated