1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2002-2011, University of Amsterdam
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(stream_pool,
   36          [ add_stream_to_pool/2,       % +Stream, :Goal
   37            delete_stream_from_pool/1,  % +Stream
   38            close_stream_pool/0,
   39            dispatch_stream_pool/1,     % +TimeOut
   40            stream_pool_main_loop/0
   41          ]).   42:- use_module(library(quintus)).   43
   44:- meta_predicate
   45    add_stream_to_pool(+, :).   46
   47:- volatile
   48    pool/2.                         % sockets don't survive a saved-state
   49:- dynamic
   50    pool/2.                         % Stream, Action
   51
   52%       add_stream_to_pool(+Stream :Goal)
   53%
   54%       Call Goal whenever there is input on Stream.
   55
   56add_stream_to_pool(Stream, Action) :-
   57    strip_module(Action, Module, Plain),
   58    register_stream(Stream, Module:Plain).
   59
   60register_stream(Stream, Goal) :-
   61    assert(pool(Stream, Goal)).
   62
   63%       delete_stream_from_pool(+Stream)
   64%
   65%       Retract stream from the pool
   66
   67delete_stream_from_pool(Stream) :-
   68    retractall(pool(Stream, _)).
   69
   70%       close_stream_pool
   71
   72close_stream_pool :-
   73    (   retract(pool(Stream, _)),
   74        close(Stream, [force(true)]),
   75        fail
   76    ;   true
   77    ).
   78
   79%       dispatch_stream_pool(+TimeOut)
   80%
   81%       Wait for input on one or more streams and handle that.  Wait for
   82%       at most TimeOut seconds (0 means infinite).
   83
   84dispatch_stream_pool(Timeout) :-
   85    findall(S, pool(S, _), Pool),
   86    catch(wait_for_input(Pool, Ready, Timeout), E, true),
   87    debug(tcp, 'Select ~w --> ~w (E=~w)', [Pool, Ready, E]),
   88    (   var(E)
   89    ->  actions(Ready)
   90    ;   E = error(existence_error(stream, Stream), _)
   91    ->  delete_stream_from_pool(Stream)
   92    ).
   93
   94actions([]).
   95actions([H|T]) :-
   96    action(H),
   97    actions(T).
   98
   99action(Stream) :-
  100    pool(Stream, Action),
  101    (   catch(Action, E, true)
  102    ->  (   var(E)
  103        ->  true
  104        ;   print_message(error, E)
  105        )
  106    ;   print_message(warning,
  107                      goal_failed(Action, stream_pool))
  108    ).
  109
  110%       stream_pool_main_loop
  111%
  112%       Keep handling input from the streams in the pool until they have
  113%       all died away.
  114
  115stream_pool_main_loop :-
  116    pool(_, _),
  117    !,
  118    (   current_prolog_flag(windows, true)
  119    ->  dispatch_stream_pool(1)     % so we can break out easily
  120    ;   dispatch_stream_pool(0)
  121    ),
  122    stream_pool_main_loop.
  123stream_pool_main_loop